PATENT DOCUMENT

Publication Number: US-10381881-B2
Application Number: US-201816122766-A
Country: US
Kind Code: B2

Title: Architecture of portable electronic devices with wireless charging receiver systems

Abstract:
Embodiments disclosed herein describe a wireless power receiving system for an electronic device includes: a first inductor coil configured to receive power primarily at a first frequency and from magnetic fields propagating in a first direction; and a second inductor coil configured to receive power primarily at a second frequency and from magnetic fields propagating in a second direction, wherein the first frequency is different than the second frequency.

Claims:
What is claimed is: 
     
       1. A portable electronic device, comprising:
 a housing comprising a top portion including a display and a bottom portion including a window, the bottom portion is configured to mate with the top portion to form an internal cavity; 
 an antenna disposed within the internal cavity and comprising an antenna element and a conductive antenna body coupled to a bottom surface of the antenna element, the antenna having an opening disposed at the center of the antenna and defined by an inner edge of the antenna; 
 a wireless charging receiver system disposed within the internal cavity and the antenna opening, the wireless charging receiver system comprising a primary coil having an inner diameter and an outer diameter, a ferromagnetic shield covering a portion of at least two surfaces of the primary coil, and a secondary coil wound about overlapping portions of the primary coil and the ferromagnetic shield; and 
 a sensor module disposed within the internal cavity and the inner diameter of the primary coil, the sensor module comprising at least one sensing device configured to measure a parameter of an environment external to the portable electronic device. 
 
     
     
       2. The portable electronic device of  claim 1 , wherein the primary coil is configured to receive time-varying magnetic flux propagating in a first direction and at a first frequency, and wherein the secondary coil is configured to receive time-varying magnetic flux propagating in a second direction different from the first direction and at a second frequency different from the first frequency. 
     
     
       3. The portable electronic device of  claim 1 , wherein the conductive antenna body is a layer of conductive material that conforms to the bottom surface of the antenna element and is configured to send and receive communication signals through radio waves. 
     
     
       4. The portable electronic device of  claim 1 , wherein the ferromagnetic shield extends from a first radial location to a second radial location different from the first radial location. 
     
     
       5. The portable electronic device of  claim 1 , wherein the inner edge of the antenna conforms to an outer profile of the wireless charging receiver system. 
     
     
       6. The portable electronic device of  claim 1 , wherein the sensor module is configured to measure the parameter of the environment through the window of the bottom portion of the housing. 
     
     
       7. The portable electronic device of  claim 1 , wherein the antenna comprises:
 a top level forming the outer edge of the antenna; 
 a bottom level forming the antenna opening and the inner edge of the antenna; and 
 a step region disposed between the top level and the bottom level. 
 
     
     
       8. The portable electronic device of  claim 7 , wherein the top level and the bottom level are each planar structures that are oriented along separate but parallel planes, and the step region is a vertical portion of the antenna that has a circular profile and couples the top level to the bottom level. 
     
     
       9. A portable electronic device, comprising:
 a housing comprising a top portion including a display and a bottom portion including a window, the bottom portion is configured to mate with the top portion to form an internal cavity, wherein the window includes a plurality of ink layers coated on portions of an inner surface and an outer surface of the window; 
 a spacer disposed within the internal cavity and comprising a non-conductive material, the spacer having an opening disposed at the center of the spacer and defined by an inner edge of the spacer; 
 a wireless charging receiver system disposed within the internal cavity and the opening, the wireless charging receiver system comprising a primary coil having an inner diameter and an outer diameter, a ferromagnetic shield covering a portion of at least two surfaces of the primary coil, and a secondary coil wound about overlapping portions of the primary coil and the ferromagnetic shield; 
 a sensor module disposed within the internal cavity and the inner diameter of the primary coil, the sensor module comprising at least one sensing device configured to measure a parameter of an environment external to the portable electronic device; 
 an alignment module coupled to the sensor module, the alignment module comprising an alignment magnet and a DC shield attached to a top surface of the alignment magnet; and 
 an electromagnetic shield layer positioned between the wireless charging receiver system and the window of the bottom portion of the housing. 
 
     
     
       10. The portable electronic device of  claim 9 , wherein the at least one IR transparent layer and at least one IR opaque layer are coated on a portion of the inner surface of the window such that the center of the window is uncovered by the plurality of ink layers. 
     
     
       11. The portable electronic device of  claim 9 , wherein at least one conductive ink layer is coated on a portion of the outer surface of the window such that the center of the window is uncovered by the at least one conductive ink layer. 
     
     
       12. The portable electronic device of  claim 9 , further comprising a system-in-package disposed between the top portion of the housing and the spacer. 
     
     
       13. The portable electronic device of  claim 9 , wherein the spacer comprises:
 a top level forming the outer edge of the spacer; 
 a bottom level forming the opening and the inner edge of the spacer; and 
 a step region disposed between the top level and the bottom level. 
 
     
     
       14. The portable electronic device of  claim 13 , wherein the inner edge of the spacer and the step region both have circular profiles. 
     
     
       15. A wireless charging system, comprising:
 a first wireless charging transmitter comprising:
 a first housing having a first charging surface; and 
 at least one first transmitter coil formed of a plurality of turns of stranded wire disposed within the first housing and below the first charging surface, the at least one first transmitter coil configured to generate first time-varying magnetic fields through and above the first charging surface; and 
 
 a wireless charging receiver comprising:
 a housing comprising a top portion including a display and a bottom portion including a window, the bottom portion is configured to mate with the top portion to form an internal cavity; 
 an antenna disposed within the internal cavity and comprising an antenna element and a conductive antenna body coupled to a bottom surface of the antenna element, the antenna having an opening disposed at the center of the antenna and defined by an inner edge of the antenna; 
 a wireless charging receiver system disposed within the internal cavity and the antenna opening, the wireless charging receiver system comprising a primary receiver coil having an inner diameter and an outer diameter and configured to receive the first time-varying magnetic fields generated by the at least one first transmitter coil, a ferromagnetic shield covering a portion of at least two surfaces of the primary receiver coil, and a secondary receiver coil wound about overlapping portions of the primary receiver coil and the ferromagnetic shield; and 
 a sensor module disposed within the internal cavity and the inner diameter of the primary receiver coil, the sensor module comprising at least one sensing device configured to measure a parameter of an environment external to the portable electronic device. 
 
 
     
     
       16. The wireless charging system of  claim 15 , wherein the at least one transmitter coil is configured to generate the time-varying magnetic fields in the first direction at the first frequency. 
     
     
       17. The wireless charging system of  claim 15 , further comprising a second wireless charging transmitter comprising:
 a second housing having a second charging surface; and 
 at least one second transmitter coil formed of a plurality of turns of stranded wire disposed within the second housing and below the second charging surface, the at least one second transmitter coil configured to generate second time-varying magnetic fields through and above the second charging surface and in a second direction different from the first direction at a second frequency different from the first frequency. 
 
     
     
       18. The wireless charging system of  claim 17 , wherein the secondary receiver coil is configured to receive the second time-varying magnetic fields generated by the at least one second transmitter coil of the second wireless charging transmitter. 
     
     
       19. The wireless charging system of  claim 15 , wherein the antenna comprises:
 a top level forming the outer edge of the antenna; 
 a bottom level forming the antenna opening and the inner edge of the antenna; and 
 a step region disposed between the top level and the bottom level. 
 
     
     
       20. The wireless charging system of  claim 15 , wherein the conductive antenna body is a layer of conductive material that conforms to the bottom surface of the antenna element and is configured to send and receive communication signals through radio waves.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a non-provisional patent application of and claims the benefit to U.S. Provisional Patent Application No. 62/554,945, filed Sep. 6, 2017 and titled “Wireless Charging Receiver Systems For Portable Electronic Devices,”, and is related to the following concurrently filed and commonly assigned U.S. Non-Provisional patent applications: U.S. patent application Ser. No. 16/122,787, filed Sep. 5, 2018, entitled “Single-Structure Wireless Charging Receiver Systems having Multiple Receiver Coils”; U.S. patent application Ser. No. 16/122,799, filed Sep. 5, 2018, entitled “Antenna Integration for Portable Electronic Devices having Wireless Charging Receiver Systems”; and U.S. patent application Ser. No. 16/122,811, filed Sep. 5, 2018, entitled “Multiple-Structure Wireless Charging Receiver Systems having Multiple Receiver Coils”, the disclosures of which are herein incorporated by reference in their entirety for all purposes. 
    
