PATENT DOCUMENT

Publication Number: US-9318806-B2
Application Number: US-201314058024-A
Country: US
Kind Code: B2

Title: Electronic device with balanced-fed satellite communications antennas

Abstract:
An electronic device may include balance-fed antenna structures that do not have direct paths to ground. The antenna structures may serve as a Global Positioning System (GPS) antenna and may have a dipole structure having a first and second antenna resonating element arms. The antenna structures may include a conductive path that conveys antenna signals between a first feed terminal on the first antenna resonating element arm and a transmission line. The conductive path may overlap with the second antenna resonating element arm such that current flow through the conductive path induces corresponding current flow in the second antenna resonating element arm. The antenna structures may include an impedance matching short-circuit stub path that couples the first antenna resonating element arm to the second antenna resonating element arm. Choke inductors may be used to help block indirect paths from the antenna structures to ground through adjacent circuitry.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 ground structures; 
 balance-fed dipole antenna structures that are not electrically connected to any of the ground structures and that receive satellite communications signals, wherein the balance-fed dipole antenna structures comprise a conductive path and a first antenna resonating element arm that comprises a plurality of antenna resonating element arm portions, the conductive path being connected to a given antenna resonating element arm portion that is located at a distance from the ground structures that is greater than each other antenna resonating element arm portion of the plurality of antenna resonating element arm portions; and 
 radio-frequency receiver circuitry that processes the received satellite communications signals. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the balance-fed dipole antenna structures form a Global Positioning System antenna. 
     
     
       3. The electronic device defined in  claim 2  further comprising:
 an unbalanced transmission line that is coupled to the balance-fed dipole antenna structures and is coupled to the ground structures. 
 
     
     
       4. The electronic device defined in  claim 3  wherein the conductive path conveys antenna signals between the unbalanced transmission line and the first antenna resonating element arm, the balance-fed dipole antenna structures further comprising:
 a second antenna resonating element arm that overlaps with the conductive path, wherein current flow through the conductive path induces corresponding current flow in the second antenna resonating element arm. 
 
     
     
       5. The electronic device defined in  claim 4  wherein the balance-fed dipole antenna structures further comprise:
 a stub path that couples the first antenna resonating element arm to the second antenna resonating element arm and is configured to match the impedance of the balance-fed dipole antenna structures to the unbalanced transmission line. 
 
     
     
       6. The electronic device defined in  claim 5  wherein the first antenna resonating element arm has a meandering structure with at least two bends. 
     
     
       7. The electronic device defined in  claim 5  further comprising:
 a carrier structure on which the balance-fed dipole antenna structures are formed. 
 
     
     
       8. The electronic device defined in  claim 7  wherein the carrier structure comprises a flexible circuit substrate, the first and second antenna resonating element arms are formed in a first patterned metal layer on the flexible circuit substrate, and the conductive path is formed in a second patterned metal layer on the flexible circuit substrate. 
     
     
       9. The electronic device defined in  claim 8  further comprising:
 a via extending through the flexible circuit substrate that electrically connects the conductive path to the first antenna resonating element. 
 
     
     
       10. The electronic device defined in  claim 7  wherein the carrier structure comprises a plastic carrier structure and wherein the first and second antenna resonating element arms are plated onto the plastic carrier structure. 
     
     
       11. The electronic device defined in  claim 10  wherein the carrier structure comprises a camera housing, the electronic device further comprising:
 a flexible circuit substrate on which the camera housing is mounted; 
 an additional conductive path on the flexible circuit substrate that couples the camera housing to the ground structures; and 
 a choke inductor in the additional conductive path. 
 
     
     
       12. The electronic device defined in  claim 2  further comprising:
 ground structures; and 
 a chip balun having a first terminal coupled to the first antenna resonating element, a second terminal coupled to the second antenna resonating element, a third terminal coupled to the ground structures, and a fourth terminal, wherein the chip balun converts balanced radio-frequency receive signals at the first and second terminals to unbalanced radio-frequency receive signals at the fourth terminal. 
 
