PATENT DOCUMENT

Publication Number: US-10644383-B2
Application Number: US-201715654915-A
Country: US
Kind Code: B2

Title: Wristwatch antennas

Abstract:
An electronic device such as a wristwatch may have a housing with metal sidewalls and a dielectric rear wall. The metal sidewalls may form an antenna ground for an antenna. The antenna may include an antenna resonating element formed from conductive traces patterned directly onto an interior surface of the dielectric rear wall. The conductive traces may define a slot at the dielectric rear wall. A coil and a sensor may be mounted to the dielectric rear wall within the slot. Radio-frequency transceiver circuitry may be coupled to the conductive traces and the antenna ground and may transmit and receive radio-frequency signals through the dielectric rear wall using the antenna. Wireless power receiver circuitry may use the coil to receive wireless power signals through the dielectric rear wall. The sensor may emit and/or receive light through a transparent window in the dielectric rear wall.

Claims:
What is claimed is: 
     
       1. An electronic device having opposing front and rear faces, the electronic device comprising:
 a dielectric rear housing wall that forms the rear face of the electronic device; 
 a display having a display cover layer that forms the front face of the electronic device; 
 a coil on the dielectric rear housing wall; 
 wireless power receiver circuitry that uses the coil to receive wireless power signals through the dielectric rear housing wall; 
 an antenna resonating element formed from conductive traces on the dielectric rear housing wall, the conductive traces surrounding the coil at the dielectric rear housing wall; and 
 radio-frequency transceiver circuitry that is coupled to the conductive traces of the antenna resonating element and that is configured to transmit and receive radio-frequency signals through the dielectric rear housing wall using the antenna resonating element. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the coil contacts the dielectric rear housing wall. 
     
     
       3. The electronic device defined in  claim 1 , further comprising:
 a sensor mounted to the dielectric rear housing wall, wherein the conductive traces of the antenna resonating element surround three sides of the sensor at the dielectric rear housing wall. 
 
     
     
       4. The electronic device defined in  claim 3 , wherein the dielectric rear housing wall is opaque, the electronic device further comprising:
 an optically transparent window in the dielectric rear housing wall, wherein the sensor is aligned with the optically transparent window and is configured to receive light through the optically transparent window. 
 
     
     
       5. The electronic device defined in claim  1 , further comprising:
 a printed circuit board having a conductive layer; and 
 a return path that shorts the antenna resonating element to the conductive layer. 
 
     
     
       6. The electronic device defined in  claim 5 , further comprising:
 conductive housing sidewalls that extend from the dielectric rear housing wall to the display cover layer, wherein the conductive housing sidewalls are shorted to the conductive layer. 
 
     
     
       7. The electronic device defined in  claim 5 , further comprising:
 a positive antenna feed terminal coupled to the conductive traces of the antenna resonating element; 
 a ground antenna feed terminal coupled to the conductive layer; and 
 a radio-frequency transmission line having a signal conductor coupled between the radio-frequency transceiver circuitry and the positive antenna feed terminal and a ground conductor coupled between the radio-frequency transceiver circuitry and the ground antenna feed terminal. 
 
     
     
       8. The electronic device defined in  claim 7 , wherein the conductive traces of the antenna resonating element form a conductive loop having opposing first and second ends, the positive antenna feed terminal is coupled to the conductive traces at the first end of the conductive loop, and the return path is coupled to the conductive traces at the second end of the conductive loop. 
     
     
       9. The electronic device defined in  claim 5 , further comprising:
 a conductive housing sidewall that is configured to receive a strap for the electronic device, wherein the return path is coupled to the conductive traces at a location adjacent to the conductive housing sidewall. 
 
     
     
       10. The electronic device defined in  claim 1 , further comprising:
 a flexible printed circuit formed over and in contact with the dielectric rear housing wall, wherein the conductive traces are formed on the flexible printed circuit. 
 
     
     
       11. An electronic device having opposing front and rear faces, the electronic device comprising:
 a display at the front face of the electronic device; 
 a housing having a dielectric rear wall at the rear face of the electronic device and having a metal sidewall, wherein the dielectric rear wall has an interior surface that defines an interior of the electronic device and the metal sidewall forms at least part of an antenna ground for an antenna; 
 conductive traces that form a planar antenna resonating element for the antenna, wherein the conductive traces are patterned onto the interior surface of the dielectric rear wall of the housing; 
 a feed for the antenna that includes a first antenna feed terminal coupled to the conductive traces and a second antenna feed terminal coupled to the antenna ground; 
 radio-frequency transceiver circuitry; and 
 a radio-frequency transmission line that couples the radio-frequency transceiver circuitry to the first and second antenna feed terminals, wherein the radio-frequency transceiver circuitry is configured to transmit and receive radio-frequency signals through the dielectric rear wall of the housing using the antenna. 
 
     
     
       12. The electronic device defined in claim  11 , wherein the radio-frequency transceiver circuitry comprises:
 wireless local area network transceiver circuitry that is configured to transmit and receive wireless local area network signals through the dielectric rear wall of the housing using the antenna; and 
 satellite navigation receiver circuitry that is configured to receive satellite navigation signals through the dielectric rear wall of the housing using the antenna. 
 
     
     
       13. The electronic device defined in  claim 12 , further comprising:
 a cellular telephone transceiver that is configured to transmit and receive signals from 700 MHz to 960 MHz through the dielectric rear wall of the housing using the antenna. 
 
     
     
       14. The electronic device defined in  claim 11 , further comprising:
 a coil; and 
 wireless power receiver circuitry that uses the coil to receive wireless power signals through the dielectric rear wall of the housing. 
 
     
     
       15. The electronic device defined in  claim 14 , wherein the coil is mounted to a substrate, the electronic device further comprising:
 a printed circuit board; 
 a conductive layer formed on the printed circuit board; and 
 conductive foam coupled between the substrate and the printed circuit board, wherein the conductive foam is configured to short conductive structures on the substrate to the conductive layer on the printed circuit board. 
 
     
     
       16. The electronic device defined in  claim 11 , further comprising:
 adjustable tuning circuitry coupled to the antenna; 
 a sensor that is configured to generate sensor data; and 
 control circuitry that is configured to process the sensor data and adjust the tuning circuitry to tune the antenna based on the sensor data. 
 