    
     BACKGROUND 
     Portable electronic devices (e.g., mobile phones, media players, smart watches, and the like) operate when there is charge stored in their batteries. Some portable electronic devices include a rechargeable battery that can be recharged by coupling the portable electronic device to a power source through a physical connection, such as through a charging cord. Using a charging cord to charge a battery in an electronic device, however, requires the portable electronic device to be physically tethered to a power outlet. Additionally, using a charging cord requires the portable electronic device to have a connector, typically a receptacle connector, configured to mate with a connector, typically a plug connector, of the charging cord. The receptacle connector typically includes a cavity in the portable electronic device that provides an avenue within which dust and moisture can intrude and damage the device. Furthermore, a user of the portable electronic device has to physically connect the charging cable to the receptacle connector in order to charge the battery. 
     To avoid such shortcomings, portable electronic devices have been configured with receiver coils that can receive power from a wireless charging device without the need for a charging cord. For example, some portable electronic devices can be recharged by merely resting the device on a charging surface of a wireless charging device. A transmitter coil disposed below the charging surface may produce a time-varying magnetic field that induces a current in a corresponding receiver coil in the portable electronic device. The induced current can be used by the portable electronic device to charge its internal battery. 
     Some existing portable electronic devices configured to receive wireless power have a number of disadvantages. For instance, some portable electronic devices require that it be placed in a very confined charging region on a charging surface of a wireless charging device in order to receive power. If the portable electronic device is placed outside of the charging region, the portable electronic device may not wirelessly charge or may charge inefficiently and waste power. Additionally, some portable electronic devices are configured to charge from only one type of wireless charging device. Thus, these portable electronic devices can only charge at one frequency and require the use of a specific type of wireless charging device. This limits the ease at which the portable electronic device can be wirelessly charged. 
     Furthermore, portable electronic devices, especially wearable portable electronic devices such as smart watches and the like, are designed to be compact so that they do not interfere with a user&#39;s mobility in his or her day-to-day activities. Having this compact design constrains the size limitations of internal components within the portable electronic device. As the functionality of the portable electronic devices increases, a larger number of electronic components will need to be housed within the portable electronic device, where some components will require larger amounts of space than other electronic components. Finding the right balance between size requirements of each internal component and its proper operation is difficult to achieve for such compact portable electronic devices. 
     SUMMARY 
     Some embodiments of the disclosure provide a wireless power receiver system for a portable electronic device. The wireless power receiving system can be configured to receive charge from various wireless charging devices and can fit within a compact enclosure of the portable electronic device along with an antenna configured for wireless (e.g., radio wave) communication. In some embodiments, the portable electronic device can be a smart watch that has a receiver system designed to include at least two different receiver coils for receiving wireless power from different wireless charging devices. The portable electronic device can have a compact footprint while having the ability to charge from multiple wireless charging devices, thereby easing the way in which the portable electronic device can receive power to charge its battery. 
     In some embodiments, a portable electronic device according to the disclosure includes a housing, an antenna, a wireless charging receiver system and a sensor module. The housing can include a top portion including a display and a bottom portion including a window where the bottom portion is configured to mate with the top portion to form an internal cavity. The antenna can be disposed within the internal cavity and include an antenna element and a conductive antenna body coupled to a bottom surface of the antenna element. The antenna can include an opening disposed at the center of the antenna and defined by an inner edge of the antenna. The wireless charging receiver system can be disposed within the internal cavity and the antenna opening and include a primary coil having an inner diameter and an outer diameter, a ferromagnetic shield covering a portion of at least two surfaces of the primary coil, and a secondary coil wound about overlapping portions of the primary coil and the ferromagnetic shield. The sensor module can be disposed within the internal cavity and the inner diameter of the primary coil and include at least one sensing device configured to measure a parameter of an environment external to the portable electronic device. 
     A portable electronic device according to some embodiments includes a housing, a spacer, a wireless charging receiver system, a sensor module, an alignment module and an electromagnetic shield layer. The housing can include a top portion including a display and a bottom portion including a window where the bottom portion is configured to mate with the top portion to form an internal cavity and the window includes a plurality of ink layers coated on portions of an inner surface and an outer surface of the window. The spacer can be disposed within the internal cavity and comprise a non-conductive material, the spacer can include an opening disposed at the center of the spacer and defined by an inner edge of the spacer. The wireless charging receiver system can be disposed within the internal cavity and the opening and include a primary coil having an inner diameter and an outer diameter, a ferromagnetic shield covering a portion of at least two surfaces of the primary coil, and a secondary coil wound about overlapping portions of the primary coil and the ferromagnetic shield. The sensor module can be disposed within the internal cavity and the inner diameter of the primary coil and include at least one sensing device configured to measure a parameter of an environment external to the portable electronic device. The alignment module can be coupled to the sensor module and include an alignment magnet and a DC shield attached to a top surface of the alignment magnet, and the electromagnetic shield layer can be positioned between the wireless charging receiver system and the window of the bottom portion of the housing. 
     In some embodiments a wireless charging system is provided. The system can include a first wireless charging transmitter and a wireless charging receiver. The wireless charging transmitter can include: a first housing having a first charging surface; and at least one first transmitter coil formed of a plurality of turns of stranded wire disposed within the first housing and below the charging surface, the at least one first transmitter coil configured to generate first time-varying magnetic fields through and above the first charging surface. The wireless charging receiver can include: a housing having a top portion including a display and a bottom portion including a window where the bottom portion is configured to mate with the top portion to form an internal cavity; an antenna disposed within the internal cavity and including an antenna element and a conductive antenna body coupled to a bottom surface of the antenna element where the antenna includes an opening disposed at the center of the antenna and defined by an inner edge of the antenna; a wireless charging receiver system disposed within the internal cavity and the antenna opening, the wireless charging receiver system including a primary receiver coil having an inner diameter and an outer diameter and configured to receive the first time-varying magnetic fields generated by the at least one first transmitter coil, a ferromagnetic shield covering a portion of at least two surfaces of the primary receiver coil, and a secondary receiver coil wound about overlapping portions of the primary receiver coil and the ferromagnetic shield; and a sensor module disposed within the internal cavity and the inner diameter of the primary receiver coil, the sensor module comprising at least one sensing device configured to measure a parameter of an environment external to the portable electronic device. 
     In some embodiments a wireless charging receiver system is provided that includes a primary coil, a ferromagnetic shield and a secondary coil. The primary can coil can be formed of a plurality of turns of stranded wire wound about a primary axis and configured to receive wireless power from time-varying magnetic fields generated at a first frequency and in a first direction. The ferromagnetic shield can be disposed over at least two adjacent surfaces of the primary coil and over a portion of the entire circumference of the at least two adjacent surfaces such that an annular segment of the primary coil is uncovered by the ferromagnetic shield, and the secondary coil can be formed of a plurality of turns of stranded wire wound about a secondary axis disposed along a circumference centered around the primary axis, the secondary coil covers overlapping portions of the ferromagnetic shield and the primary coil and is configured to receive wireless power from time-varying magnetic fields generated at a second frequency different from the first frequency and in a second direction different from the first direction. 
     Some additional embodiments pertain to an antenna for an electronic device. The antenna can include a non-conductive antenna element having a bottom surface, a conductive body attached to the bottom surface of the non-conductive antenna element and at least one capacitor. The non-conductive antenna element can include: a first planar top level comprising an outer edge; a first planar bottom level comprising an antenna opening and an inner edge; and a first step region disposed between the first top level and the first bottom level, the first step region coupling the first top level with the first bottom level and having a circular profile. The conductive body can attached conform to the non-conductive antenna element and include: a second planar top level below the first planar top level and a slit that divides a section of the conductive body into two parts; a second planar bottom level below the first planar top level; and a second step region disposed beside the first step region. The at least one capacitor can be disposed on the first planar top level and electrically coupled between the two parts of the conductive body and can be configured to electrically couple the two parts together when the conductive body is exposed to electrical signals at a first frequency and electrically disconnect the two parts from one another when the conductive body is exposed to magnetic fields at a second frequency different from the first frequency. 
     Some embodiments pertain to a portable electronic device that includes a housing having a top portion and a bottom portion configured to mate with the top portion to form an internal cavity. The portable electronic device can further include an antenna as described herein. 
     In some additional embodiments, a wireless charging receiver system is provided that includes: a primary coil formed of a plurality of turns of stranded wire wound about a primary axis and configured to receive wireless power from time-varying magnetic fields generated at a first frequency and in a first direction; a primary ferromagnetic shield disposed on a top surface of the primary coil; a pair of secondary ferromagnetic structures disposed coplanar with one another and positioned apart from the primary ferromagnetic shield, the pair of secondary ferromagnetic structures include a first ferromagnetic structure and a second ferromagnetic structure; and a secondary coil including a first sub-coil and a second sub-coil, each sub-coil formed of a plurality of turns of stranded wire wound about a center portion of respective first and second ferromagnetic structures, and configured to receive wireless power from time-varying magnetic fields generated at a second frequency different from the first frequency and in a second direction different from the first direction. 
     Some embodiments pertain to a portable electronic device that includes a housing having a top and bottom portions and defining an internal cavity and a wireless charging receiver system as described herein disposed within the internal cavity. 
     A better understanding of the nature and advantages of embodiments of the present invention may be gained with reference to the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an exemplary portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 2  is a block diagram illustrating the inner components of a wireless charging receiver system, according to some embodiments of the present disclosure. 
         FIG. 3A  is a block diagram of a portable electronic device placed against a wireless charging device that is specifically designed to provide wireless power to the portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 3B  is a block diagram of a portable electronic device placed against a wireless charging device that is configured to provide power to more than one type of portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 4A  is a perspective view illustration of an exemplary primary receiving element that includes a primary receiver coil formed as a flex coil, according to some embodiments of the present disclosure. 
         FIG. 4B  is a top-down view of an exemplary symmetrical primary receiver coil having symmetric windings, according to some embodiments of the present disclosure. 
         FIG. 5A  is a perspective view of an exemplary primary receiving element including a stranded primary receiver coil, according to some embodiments of the present disclosure. 
         FIG. 5B  is a cross-sectional illustration of the primary receiving element illustrated in  FIG. 5A , according to some embodiments of the present disclosure. 
         FIG. 6A  is a perspective view of an exemplary primary receiving element including a stranded primary receiver coil and a modified ferromagnetic shield, according to some embodiments of the present disclosure. 
         FIG. 6B  is a cross-sectional illustration of the primary receiving element illustrated in  FIG. 6A , according to some embodiments of the present disclosure. 
         FIG. 7  is a perspective view illustration of an exemplary secondary receiving element, according to some embodiments of the present disclosure. 
         FIG. 8  is an exploded view illustration of an exemplary coil subassembly, according to some embodiments of the present disclosure. 
         FIG. 9  is an exploded view illustration of an exemplary portable electronic device, according to some embodiments of the present disclosure. 
         FIGS. 10A-10C  are top down view illustrations of different sizing arrangements between secondary receiving elements and an antenna when assembled in a portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 11  is a cross-sectional view illustration of an assembled portion of a portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 12A  is a perspective view illustration of an exemplary wireless charging receiver system  1200  whose primary and secondary receiving elements are formed as a single structure, according to some embodiments of the present disclosure. 
         FIG. 12B  is a top-down illustration of the wireless charging receiver system shown in  FIG. 12A , according to some embodiments of the present disclosure. 
         FIG. 12C  is a bottom-up illustration of the wireless charging receiver system shown in  FIG. 12A , according to some embodiments of the present disclosure 
         FIGS. 12D-12E  are simplified cross-sectional illustrations of a ferromagnetic structure across different planes through its extended region shown in  FIGS. 12A-12C , according to some embodiments of the present disclosure. 
         FIG. 13  is an exploded view illustration of the wireless charging receiver system shown in  FIGS. 12A-12C , according to some embodiments of the present disclosure. 
         FIG. 14A  is a perspective view illustration of an exemplary wireless charging receiver system whose primary and secondary receiving elements are formed as a single structure but altered to minimize its size, according to some embodiments of the present disclosure. 
         FIG. 14B  is a top-down illustration of the wireless charging receiver system shown in  FIG. 14A , according to some embodiments of the present disclosure. 
         FIG. 14C  is a bottom-up illustration of the wireless charging receiver system shown in  FIG. 14A , according to some embodiments of the present disclosure. 
         FIGS. 14D-14E  are simplified cross-sectional illustrations of the ferromagnetic structure across different planes through the straight segment shown in  FIGS. 14A-14C , according to some embodiments of the present disclosure. 
         FIG. 15  is an exploded view illustration of the wireless charging receiver system shown in  FIGS. 14A-14C , according to some embodiments of the present disclosure. 
         FIG. 16  is an exploded view illustration of an exemplary portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 17  is a bottom-up view illustration of an alignment module, according to some embodiments of the present disclosure. 
         FIG. 18  is an exploded view diagram of an antenna system, according to some embodiments of the present disclosure. 
         FIG. 19  is a top-down illustration of a partially assembled portion of portable electronic device, according to some embodiments of the present disclosure. 
         FIGS. 20A-20D  are various top-down and cross-sectional views of a grounding bracket, according to some embodiments of the present disclosure. 
         FIG. 21  is a perspective view of a partially assembled portable electronic device including a spacer and a receiver system, according to some embodiments of the present disclosure. 
         FIG. 22  is an exploded view of a bottom housing portion for a portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 23  is a simplified diagram illustrating a perspective view of a sensor module mounted on a bottom housing portion of a portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 24  is a bottom perspective view illustration of a bottom housing portion of a portable electronic device, according to some embodiments of the present disclosure. 
         FIG. 25A  is a cross-sectional view illustration of the assembled portion shown in  FIG. 19  across the horizontal cut line, according to some embodiments of the present disclosure. 
         FIG. 25B  is a cross-sectional view illustration of the assembled portion shown in  FIG. 19  across the vertical cut line, according to some embodiments of the present disclosure. 
         FIGS. 26A-D  are illustrations showing the different layers that are coated on a window of a bottom housing portion, according to some embodiments of the present disclosure. 
         FIGS. 27A-H  are a series of illustrations showing how an internal surface of a window can be coated with different layers in a second configuration, according to some embodiments of the present disclosure. 
         FIG. 28A  is a top-down view of a window after all of the layers have been patterned as shown in  FIG. 27H  to show the two cut lines for the cross-sectional views in  FIGS. 28B-28C , according to some embodiments of the present disclosure. 
         FIG. 28B  is a cross-sectional view of a window through a contact pad, according to some embodiments of the present disclosure. 
         FIG. 28C  is a cross-sectional view of a window through an opaque patch, according to some embodiments of the present disclosure. 
         FIG. 29A  is a simplified diagram illustrating an exemplary configuration where a contact wraps around an edge of a window, according to some embodiments of the present disclosure. 
         FIG. 29B  is a simplified diagram illustrating an exemplary configuration where a contact is coupled to a via, according to some embodiments of the present disclosure. 
         FIG. 29C  is a simplified diagram illustrating another exemplary configuration where a contact is configured as a standalone structure that can route signals from an outer surface to an inner surface of a window, according to some embodiments of the present disclosure. 
         FIG. 30  is a simplified diagram illustrating a top-down view of an external region of a bottom housing portion having first and second contacts and configured as any of the contacts discussed in  FIGS. 29A-29C , according to some embodiments of the present disclosure. 
         FIG. 31A  is a simplified diagram illustrating an exemplary configuration where an intermediate structure is disposed between a via and a structure body, according to some embodiments of the present disclosure. 
         FIG. 31B  is a simplified diagram illustrating an exemplary configuration where an inner surface of a window includes a flattening insert, according to some embodiments of the present disclosure. 
         FIG. 32  is a simplified diagram illustrating a top-down view of an external region of a bottom housing portion including an intermediate structure and first and second contacts configured as shown in  FIGS. 31A-31B , according to some embodiments of the present disclosure. 
         FIG. 33A  is a simplified diagram illustrating an exemplary configuration where an intermediate structure is disposed between a contact on a window and a structure body, according to some embodiments of the present disclosure. 
         FIG. 33B  is a simplified diagram illustrating an exemplary configuration where an intermediate structure is formed as part of a structure body, according to some embodiments of the present disclosure. 