     
     
       13. Antenna structures, comprising:
 a first antenna resonating element arm; 
 a second antenna resonating element arm; 
 a first conductive path that is coupled to a first feed terminal on the first antenna resonating element arm and overlaps the second antenna resonating element arm, wherein a second feed terminal on the second antenna resonating element arm is indirectly fed by the conductive path; 
 a camera housing; 
 a flexible circuit substrate on which the camera housing is mounted; and 
 a second conductive path on the flexible circuit substrate that is coupled to the camera housing. 
 
     
     
       14. The antenna structures defined in  claim 13  further comprising:
 a stub path that couples the first antenna resonating element arm to the second antenna resonating element arm and impedance matches the antenna structures to a transmission line. 
 
     
     
       15. The antenna structures defined in  claim 14  further comprising:
 an additional flexible circuit substrate having opposing front and rear surfaces, wherein the first and second antenna resonating element arms are formed on the front surface, the first conductive path is formed on the rear surface, and the first conductive path is coupled to the first feed terminal on the first antenna resonating element arm by a via that extends through the flexible circuit substrate. 
 
     
     
       16. The antenna structures defined in  claim 14  further comprising:
 a plastic carrier, wherein the first and second resonating element arms are formed on multiple surfaces of the plastic carrier. 
 
     
     
       17. An electronic device, comprising:
 a balance-fed radio-frequency antenna; 
 ground structures; 
 circuitry that is coupled to the ground structures and adjacent to the balance-fed radio-frequency antenna; and 
 at least one choke inductor that is coupled between the circuitry and the ground structures. 
 
     
     
       18. The electronic device defined in  claim 17  wherein the balance-fed radiofrequency antenna comprises a Global Positioning System antenna that is not electrically connected to the ground structures. 
     