     
     
       17. An electronic device having opposing first and second faces, the electronic device comprising:
 a housing having a dielectric wall at the second face and having sidewalls that extend from the dielectric wall to the first face; 
 an antenna, wherein the antenna comprises:
 an antenna ground, 
 an antenna resonating element formed from conductive traces that are patterned directly onto the dielectric wall and that define a slot, 
 a first antenna feed terminal coupled to the conductive traces, and 
 a second antenna feed terminal coupled to the antenna ground; 
 
 sensor circuitry mounted to the dielectric wall within the slot defined by the conductive traces, wherein the sensor circuitry is configured to receive light through the dielectric wall; and 
 radio-frequency transceiver circuitry that is coupled to the first and second antenna feed terminals and that is configured to transmit and receive radio-frequency signals through the dielectric wall using the antenna. 
 
     
     
       18. The electronic device defined in  claim 17 , further comprising:
 a coil mounted to the dielectric wall within the slot; and 
 wireless power receiver circuitry that uses the coil to receive wireless power signals through the dielectric wall. 
 
     
     
       19. The electronic device defined in  claim 17 , wherein the sidewalls of the housing comprise metal sidewalls, the electronic device further comprising:
 a printed circuit board having a conductive layer that is electrically coupled to the metal sidewalls; and 
 a return path for the antenna that couples the conductive traces to the conductive layer, wherein antenna ground comprises the metal sidewalls and the conductive layer.