         FIG. 34  is a simplified diagram illustrating a top-down view of an external region of a bottom housing portion including an intermediate structure and first and second contacts configured as shown in  FIGS. 33A-33B , according to some embodiments of the present disclosure. 
         FIG. 35  is a simplified diagram illustrating an exploded view of an exemplary touch-sensitive dial, according to some embodiments of the present disclosure. 
         FIG. 36  is a cross-sectional illustration of an exemplary electrical pathway through a dial, according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the disclosure describe a portable electronic device that is configured to receive charge from various wireless charging devices and that can fit within a compact enclosure along with an antenna configured for wireless communication. The portable electronic device can be a wearable portable electronic device, such as a smart watch, that has a receiver system designed to include at least two different receiver coils for receiving wireless power from different wireless charging devices. The manner in which the portable electronic device receives power from each wireless charging device can be different from each other. 
     As an example, each receiver coil can be configured to operate at a specific frequency based on the operating frequency of a wireless charging device from which it receives power. For instance, one receiver coil can be configured to operate at a first frequency, and the other receiver coil can be configured to operate at a second frequency that is different than the first frequency. As another example, each receiver coil can be configured to operate according to different alignment constraints. For instance, one receiver coil can operate when the portable electronic device is substantially aligned with a wireless charging device, whereas the other receiver coil can operate when the portable electronic device is placed upon any region of a broad charging surface. Furthermore, each receiver coil can be configured to receive magnetic field that is propagating in a specific direction. For instance, one receiver coil can be configured to receive magnetic field propagating in a vertical direction, while the other is configured to receive magnetic field propagating in a horizontal direction. 
     Accordingly, the portable electronic device can receive power from various wireless charging devices, thereby increasing the ease at which the portable electronic device can be charged. Aspects and features of embodiments of such a portable electronic device are discussed in further detail herein. 
     I. Portable Electronic Device 
     A portable electronic device is an electronic device that can operate without being coupled to a power grid by running on its own locally stored electrical power.  FIG. 1  is a block diagram illustrating an exemplary portable electronic device  100 , according to some embodiments of the present disclosure. Device  100  includes a computing system  102  coupled to a memory bank  104 . Computing system  102  can execute instructions stored in memory bank  104  for performing a plurality of functions for operating device  100 . Computing system  102  can be one or more suitable computing devices, such as microprocessors, computer processing units (CPUs), graphics processing units (GPUs), field programmable gate arrays (FPGAs), and the like. 
     Computing system  201  can also be coupled to a user interface system  106 , communication system  108 , and a sensor system  110  for enabling electronic device  100  to perform one or more functions. For instance, user interface system  106  can include a display, speaker, microphone, actuator for enabling haptic feedback, and one or more input devices such as a button, switch, capacitive screen for enabling the display to be touch sensitive, and the like. Communication system  108  can include wireless telecommunication components (e.g., antenna components for radio frequency telecommunication), Bluetooth components, and/or wireless fidelity (WiFi) components for enabling device  100  to make phone calls, interact with wireless accessories, and access the Internet. Sensor system  110  can be one or more sensor modules, as will be discussed further herein, that include light sensors, accelerometers, gyroscopes, temperature sensors, heart rate sensors, electrocardiography (EKG) sensors, and any other type of sensor that can measure a parameter of an external entity and/or environment. 
     All of these electrical components require a power source to operate. Accordingly, portable electronic device  100  also includes a battery  112  for discharging stored energy to power the electrical components of device  100 . To replenish the energy discharged to power the electrical components, portable electronic device  100  includes a wireless charging receiver system  114 . According to some embodiments of the present disclosure, wireless charging receiver system  114  can be configured to wirelessly receive power from an external source, such as a wireless charging device. For instance, wireless charging receiver system  114  can be one or more inductive receiver coils configured to receive power from one or more transmitter coils in a wireless charging device. The wireless charging device can generate a time-varying magnetic field that interacts with and generates a corresponding current in wireless charging receiver system  114 . The generated current can be used to provide energy to battery  112  for replenishing its energy storage so that battery  112  can be discharged at a later time to operate portable electronic device  100  when it is not connected to an external power supply. 
     In some embodiments, portable electronic device  100  is a consumer electronic device that can perform one or more functions for a user. For instance, portable electronic device  100  can be a smart phone, wearable device, smart watch, tablet, personal computer, and the like. 
     II. Wireless Charging Receiver System for a Portable Electronic Device 
     According to some embodiments of the present disclosure, a wireless charging system for a portable electronic device can include at least two receiver coils for receiving power from different wireless charging devices. Each receiver coil can be configured to receive power according to different charging constraints and parameters, such as alignment constraints and operating frequency, that are defined by the particular wireless charging device from which it receives power. 
       FIG. 2  is a block diagram illustrating the inner components of wireless charging receiver system  114 , according to some embodiments of the present disclosure. Wireless charging receiver system  114  can include two elements: a primary receiving element  200  and a secondary receiving element  210 , for receiving power from different wireless charging devices. Each element can include a receiver coil and at least one element can include a shield or structure for redirecting the flow of magnetic field and/or for capturing stray electric fields. 
     In some embodiments, primary receiving element  200  can include a primary receiver coil  202 , a primary ferromagnetic shield  204 , and an optional electromagnetic shield  206  that are tuned to maximize the efficiency of power transfer from a wireless charging device that is specifically designed to provide power to portable electronic device  100 . Thus, primary receiver coil  202  can be configured to receive power according to an alignment constraint and operating frequency defined by the wireless charging device, as discussed herein with respect to  FIG. 3A . 
       FIG. 3A  is a block diagram of portable electronic device  100  placed against a wireless charging device  300  that is specifically designed to provide wireless power to portable electronic device  100 , according to some embodiments of the present disclosure. Wireless charging device  300  includes a transmitter coil  302  that is configured to generate a time-varying magnetic field  304  at a primary frequency, and provide power to a receiving device when it is substantially aligned with a receiver coil in the receiving device. Thus, in some embodiments, primary receiver coil  202  in device  100  is configured to operate at the primary frequency and to receive power when it is substantially aligned with transmitter coil  302 . As an example, primary receiver coil  202  can receive power from time-varying magnetic field  304  at a primary frequency of between 6 to 7 MHz, particularly approximately 6.78 MHz in some embodiments, and when its axis is aligned with the axis of transmitter coil  302 . 
     During operation of transmitter coil  302 , time-varying magnetic field  304  can propagate along field loops around transmitter coil  302  as shown in  FIG. 3A . The direction of propagation can include vertical components  306  and horizontal components  308  as time-varying magnetic field  304  propagates along the field loops. By being able to substantially align with transmitter coil  302 , primary receiver coil  202  can receive power from vertical components  306  of transmitter coil  302 . Thus, primary receiver coil  202  can be configured to receive magnetic field propagating in the vertical direction. For instance, primary receiver coil  202  can have a central axis that is parallel to the vertical direction such that magnetic field propagating in the vertical direction can induce a corresponding current in primary receiver coil  202 . Field propagating with a degree of horizontal movement  308  may not substantially pass through the inner diameter of primary receiver coil  202  and thus may result in little to no generation of power in primary receiver coil  202 . 
     With reference back to  FIG. 2 , unlike primary receiving element  200 , a secondary receiving element  210  can include a secondary receiver coil  212  and an optional secondary ferromagnetic structure  214  that are configured to receive power from a wireless charging device that is designed to provide power to a several different types of electrical devices. For instance, receiver coil  212  can be configured to receive power from a wireless charging mat that has a broad charging surface for charging different types of devices, including portable electronic device  100 . Thus, secondary receiver coil  212  can be configured to receive power according to the alignment constraint and operating frequency defined by the wireless charging device. As will be discussed further herein, for embodiments where the primary and secondary receiving elements  200  and  210  are formed as separate structures, secondary receiving element  210  may include ferromagnetic structure  214 , and in embodiments where the primary and secondary receiving elements  200  and  210  are formed as a single structure, secondary receiving element  210  may not include ferromagnetic structure  214 . 
       FIG. 3B  is a block diagram of portable electronic device  100  placed against a wireless charging device  310  that is configured to provide power to more than one type of portable electronic device, according to some embodiments of the present disclosure. Wireless charging device  310  can include N number of transmitter coils ranging from  312 - 1  to  312 -N. Transmitter coils  312 - 1  to  312 -N can be organized as a transmitter coil arrangement that provides a broad charging surface  316  upon which electronic devices can be charged. The broad charging surface allows electronic devices to be charged anywhere within charging surface  316 . Thus, portable electronic device  100  can be positioned along any area  318  of charging surface  316  to receive power from wireless charging device  310 . Furthermore, the broad charging surface allows more than one electronic device of the same type or different types to charge from wireless charging device  310 . 
     Transmitter coils  312 - 1  to  312 -N can be configured to generate time-varying magnetic field  314  at a secondary frequency, and provide power to a receiving device when the receiving device is resting upon any region of charging surface  316 . Thus, in some embodiments, secondary receiving element  210  in device  100  is configured to operate at the secondary frequency and to receive power when it is resting on charging surface  316  in any degree of alignment with transmitter coils  312 - 1  to  312 -N. According to some embodiments, the secondary frequency at which secondary receiving element  210  operates can be different than the primary frequency at which primary receiving element  200  operates. In some embodiments, the secondary frequency is less than the primary frequency. For instance, secondary receiver coil  212  can receive power from time-varying magnetic field  314  at a secondary frequency of between 300 to 400 kHz, particularly approximately 326 kHz in some embodiments. Because the secondary frequency is different than the primary frequency, when secondary receiving element  210  is receiving charge, primary receiving element  200  may not substantially receive charge, and vice versa. 
     During operation of each transmitter coil, such as transmitter coil  312 - 1  shown in  FIG. 3B , time-varying magnetic field  314  can propagate along field loops around transmitter coil  312 - 1  as shown in  FIG. 3B . The direction of propagation can include vertical components  320  and horizontal components  322  as time-varying magnetic field  314  propagates along the field loops. As can be seen in  FIG. 3B , portable electronic device  100  can be positioned on charging surface  316  so that it is not aligned with transmitter coil  312 - 1 . In some embodiments, secondary receiver coil  212  can be configured to receive horizontal components  322  of magnetic field  314 , and thus receive power from transmitter coil  312 - 1 . For instance, secondary receiver coil  212  can have a central axis  324  that is parallel to the horizontal direction such that magnetic field propagating in the horizontal direction can induce a corresponding current in secondary receiver coil  212 . Field propagating with a degree of vertical movement  320  may not substantially pass through the inner diameter of secondary receiver coil  212  and thus may result in little to no generation of power in secondary receiver coil  212 . 
     In some embodiments, secondary receiver coil  212  can be formed of two sub-coils: a first sub-coil  326  and a second sub-coil  328 . Both first and second sub-coils can be wound in the same direction. For instance, both first and second sub-coils can be wound in the clockwise direction or counter-clockwise direction. By winding both first and second sub-coils in the same direction, both sub-coils  326  and  328  can generate power from magnetic fields propagating in the same horizontal direction, thereby increasing the efficiency at which secondary receiver coil  212  receives power. In some embodiments, first and second sub-coils  326  and  328  are electrically coupled together, such as in a series arrangement or a parallel arrangement. When electrically coupled together, power generated in both sub-coils  326  and  328  can aggregate into a larger magnitude of received power. Details regarding the construction of the primary and secondary receiving elements  200  and  210  are discussed further herein with respect to  FIGS. 4A-9 . In some embodiments, secondary receiver coil  212  can be formed of a single coil. In such instances, secondary receiver coil  212  can be a separate component that winds around a separate ferromagnetic structure, or it can wind around a portion of primary receiver coil  202  as will be discussed further herein with respect to  FIGS. 12A-14B . 
     III. Construction of Primary and Secondary Receiving Elements 
     As can be understood from  FIGS. 3A and 3B , primary receiver coil  202  and secondary receiver coil  212  are designed to operate at different frequencies and different alignment constraints to receive power from different wireless charging devices. This difference in operation can be achieved in part by having different physical constructions and orientations. In some instances, the primary and secondary receiving elements can be separate, individual components positioned at different locations within the portable electronic device. Alternatively, the primary and secondary receiving elements can be part of a single component where the secondary receiver coil winds around a portion of the primary receiver coil. Exemplary constructions of such primary and secondary receiving elements are discussed herein with respect to  FIGS. 4A-8  and  FIGS. 12A-14B . 
     A. Primary and Secondary Receiving Elements Constructed as Separate Components 
       FIG. 4A  illustrates an exemplary primary receiving element  400  that includes a primary receiver coil  402  formed as a flex coil for a receiver system configured to have a separate secondary receiving element, according to some embodiments of the present disclosure. Primary receiving element  400  can include a ferromagnetic shield  404  attached to a first side of primary receiver coil  402  and an electromagnetic shield  406  attached to a second side of primary receiver coil  402  opposite of the first side. 
     Ferromagnetic shield  404  can help redirect magnetic field through an inner diameter  408  of primary receiver coil  402  to increase efficiency of wireless power transfer and to mitigate stray field from propagating to disturb other electrical components within the electronic device. In some embodiments, ferromagnetic shield  404  has a shape that substantially corresponds with a shape of primary receiver coil  402 . For instance, ferromagnetic shield  404  can be in the shape of a circular ring. Ferromagnetic shield  404  can be formed of any suitable material that has magnetic properties and is particularly attractive to magnetic field generated at the primary frequency and less attractive to magnetic field generated at the secondary frequency. For instance, ferromagnetic shield  404  can be particularly attractive to magnetic field generated at a high frequency, such as between 6 to 7 MHz (e.g., the frequency at which wireless charging device  300  operates). For instance, ferromagnetic shield  404  can be formed of a material containing nickel-zinc (NiZn). 
     Electromagnetic shield  406  can be configured to capture electric fields emanating from primary receiver coil  402  to prevent voltage from generating on a transmitter coil. Voltage built up in electromagnetic shield  406  from exposure to electric fields can be discharged to ground. In some embodiments, electromagnetic shield  406  is formed of a thin layer of conductive material, such as silver. Electromagnetic shield  406  can be positioned closer to the transmitter coil than ferromagnetic shield  404  during wireless power transfer. 
     Primary receiver coil  402  can be formed of one or more windings of a single length of conductive material patterned on a flexible circuit board. The one or more windings can form a spirally-wound coil that winds between an inner diameter  408  and an outer diameter  410 . In some embodiments, primary receiver coil  402  is formed of more than one layer of windings that wind from outer diameter  410  to inner diameter  408  in one layer, and back from inner diameter  408  to outer diameter  410  in an adjacent layer. In other embodiments, primary receiver coil  402  is a symmetrical coil that is formed of a winding having crossing portions, as shown in  FIG. 4B . 
       FIG. 4B  is a top-down view of an exemplary symmetrical primary receiver coil  401  having symmetric windings, according to some embodiments of the present disclosure. Winding  420  can begin and end at location  412  and have crossing-over portions  414  and  416  that allow symmetrical primary receiver coil  401  to be symmetrical across a vertical and horizontal axis. The symmetrical profile results in a decrease in capacitive coupling between symmetrical primary receiver coil  401  and a transmitter coil form which it receives power during wireless power transfer. In some embodiments, primary receiver coil  402  includes two layers of coils connected in a parallel configuration. For instance, two layers of coils where each layer is arranged as shown in  FIG. 4B  can be implemented as primary receiver coil  401 . The two layers can be positioned above and below one another such that they share the same central axis  422 . 
     Although primary receiving element  200  can include a primary receiver coil  202  formed as a flex coil, other embodiments can have receiver coil  202  formed as a stranded coil as shown in  FIGS. 5A-5B .  FIG. 5A  is a perspective view of an exemplary primary receiving element  500  including a stranded primary receiver coil  502 , ferromagnetic shield  504 , electromagnetic shield  506  and a guide structure  508  for a receiver system configured to have a separate secondary receiving element, according to some embodiments of the present disclosure. Ferromagnetic shield  504  can be disposed above primary receiver coil  502 , and electromagnetic shield  506  can be disposed below primary receiver coil  502 . Ferromagnetic shield  504  and electromagnetic shield  506  can have similar properties, materials, and functions of ferromagnetic shield  404  and electromagnetic shield  406  discussed herein with respect to  FIG. 4 . 
     In some embodiments, primary receiving element  500  can also include a guide structure  508 . Guide structure  508  can extend around at least a portion of primary receiving element  500 . In particular embodiments, guide structure  508  be a stiff structure that provides structural support for primary receiving element  500  to resist against bending or other physical deformations. 
       FIG. 5B  is a cross-sectional illustration of primary receiving element  500 , according to some embodiments of the present disclosure. As shown in  FIG. 5B , guide structure  508  and ferromagnetic shield  504  can both be disposed above primary receiver coil  502 . In some embodiments, guide structure  508  and ferromagnetic shield  504  can be attached to primary receiver coil  502  by an intermediary layer. For instance, a spacer layer  510  can attach primary receiver coil  502  to ferromagnetic shield  504 , and provide a degree of separation between them. In certain embodiments, spacer layer  510  is formed of pressure sensitive adhesive (PSA). 