     
       19. The electronic device defined in  claim 18  wherein the circuitry comprises microphone circuitry and wherein the balance-fed radio-frequency antenna comprises:
 a first antenna resonating element arm; 
 a second antenna resonating element arm; and 
 a conductive path that is coupled to a feed point on the first antenna resonating element arm and overlaps with the second antenna resonating element arm, wherein an electric field between the conductive path and the second antenna resonating element arm aligns current in the conductive path to current in the second antenna resonating element during antenna operations.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with antennas. 
     Electronic devices often include antennas. For example, cellular telephones, computers, and other devices often contain antennas for supporting wireless communications. 
     It can be challenging to form electronic device antennas with desired attributes. In some wireless devices, an antenna is used for satellite communications such as Global Positioning System communications. The antenna is often formed with an unbalanced-fed arrangement having a shorting path to a ground plane. For example, an inverted-F antenna has a resonating element that is directly coupled to the ground plane by a shorting path. However, unbalanced-fed antennas having such shorting paths may produce undesirable antenna radiation characteristics. In particular, the shorting paths allow the formation of substantial antenna ground plane currents that can undesirably alter the radiation patterns of the antenna. 
     It would therefore be desirable to be able to provide improved antenna structures for electronic devices that are used for satellite communications. 
     SUMMARY 
     An electronic device may include balanced-fed antenna structures (sometimes referred to herein as balance-fed antenna structures). Balance-fed antenna structures do not have direct paths to ground and therefore are not electrically connected to any ground structures. The balance-fed antenna structures may serve as a Global Positioning System (GPS) antenna and may have a dipole structure having a first and second antenna resonating element arms. An unbalanced transmission line such as a coaxial cable may be coupled to the balance-fed dipole antenna structures and coupled to ground structures. The antenna structures may include a conductive path that conveys antenna signals between a first feed terminal on the first antenna resonating element arm and the unbalanced transmission line. The conductive path may overlap with the second antenna resonating element arm such that current flow through the conductive path induces corresponding current flow in the second antenna resonating element arm (and vice versa). The induced current flow in the second antenna resonating element arm serves to indirectly feed a second antenna feed terminal on the second antenna resonating element arm. The antenna structures may include a short-circuit stub path that couples the first antenna resonating element arm to the second antenna resonating element arm and is configured to match the impedance of the antenna structures to the transmission line. 
     The antenna structures may be formed on a carrier structure such as a flexible circuit substrate, housing of adjacent circuitry, plastic support structures, or other carrier structures on which the antenna resonating element arms may be formed. For example, the first and second antenna resonating element arms may be formed as first patterned metal layer on a flexible circuit substrate, whereas the conductive path may be formed as a second patterned metal layer that is coupled to the first patterned metal layer by a via that extends through the flexible circuit substrate. As another example, the antenna resonating element arms may be plated onto a plastic carrier. 
     Circuitry such as microphone circuitry, camera circuitry, or other circuitry may be adjacent to the antenna structures. The adjacent circuitry may be coupled to the ground structures via conductive paths. Choke inductors may be interposed in the conductive paths between the adjacent circuitry and the ground structures and serve to help block indirect paths from the antenna structures to ground while accommodating normal operations of the adjacent circuitry. The choke inductors block radio-frequency antenna signals while passing signals at lower frequencies associated with the adjacent circuitry. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a handheld electronic device with wireless circuitry in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a tablet computer with wireless circuitry in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an electronic device with wireless circuitry in accordance with an embodiment. 
         FIG. 4  is a schematic diagram of an illustrative electronic device with wireless circuitry in accordance with an embodiment. 
         FIG. 5  is a diagram showing how an electronic device may communicate with satellites in accordance with an embodiment. 
         FIG. 6  is an illustrative diagram of a balance-fed dipole antenna in accordance with an embodiment. 
         FIG. 7  is cross-sectional side view of an illustrative balance-fed dipole antenna formed on a substrate in accordance with an embodiment. 