Description:
This application claims the benefit of provisional patent application No. 62/399,119, filed Sep. 23, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates to electronic devices, and more particularly, to antennas for electronic devices with wireless communications circuitry. 
     Electronic devices are often provided with wireless communications capabilities. To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. At the same time, there is a desire for wireless devices to cover a growing number of communications bands. 
     Because antennas have the potential to interfere with each other and with components in a wireless device, care must be taken when incorporating antennas into an electronic device. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to exhibit satisfactory performance over a range of operating frequencies. 
     It would therefore be desirable to be able to provide improved wireless communications circuitry for wireless electronic devices. 
     SUMMARY 
     An electronic device such as a wristwatch may have a housing with metal portions such as metal sidewalls. A display may be mounted on a front face of the device. Light-based components such as light-emitting diodes and detectors may be mounted on a rear face of the device. The rear face of the electronic device may be formed using a dielectric rear housing wall. 
     The electronic device may include wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and an antenna. The antenna may include an antenna ground. The antenna ground may be formed using the metal housing sidewalls and/or a conductive layer on a printed circuit board within the electronic device. The antenna may include an antenna resonating element formed from conductive traces that are patterned directly onto an interior surface of the dielectric rear housing wall. The antenna may include a positive antenna feed terminal coupled to the conductive traces and a negative antenna feed terminal coupled to the antenna ground. A short circuit leg may couple the conductive traces to the antenna ground (e.g., to the conductive layer on the printed circuit board or to the metal housing sidewalls). The radio-frequency transceiver circuitry may be coupled to the positive and ground antenna feed terminals and may transmit and receive radio-frequency signals through the dielectric rear housing wall using the antenna. 
     The conductive traces on the dielectric rear housing wall may define a slot. The conductive traces may form a conductive loop that surrounds the slot and that has opposing first and second ends. The positive antenna feed terminal may be coupled to the first end of the conductive loop whereas the short circuit leg is coupled to the second end of the conductive loop. A coil and one or more sensors may be mounted to the dielectric rear housing wall within the slot. The electronic device may include wireless power receiver circuitry that uses the coil to receive wireless power signals through the dielectric rear housing wall. The sensor may emit and/or receive light through at least one transparent window in the dielectric rear housing wall. 
     The transceiver circuitry may include cellular telephone transceiver circuitry, wireless local area network transceiver circuitry, and satellite navigation receiver circuitry. The cellular telephone transceiver circuitry may use the antenna resonating element to transmit and receive signals from 700 MHz to 960 MHz and/or in other cellular telephone communications bands through the dielectric rear wall of the housing. The wireless local area network transceiver circuitry may use the antenna resonating element to transmit and receive wireless local area network signals through the dielectric rear wall of the housing. The satellite navigation receiver circuitry may use the antenna resonating element to receive satellite navigation signals through the dielectric rear wall of the housing. The antenna may be used to cover any other frequencies if desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG. 3  is a diagram of illustrative wireless circuitry in an electronic device in accordance with an embodiment. 
         FIG. 4  is a diagram of an illustrative inverted-F antenna structure in accordance with an embodiment. 
         FIG. 5  is a perspective view showing how an illustrative antenna may include an antenna resonating element, an antenna ground, a return path, and an antenna feed (e.g., in a planar inverted-F antenna configuration) in accordance with an embodiment. 
         FIG. 6  is a perspective view showing how an illustrative antenna resonating element may have a slot that accommodates other device components in accordance with an embodiment. 
         FIG. 7  is a schematic diagram of an illustrative wireless power coil in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of an illustrative electronic device having an antenna resonating element patterned directly onto a dielectric rear housing wall in accordance with an embodiment. 
         FIG. 9  is a perspective rear view of an illustrative electronic device from which a dielectric rear housing wall has been removed to show how an antenna resonating element may be patterned directly onto the dielectric rear housing wall in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of a rear portion of an illustrative electronic device when placed over a user&#39;s wrist in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative electronic device showing how an antenna resonating element at the rear of the device and a user&#39;s wrist may guide electromagnetic energy away from the device in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG. 1  may be provided with wireless circuitry. The wireless circuitry may include antennas. Antennas such as cellular telephone antennas and wireless local area network and satellite navigation system antennas may be formed from electrical components such antenna resonating element traces and device housing structures. 
     Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a wristwatch. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14 . Display  14  has been mounted in a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). Housing  12  may have metal sidewalls such as sidewalls  12 W or sidewalls formed from other materials. Examples of metal materials that may be used for forming sidewalls  12 W include stainless steel, aluminum, silver, gold, metal alloys, or any other desired conductive material. 
     Display  14  may be formed at the front side (face) of device  10 . Housing  12  may have a rear housing wall such as rear wall  12 R that opposes front face of device  10 . Housing sidewalls  12 W may surround the periphery of device  10  (e.g., housing sidewalls  12 W may extend around peripheral edges of device  10 ). Rear housing wall  12 R may be formed from dielectric. Examples of dielectric materials that may be used for forming rear housing wall  12 R include plastic, glass, sapphire, ceramic, wood, polymer, combinations of these materials, or any other desired dielectrics. Rear housing wall  12 R and/or display  14  may extend across some or all of the length (e.g., parallel to the x axis of  FIG. 1 ) and width (e.g., parallel to the y axis) of device  10 . Housing sidewall  12 W may extend across some or all of the height of device  10  (e.g., parallel to z axis). 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. 
     Display  14  may be protected using a display cover layer. The display cover layer may be formed from a transparent material such as glass, plastic, sapphire or other crystalline dielectric materials, ceramic, or other clear materials. The display cover layer may extend across substantially all of the length and width of device  10 , for example. 
     Device  10  may include buttons such as button  18 . There may be any suitable number of buttons in device  10  (e.g., a single button, more than one button, two or more buttons, five or more buttons, etc. Buttons may be located in openings in housing  12  (e.g., in side wall  12 W or rear wall  12 R) or in an opening in display  14  (as examples). Buttons may be rotary buttons, sliding buttons, buttons that are actuated by pressing on a movable button member, etc. Button members for buttons such as button  18  may be formed from metal, glass, plastic, or other materials. Button  18  may sometimes be referred to as a crown in scenarios where device  10  is a wristwatch device. 
     Device  10  may, if desired, be coupled to a strap such as strap  16 . Strap  16  may be used to hold device  10  against a user&#39;s wrist (as an example). In the example of  FIG. 1 , strap  16  is connected to opposing sides  8  of device  10 . Housing walls  12 W on sides  8  of device  10  may include attachment structures for securing strap  16  to housing  12  (e.g., lugs or other attachment mechanisms). Configurations that do not include straps may also be used for device  10 . 
     A schematic diagram showing illustrative components that may be used in device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  28  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, MIMO protocols, antenna diversity protocols, etc. 