     As shown in  FIGS. 5A and 5B , ferromagnetic shield  504  can be a structure that is disposed above primary receiver coil  502  and that functions to help redirect magnetic field through primary receiver coil  502 . In some cases, the structure of ferromagnetic shield can be modified to improve its ability to redirect magnetic field through primary receiver coil  502  and thus improve wireless charging efficiency. An example of a modified ferromagnetic shield is discussed herein with respect to  FIGS. 6A and 6B . 
       FIG. 6A  is a perspective view of an exemplary primary receiving element  600  including a stranded primary receiver coil  602 , a modified ferromagnetic shield  604 , and an electromagnetic shield  606 , according to some embodiments of the present disclosure. 
     Ferromagnetic shield  604  and electromagnetic shield  606  can have similar properties, materials, and functions of ferromagnetic shield  404  and electromagnetic shield  406  discussed herein with respect to  FIG. 4 . As shown in  FIG. 6A , ferromagnetic shield  604  may differ from ferromagnetic shield  504  in  FIG. 5B  in that a portion of modified ferromagnetic shield  604  can extend downward and be positioned lateral to primary receiver coil  602 . In some embodiments, the side of primary receiver coil  602  to which modified ferromagnetic shield  604  is laterally disposed is a side that is closest to a center axis of primary receiver coil  602 . By positioning modified ferromagnetic shield  604  on that side, it can better assist in redirecting magnetic field through primary receiver coil  602  to increase charging efficiency. 
       FIG. 6B  is a cross-sectional illustration of primary receiving element  600 , according to some embodiments of the present disclosure. As shown in  FIG. 6B , modified ferromagnetic shield  604  can be disposed both above and beside primary receiver coil  602 . By extending shield  604  downward to a position lateral to receiver coil  602 , modified ferromagnetic shield  604  can be positioned closer to the transmitter coil from which it receives magnetic field, and can be better positioned to redirect the received magnetic field through primary receiver coil  602 . In some embodiments, modified ferromagnetic shield  604  can be attached to primary receiver coil  602  by at least one intermediate layer, such as spacer layer  606   a  and  606   b . Spacer layer  606   a  can be positioned to attach a portion of modified ferromagnetic shield  604  disposed above primary receiver coil  602  with a top surface of primary receiver coil  602 . Spacer layer  606   b  can be positioned to attach a portion of modified ferromagnetic shield  604  disposed lateral to primary receiver coil  602  with a side surface of primary receiver coil  602 . The side surface can be an inner side surface that is positioned closest to a center axis of primary receiver coil  602 . Similar to spacer layer  510 , spacer layer  610  can be formed of PSA. 
       FIG. 7  illustrates a perspective view of an exemplary secondary receiving element  700 , according to some embodiments of the present disclosure. Secondary receiving element  700  can include a secondary receiver coil formed of a first coil subassembly  701  and a second coil subassembly  703 . First and second coil subassemblies  701  and  703  can be positioned a distance D away from each other to minimize coupling between the two subassemblies, and to provide space within which other electronic components within the portable electronic device can be positioned. 
     Each coil subassembly can include multiple parts; for instance, first coil subassembly  701  can include a first sub-coil  702  and a first ferromagnetic structure  706 , and second coil subassembly  703  can include a second sub-coil  704  and a second ferromagnetic structure  708 . First sub-coil  702  can be wound about a central portion of first ferromagnetic structure  706 , and second sub-coil  704  can be wound about a central portion of second ferromagnetic structure  708 . By winding sub-coils  702  and  704  around their respective ferromagnetic structures  706  and  708 , first and second ferromagnetic structures  706  and  708  can redirect magnetic field through first and second transmitter sub-coils  702  and  704 , respectively, and thereby increase power transfer efficiency. 
     In some embodiments, first and second sub-coils  702  and  704  are coupled together in a series configuration. Thus, power received by both first and second sub-coils  702  and  704  can be inputted into a single rectifier to convert alternating current (AC) power to direct current (DC) power. By coupling the first and second sub-coils  702  and  704  together, secondary receiving element can cover more surface area as it rests on the wireless charging device, thereby allowing the portable electronic device to capture more magnetic field during wireless power transfer and minimizing instances where portable electronic device is not capturing any magnetic field (e.g., sitting in a dead zone). Although it is disclosed that first and second sub-coils  702  and  704  share a single rectifier, embodiments are not so limited. Other embodiments can decouple first and second sub-coils  702  and  704  so that each sub-coil is coupled to its own rectifier. In such instances, each sub-coil can operate independently from each other. 
     Ferromagnetic structures  706  and  708  can be formed of any suitable material that has magnetic properties and is particularly attractive to magnetic field generated at the secondary frequency and less attractive to magnetic field generated at the primary frequency. In some embodiments, the secondary frequency is lower than the primary frequency. For instance, ferromagnetic structures  706  and  708  can be formed of a material that is particularly attractive to magnetic field generated at a low frequency, such as between 300-400 kHz, particularly 326 kHz (e.g., the frequency at which wireless charging device  310  in  FIG. 3B  operates). In certain embodiments, the magnetic permeability of the material used to form ferromagnetic structures  706  and  708  in secondary receiving element  700  is substantially larger than the magnetic permeability of the material used to form ferromagnetic shields  404 ,  504 , and  604  in primary receiving elements  400 ,  500 , and  600 , respectively. As an example, ferromagnetic structures  706  and  708  are formed of a material having a magnetic permeability of greater than 3000, such as a material containing manganese-zinc (MnZn), while ferromagnetic shields  404 ,  504 , and  604  can be formed of a material having a magnetic permeability of less than 500, such as 200 in some embodiments. Thus, ferromagnetic structures  706  may have greater losses for magnetic fields generated in higher frequencies (e.g., 6-7 MHz) and less losses for magnetic fields generated in lower frequencies (e.g., 300-400 KHz). The opposite can be said for ferromagnetic shields  404 ,  504 , and  604 . 
     Each ferromagnetic structure  706  or  708  can be formed of a plurality of individual parts.  FIG. 8  is an exploded view illustration of an exemplary coil subassembly  800 , according to some embodiments of the present disclosure. Coil subassembly  800  can include a ferromagnetic structure  802  and a coil of wire  804 . Ferromagnetic structure  802  can include a ferrite body  806  sandwiched between two support layers  808   a  and  808   b . Ferrite body  806  can be a structure that forms the bulk of ferromagnetic structure  802  and includes material suitable for redirecting magnetic field, such as sintered ferrite formed of MnZn. Support layers  808   a  and  808   b  can be layers of tape that protect surfaces of ferrite body  806  from physical damage, such as damage from coil of wire  804  when coil of wire  804  is wound around ferrite body  806 . Thus, in some embodiments, coil of wire  804  is wound around ferrite body  806  and both support layers  808   a  and  808   b . In some embodiments, support layers  808   a  and  808   b  can be disposed on opposite surfaces of ferrite body  806 . As an example, support layer  808   a  can be disposed on a top surface of ferrite body  806 , and support layer  808   b  can be disposed on a bottom surface of ferrite body  806 . Support layers  808   a  and  808   b  can be formed of any non-conductive material that can withstand physical stresses, such as Polyethylene Terephthalate (PET). 
     Ferromagnetic structure  802  can also include protective layers  810   a  and  810   b  that are attached to a surface of ferrite body  806 . For instance, protective layers  810   a  and  810   b  can be attached to a top surface of ferrite body  806  where support layer  808   a  is not positioned. Protective layers  810   a  and  810   b  can protect top surfaces of ferrite body  806  from damage during assembly. In some embodiments, protective layers  810   a  and  810   b  are also formed of a magnetic material including ferrite. 
     In some embodiments, adhesive layers  812   a  and  812   b  can be disposed on a surface of ferrite body  806 . For instance, adhesive layers  812   a  and  812   b  can be disposed on a bottom surface of ferrite body  806  where support layer  808   b  is not positioned. Adhesive layers  812   a  and  812   b  can be formed of any suitable material that can attach two structures together, such as a pressure sensitive adhesive (PSA). Adhesive layers  812   a  and  812   b  can fix coil subassembly  800  in position when assembled in a portable electronic device. Although  FIGS. 7 and 8  show a secondary receiving element formed with two sub-coils, embodiments are not limited to such configurations. Other embodiments can have more or less than two coils wound about respective ferromagnetic structures, such as a single coil wound about a single ferromagnetic structure, or three or more coils wound about three or more respective ferromagnetic structures without departing from the spirit and scope of the present disclosure. 
     1. Construction of a Portable Electronic Device Having a Secondary Receiving Element Formed of at Least Two Sub Coils 
     The size and shape of primary and secondary receiver elements depend on the amount of available space provided by the other electrical components in the portable electronic device. As can be appreciated by disclosures herein, the size and shape of the receiver elements can be determined by balancing the trade-off between performance of the receiver elements and the performance of other electrical components in the portable electronic device. 
       FIG. 9  illustrates an exploded view of an exemplary portable electronic device  900 , according to some embodiments of the present disclosure. Portable electronic device  900  can include a top housing portion  902  and a bottom housing portion  904  that can mate to define an interior cavity. Top housing portion  902  can include a device chassis  906  and a transparent panel  908 . Transparent panel  908  is a protective, optically transparent structure for a display so that a user can view the display through transparent panel  908  while transparent panel  908  protects the display from damage. Top housing portion  902  can include one or more user interface components, such as a dial  910 , microphone  912 , power button  914 , and any other suitable user interface components. 
     In some embodiments, dial  910  can be a touch sensitive dial that can act as a contact for performing EKG sensing. Dial  910  can include various components that, when coupled together, form a conductive pathway from an outer surface of dial  910  to inner touch components, which is discussed further herein with respect to  FIGS. 35 and 36 . 
     Portable electronic device  900  can further include a system in package (SIP)  916  that is housed within the interior cavity. SIP  916  can be a number of integrated circuits (ICs) enclosed in a single module that can operate to perform several functions of portable electronic device  900 . Each IC in SIP  916  can perform one or more different functions, such as performing heart rate monitoring, operating a touch screen display, outputting sound through one or more speakers, processing sound received by microphone  912 , managing wireless power transfer, and the like. 
     According to some embodiments of the present disclosure, portable electronic device  900  can include a primary receiving element  918  and a secondary receiving element  920 . Primary and secondary receiving elements  918  and  920  can be positioned within the interior cavity and below SIP  916 . As discussed herein, primary receiving element  918  can include a primary receiver coil  922  (shown with a ferromagnetic shield) and an electromagnetic shield  924  that are configured to receive magnetic field generated at a primary frequency and propagating in a vertical direction, as discussed herein with respect to  FIGS. 3A and 4A-6B . Secondary receiving element  920  can include first and second coil subassemblies  926   a  and  926   b  configured to receive magnetic field generated at a secondary frequency lower than the primary frequency and propagating in a horizontal direction, as discussed herein with respect to  FIGS. 3B, 7 and 8 . First and second subassemblies  926   a  and  926   b  can include first and second ferromagnetic structures  928   a  and  928   b  and first and second sub-coils  925   a  and  925   b , respectively. 
     In some embodiments, portable electronic device  900  can also include an antenna  929  within the interior cavity and below SIP  916 . Antenna  929  can include an opening  930  within which one or more other electronic components of portable electronic device  900  can be positioned. For instance, primary receiving element  918  can be disposed within opening  930  and below at least a portion of antenna  929 , and secondary receiving element  920  can be positioned above at least a portion of antenna  929 . In some embodiments, first and second subassemblies  926   a  and  926   b  are positioned on opposite ends of antenna  929 . As mentioned herein with respect to  FIG. 7 , first and second subassemblies  926   a  and  926   b  can be separated by a distance D. Accordingly, antenna  929  can be positioned within the space provided by distance D. Further details of their positioning will be discussed herein with respect to  FIG. 11 . Antenna  929  can be a structure configured to receive and/or send data through radio waves. As an example, antenna  929  can be an antenna configured for long-term evolution (LTE) wireless communications. Such antennas may perform better when their size is maximized, and when conductive electronic components are positioned away from it. 
     As discussed herein with respect to  FIG. 7 , the size of ferromagnetic structures  928   a  and  928   b  impacts the efficiency at which secondary receiving element  920  receives wireless power. Larger ferromagnetic structures  928   a  and  928   b  can increase the efficiency of wireless power transfer because the larger structures can redirect more magnetic field. However, larger ferromagnetic structures take up more space within the portable electronic device and leave less space for antenna  929 . Decreasing the amount of space for antenna  929  can negatively affect the performance of antenna  929 . Thus, a conflict of interest with respect to component size can exist between antenna  929  and secondary receiving element  920  due to their close proximity with one another. Details of this relationship is discussed further herein with respect to  FIGS. 10A-C . 
       FIGS. 10A-10C  illustrate top down views of different sizing arrangements between secondary receiving elements  920  and antenna  929  when assembled in a portable electronic device, according to some embodiments of the present disclosure. Specifically,  FIG. 10A , illustrates a top-down view of a sizing arrangement  1000  that is more beneficial for antenna  929 ,  FIG. 10B  illustrates a top down-view of a sizing arrangement  1002  that is more beneficial for secondary receiving element  920 , and  FIG. 10C  illustrates a top-down view of a sizing arrangement  1004  that strikes a balance between operating efficiencies of both antenna  929  and secondary receiving element  920 . 
     As shown by sizing arrangement  1000  in  FIG. 10A , the size of antenna  929  and space  1001  surrounding antenna  929  is enlarged to enhance the operation of antenna  929 . This, however, results in a shrinkage of ferromagnetic structures  928   a  and  928   b . Shrinking the size of ferromagnetic structures  928   a  and  928   b  decreases wireless charging efficiency because ferromagnetic structures  928   a  and  928   b  become smaller and thus less effective at redirecting magnetic field. 
     On the other hand, enlarging ferromagnetic structures  928   a  and  928   b  to maximize charging efficiency can hinder the operation of antenna  929 . As shown by sizing arrangement  1002  in  FIG. 10B , the size of ferromagnetic structures  928   a  and  928   b  can be enlarged to increase the charging efficiency of secondary receiving element  920 . One way to enlarge ferromagnetic structures  928   a  and  928   b  is to provide protruding portions  1006  that encroach into the space for antenna  929 . These protruding portions can extend toward antenna  929  past edges of sub-coils  925   a  and  925   b . Enlarging the size of ferromagnetic structures  928   a  and  928   b  however results in a corresponding decrease in the size of antenna  929  and its surrounding space  1001 . This decrease in size and space hinders the operation of antenna  929 . 
     Thus, according to some embodiments of the present disclosure, the sizes of ferromagnetic structures  928   a  and  928   b , antenna  929 , and space  1001  surrounding antenna  929  can be optimized to achieve acceptable levels of both antenna operation and charging efficiency, as shown in sizing arrangement  1004  in  FIG. 10C . The resulting ferromagnetic structures  928   a  and  928   b  can still have protruding portions  1006 , but the degree at which protruding portions  1006  extend past edges of sub-coils  925   a  and  925   b  may be lessened. 
     With reference back to  FIG. 9 , portable electronic device  900  can also include an alignment mechanism  932  disposed between a DC shield  934  and a sensor module  936 . Alignment module  932  can be a permanent magnet designed to attract another alignment magnet in a wireless charging device for aligning with the wireless charging device, such as wireless charging device  300  in  FIG. 3A . Sensor module  936  can be an electrical component that houses and operates one or more sensors for performing one or more functions. For instance, sensor module  936  can be a circuit board (e.g., a printed circuit board (PCB)) that has one or more sensors for sensing heart rate and the like. DC shield  934  can be positioned above alignment module  932  to prevent magnetic fields from alignment module  932  from being exposed to other electrical components within portable electronic device  900 , such as SIP  916  and secondary receiving element  920 . Sensor module  936  can be attached to a surface of bottom hosing  904 , as shown in  FIG. 11 . 
     2. Assembled Bottom Housing Portion of a Portable Electronic Device Having a Secondary Receiving Element Formed of at Least Two Sub Coils 
       FIG. 11  illustrates a cross-sectional view of an assembled portion  1100  of portable electronic device  900  to better illustrate the construction of portable electronic device  900  when assembled, according to some embodiments of the present disclosure. The cross-section shown in  FIG. 11  can be taken along the line shown in  FIG. 10C . Assembled portion  1100  illustrated in  FIG. 11  does not include top housing portion  902  for ease of discussion. 
     As shown in  FIG. 11 , sensor module  936  can be mounted on an inner surface of window  1103  of bottom structure body  1101 . Sensor module  936  can include a thin heart rate sensor  1102  and one or more photo diodes  1104  for performing sensing functions. Alignment module  932  can be a permanent magnet that is coupled to sensor module  936  and disposed between sensor module  932  and DC shield  934 . Second contact  1106  can be positioned on an outer surface of window  1103  and wrap around edges of window  1103  so that it is also positioned on a portion of an inner surface of window  1103 . Second contact  1106  can be coupled with sensor module  936  so that sensor module  936  can receive measurements from second contact  1106 . 
     In some embodiments, sensor module  936 , alignment module  932 , and DC shield  934  are all positioned within opening  930  of antenna  929 . As shown in  FIG. 11 , antenna  929  can be formed of an antenna body  1106  and a conductive layer  1108 . Antenna body  1106  can be a support structure upon which conductive layer  1108  can be disposed; and conductive layer  1108  can be a structure that performs the functions of sending and receiving wireless communication through radio waves. 
     According to some embodiments of the present disclosure, primary receiving element  918  can be disposed within opening  930  and below at least a portion of antenna  929 . Furthermore, secondary receiving element  920  can be disposed above at least a portion of antenna  929 . Both primary and secondary receiving elements  918  and  920  can be disposed laterally to at least a portion of antenna  929 . Primary and secondary receiving elements  918  and  920  can be used to perform wireless charging, as discussed herein with respect to  FIGS. 3A and 3B . 
     B. Primary and Secondary Receiving Elements Constructed as a Single Structure 
     Although the secondary receiving element can be formed of two sub-coils that are physically separate structures from the primary element as discussed herein with respect to  FIGS. 7-9 , embodiments are not limited to such configurations. In some embodiments, the secondary receiving element can be formed of a coil wound about a portion of the primary coil such that the structures of the primary receiving element and secondary receiving element are intertwined, as will be discussed herein with respect to  FIGS. 12A-12C and 13A-13C . 