         FIG. 8  is an illustrative diagram of a balance-fed dipole antenna that is coupled to a balun in accordance with an embodiment. 
         FIG. 9  is an illustrative diagram showing how choke inductors may be provided for circuitry adjacent to a balance-fed antenna to block indirect grounding paths in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of an illustrative electronic device having balance-fed antenna structures and adjacent circuitry in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative electronic device having balance-fed antenna structures formed on the housing of adjacent circuitry in accordance with an embodiment. 
         FIG. 12  is a perspective view of antenna structures formed in a first configuration on a carrier in accordance with an embodiment. 
         FIG. 13  is a perspective view of antenna structures formed in a second configuration on a carrier in accordance with an embodiment. 
         FIG. 14  is a perspective view of antenna structures formed on a carrier having a curved surface in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with antenna structures for satellite communications such as Global Positioning System (GPS) communications and the Global Navigation Satellite System (GLONASS). Satellite antenna structures may have an upper-hemisphere orientation that helps improve reception from GPS satellites located in the upper hemisphere. The GPS antenna structures may have a balance-fed architecture such that antenna currents are focused in antenna resonating elements and ground plane currents are reduced. 
     Illustrative electronic devices that have antenna structures with balance-fed architectures are shown in  FIGS. 1 and 2 . 
       FIG. 1  shows an illustrative configuration for electronic device  10  based on a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  has opposing front and rear surfaces. Display  14  is mounted on a front face of housing  12 . Display  14  may have an exterior layer that includes openings for components such as button  26 , speaker port  28 , and camera  38 . Antennas in device  10  of  FIG. 1  may be located at locations in housing  12  such as upper end  32  and lower end  34 . 
     In the example of  FIG. 2 , electronic device  10  is a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  has opposing front and rear surfaces. Display  14  is mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  has an external layer with an opening to accommodate button  26 . Antennas may be located in regions such as one or more regions  36  (e.g.,  36 A or  36 B) along the edge of housing  12  and display  14 . 
     Antennas may be provided in other electronic devices if desired. In general, device  10  may be 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 wrist-watch device, a pendant device, a headphone or earpiece device, 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. The illustrative configurations for device  10  that are shown in  FIGS. 1 and 2  are merely illustrative. 
     Housing  12  of device  10 , which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Display  14  of device  10  may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display  14  may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components. 
     A cross-sectional side view of an illustrative electronic device of the type that may be provided with antenna structures is shown in  FIG. 3 . As shown in  FIG. 3 , display  14  in device  10  may have display cover layer  40  and display module  42 . Display layers in display module  42  may include display pixels formed from liquid crystal display (LCD) components or other suitable display pixel structures such as organic light-emitting diode display pixels, electrophoretic display pixels, plasma display pixels, etc. The display pixels may be arranged in an array having numerous rows and columns to form a rectangular active area AA that is surrounded by an inactive border region such as inactive area IA. When viewed from the front of display  14 , inactive area IA may have the shape of a rectangular ring. 
     Display cover layer  40  may cover the surface of display  14  or a display layer such as a color filter layer (e.g., a layer formed from a clear substrate covered with patterned color filter elements) or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. To hide internal components from view, the underside of the outermost display layer or other display layer surface in inactive area IA may be coated with opaque masking layer  52  (e.g., a layer of opaque ink such as a layer of black ink). 
     Antenna structures  50  may be mounted under inactive area IA. Antenna structures  50  may include one or more antennas for device  10 . Antenna structures  50  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, closed and open slot antenna structures, planar inverted-F antenna structures, helical antenna structures, strip antennas, monopoles, dipoles, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. The example of  FIG. 3  in which antenna structures  50  are mounted under inactive area IA is merely illustrative. If desired, one or more antenna structures  50  may be mounted in any desired regions of device  10  (e.g., regions  32  or  34  of  FIG. 1 , regions  36 A or  36 B of  FIG. 2 , etc.). 