     Input-output circuitry  44  may include input-output devices  32 . Input-output devices  32  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  32  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  32  may include touch screens, displays without touch sensor capabilities, buttons, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, light-emitting diodes, motion sensors (accelerometers), capacitance sensors, proximity sensors, magnetic sensors, force sensors (e.g., force sensors coupled to a display to detect pressure applied to the display), etc. 
     Input-output circuitry  44  may include wireless circuitry  34 . Wireless circuitry  34  may include coil  50  and wireless power receiver  48  for receiving wirelessly transmitted power from a wireless power adapter. To support wireless communications, wireless circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas such as antennas  40 , transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless circuitry  34  may include radio-frequency transceiver circuitry  90  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 ,  42 , and  46 . Transceiver circuitry  36  may be wireless local area network transceiver circuitry that may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and that may handle the 2.4 GHz Bluetooth® communications band. Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a midband from 1400 MHz or 1500 MHz to 2170 MHz (e.g., a midband with a peak at 1700 MHz), and a high band from 2170 or 2300 to 2700 MHz (e.g., a high band with a peak at 2400 MHz) or other communications bands between 700 MHz and 2700 MHz or other suitable frequencies (as examples). Circuitry  38  may handle voice data and non-voice data. Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include 60 GHz transceiver circuitry, circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) transceiver circuitry  46  (e.g., an NFC transceiver operating at 13.56 MHz or other suitable frequency), etc. Wireless circuitry  34  may include satellite navigation system circuitry such as global positioning system (GPS) receiver circuitry  42  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, monopole antennas, dipole antenna structures, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna whereas another type of antenna is used in forming a remote wireless link antenna. If desired, space may be conserved within device  10  by using a single antenna to handle two or more different communications bands. For example, a single antenna  40  in device  10  may be used to handle communications in a WiFi® or Bluetooth® communication band at 2.4 GHz, a GPS communications band at 1575 MHz, and one or more cellular telephone communications bands such as a low cellular telephone band at 700-960 MHz. 
     However, in practice, the general size required for the antenna increases as the desired frequency for operation decreases (i.e., as the corresponding wavelength increases). In addition, space is at a premium in compact electronic devices such as device  10  (e.g., especially as the demand for smaller and more aesthetically pleasing device form factors increases). If care is not taken, it can be difficult to be able to provide compact electronic devices with satisfactory antenna coverage in all communications bands of interest, particularly for relatively low frequencies (i.e., relatively long wavelengths) such as low band cellular telephone frequencies at 700-960 MHz. 
       FIG. 3  is a diagram showing how transceiver circuitry  90  in wireless circuitry  34  may be coupled to antenna structures  40  using paths such as path  60 . Wireless circuitry  34  may be coupled to control circuitry  28 . Control circuitry  28  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures  40  with the ability to cover communications frequencies of interest, antenna structures  40  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna structures  40  may be provided with adjustable circuits such as tunable components  62  to tune antennas over communications bands of interest. Tunable components  62  may include tunable inductors, tunable capacitors, or other tunable components. Tunable components such as these may be based on switches and networks of fixed components, distributed metal structures that produce associated distributed capacitances and inductances, variable solid state devices for producing variable capacitance and inductance values, tunable filters, or other suitable tunable structures. 
     During operation of device  10 , control circuitry  28  may issue control signals on one or more paths such as path  64  that adjust inductance values, capacitance values, or other parameters associated with tunable components  62 , thereby tuning antenna structures  40  to cover desired communications bands. 
     Path  60  may include one or more radio-frequency transmission lines. As an example, signal path  60  of  FIG. 3  may be a transmission line having first and second conductive paths such as paths  66  and  68 , respectively. Path  66  may be a positive signal line and path  68  may be a ground signal line. Lines  66  and  68  may form parts of a coaxial cable, a stripline transmission line, and/or a microstrip transmission line (as examples). A matching network formed from components such as inductors, resistors, and capacitors may be used in matching the impedance of antenna structures  40  to the impedance of transmission line  60 . Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Matching network components may, for example, be interposed on line  60 . The matching network components may be adjusted using control signals received from control circuitry  28  if desired. Components such as these may also be used in forming filter circuitry in antenna structures  40 . 
     Transmission line  60  may be directly coupled to an antenna resonating element and ground for antenna  40  or may be coupled to near-field-coupled antenna feed structures that are used in indirectly feeding a resonating element for antenna  40 . As an example, antenna structures  40  may form an inverted-F antenna, a loop antenna, a patch antenna, a slot antenna, or other antenna having an antenna feed with a positive antenna feed terminal such as terminal  70  and a ground antenna feed terminal such as ground antenna feed terminal  72 . Positive transmission line conductor  66  may be coupled to positive antenna feed terminal  70  and ground transmission line conductor  68  may be coupled to ground antenna feed terminal  72 . If desired, antenna  40  may include an antenna resonating element that is indirectly fed using near-field coupling. In a near-field coupling arrangement, transmission line  60  is coupled to a near-field-coupled antenna feed structure that is used to indirectly feed antenna structures such as the antenna resonating element. This example is merely illustrative and, in general, any desired antenna feeding arrangement may be used. 
     In one suitable arrangement, antenna  40  may be formed using an inverted-F antenna structure (e.g., a planar inverted-F antenna structure). An illustrative inverted-F antenna structure that may be used for forming antenna  40  is shown in  FIG. 4 . As shown in  FIG. 4 , antenna  40  may include an antenna resonating element  104  and antenna ground (ground plane)  102 . Antenna resonating element  104  may one or more resonating element arms. The length or perimeter of antenna resonating element  104  may be selected so that antenna  40  resonates at desired operating frequencies. For example, the length or perimeter of arm  104  may be a quarter of a wavelength at a desired operating frequency for antenna  40 . Antenna  40  may also exhibit resonances at harmonic frequencies if desired. 
     Antenna resonating element  104  may be coupled to ground  102  by return path  110 . Antenna ground  102  may be formed from metal components within device  10  such as one or more metal printed circuit board layers, metal housing structures (e.g., housing sidewall structures  12 W, metal frame structures, metal bracket structures, metal midplate structures, etc.), any other desired conductive components within device  10 , or any desired combination of these components. Antenna feed  112  may include positive antenna feed terminal  70  and ground antenna feed terminal  72  and may run in parallel to return path  110  between arm  104  and ground  102 . If desired, antenna resonating element  104  of  FIG. 4  may have more than one resonating arm branch (e.g., to create multiple frequency resonances to support operations in multiple communications bands) or may have other antenna structures (e.g., parasitic antenna resonating elements, tunable components to support antenna tuning, etc.). A planar inverted-F antenna (PIFA) may be formed by implementing antenna resonating element  104  using planar structures (e.g., a planar metal structure such as a metal patch or strip of metal that extends into the page of  FIG. 4 ). 