       FIG. 12A  is a perspective view illustration of an exemplary wireless charging receiver system  1200  whose primary and secondary receiving elements are formed as a single structure, according to some embodiments of the present disclosure. The primary receiving element can include a primary coil  1202  and a primary ferromagnetic shield  1204 , and the secondary receiving element can be formed of a secondary coil  1206  that is wound about a portion of both primary coil  1202  and primary ferromagnetic shield  1204 . That is, the axis of secondary coil  1206  can be a curved axis that runs along a length of a turn of wire of primary coil  1202 . Details regarding the construction of, and the relationship between, the primary and secondary receiving elements can be better understood with reference to  FIGS. 12B-12E . 
       FIG. 12B  is a top-down illustration  1201  of exemplary wireless charging receiver system  1200 , and  FIG. 12C  is a bottom-up illustration  1211  of wireless charging receiver system  1200 , according to some embodiments of the present disclosure. Primary coil  1202  can be a stranded coil of wire that has a circular profile centered around a center axis  1208 . Ferromagnetic shield  1204  can be configured to overlap a portion of the entire circular profile of primary coil  1202 . In some embodiments, ferromagnetic shield  1204  extends between a first radial location  1210  and a second radial location  1212  of primary coil  1202 , where the first and second radial locations  1210  and  1212  are different, non-overlapping radial locations. That is, ferromagnetic shield  1204  can be configured to cover only a portion of the entire circumferences of a top surface and two side surfaces of primary coil  1202 . Accordingly, ferromagnetic shield  1204  may not cover any surface of a first annular segment  1214  of primary coil  1202 . The uncovered area of first annular segment  1214  provides space for the wire of primary coil  1202  to fold over itself so that termination ends  1216  and  1218  can be positioned within an inner diameter of primary coil  1202 , as well as space for interconnection structures, such as a flex circuit, to be positioned without significantly affecting the overall z-height. First and second radial locations  1210  and  1212  can form an angle of less than 90 degrees such that ferromagnetic shield  1204  covers an annular section of at least 270 degrees of primary coil  1202 . Termination ends  1216  and  1218  are opposite ends of the stranded wire that forms primary coil  1202  where the monolithic structure of the wire physically ends. 
     In some embodiments, secondary coil  1206  winds around a portion of primary coil  1202  and ferromagnetic shield  1204 . For instance, secondary coil  1206  can wrap around a second annular segment  1220  containing overlapping segments of both primary coil  1202  and ferromagnetic shield  1204  such that secondary coil  1206  extends between a third radial location  1222  and a fourth radial location  1224 . Winding around ferromagnetic shield  1204  improves the capture of magnetic fields propagating in the horizontal direction because ferromagnetic shield  1204  helps redirect a greater amount of magnetic fields through the inner diameter of secondary coil  1206  than if ferromagnetic shield  1204  was not present. In certain embodiments, first annular segment  1214  and second annular segment  1220  are positioned in a non-overlapping arrangement. That is, secondary coil  1206  does not wind around a portion of first annular segment  1214  where ferromagnetic shield  1204  is not positioned. In some embodiments, first annular segment  1214  and second annular segment  1220  are positioned on opposite halves of receiver system  1200  when drawing a line (not shown) across center axis  1208  of primary coil  1202 . As shown in  FIGS. 12B and 12C , first and second annular segments  1214  and  1220  are positioned in the top and bottom halves of receiver system  1200 , respectively. In some embodiments, termination ends  1219  and  1221  of secondary coil  1206  are positioned within the inner diameter of primary coil  1202 . Like termination ends  1216  and  1218 , termination ends  1219  and  1221  are opposite ends of the stranded wire that forms secondary coil  1206  where the monolithic structure of the wire physically ends. In certain embodiments, termination ends  1216  and  1218  of primary coil  1202  are positioned adjacent to one another at a location along first annular segment  1214 , while termination ends  1219  and  1221  of secondary coil  1206  are positioned on opposite ends of second annular segment  1220 . 
     According to some embodiments of the present disclosure, primary coil  1202  is configured to receive wireless power from magnetic fields propagating in the vertical direction, i.e., into and out of the page, while secondary receiver coil is configured to receive wireless power from magnetic fields propagating in the horizontal direction, i.e., within the plane of the page. Furthermore, primary coil  1202  can be tuned to receive power from time-varying magnetic fields at a first frequency, while secondary coil  1206  can be tuned to receive power from time-varying magnetic fields at a second frequency different from the first frequency. For instance, primary coil  1202  is configured to receive power from magnetic fields at a primary frequency of between 6 to 7 MHz, particularly approximately 6.78 MHz in some embodiments, and secondary coil  1206  is configured to receive power from magnetic fields at a secondary frequency of between 300 to 400 kHz, particularly approximately 326 kHz in some embodiments. 
     Ferromagnetic shield  1204  can be positioned and configured to improve the efficiency at which primary coil  1202  and secondary coil  1206  receive wireless power. As an example, ferromagnetic shield  1204  can have an outer edge  1226  and an inner edge  1228  when viewed from top-down perspective  1201  and bottom-up perspective  1203  as shown in  FIGS. 12B and 12C . Outer edge  1226  can be substantially circular, while inner edge  1228  can include curved and flat edges. For instance, inner edge  1228  can include flat edges  1230  and  1232  that are positioned on opposite halves of receiver system  1200 , a curved edge  1229  that extends between flat edges  1230  and  1232 , and a curved edge  1231  that extends part of the way between flat edges  1230  and  1232 . As shown in  FIGS. 12B and 12C , flat edges  1230  and  1232  are positioned at the left and right halves of receiver system  1200 . Flat edges  1230  and  1232  can be edge surfaces of respective extended regions  1234  and  1236  of ferromagnetic shield  1204  as shown in  FIG. 12C . Extended regions  1234  and  1236  improve the performance of receiver system  1200  by providing shield  1204  more area with which to interact and redirect time-varying magnetic fields generated by a transmitter coil through primary coil  1202  and/or secondary coil  1206 . Thus, according to some embodiments, ferromagnetic shield  1204  improves the efficiency of wireless charging for both primary coil  1202  and secondary coil  1206 . 
     As shown in  FIG. 12C , extended regions  1234  and  1236  are D-shaped extensions of ferromagnetic shield  1204 . Thus, the thickness of a sidewall of ferromagnetic shield  1204  gradually increases from one end to the midpoint of the extended region, and then gradually decreases from the midpoint to the opposite end of the midpoint, as better shown in  FIGS. 12D and 12E .  FIGS. 12D and 12E  are simplified cross-sectional illustrations of ferromagnetic shield  1204  across different planes through extended region  1236 , according to some embodiments of the present disclosure. Specifically,  FIG. 12D  is a simplified cross-sectional illustration of ferromagnetic shield  1204  and primary coil  1202  across the midpoint of extended region  1236 , and  FIG. 12E  is a simplified cross-sectional illustration of ferromagnetic shield  1204  and primary coil  1202  across one end of extended region  1236 . 
     As shown in  FIG. 12D , ferromagnetic shield  1204  can be a monolithic structure that includes a back wall  1240  and two sidewalls: an inner sidewall  1242  (i.e., extended region  1236 ) and an outer sidewall  1244 . Both sidewalls  1242  and  1244  can extend away from back wall  1240  toward a transmitter coil (not shown). As further shown in  FIG. 12D , primary coil  1202  can include a top surface  1203 , a bottom surface  1205 , inner side surface  1207 , and outer side surface  1209 , where both side surfaces  1207  and  1209  are vertically positioned between top surface  1203  and the bottom surface  1205 . In some embodiments, ferromagnetic shield  1204  covers three side surfaces of primary coil  1202 . That is, back wall  1240  can cover top surface  1203 , inner sidewall  1242  can cover inner side surface  1207 , and outer sidewall  1244  can cover outer side surface  1207 . Accordingly, bottom surface  1205  of primary coil  1202  may not be covered by ferromagnetic shield  1204  and may be oriented away from back wall  1240  toward the transmitter coil to improve the propagation of magnetic fields between primary coil  1202  and the transmitter coil. Inner sidewall  1242  can form inner edge  1228  (including flat edges  1232 ) of ferromagnetic shield  1204 , and outer sidewall  1244  can form outer edge  1226 . As discussed herein with respect to  FIGS. 12B and 12C , inner edge  1228  can include flat edge  1232  that is formed as part of extended region  1236 . Thus, as shown in  FIG. 12D , inner sidewall  1242  can have a thickness T2 that is greater than a thickness T1 of outer sidewall  1244 , and the left surface of inner sidewall  1242  can be a part of flat edge  1232 . With reference to  FIG. 12E , as you move toward the end of extended region  1236  (i.e., the beginning of curved edge  1229 ), thickness T2 of inner sidewall  1242  gradually decreases to thickness T3. In some embodiments, thickness T3 of inner sidewall  1242  at the end of extended region  1236 —and throughout the regions outside of extended regions  1236  and  1234  that can include curved edge  1229 —can be substantially equal to thickness T1 of outer sidewall  1224 . It is to be appreciated that the cross-sections shown in  FIGS. 12D and 12E  can be present in other points round receiver system  1200 , as one skilled in the art can deduce with reference to  FIGS. 12B-12E   
       FIG. 13  is an exploded view illustration  1300  of wireless charging receiver system  1200 , according to some embodiments of the present disclosure. Wireless charging receiver system  1200  can include primary coil  1202  attached to ferromagnetic shield  1204 . Primary coil  1202  can be a substantially circular coil formed of stranded wire, such as stranded copper wire. An adhesive layer  1302  can be positioned between primary coil  1202  and ferromagnetic shield  1204  to attach primary coil  1202  to ferromagnetic shield  1204 . In some embodiments, adhesive layer  1302  is directly positioned between a top surface of primary coil  1202  and a portion, i.e., back wall  1240 , of ferromagnetic shield  1204 . Adhesive layer  1302  can be substantially circular like the circular profile of primary coil  1202  and only extend along a portion of the top surface of primary coil  1202  where ferromagnetic shield  1204  is positioned. That is, adhesive layer  1302  may be positioned against less than an entire circumference of the top surface of primary coil  1202 . Adhesive layer  1302  can be formed of any suitable adhesive material such as hot melt glue. 
     Secondary coil  1206  can be wound around a portion of ferromagnetic shield  1204  and primary coil  1202 . In some embodiments, secondary coil  1206  is formed of a stranded coil of wire, such as stranded copper wire. Portions of back wall  1240  of ferromagnetic shield  1204  that are not covered by secondary coil  1206  can be attached to a pair of ferrite sheets  1304 . Ferrite sheets  1304  can be ferromagnetic structures that are formed of a ferromagnetic material different from the ferromagnetic material forming ferromagnetic shield  1204 . For instance, ferrite sheets  1304  can be formed of EMFS-C, while ferromagnetic shield  1204  is formed of Mn—Zn. Utilizing ferrite sheets  1304  can increase the magnetic permeability of ferromagnetic structure and thus improve the ability of ferromagnetic shield  1204  to redirect magnetic field through secondary coil  1206 . In some embodiments, receiver system  1200  can also include a shim  1306  attached to a bottom surface of primary coil  1202 . Shim  1306  can only extend along a portion of a bottom surface of primary coil  1202  where secondary coil  1206  is not positioned. Shim  1306  can provide structural support for primary coil  1202  and thus be formed of any suitable stiff and non-conductive material. 
     The specific configuration of the structure and position of each layer of receiver system  1200  can be designed to achieve maximum functionality with minimal footprint. In some instances, however, other components within the portable electronic device (e.g., an antenna) can constrain the space available for the receiver system. Thus, the construction of one or more components of wireless charging receiver system  1200  can be modified to have a minimal footprint to enable proper operation of other internal components, as will be discussed further herein with respect to  FIGS. 14A-14C . 
       FIG. 14A  is a perspective view illustration of an exemplary wireless charging receiver system  1400  whose primary and secondary receiving elements are formed as a single structure but altered to minimize its size, according to some embodiments of the present disclosure. The primary receiving element can include a primary coil  1402  and a ferromagnetic shield  1404 , and the secondary receiving element can be formed of a secondary coil  1406  that is wound about a portion of both primary coil  1402  and ferromagnetic shield  1404 . That is, primary coil  1402  can be wound around a primary axis, and secondary coil  1406  can be wound around a secondary axis positioned along a circumference around and centered to the primary axis. In some embodiments, the secondary axis can be a curved axis that runs along a length of a turn of wire of primary coil  1402 . When compared to receiver system  1200  in  FIGS. 12A-12E , receiver system  1400  can have corresponding components, but some of which may have different construction and dimensions. Details regarding the construction of, and the relationship between, the primary and secondary receiving elements for receiver system  1400 , as well as the differences between receiver system  1400  when compared to receiver system  1200 , can be better understood with reference to  FIGS. 14B-14E . 
       FIG. 14B  is a top-down illustration  1401  of exemplary wireless charging receiver system  1400 , and  FIG. 14C  is a bottom-up illustration  1413  of wireless charging receiver system  1400 , according to some embodiments of the present disclosure. Like primary coil  1202 , primary coil  1402  can be a stranded coil of wire wound about a center axis  1408  and formed of a conductive material, such as copper. However, unlike primary coil  1202  which has a circular profile, primary coil  1402  can have an oblong profile. For instance, as shown in  FIG. 14C , primary coil  1402  can be a coil of wire whose windings form a profile that includes two straight segments  1403  and  1405  and two curved segments  1407  and  1409  positioned between straight segments  1403  and  1405 . Configuring primary coil  1402  to have an oblong profile provides more space beside coil  1402  for another component, such as an antenna, to be positioned as will be discussed further herein. 
     Ferromagnetic shield  1404  can be configured to overlap a portion of the entire oblong profile of primary coil  1402 . Ferromagnetic shield  1404  can be configured to extend between a first radial location  1410  and a second radial location  1412  of primary coil  1402 , where the first and second radial locations  1410  and  1412  are non-overlapping. That is, ferromagnetic shield  1404  can be configured to cover only a portion of the entire circumference of a top surface and an inner side surface of primary coil  1402 . Accordingly, a first annular segment  1414  of primary coil  1402  may not be covered by ferromagnetic shield  1404 . The uncovered area of first annular segment  1414  provides space for the wire of primary coil  1402  to fold over itself so that termination ends  1416  and  1418  can be positioned within an inner diameter of primary coil  1402 , as well as space for interconnection structures, such as a flex circuit, to be positioned without significantly affecting the overall z-height. First and second radial locations  1410  and  1412  can form an angle of less than 90 degrees such that ferromagnetic shield  1404  covers an annular region of at least 270 degrees of primary coil  1402 . In some embodiments, ferromagnetic shield  1404  can include a flat outer bottom edge  1411  positioned at a bottom of primary coil  1402  between straight segments  1403  and  1405 . Flat outer bottom edge  1411  may not have a curved edge that follows the profile of primary coil  1402 , but may instead straighten out and align with the bottom edge of primary coil  1402  such that the outer surface of ferromagnetic shield  1404  at the center of flat outer bottom edge  1411  is substantially coplanar with the bottommost edge of primary coil  1402 , thereby reducing the amount of overhang of ferromagnetic shield  1404  with respect to primary coil  1402 . 
     Secondary coil  1406  can be similar in construction and function as secondary coil  1206 . That is, secondary coil  1406  can wind around a second annular segment  1420  containing overlapping segments of both primary coil  1402  and ferromagnetic shield  1404  such that secondary coil  1406  extends between a third radial location  1422  and a fourth radial location  1424 . Additionally, in some embodiments, first annular segment  1414  and second annular segment  1420  can be positioned on opposite halves (e.g., top and bottom halves) of receiver system  1400 , and secondary coil  1406  can have termination ends  1419  and  1421  that are positioned within the inner diameter of primary coil  1402 . By winding around ferromagnetic shield  1404 , secondary coil  1406  can have improved power transfer efficiency as shield  1404  can help redirect and increase an amount of flux through the inner diameter of secondary coil  1406 . 
     However, unlike secondary coil  1206  for receiver system  1200  in  FIG. 12 , secondary coil  1406  for receiver system  1400  can also include a flat region that overlaps and follows flat outer bottom edge  1411  of ferromagnetic shield  1404 . By reducing the amount of overhang between ferromagnetic shield  1404  and primary coil  1402  and winding secondary coil  1406  around flat outer bottom edge  1411 , more vacant space can be provided between the bottom of secondary coil  1406  and another component, such as an antenna, to provide more electrical isolation between secondary coil  1406  and the antenna to minimize electrical interference with the operation of the antenna as will be discussed further herein. 
     Ferromagnetic shield  1404  can be positioned and configured to improve the efficiency at which primary coil  1402  and secondary coil  1406  receive wireless power, and can also be constructed to maximize space for other components of the portable electronic device. As an example, ferromagnetic shield  1404  can have an outer edge  1426  and an inner edge  1428  when viewed from top-down perspective  1401  and bottom-up perspective  1403  as shown in  FIGS. 14B and 14C . Unlike outer and inner edges  1226  and  1228  of ferromagnetic shield  1204 , both outer edge  1426  and inner edge  1428  of ferromagnetic shield  1404  can have substantially oblong profiles. For instance, outer edge  1426  can include flat outer side edges  1450  and  1452  that are positioned on opposite halves of receiver system  1400 , flat outer bottom edge  1411  positioned on a bottom region of receiver system  1400 , curved edges  1456  and  1458  that extend between flat outer bottom edge  1411  and both flat outer side edges  1450  and  1452 , and a curved edge  1460  that extends part of the way between flat outer side edges  1450  and  1452 . And, inner edge  1428  can include flat edges  1430  and  1432  that are positioned on opposite halves of receiver system  1400 , a curved edge  1429  that extends between flat edges  1430  and  1432 , and a curved edge  1431  that extends part of the way between flat edges  1430  and  1432 . By flattening outer surfaces of ferromagnetic shield  1404 , more space can be provided for other electrical components and greater electrical isolation can be provided between the other electrical components and secondary coil  1406 . 
     In some embodiments, flat outer side edges  1450  and  1452  can have an edge that is coplanar with respective edges of straight segments  1403  and  1405 . For instance, flat outer side edge  1450  can be coplanar with the outermost left edge of straight segment  1403  of primary coil  1402 , and flat edge  1452  can be coplanar with the outermost right edge of straight segment  1405  of primary coil  1402 . By arranging flat outer side edges  1450  and  1452  to be coplanar with respective edges of straight segments  1403  and  1405 , overhang of ferromagnetic shield  1404  with respect to primary coil  1402  can be minimized, thereby providing more space for other components, e.g., an antenna, to be positioned. Additionally, flat outer bottom edge  1411  can be coplanar with a bottommost edge of primary coil  1402 . By arranging flat outer bottom edge  1411  to be coplanar with bottommost edge of primary coil  1402 , overhang of ferromagnetic shield  1404  with respect to primary coil  1402  can be minimized, thereby providing more electrical isolation between secondary coil  1406  and other components e.g., an antenna, within the portable electronic device. A better view of such relationships between ferromagnetic shield  1404  and primary coil  1402  can be seen in  FIGS. 14D and 14E . 
       FIGS. 14D and 14E  are simplified cross-sectional illustrations of ferromagnetic shield  1404  across different planes through straight segment  1405 , according to some embodiments of the present disclosure. Specifically,  FIG. 14D  is a simplified cross-sectional illustration of ferromagnetic shield  1404  and primary coil  1402  across the midpoint of straight segment  1405 , and  FIG. 14E  is a simplified cross-sectional illustration of ferromagnetic shield  1404  and primary coil  1402  across one end of straight segment  1405 . 