     Opaque masking layer  52  and display cover layer  40  may be radio-transparent, so that radio-frequency antenna signals can be transmitted and received through display cover layer  40  in inactive area IA and opaque masking layer  52 . Housing  12  may be formed from a dielectric such as plastic that is transparent to radio-frequency signals or may be formed from a material such as metal in which an antenna window such as antenna window  56  has been formed. Antenna window  56  may be formed from a dielectric such as plastic, so that antenna window  56  is transparent to radio-frequency signals. During operation, antenna signals associated with antenna structures  50  may pass through the portions of display  14  in inactive area IA that overlap antenna structures  50  and/or through antenna window  56  and/or other dielectric portions of housing  12 . 
     Device  10  may contain electrical components  46 . Components  46  may be mounted on one or more substrates such as printed circuit  44 . Printed circuit  44  may be a rigid printed circuit board (e.g., a printed circuit formed from a rigid printed circuit board material such as fiberglass-filled epoxy) or a flexible printed circuit (e.g., a flex circuit formed from a sheet of polyimide or other layer of flexible polymer). Electrical components  46  may include integrated circuits, connectors, sensors, light-emitting components, audio components, discrete devices such as inductors, capacitors, and resistors, switches, and other electrical devices. Paths such as path  48  may be used to couple antenna structures  50  to wireless circuitry on substrates such as printed circuit  44 . Paths such as path  48  may include transmission line paths such as stripline transmission lines, microstrip transmission lines, coplanar transmission lines, coaxial cable transmission lines, transmission lines formed on flexible printed circuits, transmission lines formed on rigid printed circuit boards, or other signal paths. 
       FIG. 4  is a diagram showing how antenna structures  50  may have a balance-fed arrangement. As shown in  FIG. 4 , electronic device  10  may include wireless circuitry  60 . Wireless circuitry  60  may include antenna structures  50 , radio-frequency transceiver circuitry  68 , and, if desired, other circuitry such as front-end circuitry (e.g., matching circuitry, etc.). 
     Antenna structures  50  may include one or more antennas. Antenna structures  50  may be used for transmitting and receiving wireless signals (as an example). Transceiver circuitry  68  may include transmitters and receivers for transmitting and receiving antenna signals through antenna structures  50 . For example, transceiver circuitry  68  may have a transmitter-receiver  72  for transmitting and receiving antenna signals and a receiver such as receiver  70  for receiving antenna signals such as cellular communications signals. Receiver  70  may, as an example, be configured to receive signals at GPS frequencies and/or GLONASS frequencies. Examples of GPS frequencies include 1575 MHz and 1227 MHz, whereas GLONASS frequencies may include 1602 MHz. Transmission line  74  may be used to route signals between transceiver circuitry  68  (e.g., receiver  70 ) and antenna structures  50 . Transmission line  74  may be an unbalanced transmission line such as a coaxial cable. For example, positive antenna feed signals may be conveyed between receiver  70  and antenna structures  50 , whereas ground antenna feed signals may be conveyed between receiver  70  and a ground terminal  76 . The ground terminal may be a point on ground structures such as the device housing, a ground plane, or other conductive ground structures. Antenna structures  50  has a balanced-fed configuration in which antenna structures  50  are not electrically connected (i.e., directly coupled by a conductive path) to ground. Balanced signals from the antenna structures may be converted to unbalanced signals for the transmission line using feed structures on antenna structures  50  or using a balun such as a chip balun. 
     The antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting GPS communications or other satellite navigation system communications, local area network communications, voice and data cellular telephone communications, Bluetooth® communications, etc. 
     As shown in  FIG. 4 , electronic device  10  may include control circuitry  62 . Control circuitry  62  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry 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 control circuitry  62  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Control circuitry  62  may be used to run software on device  10 , such as satellite navigation applications, 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, control circuitry  62  may be used in implementing communications protocols. Communications protocols that may be implemented using the storage and processing circuitry of control circuitry  62  include satellite navigation communications protocols, 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, etc. 
     Input-output circuitry in device  10  such as input-output devices  64  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  64  may include touch screens, buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  64  and may receive status information and other output from device  10  using the output resources of input-output devices  64 . 