       FIG. 5  is a perspective view of antenna  40  when antenna resonating element  104  is implemented using a planar metal structure such as a metal patch (e.g., when antenna  40  is implemented using a planar inverted-F structure). As shown in  FIG. 5 , antenna  40  may have an antenna feed such as feed  112  that includes a downwardly protruding feed leg such as leg  120 . Positive antenna feed terminal  70  may be coupled to leg  120 . If desired, feed leg  120  may be omitted and positive antenna feed terminal  70  may be directly connected to antenna resonating element  104 . Ground antenna feed terminal  72  may be coupled to ground  102  and may be separated from positive antenna feed terminal  70  by a gap. Return path (short circuit path)  110  may be formed from downwardly protruding leg  122  that couples antenna resonating element structure  104  to ground plane  102 . Structure  104  may be substantially or completely planar and may lie in a plane that is parallel to the plane of ground  102 , if desired. In the example of  FIG. 5 , structure  104  has a rectangular plate shape. Configurations in which structure  104  has a meandering arm shape, shapes with multiple branches, one or more curved edges, one or more straight edges, or other shapes may also be used for forming antenna resonating element  104 . Antenna resonating element  104  may be fed using other feeding schemes if desired (e.g., antenna resonating element  104  may be a resonating element in a patch antenna, monopole antenna, dipole antenna, slot antenna, loop antenna, etc.). 
     As space is at a premium in device  10 , antenna resonating element  104  may have a shape that is configured to accommodate other components within device  10 .  FIG. 6  is a perspective view of antenna  40  showing how antenna resonating element  104  may have a shape that accommodates other components within device  10 . 
     As shown in  FIG. 6 , a notch or slot  136  may be formed in antenna resonating element  104 . Slot  136  may be defined by interior edge  130  of resonating element  104  (e.g., slot  136  may be formed by a cut or notch extending from one side of outer edge  132  of antenna resonating element  104  towards the interior of antenna resonating element  104 ). Slot  136  may have a closed end defined by interior edge  130  of resonating element  104  and an opposing open end adjacent to feed leg  120  (i.e., slot  136  may sometimes be referred to as an open slot). In another suitable arrangement, slot  136  may be entirely enclosed by inner edge  130  (e.g., slot  136  may be a closed slot and planar antenna resonating element  104  may be continuous between feed leg  120  and return leg  122 ). 
     Slot  136  may have any desired perimeter or shape. In the example of  FIG. 6 , slot  136  has a curved (e.g., circular or oval) shape. The shape of slot  136  may accommodate other components such as components  134  that are placed within slot  136 . If desired, the shape of slot  136  (i.e., interior edge  130 ) may be configured to conform to the shape of components  134  (e.g., the edges of internal components  134  may extend parallel to internal edge  130  of antenna resonating element  104 ). Components  134  may lie in a common plane with antenna resonating element  104  and/or may lie below the plane of antenna resonating element  104 . 
     Internal components  134  may include one or more input-output devices  32  ( FIG. 2 ), other antennas  40 , coil  50 , components from transceiver circuitry  90 , a portion of control circuitry  28 , portions of housing  12 , or any other desired components. If desired, internal components  134  may include conductive components that are shorted to ground plane  102  (as shown by ground terminal  138 ). 
     When configured in this way, antenna resonating element  104  may have a first portion  140 , a second portion  142  that extends substantially perpendicular to first portion  140 , a third portion  144  that extends substantially perpendicular to second portion  142  (and parallel to first portion  140 ), and a fourth portion  146  that extends substantially perpendicular to third portion  144  (and parallel to second portion  144 ). First portion  140 , second portion  142 , and third portion  144  may surround three sides of components  134 . Fourth portion  146  may be discontinuous (i.e., divided by slot  136 ). 
     Antenna feed  112  (e.g., antenna feed leg  120 ) and return path  110  (e.g., return leg  122 ) may be coupled to portion  146  of antenna resonating element  104 . In the example of  FIG. 6 , feed leg  120  and return leg  122  are both coupled to portion  146  along exterior edge  132  and on opposing sides of slot  136 . This is merely illustrative. If desired, feed leg  120  may be coupled to resonating element  104  at any desired location along portion  146  (e.g., along exterior edge  132 , along interior edge  130 , to a location between interior edge  130  and exterior edge  132 , etc.). Return leg  122  may be coupled to resonating element  104  at any desired location along portion  146  (e.g., along exterior edge  132 , along interior edge  130 , to a location between interior edge  130  and exterior edge  132 , etc.). If desired, feed leg  120  may be coupled to antenna resonating element  104  at any desired location along portion  144 ,  142 , or  140 . Similarly, return leg  120  may be coupled to antenna resonating element  104  at any desired location along portion  144 ,  142 , or  140 . In one suitable arrangement, feed leg  120  is coupled to resonating element  104  along portion  146  whereas return leg  122  is coupled to resonating element  104  at a location along exterior edge  132  of portion  140 . 
     In the example of  FIG. 6 , exterior edge  132  of resonating element  104  has a rectangular shape (outline) whereas interior edge  130  has a curved shape. This is merely illustrative. In general, exterior edge  132  and interior edge  130  may have any desired shapes. For example, exterior edge  132  may have one or more curved sides, one or more straight sides, or more than four sides. Interior edge  130  may have one or more curved sides, one or more straight sides, etc. Resonating element  104  may have any desired number of portions extending in any desired directions. In the example of  FIG. 6 , antenna resonating element  104  is substantially planar. However, in general, antenna resonating element  104  may be formed on a surface having any desired shape. For example, antenna resonating element  104  may be formed on a concave or convex surface or may have a combination of flat, concave, and convex portions. 
       FIG. 7  is a circuit diagram showing how wireless power receiver  48  of  FIG. 2  may be coupled to coil  50 . As shown in  FIG. 7 , wireless power receiver  48  may be coupled to coil  50  over conductive path  160 . When receiving wireless power, coil  50  may receive wirelessly transmitted alternating-current signals that have been transmitted from a wireless power adapter or other wireless power transmitting device. The wirelessly transmitted alternating-current signals may induce current flow around the loops of coil  50 . The induced current may be conveyed to wireless power receiver  48 . Wireless power receiver  48  may have rectifier circuitry that rectifies the received alternating-current wireless power signals to produce direct-current power for device  10 . The direct-current power may power any desired components of device  10  and/or may be used to charge a battery on device  10 . Coil  50  may receive wireless power signals at any desired frequency. As an example, coil  50  may receive wireless power at frequencies in the range of 1 kHz to 100 MHz or other suitable frequencies. Wireless coil  50  may, if desired, be formed as a portion of components  134  within slot  136  of antenna resonating element  104  ( FIG. 6 ). 
     Antenna resonating element  104  of  FIG. 6  may be formed on a dielectric substrate. For example, a dielectric substrate such as a plastic carrier may be formed between ground plane  102  and antenna resonating element  104  for supporting antenna resonating element  104 . In order to further conserve space within device  10 , antenna resonating element  104  may, if desired, be formed from metal traces that are patterned directly onto a portion of housing  12  (e.g., onto dielectric rear housing wall  12 R). If desired, some or all of components  134  that are surrounded by antenna resonating element  104  may be in contact with rear housing wall  12 R. For example, coil  50  may be formed directly on rear housing wall  12 R. 
       FIG. 8  is a cross-sectional side view of illustrative device  10  showing how antenna resonating element  104  may be patterned directly onto rear housing wall  12 R. The plane of the page of  FIG. 8  may be, for example, the X-Z plane or the Y-Z plane of  FIG. 1 . 