     As shown in  FIG. 14D , ferromagnetic shield  1404  can be a monolithic structure that includes a back wall  1440  and an inner sidewall  1442  for covering two side surfaces of primary coil  1402 . Specifically, back wall  1440  can cover a back surface  1441  of primary coil  1402  and inner sidewall  1442  can cover an inner surface  1443  of primary coil  1402 . Two sides of primary coil  1402  may not be covered by ferromagnetic shield  1404 , but inner sidewall  1442  may extend away from back wall  1440  toward a transmitter coil (not shown) to improve the propagation of magnetic fields between primary coil  1402  and the transmitter coil. As discussed herein with respect to  FIGS. 14B and 14C , outer edge  1426  can include flat edge  1452  that is coplanar with the rightmost edge of straight segment  1405  of primary coil  1402 . Thus, as shown in  FIG. 14D , flat edge  1452  can be coplanar with the rightmost edge  1462  of straight segment  1405  of primary coil  1402 . With reference to  FIG. 14E , as you move toward the end of straight segment  1405  (i.e., the beginning of curved edge  1458 ), curved edge  1458  gradually extends away from edge  1464  of primary coil  1402 , thereby creating an overhang  1466 . It is to be appreciated that the cross-sections shown in  FIGS. 14D and 14E  can be present in other points round receiver system  1400 , as one skilled in the art can deduce with reference to  FIGS. 14B-14E . Flat edges  1450 ,  1452 , and  1411  can all be a part of back wall  1440 . 
       FIG. 15  is an exploded view illustration  1500  of wireless charging receiver system  1400 , according to some embodiments of the present disclosure. Wireless charging receiver system  1400  can include primary coil  1402  attached to ferromagnetic shield  1404 . Primary coil  1402  can be a substantially oblong coil formed of stranded wire, such as stranded copper wire, and include straight segments  1403  and  1405  and curved segments  1407  and  1409  positioned between straight segments  1403  and  1405 . An adhesive layer  1502  can be positioned between primary coil  1402  and ferromagnetic shield  1404  to attach primary coil  1402  to ferromagnetic shield  1404 . In some embodiments, adhesive layer  1502  is directly positioned between a top surface of primary coil  1402  and a portion, i.e., back wall  1440 , of ferromagnetic shield  1404 . Adhesive layer  1502  can be substantially oblong in shape like primary coil  1402  and only extend along a portion of the top surface of primary coil  1402  where ferromagnetic shield  1404  is positioned. That is, adhesive layer  1502  may be positioned against less than an entire circumference of the top surface of primary coil  1402 . Adhesive layer  1502  can be formed of any suitable adhesive material such as hot melt glue. 
     Secondary coil  1406  can be wound around a portion of ferromagnetic shield  1404  and primary coil  1402 . In some embodiments, secondary coil  1406  is formed of a stranded coil of wire, such as stranded copper wire. Portions of back wall  1440  of ferromagnetic shield  1404  that are not covered by secondary coil  1406  can be attached to a pair of ferrite sheets  1504 , which can be ferromagnetic structures that are formed of a ferromagnetic material different from the ferromagnetic material forming ferromagnetic shield  1404 . For instance, ferrite sheets  1504  can be formed of EMFS-C, while ferromagnetic shield  1404  is formed of Mn—Zn. Utilizing ferrite sheets  1504  can increase the magnetic permeability of ferromagnetic structure and thus improve the ability of ferromagnetic shield  1404  to redirect magnetic field through secondary coil  1406 . In some embodiments, receiver system  1400  can also include a shim  1506  attached to a bottom surface of primary coil  1402 . Shim  1506  can only extend along a portion of a bottom surface of primary coil  1402  where secondary coil  1406  is not positioned. Shim  1506  can provide structural support for primary coil  1402  and thus be formed of any suitable stiff and non-conductive material. 
     1. Construction of a Portable Electronic Device Having Secondary Receiving Element Formed of a Coil Wound about a Portion of the Primary Coil 
     As mentioned herein, the size and shape of primary and secondary receiver elements can affect the amount of available space for other electrical components in the portable electronic device, while also enabling the portable device to achieve a compact size and high functionality. As can be appreciated by disclosures herein, the size and shape of the receiver elements can be determined by balancing the trade-off between performance of the receiver elements and the performance of other electrical components in the portable electronic device. 
     a) Top Housing Portion 
       FIG. 16  illustrates an exploded view of an exemplary portable electronic device  1600 , according to some embodiments of the present disclosure. Portable electronic device  1600  can include a top housing portion  1602  and a bottom housing portion  1604  that can mate to define an interior cavity. A sealing component  1603  can be positioned at the interface between top housing portion  1602  and bottom housing portion  1604  to seal the interior cavity from the external environment. Sealing component  1603  can be any suitable component that can hermetically seal an interface between two structures such as an O-ring formed of silicone. Top housing portion  1602  can include a device chassis  1606  and a transparent panel  1608 . Transparent panel  1608  is a protective, optically transparent structure for a display so that a user can view the display through transparent panel  1608  while transparent panel  1608  protects the display from damage. Top housing portion  1602  can include one or more user interface components, such as a dial  1610 , microphone  1612 , power button  1614 , and any other suitable user interface components. The compact size and unique arrangement of the internal components of portable electronic device  1600  can enable microphone  1612  to be positioned on the same side of device chassis  1606  as dial  1610 . 
     In some embodiments, dial  1610  can be a touch sensitive dial that can act as a contact for performing EKG sensing. Dial  1610  can include various components that, when coupled together, form a conductive pathway from an outer surface of dial  1610  to inner touch components, which is discussed further herein with respect to  FIGS. 35 and 36 . Portable electronic device  1600  can further include a system in package (SIP)  1616  that is housed within the interior cavity. SIP  1616  can be a number of integrated circuits (ICs) enclosed in a single module that can operate to perform several functions of portable electronic device  1600 . Each IC in SIP  1616  can perform one or more different functions, such as performing heart rate monitoring, operating a touch screen display, outputting sound through one or more speakers, processing sound received by microphone  1612 , managing wireless power transfer, and the like. 
     Portable electronic device  1600  can also include an alignment module  1632  and a sensor module  1636 . Sensor module  1636  can be an electrical component that houses and operates one or more sensors for performing one or more functions. For instance, sensor module  1636  can be a circuit board (e.g., a printed circuit board (PCB)) that has one or more sensors for sensing heart rate and the like. Sensor module  1636  can be attached to a surface of bottom housing portion  1604  via adhesive layer  1647 , which can be formed of PSA. 
     b) Alignment Module 
     Alignment module  1632  can be disposed between SIP  1616  and sensor module  1636  as shown in  FIG. 16 . Alignment module  1632  can include a permanent magnet  1642  and a DC shield  1638  positioned above magnet  1642  that are coupled together via a magnet adhesive  1640 . Magnet  1642  can be designed to attract another alignment magnet in a wireless charging device for aligning with the wireless charging device, such as wireless charging device  300  in  FIG. 3A . DC shield  1638  can be positioned above alignment module  1632  to prevent magnetic fields generated by alignment module  1632  from being exposed to other electrical components within portable electronic device  1600 , such as SIP  1616 . Alignment module  1632  can also include a module adhesive layer  1644  for coupling alignment module  1632  to sensor module  1636 . In some embodiments, module adhesive layer  1644  can be formed of multiple parts, as better illustrated in  FIG. 17 . 
       FIG. 17  is a bottom-up view illustration of alignment module  1632 , according to some embodiments of the present disclosure. As shown in  FIG. 17 , module adhesive layer  1644  can be formed of a first adhesive  1702  laterally positioned between second adhesive  1704   a  and third adhesive  1704   b . First, second, and third adhesives  1702 ,  1704   a , and  1704   b  can all be adhered to and extend across an entire length of a bottom surface of permanent magnet  1642 . First adhesive  1702  can be formed of a material different from the material used to form second and third adhesives  1704   a - b . For instance, first adhesive  1702  can be formed of hot melt glue, while second and third adhesives  1704   a - b  are formed of PSA. 
     As further shown in  FIG. 17 , a top edge  1706  of permanent magnet  1642  can be coplanar with a top edge  1708  of DC shield  1638 , while other edges of DC shield  1638  overhang from corresponding edges of magnet  1642 . Having both top edges  1706  and  1708  be coplanar can enable more space to be provided for other components on sensor module  1636 , such as a connector for coupling with a flex circuit as shown in  FIG. 18 , thereby enabling more components to be assembled within the portable electronic device and assist with decreasing its overall size. 
     c) Wireless Charging Receiver System 
     With reference back to  FIG. 16 , portable electronic device  1600  can include a wireless charging receiver system  1618  formed of a single structure having a primary receiving element and a secondary receiving element, according to some embodiments of the present disclosure. The primary receiving element can include a primary coil and a ferromagnetic structure, and the secondary receiving element can include a secondary coil wound around a portion of the primary receiving element. The specific configuration of receiver system  1618  is better discussed herein with respect to  FIGS. 14A-14E and 15 . Portable electronic device  1600  can also include an electromagnetic shield  1624  disposed between receiver system  1618  and bottom housing portion  1604 . Electromagnetic shield  1624  can intercept electric fields generated during wireless power transfer and discharge the accumulated voltage from the electric fields to ground. Electromagnetic shield  1624  and receiver system  1618  can be attached to bottom housing portion  1604  by an adhesive layer  1649 , which can be formed of any suitable adhesive such as PSA. In some embodiments, wireless charging receiver system  1618  can receive wireless power from time-varying magnetic fields generated from one or more transmitter coils in a wireless charging device, e.g., device  300  or  310  in  FIGS. 3A and 3B . Specifically, time-varying magnetic flux generated by transmitter coil  302  in  FIG. 3A  can propagate through bottom housing portion  1604  at a first frequency and interact with the primary coil, e.g., primary coil  1202  in  FIG. 12  or primary coil  1402  in  FIG. 14 , of wireless charging receiver system  1618  which can be specifically tuned to operate at the first frequency and receive fields propagating in the vertical direction. Furthermore, time-varying magnetic flux generated by transmitter coil  312 - 1  in  FIG. 3B  can propagate through bottom housing portion  1604  at a second frequency and interact with the secondary coil, e.g., secondary coil  1206  in  FIG. 12  or secondary coil  1406  in  FIG. 14 , of wireless charging receiver system  1618  which can be specifically tuned to operate at the second frequency and receive fields propagating in the horizontal direction. 
     d) Antenna 
     Portable electronic device  1600  can be configured to perform wireless communication through radio waves, e.g., LTE, GSM, CDMA, and the like, while other variations of portable electronic device  1600  can be configured to not have this functionality. To enable wireless communication functionality, portable electronic device  1600  can include an antenna  1629  within the interior cavity and below SIP  1616 , as shown in  FIG. 16 . Antenna  1629  can include an opening  1630  within which one or more other electronic components of portable electronic device  1600  can be positioned. For instance, wireless charging receiver system  1618  and alignment module  1634  can be disposed within opening  1630 . Antenna  1629  can be a structure configured to receive and/or send data through radio waves, as discussed further herein with respect to  FIG. 18 . 
       FIG. 18  is an exploded view diagram of an antenna system  1800  including antenna  1629 , according to some embodiments of the present disclosure. In addition to antenna  1629 , antenna system  1800  can include an antenna interconnection structure  1801  for coupling antenna  1629  to a controller, such as a processor in communication system  108  in  FIG. 1 , and an adhesive layer  1803  for attaching antenna  1629  to bottom housing portion  1604 . Interconnection structure  1801  can be formed of any suitable flexible interconnection structure such as a flexible printed PCB, and adhesive layer  1803  can be formed of any suitable adhesive material such as PSA. 
     As further shown in  FIG. 18 , antenna  1629  can be formed of an antenna element  1802  and a conductive antenna body  1804  attached to a bottom surface of antenna element  1802 . Antenna element  1802  can be a non-conductive structure that provides structural support for conductive antenna body  1804 , which can be formed of a thin conductive material that can transmit and receive radio waves. Antenna element  1802  can be formed of any suitable non-conductive material such as glass-filled LCP resin, and conductive antenna body  1804  can be formed of any suitable conductive material such as copper. In some embodiments, conductive antenna body  1804  can be grounded via one or more grounding brackets  1805   a - c . Details of the construction and function of grounding brackets  1804   a - c  is discussed further herein with respect to  FIGS. 19A-19D . Antenna element  1802  can also include a slit (not shown) at a bottom region of antenna element  1802  and one or more capacitors  1813  that bridge the gap created by the slit, as will be discussed further herein. 
     As shown in  FIG. 18 , antenna element  1802  can include a top level  1806 , a bottom level  1808 , and a step region  1810  between top and bottom levels  1806  and  1808 . Top and bottom levels  1806  and  1808  can be substantially planar structures that are positioned in different parallel but non-intersecting planes, and step region  1810  can be a vertical bridging portion between top and bottom levels  1806  and  1808 . Top level  1806 , bottom level  1808 , and step region  1810  can together form a monolithic structure that forms antenna element  1802 . In some embodiments, top level  1806  can include a plurality of recessed areas  1807  within which one or more foam pads can be positioned. For instance, foam pad  1809  can be positioned within a recessed area  1811  near the top edge of antenna element  1802 . Foam pad  1809  can press up against a flexible PCB (not shown) that couples with electrical components (not shown) within opening  1630 . 
     In some embodiments, step region  1810  creates open space within which at least some parts of other electrical components of the portable electronic device, such as wireless charging receiver system  1618 , alignment module  1634 , and sensor module  1636  in  FIG. 16 , can be positioned to minimize z-height. When positioned within the open space, wireless charging receiver system  1618  and alignment module  1634  can be substantially coplanar with antenna  1629 . In certain embodiments, an inner edge  1812  of antenna element  1802  can be a part of bottom level  1808  that conforms to the outer profile of receiver system  1618 . Accordingly, inner edge  1812  can have an oblong profile that conforms to an outer edge of wireless charging receiver system  1618 . In some embodiments, an outer edge  1814  of antenna element  1802  can be a part of top level  1806  that conforms to the inner profile of bottom housing portion  1604 . Accordingly, outer edge  1814  can have a substantially rectangular profile with beveled corners, as shown in  FIG. 18 . While inner edge  1812  has an oblong profile and outer edge  1814  has a rectangular profile with beveled edges, step region  1810  can have a different profile than both inner edge  1812  and outer edge  1814  such as a substantially circular profile for providing separation between antenna  1629  and any electrical components positioned within opening  1630 . 
     As shown in  FIG. 18 , conductive antenna body  1804  can conform to a bottom surface of antenna element  1802  and thus also include a top level  1816 , bottom level  1818 , step region  1820 , inner edge  1822 , and outer edge  1824  that are substantially similar in structure to corresponding parts of antenna element  1802 . That is, top level  1816  can be positioned below top level  1806 , bottom level  1818  can be positioned below bottom level  1808 , step region  1820  can be positioned beside step region  1810 , inner edge  1822  can have an oblong profile that conforms to an outer edge of wireless charging receiver system  1618 , and outer edge  1824  can have a substantially rectangular profile with beveled corners. 
     In some embodiments, conductive antenna body  1804  can include a slit  1825  that cuts through a section of conductive antenna body  1804  to separate the section into two parts: a first part  1827  and a second part  1829 . Even though the section is divided into first and second parts  1827  and  1829 , conductive antenna body  1804  can still be a single monolithic structure that has a discontinuous oblong structure, instead of a continuous oblong structure in instances where slit  1825  is not present. In some embodiments, capacitors  1813  disposed on top level  1806  of antenna element  1802  can extend through top level  1806  and bridge across slit  1825  to electrically couple the two parts of conductive antenna body  1704  together. The capacitance of capacitors  1813  can be configured to enable conductive antenna body  1804  to appear electrically as a single continuous body at the antenna&#39;s operating frequency but appear electrically disconnected at the receiver system&#39;s operating frequency, which can be different from the antenna&#39;s operating frequency. In such embodiments, the capacitors can be configured to electrically couple first and second parts  1827  and  1829  together when conductive antenna body  1704  is exposed to electrical signals at a first frequency and electrically disconnect first and second parts  1827  and  1829  from one another when conductive antenna body  1704  is exposed to time-varying magnetic fields at a second frequency different from the first frequency to minimize the generation of eddy currents in conductive antenna body  1704 . Without slit  1825 , large eddy currents can be generated in conductive antenna body  1804  and create heat that can negatively impact the power transfer efficiency of receiver system  1618 . That way, both antenna  1629  and receiver system  1618  can coexist without significantly affecting each other&#39;s performance. 
     It is to be appreciated that larger coils and ferromagnetic structures of a receiver system can improve the efficiency at which the portable electronic device receives charge, as mentioned herein with respect to  FIG. 12A-12E . However, increasing the size of these structures reduces the amount of space for the antenna, thereby negatively affecting the antenna&#39;s performance. Thus, a conflict of interest with respect to component size can exist between antenna  1629  and receiver system  1618  due to their close proximity with one another. Accordingly, the structure of the receiver system and the antenna can be optimized to achieve acceptable levels of both antenna operation and charging efficiency. Details of this relationship is discussed further herein with respect to  FIG. 19 . 
       FIG. 19  is a top-down illustration of a partially assembled portion of portable electronic device  1600 , according to some embodiments of the present disclosure. Specifically,  FIG. 19  shows a portion of device  1600  that includes receiver system  1618 , antenna  1629 , and bottom housing portion  1604 . Receiver system  1618  is shown positioned within the opening (which is not shown because it is occupied by receiver system  1618 ) of antenna  1629 , both of which are assembled into bottom housing portion  1604 . The surface area of antenna  1629  (and thus conductive antenna body  1804 ) can be tailored to achieve a certain degree of antenna performance. For instance, larger surface areas can improve the signal receiving and transmitting performance of antenna  1629 . As such, receiver system  1618  can include flat outer side edges, e.g., flat outer side edges  1450  and  1452  discussed herein with respect to  FIG. 14 , so that antenna  1629  can have more surface area. The structure of conductive antenna body  1804  can be configured to maximize the use of space provided between receiver system  1618  and bottom housing portion  1604  by fitting in available space between them. 
     In some embodiments, the antenna element, e.g., antenna element  1802 , of antenna  1629  can include a plurality of recessed areas, e.g., recessed areas  1807 . These recessed areas can be regions where components can be positioned. For instance, a plurality of foam structures  1906  can be positioned within the recessed areas to protect antenna  1629  from physical damage. Furthermore, one or more electrical components  1908  can be positioned with a recessed area. Electrical components  1908  can be configured to operate antenna  1629 , and be coupled to a communication system via interconnection  1910 , which can be a flex circuit. Utilizing the space provided by the recessed areas maximizes the use of the limited space within the portable electronic device without having to increase the size of the portable electronic device. 