       FIG. 5  is an illustrative diagram showing how satellite communications performance may be dependent on radiation patterns of an electronic device. As shown in  FIG. 5 , satellites  82  may be located in space around the Earth. Electronic device  10  that is located at the surface of the Earth may communicate with one or more satellites  82  that are located above device  10 . In other words, device  10  communicates with satellites located in the upper hemisphere. It may therefore be desirable to improve antenna sensitivity in the direction of satellites  82  that are located in the upper hemisphere (i.e., above device  10 ). Antenna performance for satellite communications performance is sometimes characterized by the sensitivity within a 0° window above device  10 . θ may, for example, be 120°. 
     Electronic devices such as device  10  may be operated in various orientations such as portrait or landscape. During satellite navigation operations, device  10  of  FIG. 2  may often be operated in a portrait mode in which antenna structures  36 A are directed towards the upper hemisphere satellites (along the Z axis) and antenna structures  36 B are closer to the Earth. It may therefore be desirable to configure an antenna in region  36 A and its radiation patterns for satellite navigation communications with upper hemisphere satellites. 
       FIG. 6  is a diagram of illustrative antenna structures  50  that may provide improved satellite navigation communications. Antenna structures  50  have a balance-fed arrangement in which antenna structures  50  are not electrically connected by a conductive path to any ground structures such as structures  92 . As shown in  FIG. 6 , antenna structures  50  may be coupled to an unbalanced transmission line at terminal  78 . The unbalanced transmission line may be grounded to ground plane  92 . For example, an outer conductor of a coaxial cable may be coupled to ground plane  92 , whereas the inner signal conductor may be coupled to terminal  78 . 
     Antenna structures  50  may include resonating element arms  94  and  96  that form a dipole structure. In the example of  FIG. 6 , resonating element arms  94  and  96  are configured in a meandering structure including multiple 90° bends, which helps to conserve space by reducing antenna area. In general, resonating element arms  94  and  96  may include bends of any desired degree (e.g., 45°, 90°, 180°, etc.) and may include zero or more bends. 
     Antenna structures  50  may be fed using a conductive path  100  that is coupled to terminal  78  and antenna resonating element arm  96 . Path  100  may be connected to antenna resonating element arm  96  via connection  102 . Conductive path  100  may be separated from antenna resonating element arms  94  and  96  by an intervening insulating layer such as a dielectric layer. Path  100  may provide positive antenna feed signals from feed terminal  78  to antenna resonating element arm  96 . Path  100  may overlap with segment  104  of antenna resonating element arm  94  so that currents flowing in path  100  generate an electric field that induces corresponding currents in segment  104  (e.g., due to near-field coupling). Similarly, currents flowing in segment  104  generate an electric field that induces corresponding currents in path  100 . In other words, the currents flowing through antenna resonating arm  94  are aligned with path  100  and are also therefore aligned with the currents flowing through antenna resonating arm  96 . Connection  102  and segment  104  effectively serve as respective first and second antenna feed terminals for antenna structures  50 . Segment  104  is indirectly fed via path  100 , whereas connection  102  is directly fed by path  100 . 
     Antenna resonating structures  50  may include conductive path  98  that electrically couples arms  94  and  96  and serves as a short-circuit stub path for impedance matching with a transmission line. Conductive path  98  includes a short-circuit portion located at a distance D away from connection  102 , which may be adjusted to match the impedance of antenna resonating structures  50  to the impedance of the transmission line coupled to feed terminal  78  at desired operating frequencies. For example, distance D may be selected based on the wavelength of a desired operating frequency for impedance matching. 
     Antenna feed path  100  may be connected to portion  108  of antenna resonating element arm  96  that is typically oriented towards the upper hemisphere (e.g., that is closer than other portions of arm  96  to satellites  82  in a portrait orientation of device  10  of  FIG. 5 ). As indicated by thicker arrows, antenna currents  110  are concentrated in portion  108  that is coupled to antenna feed path  100  and in mirror portion  112  of antenna resonating element arm  94 . In contrast, less current flows through portions such as portions  114  and  116  of the antenna resonating element arms. Portions  108  and  112  are located farther away from ground structures  92  than other portions such as portions  114  and  116 , which helps reduce any near-field coupling between antenna structures  50  and ground plane  92  and therefore helps to reduce ground plane currents. Consequently, antenna currents are substantially concentrated within antenna structures  50  and the radiation pattern of antenna structures  50  may be focused in direction Z (e.g., towards satellites in the upper hemisphere). 