     As shown in  FIG. 8 , device  10  may have conductive housing sidewalls  12 W that extend from the rear face to the front face of device  10 . Display  14  may be formed at the front face of device  10  whereas dielectric rear housing wall  12 R is formed at the rear face of device  10 . Metal housing sidewalls  12 W may be used in forming a portion of antenna ground  102  ( FIG. 6 ) if desired. Display  14  may include a display cover layer  170  and a display module  172 . Display module  172  may include active display components such as touch sensors, pixels, or other light-emitting components that emit light through display cover layer  170 . Display cover layer  170  may extend across the length and width of device  10 . Display cover layer  170  may include a transparent portion that passes the light emitted by display module  172  (e.g., so that the light may be seen by a user). If desired, an opaque masking layer such as an ink layer may be formed along the portion of display cover layer  170  that extends beyond display module  172  to hide the internal components of device  10  from view. 
     Device  10  may include printed circuit board structures such as printed circuit board  174 . Printed circuit board  174  may be a rigid printed circuit board, a flexible printed circuit board, or may include both flexible and rigid printed circuit board structures. Printed circuit board  174  may sometimes be referred to herein as main logic board  174 . Electrical components  176  may be mounted to main logic board  174 . Electrical components  176  may include, for example, transceiver circuitry  90 , one or more input-output devices  32 , some or all of control circuitry  28  ( FIG. 2 ), portions of housing  12 , or any other desired components. Main logic board  174  may include one or more conductive layers such as conductive layer  178 . Conductive layer  178  may, for example, form a portion of antenna ground  102  for antenna  40  (as shown in  FIGS. 5 and 6 ). Conductive layer  178  may therefore sometimes be referred to herein as grounded layer  178 , ground layer  178 , ground conductor  178 , or grounded conductor  178 . 
     Conductive layer  178  may, if desired, be shorted (grounded) to metal housing sidewalls  12 W. (e.g., antenna ground  102  may include conductive layer  178  and metal housing sidewalls  12 W). Conductive layer  178  may be formed using metal foil, stamped sheet metal, conductive traces patterned onto a surface of main logic board  174 , a conductive trace on a flexible printed circuit mounted to main logic board  174 , or from any other desired conductive structures. If desired, conductive layer  178  may be formed (embedded) within main logic board  174  (e.g., conductive layer  178  may be stacked between dielectric layers of logic board  174 ). In another suitable arrangement, conductive layer  178  may be omitted. 
     As shown in  FIG. 8 , rear housing wall  12 R may extend substantially across the length and width of device  10 . Rear housing wall  12 R may be formed from any desired dielectric material. For example, rear housing wall  12 R may be formed from plastic, glass, sapphire, ceramic, wood, polymer, combinations of these materials, or any other desired dielectrics. Rear housing wall  12 R may be optically opaque or optically transparent. Antenna resonating element  104  may be formed from conductive traces that are patterned directly onto the interior surface of dielectric housing wall  12 R (e.g., the patterned conductive traces may be in direct contact with the inner surface of dielectric housing wall  12 R). If desired, antenna resonating element  104  may be formed from conductive foil or other conductive structures that are placed in direct contact with rear housing wall  12 R. Antenna resonating element traces  104  may be formed using any desired conductive material (e.g., aluminum, copper, metal alloys, stainless steel, gold, etc.). If desired, the rear housing wall of device  10  may include a combination of conductive and dielectric materials. For example, a portion of the rear housing wall may be formed from metal whereas another portion of the rear housing wall is formed from dielectric (e.g., the portion of the rear housing wall formed from dielectric may extend across some but not all of the length and width of device  10 ). The dielectric portion of the rear housing wall may, for example, include a dielectric window in a conductive portion of the rear housing wall (e.g., the rear housing wall may include a metal frame for the dielectric portion of the rear housing wall or other structures that surround the dielectric portion of the rear housing wall). 
     Positive antenna feed terminal  70  of antenna feed  112  may be coupled to a portion of antenna resonating element traces  104  to feed radio-frequency antenna signals for antenna  40 . Ground antenna feed terminal  72  may be coupled to antenna ground  102 . In the example of  FIG. 8 , ground antenna feed terminal  72  is coupled to metal housing sidewall  12 W. If desired, ground antenna feed terminal  72  may be coupled to conductive layer  178  or any other desired grounded structures. Another portion of antenna resonating element traces  104  may be shorted to antenna ground  102  by return path  110 . Return path  110  may be coupled to housing sidewall  12 W, may be coupled to conductive layer  178 , or may be coupled to any other desired grounded structures. 
     By patterning antenna resonating element traces  104  directly onto rear housing wall  12 R, rear housing wall  12 R may serve as a mechanical support structure or carrier structure for antenna resonating element  104 . Antenna resonating element traces  104  may conform to the shape of the interior surface of dielectric rear housing wall  12 R. In the example of  FIG. 8 , the interior surface of dielectric rear housing wall  12 R has a curved shape (e.g., to increase the total volume for components within device  10  relative to scenarios where the interior surface of wall  12 R is flat). Antenna resonating element traces  104  may therefore be formed within a curved surface that is in direct contact with rear housing wall  12 R. In another suitable arrangement, antenna resonating element traces  104  may be formed on a flexible printed circuit or other substrate that is placed in contact with (e.g., layered over) rear housing wall  12 R. Antenna  40  may receive and/or transmit radio-frequency signals through rear housing wall  12 R. Radio-frequency signals transmitted by antenna  40  may, for example, be shielded from electrical components  176  by conductive layer  178  and main logic board  174 . Similarly, conductive layer  178  and main logic board  174  may shield antenna  40  from components  176 , thereby mitigating electromagnetic interference between antenna  40  and components  176 . 
     Components  134  may be mounted to rear housing wall  12 R. Antenna resonating element trace  104  may surround or be formed around the periphery of components  134  at rear housing wall  12 R. In the example of  FIG. 8 , coil  50  is formed on support structures  180  and placed in direct contact with rear housing wall  12 R. Coil  50  and support structures  180  may be mounted to a substrate such as substrate  182 . Coil  50  may receive wireless power (e.g., wireless charging signals) through dielectric rear housing wall  12 R. 
     Substrate  182  may be a rigid or flexible printed circuit board or any other desired substrate. Substrate  182  may include conductive structures that are grounded to antenna ground  102  if desired. For example, conductive foam  206  may be placed on substrate  182  to short conductive structures on substrate  182  to conductive layer  178  (e.g., conductive foam  206  may form ground terminal  138  of  FIG. 6 ). Conductive foam  206  may also provide mechanical support to substrate  182  (e.g., by maintaining a separation between substrate  182  and main logic board  174 ). Other components such as sensor circuitry  186  may be mounted to substrate  182 . Sensor circuitry  186  may include one or more sensors (e.g., sensors of input-output devices  32  of  FIG. 2 ). The sensors may include touch sensors, proximity sensors (e.g., capacitive proximity sensors), light sensors, or any other desired sensors. 
     If desired, rear wall  12 R may have one or more openings that are filled with an optically transparent window such as window  188  (e.g., in scenarios where rear housing wall  12 R is optically opaque). Light-based sensor components  186  may be mounted in alignment with windows such as window  188 . Components  186  may include light-emitting diodes (e.g., infrared light-emitting diodes, visible light-emitting diodes, etc.) and may include light detectors (e.g., detectors for detecting light that has been emitted by the light-emitting diodes after reflection off an external object). Configurations such as these may allow light-based components  186  to be used to monitor a user&#39;s physiological parameters (heart rate, blood oxygen level, etc.). In another suitable arrangement, conductive electrodes may be formed within openings in rear housing wall  12 R. The conductive electrodes may sense changes in capacitance associated with the approach of an external object (e.g., a user&#39;s body) or may sense when the external object is in contact with rear housing wall  12 R, for example. In general, any desired number of sensors may be aligned with any desired number of windows  188  or openings in rear housing wall  12 R (e.g., one window  188 , two windows  188 , three windows  188 , four windows  188 , more than four windows  188 , etc.). Components  186  and windows  188  may be surrounded by coil  50  and antenna resonating element traces  104  at rear housing wall  12 R. 