     As briefly discussed herein, antenna  1629  can have a slit  1902  that extends from the inner diameter to the outer diameter of antenna  1629  and through conductive antenna body  1804  such that the bottom section of conductive antenna body  1804  is divided in half lengthwise. Secondary coil of receiver system  1618  can overlap at least a portion of slit  1902 . Separating the continuity of antenna  1629  can minimize eddy current generation when receiver system  1618  (more particularly the secondary coil of receiver system  161 ) is operating, thereby minimizing excessive heat generation which can negatively affect the performance of receiver system  1618 . However, separating the continuity of antenna  1629  can hinder the performance of antenna  1629 . Thus, in some embodiments, one or more capacitors  1813  can be implemented in antenna  1629  to electrically bridge the two halves of the bottom section of antenna  1629 . The capacitance of capacitors  1813  can be tailored such that antenna  1629  appears electrically as a single continuous body at the operating frequency of antenna  1629 , but appear separated at the operating frequency of receiver system  1618 , which can be different from the operating frequency of antenna  1629 . That way, both antenna  1629  and receiver system  1618  can coexist without significantly affecting each other&#39;s performance. 
     Evident in  FIG. 19 , the bottom edge of wireless charging receiver system  1618  can be separated from the step region of antenna  1629  by a distance  1904 . Because both the secondary coil of receiver system  1618  and the conductive antenna body of antenna  1629  are formed of a conductive material, the two components can interfere with each other&#39;s performance the closer they are to one another. Thus, larger distances  1904  can improve the electrical isolation between the two components, and thus help ensure that both components work properly. In some embodiments, the flat bottom edge of receiver system  1618  (e.g., flat bottom surface of secondary coil  1406  created by winding around flat outer bottom edge  1411  of ferromagnetic shield  1404  as discussed herein with respect to  FIG. 14 ) can increase distance  1904 , thereby improving the electrical isolation between receiver system  1618  and antenna  1629 . 
     According to some embodiments of the present disclosure, antenna  1629  can be coupled to ground via any one or more grounding brackets  1805   a - c . With brief reference back to  FIG. 18 , each grounding bracket  1805   a - c  can be a monolithic structure formed of an anchor  1815 , an interface  1817 , and a connecting portion  1819  that couples anchor  1815  to interface  1817 . Anchor  1815  can include a hole through which one or more mechanical fasteners, e.g., a bolt, screw, and the like, can tunnel to clamp grounding bracket  1805   a  to bottom housing portion  1604 . When clamped, anchor  1815  can couple to both SIP  1616  and top housing portion  1602  in  FIG. 16  so that any device, such as antenna  1629 , contacting interface  1817  can be coupled to ground in embodiments where ground is formed by top and bottom housing portions  1602  and  1604 . A better understanding of how anchor  1815  couples to top and bottom housing portions  1602  and  1604  can be ascertained with reference to  FIGS. 20A-20D . 
       FIGS. 20A-20D  are various top-down and cross-sectional views of a grounding bracket, e.g., any of grounding brackets  1805   a - c , according to some embodiments of the present disclosure. Specifically,  FIG. 20A  is a close-up top-down view  2000  of an anchor  2004  of grounding bracket  1805   b  that is placed against bottom housing  1604 ,  FIG. 20B  is a top-down view  2001  of a bolt  2012  fastening top housing portion  1602  to bottom housing portion  1604  while clamping down against anchor  2004  of grounding bracket  1805   b  and SIP  1616 ,  FIG. 20C  is a cross-sectional view  2002  across anchor  2004  to show how anchor  2004  is coupled to top housing portion  1602 , and  FIG. 20D  is a cross-sectional view  2003  across anchor  2004  to show how anchor  2004  is coupled to bottom housing portion  1604  and SIP  1616 . It is to be appreciated that the disclosure with respect to grounding bracket  1805   b  in  FIGS. 20A-20D  can apply to all other grounding brackets,  1805   a  and  1508   c.    
     As shown in  FIG. 20A , anchor  2004  can be a conductive plate that includes a hole  2006  and a plurality of dimples including a housing dimple  2008  and two SIP dimples  2010   a - b . Hole  2006  can be a vacant space through which bolt  2012  can thread to fasten top housing portion  1602  and SIP  1616  to bottom housing portion  1604 , as shown in  FIG. 20B  while clamping down against anchor  2004  of grounding bracket  1805   b . Each dimple can be a deflection of a section of anchor  2004  that has an arch structure forming a crest for making contact with other structures (see grounding bracket  1805   b  in  FIG. 18  for a better perspective). For instance, as shown in  FIG. 20C , housing dimple  2008  can have a crest that makes contact with top housing portion  1602 ; and, as shown in  FIG. 20D , SIP dimples  2010   a - b  can have respective crests that make contact with SIP  1616  and bottom housing portion  1604 . Thus, anchor  2004  can be a single structure that simultaneously contacts a plurality of physically distinct structures, i.e., top housing portion  1602 , bottom housing portion  1604 , and SIP  1616 . Furthermore, by design of dimples  2008  and  2010   a - b , anchor  2004  of grounding bracket  1805   b  can contact the structures via discrete contact locations instead of a broad interface surface across the entire surface area of anchor  2004 . Dimples  2008  and  2010   a - b  of anchor  2004  are simple in design/manufacturability and can enable grounding bracket  1805  to provide a more robust and reliable connection with top housing portion  1602  and SIP  1616  by applying a constant contact pressure against top and bottom housing portions  1602  and  1604  and SIP  1616  due to the curved structure of dimples  2008  and  2010   a - b.    
     e) Spacer and Wireless Charging Receiver System 
     In some embodiments, a portable electronic device can have different architectural configurations. For instance, with reference back to  FIG. 16 , one or more components of portable electronic device  1600  can be altered to provide different functionality. In one instance, antenna  1629  can be replaced with a spacer  1646 , and receiver system  1618  can be replaced with a different receiver system  1648  so that portable electronic device  1600  is not capable of performing wireless telecommunication through radio waves but may have slightly improved inductive power transfer efficiency. Spacer  1646  can have a construction substantially similar to that of antenna  1629  except that spacer  1646  may not include a conductive body or grounding brackets, and an inner edge  1650  of spacer  1646  may not be oblong in shape. Instead, spacer  1646  may be completely formed of an insulating material, such as PSA, and inner edge  1650  can have a substantially circular profile that conforms to the outer profile of receiver system  1648 , which may be configured according to receiver system  1200  discussed herein with respect to  FIGS. 12A-12E . In some embodiments, both spacer  1646  and receiver system  1648  are implemented in portable electronic device  1600  and not only one without the other. 
       FIG. 21  is a perspective view of a partially assembled portable electronic device  2100  including spacer  1646  and receiver system  1648 , according to some embodiments of the present disclosure. Similar to antenna  1629  in  FIG. 16 , the structure of spacer  1646  can be configured to maximize the use of space provided between receiver system  1648  and bottom housing portion  1604  by fitting in available space between them. Accordingly, spacer  1646  can have an outer edge  2102  that conforms to an inner edge of bottom housing  1604 , and an inner edge  1650  that conforms to the outer circular profile of receiver system  1648 . As such, both inner edge  1650  and step region  2108  can have a circular profile instead of only configuring step region  2108  to have a circular profile as discussed herein with respect to  FIGS. 18 and 19 . In some embodiments, spacer  1646  can include a top level  2104 , a bottom level  2106 , and a step region  2108  coupled between top level  2104  and bottom level  2106 . As can be seen in  FIG. 21 , spacer  1646  can also include a plurality of recessed areas  2110 , of which some are filled with foam structures  2112 . Components of spacer  1646  that correspond with respective components of antenna  1629  can be substantially similar in construction and material, and thus details of such components can be referenced in the disclosure with respect to  FIGS. 18 and 19 . 
     According to some embodiments of the present disclosure, unlike antenna  1629  which includes a non-conductive element and a conductive body attached to the element, spacer  1646  may be completely formed of a non-conductive material and may not include a conductive body attached to it. Thus, spacer  1646  can be configured to occupy space between bottom housing  1604  and receiver system  1618  to confine receiver system  1618  in position within the portable electronic device and help keep receiver system  1618  in place. By using spacer  1646  when the portable electronic device is not configured to need an antenna to perform wireless communication through radio waves, the architecture of the portable electronic device will not need to be completely altered, thereby saving manufacturing time and cost as the configurations of the vast majority of the other electrical components, e.g., those components other than receiver system  1618 , can be used for both embodiments without modification to their structure/size. 
     f) Bottom Housing Portion 
     As briefly mentioned herein with respect to  FIG. 16 , a bottom housing portion can mate with a top housing portion to form an interior cavity within which electronic components can be positioned. The bottom housing portion can include a window through which one or more electrical signals can be transmitted to enable certain functionality of the portable electronic device. A better understanding of the construction of the bottom housing portion can be ascertained with reference to  FIG. 22 . 
       FIG. 22  is an exploded view  2200  of bottom housing portion  1604  for a portable electronic device, e.g., portable electronic device  1600  in  FIG. 16 , according to some embodiments of the present disclosure. Bottom housing portion  1604  can also include a plurality of fastening mechanisms  2212  positioned at corners of structure body  2202 . Fastening mechanisms  2212  can enable bolts to secure a top housing portion, e.g., top housing portion  1602  in  FIG. 16 , to bottom housing portion  1604 . Fastening mechanisms can be T-nuts having flanges that slide into corresponding undercut regions within bottom structure body  2202 . The undercut regions enable the T-nuts to secure top housing portion  1602  to bottom housing portion  1604  without adhesive materials while providing a mechanical interlocking mechanism that substantially prevents separation of the two housings. 
     In some embodiments, bottom housing portion  1604  can include a structure body  2202  and a window  2204  coupled to a bottom of bottom housing portion  1604  via an adhesive layer  2206 . Structure body  2202  can be formed of a stiff material with insulating electrical properties, such as a crystalline structure formed of black zirconia. Structure body  2202  can include a circular opening  2203  at its center where one or more electrical devices can be positioned. In some embodiments, window  2204  is a circular dome-shaped structure that is adhered to the bottom of bottom housing portion  1604  such that the circular edge of window  2204  is adhered along the circular edge of opening  2203 . Window  2204  can be formed of any suitable transparent and durable material, such as sapphire crystal. One or more components, such as a Fresnel lens  2208  and a wheel  2210  can be adhered to window  2204  for enabling functionality of one or more sensor components within the portable electronic device, such as sensor module  1636  in  FIG. 16 , the arrangement of which is better shown in  FIG. 23 . 
       FIG. 23  is a simplified diagram illustrating a perspective view of sensor module  1636  mounted on bottom housing portion  1604 , according to some embodiments of the present disclosure. Sensor module  1636  can be mounted in the center of bottom housing portion  1604  and against window  2204  such that its sensors are also positioned at the center of bottom housing portion  1604 . In some instances, a heart rate sensor (e.g., heart rate sensor  1102  in  FIG. 11 ) comprising a thin layer of platinum can be positioned at the center of bottom housing portion  1604 . Sensors of sensor module  1636  can perform sensing through window  2204 . In some embodiments, fastening mechanisms  2212  can be positioned at each corner of bottom housing portion  1604  to fasten bottom housing portion  1604  with top housing portion  1602 . 
       FIG. 24  illustrates a bottom perspective view of bottom housing portion  1604 , according to some embodiments of the present disclosure. Bottom housing portion  1604  can include window  2204  that provides an avenue through which one or more parameters of an external environment can be monitored by sensors coupled to sensor module  1636 . Furthermore, bottom housing portion  1604  can include one or more contacts for making contact with an external surface, such as a user&#39;s wrist or arm. For instance, bottom housing portion  1604  can include a first external contact  2402  and a second external contact  2404 . According to some embodiments of the present disclosure, first and second external contacts  2402  and  2404  can be utilized to perform EKG sensing of a user&#39;s heart. This sensing can be performed by forming a closed-loop circuit through an external structure, such as the user&#39;s body. For instance, a closed-loop circuit can be formed when a user touches a dial, such as dial  1610  in  FIG. 16 . The closed-loop circuit can begin at portable electronic device  1600 , then continue into the user&#39;s arm through at least one of first and second external contacts  2402  and  2404 . The circuit can flow through the user&#39;s body and out of the finger on the other arm into dial  1610  when the user touches dial  1610 . By forming this closed-loop circuit, one or more processing devices in portable electronic device  1600  can perform EKG measurement functions of a user&#39;s body. In some embodiments, first external contact  2402  is used for a ground reference to minimize noise, and second external contact  2404  is used as the contact for sending a signal through the user&#39;s body. 
     2. Assembled Bottom Housing Portion of a Portable Electronic Device Having a Secondary Receiving Element Formed of a Coil Wound about a Portion of the Primary Coil 
       FIGS. 25A-25B  are cross-sectional view illustrations of assembled portions of a portable electronic device to show the positional relationship between components within the portable electronic device, according to some embodiments of the present disclosure. Specifically,  FIG. 25A  is a cross-sectional view illustration  2500  of the assembled portion shown in  FIG. 19  across the horizontal cut line, and  FIG. 25B  is a cross-sectional view illustration  2501  of the assembled portion shown in  FIG. 19  across the vertical cut line. The assembled portion does not include a majority of top housing portion  1602  for ease of discussion. 
     As shown in the horizontal cross-sectional view in  FIG. 25A , top housing portion  1602  and bottom housing portion  1604  can be mated to form an internal cavity within which a plurality of internal components can be housed. In some embodiments, SIP  1616  can be positioned near the top of bottom housing portion  1604  and be positioned above a plurality of other internal components within bottom housing portion  1604 , such as receiver system  1618 , antenna  1629 , sensor module  1636 , and alignment module  1634 . Receiver system  1618  can be positioned within opening  1630  of antenna  1629 ; and, receiver system  1618  can be positioned coplanar to antenna  1629 , meaning receiver system  1618  can be positioned along the same horizontal plane in which antenna  1629  is positioned. In some embodiments, sensor module  1636  can be mounted on an inner surface of window  2204  and positioned within an inner diameter of receiver system  1618 . Sensor module  1636  can include a thin heart rate sensor  2502  and one or more photo diodes  2504  for performing sensing functions. Alignment module  1634  can be coupled to a top surface of sensor module  1636  and also be positioned within an inner diameter of receiver system  1618 . DC shield  1638  can overhang from lateral edges of magnet  1642 . 
     According to some embodiments of the present disclosure, receiver system  1618 , sensor module  1636 , and alignment module  1634  are all positioned within opening  1630  of antenna  1629 . Although not shown in  FIG. 25A , conductive antenna body  1108  can be disposed on the bottom surface of antenna element  1802 . As shown in  FIG. 25A , antenna  1629  can be vertically positioned over part of bottom housing portion  1604  and window  2204 . Specifically, top level  1806  can be vertically positioned over part of bottom housing portion  1604 , bottom level  1808  can be vertically positioned over part of window  2204 , and step region  1810  can be laterally positioned beside both bottom housing portion  1604  and window  2204 . By configuring antenna  1629  to extend over portions of both bottom housing portion  1604  and window  2204 , the size of antenna  1629  can be maximized given the limited amount of space within the portable electronic device, thereby improving the operability of antenna  1629 . 
     As shown in the vertical cross-sectional view in  FIG. 25B  where the top of the device is to the right and the bottom of the device is to the left, ferromagnetic shield  1404  can be positioned over parts of primary coil  1402  near the bottom of the device, while ferromagnetic shield  1404  is not positioned over parts of primary coil  1402  near the top of the device, as discussed herein with respect to  FIGS. 14A-14E . Furthermore, secondary coil  1406  can also be positioned near the bottom of the device and not at the top of the device, and be wound around parts of both ferromagnetic shield  1404  and primary coil  1402 . Unlike the left and right parts of antenna  1629 , at least some top and bottom parts of antenna  1629  may not have a bottom level and/or a step region, as shown in  FIG. 25B . Not having the bottom level and/or the step region provides greater electrical isolation between antenna  1629  and receiver system  1618 . As further shown in  FIG. 25A , capacitors  1813  can be disposed in a recessed area of top level  1806  of antenna  1629  so that capacitors  1813  do not substantially add to the device&#39;s z-height. 
     IV. Coating of the Window for a Portable Electronic Device 
     In some embodiments, the window of the back housing can include a plurality of coated layers that include ink layers that are either transparent or opaque to infrared (IR) radiation for enabling the sensor devices to measure the outside environment.  FIGS. 26A-26D and 27A-27H  illustrate different coating configurations of a window, according to some embodiments of the present disclosure. Specifically,  FIGS. 26A-26D  are a series of illustrations showing how an internal surface of window  2204  can be coated with different layers in a first configuration, and  FIGS. 27A-27H  are a series of illustrations showing how an internal surface of window  2204  can be coated with different layers in a second configuration. When combined as a multi-layered coating, the different layers can block IR radiation in specific areas of window  2204  while enabling propagation of IR radiation in other areas of the window to enable the operation of one or more sensors of portable electronic device  1600  while minimizing IR radiation leakage out of bottom housing portion  1604  and measurement noise from the external environment. 
     With reference to  FIG. 26A  illustrating the first configuration of ink coatings on window  2204 , IR opaque layers  2602  and  2604  can be coated on select areas of window  2204 . IR opaque layers  2602  and  2604  can be formed of IR opaque ink that can substantially resist the transmission of IR radiation such that IR radiation does not substantially transmit through the IR opaque ink. IR opaque layer  2602  can be positioned at an outer region of window  2204 , and IR opaque layer  2604  can be positioned at an inner region of window  2204 , as shown in  FIG. 26A . Both IR opaque layers  2602  and  2604  can be annular in dimension and be positioned spaced apart so that a first uncoated region  2606  is not covered by IR opaque layers  2602  and  2604 . Furthermore, IR opaque layer  2604  can be annular so that a second uncoated region  2608  located at the center of window  2204  is also not covered by IR opaque layers  2602  and  2604 . 
     In some embodiments, an IR transparent layer  2612  can be coated on a surface of first uncoated region  2606 . IR transparent layer  2612  can be formed of an IR transparent ink that can substantially allow the transmission of IR radiation such that IR radiation can be transmitted through the IR transparent ink without significant resistance. IR transparent layer  2612  can be arranged such that one or more openings  2614  remain in IR transparent layer  2612 . One or more openings  2614  can be regions where window  2204  is not covered by IR transparent layer  2612 , so that one or more sensors within portable electronic device  1600  can receive input, or send output, signals through window  2204 . In some embodiments, IR transparent layer  2612  may slightly overlap a portion of IR opaque layers  2602  and  2604  at regions where IR transparent layer  2612  meets IR opaque layers  2602  and  2604  to ensure complete coverage of window  2204  at the interface between IR transparent layer  2612  and IR opaque layers  2602  and  2604 . 