     Antenna structures  50  may be formed as patterned layers on a substrate.  FIG. 7  is an illustrative cross-sectional side view of antenna structures  50  on substrate  112 . Substrate  112  may be a rigid or flexible printed circuit board on which multiple patterned metal layers are formed. In the example of  FIG. 7 , patterned metal layers  114  and  116  are formed on opposing front and rear surfaces of substrate  112 . Metal layer  114  may be patterned to form antenna resonating element arms  94  and  96 , whereas metal layer  116  may be patterned to form conductive path  100  that partially overlaps with resonating element arms  94  and  96 . Conductive path  100  of metal layer  116  may be electrically coupled to conductive path  96  of metal layer  114  by conductive via  102  that extends through substrate  112 . 
     The example of  FIG. 6  in which an unbalanced transmission line is adapted to feed balanced-fed antenna structures  50  is merely illustrative. If desired, balanced-fed antenna structures  50  may be fed using any desired balanced feeding arrangement.  FIG. 8  is an illustrative diagram of balanced-fed antenna structures  50  that is fed with antenna signals using balun  122  that adapts an unbalanced transmission line for balanced feeding. Balun  122  may receive or produce antenna feed signal RF_SIG at a positive input terminal and may be grounded at a ground input terminal. Balun  122  may convert balanced antenna signals RF_SIG′ that are received from resonating arms  94  and  96  of antenna structures  50  via connections  102  to unbalanced signal RF_SIG (and vice versa). Balun  122  may be implemented using circuitry on an integrated circuit (sometimes referred to as a chip balun). Chip balun  122  may provide improved bandwidth, whereas the feeding arrangement of  FIG. 6  may provide reduced cost. 
     Antenna structures  50  may be used in compact electronic devices such as portable electronic devices in which space is limited. In such scenarios, antenna structures  50  may be located adjacent to or within close proximity of nearby circuitry.  FIG. 9  is an illustrative diagram of a scenario in which antenna structures  50  are located adjacent to camera circuitry  138  and microphone circuitry  132 . Ground plane  92  may serve as an electrical ground for camera circuitry  138  and microphone circuitry  132 . Camera circuitry  138  may be coupled to ground plane  92  via path  140 , whereas microphone circuitry  132  may be coupled to ground plane  92  via path  134 . For example, camera circuitry  138  may be formed on a flexible circuit substrate and path  140  may be patterned metal on the flexible circuitry substrate that is connected to ground plane  92  or other ground structures. Similarly, microphone circuitry  132  or other adjacent circuitry may be formed on a flexible circuit substrate. 
     During wireless communications, radio-frequency signals received by antenna structures  50  can potentially couple to adjacent circuitry such as camera circuitry  138 , path  140 , microphone  132 , and path  134 . For example, electric fields produced by antenna currents can cause near-field coupling to camera circuitry  138 , path  140 , microphone circuitry  132 , and path  134 . Current that is induced in paths  134  and  140  by antenna currents may travel to ground plane  92  and cause ground plane  92  to resonate and produce wireless signals. Wireless emissions from ground plane  92  may be typically oriented away from the upper hemisphere during satellite navigation communications (e.g., when the electronic device is operated in a portrait mode). Ground plane emissions may therefore alter the radiation patterns of antenna structures  50 , as substantial power may be radiated by ground plane  92  instead of antenna structures  50 . Consequently, the antenna performance for satellite communications (e.g., 120° upper hemisphere performance) may be reduced. 
     Circuitry that is proximate or adjacent to antenna structures  50  may be provided with choke inductors that help to isolate ground structures from antenna currents. The choke inductors serve as high-frequency open circuits and low-frequency short circuits. In the example of  FIG. 9 , choke inductor  136  is coupled in series between path  134  and ground plane  92 . Choke inductor  136  blocks radio-frequency signals at frequencies associated with antenna structures  50  while passing low-frequency or direct-current (DC) signals associated with microphone circuitry  132 . Choke inductor  136  may therefore be sometimes referred to as a radio-frequency choke. As an example, microphone circuitry  132  may produce signals within an audible frequency range of 20 Hz to 20 kHz. In this scenario, choke inductor  136  may pass signals within the audible frequency range while blocking radio-frequency signals such as those used for GPS communications (e.g., at 1575 MHz, at 1227 MHz, etc.). In this way, choke inductor  136  may help block indirect grounding paths for antenna structures  50  without interfering with normal operation of microphone  132 . Choke inductor  136  may have an inductance between 220 nH and 520 nH (as an example). 