     By patterning antenna resonating element traces  104  directly onto the interior surface of rear housing wall  12 R, vertical height  200  of device  10  may be shorter than would otherwise be possible in scenarios where the antenna resonating element is located elsewhere on device  10  (while still allowing antenna  40  to exhibit satisfactory antenna efficiency). As an example, vertical height  200  may be less than or equal to 11.4 mm, less than 15 mm, between 8 and 11.4 mm, or any other desired height while still allowing antenna  40  to operate with satisfactory antenna efficiency. Forming antenna  40  along the rear side of device  10  may also allow for reduction of the size of the inactive region of display  14  (as shown by arrow  202 ), because antenna  40  can transmit radio-frequency signals through the rear side of device  10  without concern that the signals will be blocked by display module  172 . Forming antenna traces  104  on rear housing wall  12 R may also allow the perimeter of antenna resonating element  104  to be sufficiently large so as to allow for coverage of relatively low frequencies such as frequencies in a cellular telephone band between 700 and 960 MHz. Antenna  40  may thereby be used to cover radio-frequency signals in any desired number of communications bands between a low frequency such as 700 MHz and a high frequency such as 5.0 GHz or any other suitable frequency, for example. 
       FIG. 9  is a perspective rear view of device  10  showing how antenna resonating element  104  may be patterned directly onto rear housing wall  12 R. In the perspective view of  FIG. 9 , rear housing wall  12 R has been removed from device  10  (e.g., one end of rear housing wall  12 R has been rotated upwards off of housing sidewalls  12 W as shown by arrows  210 ) to expose the components within device  10 . When device  10  is fully assembled, rear housing wall  12 R may be mounted onto sidewalls  12 W so that rear housing wall  12 R lies flush with the bottom edges of sidewalls  12 W. 
     As shown in  FIG. 9 , antenna resonating element trace  104  is patterned directly onto the interior surface of dielectric rear housing wall  12 R. Components  134  (e.g., support structure  180 , substrate  182 , sensors  186 , and conductive foam  206 ) may be mounted to the interior surface of rear housing wall  12 R. Interior edge  130  of antenna resonating element trace  104  may be curved to accommodate components  134 . For example, antenna resonating element trace  104  may surround at least three sides of components  134  at dielectric rear housing wall  12 R. In one suitable arrangement, conductive coil  50  ( FIG. 7 ) may follow the outline of support structure  180  to loop around conductive foam  206 . In another suitable arrangement, conductive coil  50  may loop around support structure  180  (e.g., several turns of coil  50  may loop around some or all of support structure  180  so that support structure  180  forms a core for the coil). In this scenario, support structure  180  may, if desired, be formed from a conductive or magnetic core material that enhances the electromagnetic properties of coil  50 . 
     When rear housing wall  12 R is closed (e.g., by lowering wall  12 R onto sidewalls  12 W as shown by arrows  210 ), conductive foam  206  may come into contact with conductive layer  178  on main logic board  174 . In scenarios where layer  178  forms a portion of antenna ground  102 , conductive foam  206  may thereby form short circuit connection  138  between substrate  182  of components  134  and antenna ground  102  ( FIG. 6 ). Antenna resonating element trace  104  may be shorted to conductive layer  178  via return leg  122 . Return leg  122  may be a sheet of conductive material such as conductive foil or a conductive trace on a flexible printed circuit board, as examples. In another suitable arrangement, return leg  122  may be formed from a conductive spring structure. In yet another suitable arrangement, return leg  122  may be omitted and antenna resonating element  104  may be directly connected to conductor  178  (e.g., using solder or welds). When radio-frequency signals are fed to antenna resonating element trace  104  by transmission line  60 , antenna currents may be conveyed through portions  146 ,  144 ,  142 , and  140  of antenna resonating element trace  104  and may be shorted to conductive layer  178  (e.g., antenna ground  102 ) over return path  122 . Conductive layer  178  may be shorted to housing sidewalls  12 W at one or more locations so that sidewalls  12 W and conductive layer  178  collectively form antenna ground  102  of  FIG. 6 . 
     Transmission line  60  may be coupled to antenna resonating element trace  104  at positive antenna feed terminal  70  (e.g., signal conductor  66  of transmission line  60  may be coupled to positive antenna feed terminal  70 ). Transmission line  60  may be coupled to conductive layer  178  at ground antenna feed terminal  72  (e.g., ground conductor  68  of transmission line  60  may be coupled to ground antenna feed terminal  72 ). This example is merely illustrative. In general, positive antenna feed terminal  70  may be coupled to antenna resonating element trace  104  at any desired location. Ground antenna feed terminal  72  may be coupled to conductive layer  178  at any desired location or may be directly connected to metal housing sidewall  12 W. In an example where transmission line  60  is a coaxial cable, ground conductor  68  may be a braided outer conductor whereas signal conductor  66  is an inner signal conductor that is surrounded by outer conductor  68 . In general, transmission line  60  may be any desired radio-frequency transmission line structure. If desired, signal conductor  66  and antenna feed terminal  70  may be coupled to a feed leg that is coupled to antenna resonating element trace  104 . 
     Metal housing sidewalls  12 W may include mounting structures  220 . Mounting structures  220  may be metal frame structures, metal ledges, metal extensions, or other structures that are used to mount rear housing wall  12 R to housing sidewalls  12 W. Mounting structures  220  may have alignment structures such as holes  222 . When rear housing wall  12 R is placed over sidewalls  12 W (e.g., when rear wall  12 R is lowered in the direction of arrows  210 ), screws or other attachment mechanisms may pass through holes  222  for securing rear housing wall  12 R to side walls  12 W. The attachment mechanisms may also serve to short sidewalls  12 W to conductive layer  178  if desired. 
     If desired, exterior edge  132  along one or more sides of antenna resonating element trace  104  may have a curved shape that accommodates the shape of mounting structures  220 . In the example of  FIG. 9 , the exterior edge  132  of portions  140  and  144  may have a curved shape that accommodates the shape of mounting structures  220 . The curved shape of exterior edge  132  along portions  140  and  144  may prevent antenna resonating element  104  from being shorted to metal housing walls  12 W when rear housing wall  12 R is placed over conductive sidewalls  12 W. 
     Mounting structures  220  may be formed along one, two, three, or all four sides of housing sidewalls  12 W. If desired, antenna resonating element trace  104  may extend across all of the area on the interior surface of dielectric rear housing wall  12 R that is not otherwise occupied by components  134  and that is not in contact with the bottom side of sidewalls  12 W (e.g., mounting structures  220 ) when device  12 R is placed in contact with sidewalls  12 W. In this way, the area of the antenna resonating element may be maximized to optimize antenna performance without shorting the antenna resonating element to ground at locations other than return leg  122 . 
     In the example of  FIG. 9 , antenna resonating element trace  104  forms a conductive loop (ring) from antenna feed terminal  70  to return leg  122  (e.g., a loop that extends from trace portion  146  to the right of notch  136  to trace portion  144 , trace portion  142 , trace portion  140 , and trace portion  146  to the left of notch  136 ). In other words, return leg  122  and feed terminal  70  may be formed on opposing ends of the conductive loop formed by resonating element trace  104 . This example is merely illustrative. In general, return leg  122  may be coupled to antenna resonating element trace  104  at any other desired location. 