     Once the IR opaque and IR transparent layers are coated on window  2204 , a contact layer can then be coated on portions of IR opaque layer  2602 , as shown in  FIG. 26C . In some embodiments, the contact layer includes a first contact  2622  and a second contact  2624 . Both first and second contacts  2622  and  2624  can be positioned at the very outer edge of window  2204 , and can be electrically separated by gaps  2630   a  and  2630   b . First and second contacts  2622  and  2624  can wrap around the outer edge of window  2204  so that first and second contacts  2622  and  2624  are also present on the outer surface of window  2204  (see  FIG. 24  shown by external contacts  2402  and  2404 ). Contact pads  2626  and  2628  can be extensions of first and second contacts  2622  and  2624 , respectively, that provide contact surfaces with which a sensor device can make contact to receive input signals from first and second contacts  2622  and  2624 . The contact layer can be a thin layer of conductive material suitable such as a metal alloy formed of AlTiN or CrSiCN 
     As shown in  FIG. 26D , one or more adhesive layers can be coated on the IR opaque and IR transparent coatings. For instance, a first adhesive layer  2632  can be coated on IR opaque layer  2604 , and a second adhesive layer  2634  can be coated on IR transparent layer  2612 . First and second adhesive layers  2632  and  2634  can secure one or more sensor components, such as sensor module  1636 , to window  2204 . In some embodiments, first and second adhesive layers  2632  and  2634  can be formed of any suitable material for attaching two structures together, such as pressure sensitive adhesive (PSA). 
     With reference now to  FIG. 27A  illustrating the second configuration of ink coatings on window  2204 , an external contact layer can be coated directly on an outer surface of window  2204 . The contact layer can include a first external contact  2702  and a second external contact  2704  electrically and physically separated by gaps  2706   a  and  2706   b . In some embodiments, external contacts  2702  and  2704  are conductive ink layers that are coated only on the outer surface of window  2204  and the outer edge of window  2204  and do not extend to an inner surface of window  2204 . 
     In some embodiments, an IR transparent layer  2708  can be coated on an inner surface of window  2204  opposite of the outer surface as shown in  FIG. 27B . IR transparent layer  2708  can be formed of an IR transparent ink that can substantially allow the transmission of IR radiation such that IR radiation can be transmitted through the IR transparent ink without significant resistance. IR transparent layer  2708  can have an annular profile and be arranged to include one or more openings  2710 . Openings  2710  can be regions where window  2204  is not covered by IR transparent layer  2708 , so that one or more sensors of sensor module  1636  within portable electronic device  1600  can receive input, or send output, signals through window  2204 . IR transparent layer  2708  can have a diameter smaller than that of, and centered to, window  2204  so that the position of IR transparent layer  2708  results in a first uncovered region  2709  surrounding an outer diameter of IR transparent layer  2708  and a second uncovered region  2711  within an inner diameter of IR transparent layer  2708 . 
     As shown in  FIG. 27C , an IR opaque layer including a first portion  2712  and a second portion  2714  can then be coated on select areas of window  2204 . First portion  2712  can be coated on first uncovered region  2709  so that it surrounds an outer diameter of IR transparent layer  2708 ; and second portion  2714  can be coated on second uncovered region  2711  within an inner diameter of IR transparent layer  2708 . Both first and second portions  2712  and  2714  can have an annular profile as shown in  FIG. 27C . First portion  2712  can abut the outer diameter of IR transparent layer  2708  and be positioned away from the outer edge of window  2204  so that an uncovered region  2720  of window  2204  is present near the outer edge of window  2204 . Second portion  2714  can abut the inner diameter of IR transparent layer  2708  and be positioned away from the center of window  2204  so that an uncovered region  2722  is present at the center of window  2204 . In some embodiments, first portion  2712  includes an intermittently covered region  2716  that is formed of an alternating pattern of concentric IR opaque rings and uncovered surfaces of window  2204 , as shown in  FIG. 27C . Intermittently covered region  2716  can abut IR transparent layer  2708 . As further shown in  FIG. 27C , the IR opaque layer can also include IR opaque patches  2718  and  2719  positioned on the inner surface of window  2204  directly across from gaps  2706   a - b  positioned on the outer surface of window  2204 . In some embodiments, some parts of window  2204  may be exposed at regions  2717   a - b  beside IR opaque patches  2718  and  2719 . The IR opaque layer can be formed of IR opaque ink that can substantially resist the transmission of IR radiation such that IR radiation does not substantially transmit through the IR opaque ink. 
     Once the IR opaque layer is formed, a filler layer  2724  can be formed on the uncovered surface of window  2204  in intermittent region  2716 . Filler layer  2724  can be a cosmetic layer formed of a material having a pigment that is lighter than that of first portion  2712  of the IR opaque layer, such as a gray highlight ink. It is to be appreciated that any suitable cosmetic ink can be used to form filler layer  2724  such as a material having a pigment that is darker than that of first portion  2712  of the IR opaque layer. Then, as shown in  FIG. 27E , an encapsulation layer  2726  can be formed over intermittent region  2716  to cover exposed surfaces of filler layer  2724  to provide IR-resisting functionality over intermittent region  2716 . Encapsulation layer  2726  can be formed of the same material as the IR opaque layer. 
     In some embodiments, IR transparent patches  2728   a - b  can then be formed over the exposed regions  2717   a - b  beside IR opaque patches  2718  and  2719 , as shown in  FIG. 27F ; and then contact extensions  2732  and  2734  can be patterned onto the inner surface of window  2204 , as shown in  FIG. 27G . Contact extensions  2732  and  2734  can extend from the outer edge of window  2204  toward the center of window  2204  and cover a portion of encapsulation layer  2726 . Then, as shown in  FIG. 27H , contact pads  2736  and  2738  can be patterned over portions of respective contact extensions  2732  and  2734 . For instance, contact pad  2736  can be patterned over a portion of contact extension  2732  such that it covers the end of contact extension  2732  that is closest to the center of window  2204 , and likewise for contact pad  2736  with respect to contact extension  2734 . Contact pads  2736  and  2738  can provide a contact surface against which one or more electrical components, such as one or more sensing components in sensor module  1636 , can couple. Contact pads  2736  and  2738  can be electrically coupled with external contacts  2702  and  2704  shown in  FIG. 27A  via contact extensions  2732  and  2734 . Thus, by coupling to contact pads  2736  and  2738 , the one or more sensing components can utilize external contacts  2702  and  2704  to sense the external environment. 
     Although various layers shown in  FIGS. 27A-27H  are shown abutting one another, it is to be appreciated that abutting layers may overlap one another to ensure that no gaps are present between them and to ensure complete coverage of window  2204  at the interfaces. A better perspective of this concept can be appreciated with respect to  FIGS. 28A-28C .  FIG. 28A  is a top-down view of window  2204  after all of the layers have been patterned as shown in  FIG. 27H  to show the two cut lines for the cross-sectional views in  FIGS. 28B-28C . Specifically,  FIG. 28B  is a cross-sectional view  2800  of window  2204  through contact pad  2738 , and  FIG. 28C  is a cross-sectional view  2801  of window  2204  through opaque patch  2718 . 
     As shown in  FIG. 28B , window  2204  can have an inner surface  2802  configured to be positioned inside of the portable electronic device when assembled, an outer surface  2804  configured to be positioned outside of the portable electronic device when assembled, and an outer edge  2806 . IR transparent layer  2708  having openings  2710  can be patterned directly on inner surface  2802 , and first and second portions  2712  and  2714  of the IR opaque layer can be patterned directly on inner surface  2802  while overlapping a portion of the top surface of IR transparent layer  2708  at its inner and outer diameters, which are shown as left and right edges of IR transparent layer  2708  in  FIG. 28B . Filler layer  2724  can be patterned directly on inner surface  2802  while overlapping portions of intermittently covered region  2716  of first portion  2712  of the IR opaque layer; and encapsulation layer  2726  can be patterned over filler layer  2724  and on parts of first portion  2712  abutting filler layer  2724 . As further shown in  FIG. 28B , external contact  2704  can be patterned on outer surface  2804  and extend over outer edge  2806  of window  2204 . Edge  2806  can also be covered by contact extension  2734 , which can extend from edge  2806  directly on window  2204 , over part of first portion  2712  of the IR opaque layer, and end over encapsulation layer  2726 . And, contact pad  2738  can be patterned over a portion of contact extension  2734  such that contact pad  7238  covers the portion of contact extension  2734  that is closest to center  2808  of window  2204 . 
     With reference to  FIG. 28C , the cut line may pass directly between both external contacts  2702  and  2704  so no external contact can be seen in cross-sectional view  2801 , and since the cut line does not pass through a contact pad, no contact extension  2734  and contact pad  2738  can be seen. What can be seen, however, are IR opaque patch  2718  and IR transparent patch  2728   a . As shown, IR opaque patch  2718  can extend very close to, if not all the way to, edge  2806  of window  2204  and overlap a portion of the top surface of first portion  2712  of the IR opaque layer at its inner and outer diameters. IR transparent patch  2728   a  can be patterned directly on inner surface  2802  while overlapping a portion of the top surface of first portion  2712  of the IR opaque layer. Thus, as can be seen with reference to  FIGS. 28B and 28C , no gaps may exist between adjacent layers of IR opaque and IR transparent ink. 
     As mentioned in  FIG. 24 , first and second external contacts  2402  and  2404  can be used as contacts for sensing parameters of an external surface, such as user&#39;s arm, through physical contact to perform EKG sensing functions. In order for first and second external contacts  2402  and  2404  to sense the external environment and provide the sensed data to components within the portable electronic device, first and second external contacts  2402  and  2404  can be positioned on the outer surface of window  2204 , while providing an interface surface on an inner surface of window  2204  to couple with sensor devices, as will be discussed further herein with respect to  FIGS. 29A-34 . 
       FIGS. 29A-21  illustrate cross-sectional views across a portion of an external contact, a window, and a structure body for a bottom housing portion (e.g., bottom housing portion  1604 ), and top down views of an external region of the bottom housing portion, according to some embodiments of the present disclosure.  FIGS. 29A-21  show some different ways a contact can extend to an outer surface of a window to sense parameters of external surfaces, while also providing a contact surface to couple with sensor devices inside of a portable electronic device. 
       FIG. 29A  illustrates an exemplary configuration  2900  where an external contact  2902  wraps around edge  2810  of window  2204 , according to some embodiments of the present disclosure. As shown, contact  2902  can have portions that are positioned on outer surface  2802 , inner surface  2804 , and edge  2810  of window  2204 . Accordingly, external surfaces contacting external contact  2902  on outer surface  2802  can generate signals that can be measured by contacting with regions of external contact  2902  on inner surface  2804 . 
       FIG. 29B  illustrates an exemplary configuration  2901  where a contact  2909  is coupled to a via  2910 , according to some embodiments of the present disclosure. Contact  2909  can be a layer of conductive material disposed on outer surface  2802  of window  2204 . Contact  2909  can be coupled to via  2910  that extends through window  2204  to route signals from contact  2909  to a region of inner surface  2804 . 
       FIG. 29C  illustrates another exemplary configuration  2903  where a contact  2912  is configured as a standalone structure that can route signals from an outer surface  2914  to an inner surface  2916  of contact  2912 , according to some embodiments of the present disclosure. Contact  2912  can be directly attached to both structure body  2202  and window  2204  so that window  2204  is structurally coupled with structure body  2202 . In some embodiments, a bottom surface of contact  2912  can attach to structure body  2202  and a top surface of a ledge of contact  2912  can attach to a bottom surface of window  2204 . The structure of contact  2912  allows external surfaces in contact with outer surface  2914  of contact  2912  to generate signals that can be measured by contacting its inner surface  2916 . 
       FIG. 30  illustrates a top-down view of an external region of a bottom housing portion  3000  having first and second contacts  3002  and  3004  configured as any of the contacts discussed in  FIGS. 29A-29C . As shown, first and second contacts  3002  and  3004  can be positioned at the every outer edge of window  2204  such that they abut structure body  2202  of bottom housing portion  3000 . Although embodiments described in  FIGS. 29A-30  show first and second contacts  3002  and  3004  abutting structure body  2202 , embodiments are not so limited. In some embodiments, an intermediate structure can be disposed between first and second contacts  3002  and  3004  and structure body  2202 . 
       FIG. 31A  illustrates an exemplary configuration  3100  where an intermediate structure  3102  is disposed between via  2910  and structure body  2202 , according to some embodiments of the present disclosure. Intermediate structure  3102  can allow contact  2909  and via  2910  to be positioned farther away from structure body  2202  so that one or more sensors can measure an external environment through intermediate structure  3102 . Details of contact  2909  and via  2910  can be referenced from disclosures regarding  FIG. 29B . As mentioned herein with respect to  FIG. 16 , sensor module  1636  including one or more sensors, can be attached to window  2204 . Thus, in some embodiments, an additional transparent structure (e.g., a flattening insert) can be attached to window  2204  to planarize an inner surface of the bottom housing portion as shown in  FIG. 31B . 
       FIG. 31B  illustrates an exemplary configuration  3101  where an inner surface of window  2204  includes a flattening insert  3104 , according to some embodiments of the present disclosure. Flattening insert  3104  can have a curved top surface for coupling with window  2204 , and a flat bottom surface opposite of the curved top surface upon which sensor module (not shown) can attach. In some embodiments, flattening insert  3104  can be a transparent structure similar to that of window  2204 . 
       FIG. 32  illustrates a top-down view of an external region of a bottom housing portion  3200  including intermediate structure  3102  and first and second contacts  3202  and  3204  configured as shown in  FIGS. 31A-31C . Intermediate structure  3102  can be an annular structure positioned between first and second contacts  3202  and  3204  and structure body  2202  so that first and second contacts  3202  and  3204  do not abut structure body  2202 . In some embodiments, intermediate structure  3102  does not have to be formed of a transparent structure like window  2204 . Instead, intermediate structure  3102  can be formed of a non-transparent structure similar to structure body  2202 . 
       FIG. 33A  illustrates an exemplary configuration  3300  where an intermediate structure  3302  is disposed between contact  2902  on window  2204  and structure body  2202 , according to some embodiments of the present disclosure. Details of contact  2902  can be referenced from disclosures regarding  FIGS. 28B and 29A . Intermediate structure  3302  can allow contact  2902  to be positioned farther away from structure body  2202 . In some embodiments, intermediate structure  3302  is a separate structure that is attached to contact  2902  and structure body  2202 . Intermediate structure  3302  can be designed to extend window  2204 , along with contact  2902 , farther outward so that a better contact can be made between an external surface and an external surface of contact  2902 , and so that intermittent contact between the external surface and structure body  2202  is minimized (this may be desirable because noise can be generated in the system&#39;s ground when the external surface makes contact with structure body  2202 , i.e., bottom housing portion  1604 ). In some embodiments, intermediate structure  3302  can be formed of the same material as structure body  2202 , such as zirconia. 
     Although  FIG. 33A  illustrates intermediate structure  3302  as a separate structure, embodiments are not so limited.  FIG. 33B  illustrates an exemplary configuration  3301  where intermediate structure  3304  is formed as part of structure body  2202 , according to some embodiments of the present disclosure. In such embodiments, intermediate structure  3302  and structure body  2202  can form a monolithic structure and be formed of the same material. 
       FIG. 34  illustrates a top-down view of an external region of a bottom housing portion  3400  including intermediate structure  3302  and first and second contacts  3402  and  3404  configured as shown in  FIGS. 33A-33C . Intermediate structure  3302  can be an annular structure positioned between first and second contacts  3402  and  3404  and structure body  2202  so that first and second contacts  3402  and  3404  extend farther outward to make better contact with an external surface. 
     V. Touch-Sensitive Crown Dial for Portable Electronic Devices 
     As discussed herein with respect to  FIG. 16 , a top housing portion can include a dial. The dial can be a touch sensitive dial that can act as a contact for performing EKG sensing. The dial can include various components that, when coupled together, form a conductive pathway from an outer surface of the dial to inner touch components, as discussed herein with respect to  FIGS. 35 and 36 . 
       FIG. 35  is a simplified diagram illustrating an exploded view of an exemplary touch-sensitive dial  3500 , according to some embodiments of the present disclosure. Dial  3500  can include a crown dial  3502  coupled to a threaded seat  3504 . Crown dial  3502  can include a face contact  3520  and a periphery contact  3522  for receiving one or more inputs by contacting with external entities, such as a user&#39;s finger, and a threaded insert  3524 . Threaded insert  3524  can be inserted through a crown collar  3506 , an insert plate  3508 , and an opening of a switch bracket  3512  to couple with threaded seat  3504 . Switch bracket  3512  can house threaded seat  3504  and a shear plate  3510  against which threaded seat  3504  is attached. Shear plate  3510  can be coupled to capacitive touch components  3518 , which can include a plurality of electrical routing components for routing electrical signals from dial  3500  to inner components of the portable electronic device. An example of an electrical pathway through dial  3500  is illustrated in  FIG. 36 . 
       FIG. 36  is a cross-sectional view illustration  3600  of dial  3500  to show an exemplary electrical pathway  3602  through dial  3500 , according to some embodiments of the present disclosure. In some instances, electrical pathway  3602  can begin from face contact  3520  of crown dial  3502 , such as when a user&#39;s finger touches face contact  3520 . Electrical pathway  3602  can then continue through threaded insert  3524  and into threaded seat  3504 . Once at threaded seat  3504 , electrical pathway  3602  can continue through shear plate  3510  and end at capacitive touch components  3518 . Thus, an electrical input signal can route through dial  3500  to enable the portable electronic device to perform one or more functions, such as EKG sensing. 
     Although the invention has been described with respect to specific embodiments, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.

Metadata:
Filing Date: 20180905
Publication Date: 20190813
Grant Date: 20190813
Priority Date: 20170906
Inventors: WITTENBERG, MICHAEL B.
BRZEZINSKI, MAKIKO K.
KOWALSKI, STEFAN A.
GRAHAM, Christopher S.
MCCLURE, MORGAN T.
DE JONG, ERIK G.
NESS, TREVOR J.
KARDASSAKIS, PETER J.
NATH, JAYESH
CLAVELLE, Adam T.
EHMAN, REX TYLER
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B2560/0214", "inventive": false, "first": false, "tree": "[]"}, {"code": "A61B5/024", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/024", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/681", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B2560/0214", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/681", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2310/23", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6898", "inventive": true, "first": true, "tree": "[]"}, {"code": "A61B5/024", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6898", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B2560/0214", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "A61B5/6898", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 63524166