     Choke inductor  142  may be coupled between camera  138  and ground plane  92  to block radio-frequency antenna signals without interfering with camera operations (e.g., camera operations using direct-current or signals at frequencies lower than satellite communications frequencies). In general, choke inductors may be used to block indirect antenna current paths to ground, which helps to reduce ground plane currents and maintain the upper-hemisphere orientation of antenna structures  50 . 
       FIG. 10  is an illustrative cross-sectional view of a device  10  including antenna structures  50  and adjacent circuitry. In the example of  FIG. 10 , antenna structures  50  are formed on a flexible circuit substrate (e.g., as patterned layers on the flexible circuit substrate such as shown in  FIG. 7 ). Camera circuitry  138  and choke inductor  142  may be mounted on flexible circuit substrate  162 . Camera circuitry  138  may capture images from incident light received through camera lens  38 . Conductive paths such as path  140  of  FIG. 9  may be formed as a patterned metal layer on substrate  162 . Similarly, microphone  132  and choke inductor  134  may be mounted to flexible circuit substrate  164 . Antenna window  56  may pass radio-frequency signals to and/or from antenna structures  50  in scenarios in which housing  12  is formed of conductive materials. If desired, antenna window  56  may be omitted in scenarios such as when housing  12  passes radio-frequency signals (e.g., housing  12  is formed from plastic). 
     The example of  FIG. 10  in which antenna structures  50  are formed with patterned metal layers on a flexible substrate is merely illustrative. If desired, antenna structures may be formed from patterned metal layers on any desired carrier structure.  FIG. 11  is an illustrative diagram showing how antenna structures  50  may be formed on camera circuitry  138 . As shown in  FIG. 11 , antenna structures  50  may be formed as a patterned metal layer on exterior surfaces of camera module  138 . Antenna structures  50  may be formed on one or more surfaces of camera module  138  using laser direct structuring (LDS) tools. For example, camera circuitry  138  may have a plastic housing. A laser may be used to etch the pattern of antenna structures  50  on the exterior surfaces of the plastic housing, which activates the etched regions. Subsequently, the plastic housing may be plated with a metal such as copper (e.g., via electroless plating) such that the copper is only plated on the activated regions of the camera housing to form antenna structures  50 . Choke inductors such as inductors  142  and  134  may be provided for adjacent circuitry such as camera circuitry  138  and microphone circuitry  132 . 
     Antenna structures on a carrier structure may have various configurations.  FIGS. 12 and 13  are perspective views of illustrative antenna structure configurations on carrier structures  172 . In the example of  FIG. 12 , antenna structures  50  has a balance-fed dipole structure similar to antenna structures  50  of  FIG. 6 . Antenna structures  50  may be formed from an antenna resonating element having arms  94  and  96  that are electrically coupled by short-circuit stub path  98 . As shown in  FIG. 12 , antenna structures  50  may be formed on multiple exterior surfaces of carrier structures  172  (e.g., on opposing top surface  174  and bottom surface  176 , and two opposing side surfaces  178  and  180 ). If desired, arms  94  and  96  may have meandering patterns including one or more bends on any given surface of carrier structure  172 . In the example of  FIG. 13 , antenna resonating element arm  94  may be formed on bottom surface  176 , top surface  174 , and side surfaces  182  and  178 , whereas antenna resonating element arm  96  may be formed on bottom surface  176 , top surface  174 , and side surfaces  184  and  178 . These examples are merely illustrative. Antenna structures  50  may be formed on any desired number of surfaces of a carrier structure and may include zero or more bends on each surface. The antenna structures may be formed by plating metal on the carrier structure using LDS tools. 
     If desired, carrier structures may include one or more curved surfaces on which antenna structures may be formed.  FIG. 14  is an illustrative perspective view of carrier structures  172  having a curved surface  192 . Non-linear surfaces such as curved surface  192  may help to accommodate constrained or irregular space within a device housing. For example, curved surface  192  may mate with a curved surface of device housing  12  of  FIG. 10  to more efficiently utilize the available space within housing  12 . Antenna resonating element arms  94  and  96  may be formed on curved surface  192  and other surfaces of carrier structure  172 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20131018
Publication Date: 20160419
Grant Date: 20160419
Priority Date: 20131018
Inventors: YARGA SALIH
SAMARDZIJA MIROSLAV
VAZQUEZ ENRIQUE AYALA
RAJAGOPALAN HARISH
LI QINGXIANG
SCHLUB ROBERT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/371", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/328", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 52825708