     In one suitable arrangement, return leg  122  may be coupled to antenna resonating element trace  104  along a side of device  10  that is coupled to a strap  16 . For example, return leg  122  may be coupled to portion  140  of antenna resonating element  104  at a location such as location  240 . When rear housing  12 R is secured to sidewalls  12 W, location  240  may be adjacent to the side of device  10  to which strap  16  is connected (e.g., side  8  of  FIG. 1 ). Placing return leg  122  at a location such as location  240  may minimize electromagnetic loading of antenna  40  by strap  16  (and any corresponding deterioration in antenna efficiency) in scenarios where strap  16  is formed from metal or other conductive materials. 
     The example of  FIG. 9  is merely illustrative. In general, antenna resonating element trace  104  may have any desired shape and may extend across any desired portions of rear housing wall  12 R. In general, antenna resonating element trace  104  need not surround components  180 ,  182 , and  206  on rear housing wall  12 R. For example, antenna resonating element trace  104  may be formed within region  242 , region  244 , region  246 , combinations of these regions, or any other desired region of rear housing wall  12 R adjacent to the periphery of components  134 . If desired, components  134  may be formed at other locations along rear housing wall  12 R such as in regions  242 ,  244 ,  246 , a combination of these regions, or other regions. Other feeding arrangements may be used if desired. For example, ground antenna feed terminal  72  may be coupled (e.g., directly connected) to antenna resonating element trace  104  instead of grounded conductor  178 . Ground antenna feed terminal  72  may be coupled to antenna resonating element trace  104  along portion  146 ,  140 ,  142 , or  144 . If desired, return leg  122  may be omitted in scenarios where ground antenna feed terminal  72  is coupled to antenna resonating element  104 . 
     If desired, tunable components such as tunable components  62  of  FIG. 3  may be coupled to antenna  40  at any desired locations for adjusting the performance and/or resonant frequency of antenna  40 . Tunable components  62  may, if desired, include adjustable matching circuitry coupled between transmission line  60  and antenna resonating element trace  104  or at any other desired location. 
     When configured in this way, antenna  40  may cover any desired frequency bands of interest, including cellular frequencies within a cellular telephone communications band from 700-960 MHz. In general, antenna  40  may handle radio-frequency signals above 700 MHz, such as signals at 2.4 GHz and/or 5 GHz for IEEE 802.11 communications, Bluetooth®, and/or other wireless local area network communications may be handled by peripheral antenna  40 P (as an example), low band cellular telephone signals (e.g., cellular telephone communications at frequencies between 700 MHz and 960 MHz), cellular telephone signals and GPS signals in a mid-band, a high band, and other bands that are above 960 MHz such as cellular telephone and GPS signals at 960-2700 MHz, radio-frequency signals at 2.4 GHz and/or 5 GHz for IEEE 802.11 communications, Bluetooth®, and/or other wireless local area network communications, and any other desired bands. By covering all of these bands using a single antenna  40 , the space that would have otherwise been occupied by additional antennas within device  10  may be used for other electronic device components or to further reduce the size (e.g., dimension  200  and/or  202  of  FIG. 8 ) of device  10  without sacrificing antenna efficiency. 
     If desired, control circuitry  28  may adjust tunable components  62  to cover the desired bands of interest and to compensate for any detuning of antenna  40  due to loading of the antenna by external objects. If desired, control circuitry  28  may adjust the tunable components based on instructions received from external equipment such as a wireless base station or access point. Control circuitry  28  may adjust the tunable components based on the current operating state of device  10 . For example, control circuitry  28  may identify a usage scenario (e.g., whether device  10  is being used to browse the internet, conduct a phone call, send an email, access GPS, etc.) to determine how to adjust tunable components  62 . As another example, control circuitry  28  may identify sensor data that is used to identify how to adjust tunable components  62  (e.g., optical sensor data, proximity sensor data, touch sensor data, data indicative of how close a user&#39;s body is to rear housing wall  12 R, impedance sensor data that is gathered by obtaining antenna impedance measurements from antenna  40  or other antennas in device  10 , etc.). In general, control circuitry  28  may process any desired combination of this information (e.g., information about a usage scenario of device  10 , sensor data, information from a wireless base station, user input, etc.) to identify how to adjust tunable components  62 . 
     In practice, the performance of antenna  40  may be optimized by the presence of an external object adjacent to rear housing wall  12 R. For example, the presence of a user&#39;s wrist adjacent to rear housing wall  12 R when the user is wearing device  10  may enhance the performance of antenna  40 . 
     Consider, as an example, the side view of the rear of device  10  of  FIG. 10 . In a configuration of the type shown in  FIG. 10 , dielectric rear housing wall  12 R may have a curved/circular shape or other shape that allows rear wall  12 R to be received within other portions of housing  12  (e.g., by metal housing sidewalls  12 W). Coil  50  may be formed from loops of conductive wire, loops of metal traces on a printed circuit, or other loops of conductive signal paths. Coil  50  may be placed into direct contact with the interior surface of rear housing wall  12 R. Antenna resonating element traces  104  may be patterned directly onto the interior surface of rear housing wall  12 R and may surround coil  50 . Rear housing wall  12 R may have a curved outer surface that rests against a user&#39;s body (e.g., wrist  250 ) when device  10  is worn by a user. If desired, rear wall  12 R may have an opening with one or more transparent windows such as window  188 . Light-based components such as sensors  186  may be mounted in alignment with windows such as window  188 . 
     During operation, antenna resonating element  104  may transmit and/or receive radio-frequency signals having electric fields that are oriented normal to the surfaces of rear face  12 R and wrist  180 . These signals may sometimes be referred to as surface waves, which are then propagated along the surface of wrist  250  and outwards (e.g., antenna resonating element traces  104  and wrist  250  may serve as a waveguide that directs the surface waves outwards). 
       FIG. 11  is a cross-sectional side view showing how the electromagnetic signals generated by antenna  40  may be propagated outwards due to the presence of the user&#39;s wrist. As shown in  FIG. 11 , contour lines  270  indicate contours of constant electric field magnitude. The magnitude of the electric field generated by antenna  40  is highest in the space between device  10  and wrist  250 . The signals may propagate along resonating element trace  104  and the surface of wrist  250  in an outward direction away from device  10 , as shown by paths  272 . This may allow the signals to be properly received by external communications equipment even though antenna  40  is located close to wrist  250 . In practice, the presence of wrist  250  may even serve to enhance the propagation of the electromagnetic waves relative to situations when wrist  250  is not present. For example, the radio-frequency signals emitted by antenna  40  may not be properly directed in the absence of wrist  250 , resulting in poor or unsatisfactory wireless link quality with the external equipment. However, in the presence of wrist  250 , the signals may be properly directed as shown by arrows  272 , thereby allowing for a satisfactory link quality to be obtained. The example of  FIG. 11  is merely illustrative. In general, the electric field patterns may have any desired shape or configuration. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20170720
Publication Date: 20200505
Grant Date: 20200505
Priority Date: 20160923
Inventors: DA COSTA BRAS LIMA, EDUARDO JORGE
Ruaro, Andrea
DI NALLO, CARLO
NATH, JAYESH
Martinis, Mario
WANG, ZHEYU
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/273", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/273", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/385", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M2201/38", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/521", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/521", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/385", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M2201/38", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/273", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 60409641