PATENT DOCUMENT

Publication Number: US-11239550-B2
Application Number: US-202016849776-A
Country: US
Kind Code: B2

Title: Electronic devices having compact ultra-wideband antennas

Abstract:
An electronic device may be provided with an antenna for receiving signals in first and second ultra-wideband communications bands. The antenna may include a shielding ring that runs around first and second arms. The first arm may radiate in the first band and the second arm may radiate in the second band. The first arm may have an end formed from a first segment of the ring and a radiating edge facing the second arm. The second arm may have an end formed from a second segment of the ring and a radiating edge facing the first arm. First and second sets of conductive vias may couple the ring to ground. The first set may form a return path for the first arm. The second set may form a return path for the second arm.

Claims:
What is claimed is: 
     
       1. Apparatus comprising:
 a substrate having at least first and second stacked dielectric layers; 
 ground traces on the first dielectric layer; 
 a shielding ring on the second dielectric layer, wherein the shielding ring has first and second segments; 
 conductive vias that couple the shielding ring to the ground traces through the substrate; 
 a first antenna resonating element arm on the second dielectric layer, wherein the first antenna resonating element arm extends from the first segment of the shielding ring to a first radiating edge; and 
 a second antenna resonating element arm on the second dielectric layer, wherein the second antenna resonating element arm extends from the second segment of the shielding ring to a second radiating edge, the second radiating edge being separated from the first radiating edge by a gap. 
 
     
     
       2. The apparatus of  claim 1 , wherein the conductive vias comprise first and second sets of conductive vias, the first set of conductive vias couples the first segment of the shielding ring to the ground traces, the first set of conductive vias forms a first return path for the first antenna resonating element arm, the second set of conductive vias couples the second segment of the shielding ring to the ground traces, and the second set of conductive vias forms a second return path for the second antenna resonating element arm. 
     
     
       3. The apparatus of  claim 2 , wherein the first segment of the shielding ring is located at a first side of the shielding ring and the second segment of the shielding ring is located at a second side of the shielding ring opposite the first side. 
     
     
       4. The apparatus of  claim 1 , further comprising:
 signal traces on the substrate, wherein the signal traces comprise first and second branches; 
 a first conductive feed via that couples the first branch to a first positive antenna feed terminal on the first antenna resonating element arm; and 
 a second conductive feed via that couples the second branch to a second positive antenna feed terminal on the second antenna resonating element arm. 
 
     
     
       5. The apparatus of  claim 1 , wherein the first antenna resonating element arm is configured to radiate in a first frequency band and the second antenna resonating element is configured to radiate in a second frequency band that is different from the first frequency band. 
     
     
       6. The apparatus of  claim 5 , wherein the first frequency band comprises a 6.5 GHz ultra-wideband communications band and the second frequency band comprises an 8.0 GHz ultra-wideband communications band. 
     
     
       7. The apparatus of  claim 1 , wherein the substrate comprises a flexible printed circuit substrate. 
     
     
       8. An electronic device comprising:
 a substrate; 
 a ground plane on a first surface of the substrate; 
 conductive traces on a second surface of the substrate, wherein the conductive traces comprise:
 a first antenna arm configured to radiate in a first frequency band, 
 a second antenna arm configured to radiate in a second frequency band that is different from the first frequency band, and 
 a ring that runs around the first and second antenna arms; 
 
 a first set of conductive vias that couple the ring to the ground plane through the substrate and that short the first antenna arm to the ground plane; and 
 a second set of conductive vias that couple the ring to the ground plane through the substrate and that short the second antenna arm to the ground plane. 
 
     
     
       9. The electronic device of  claim 8 , wherein the first antenna arm has a first radiating edge and the first antenna arm extends from a first segment of the ring to the first radiating edge. 
     
     
       10. The electronic device of  claim 9 , wherein the second antenna arm has a second radiating edge, the second antenna arm extends from a second segment of the ring to the second radiating edge, and the first radiating edge is separated from the second radiating edge by a gap at the second surface of the substrate. 
     
     
       11. The electronic device of  claim 10 , further comprising:
 a dielectric cover layer; and 
 a conductive support plate on the dielectric cover layer, wherein the conductive support plate has an opening, the substrate is mounted within the opening and against the dielectric cover layer, and the first and second resonating element arms are configured to radiate through the dielectric cover layer. 
 
     
     
       12. The electronic device of  claim 11 , further comprising:
 a display, wherein the dielectric cover layer forms a housing wall for the electronic device opposite the display. 
 
     
     
       13. The electronic device of  claim 11 , further comprising:
 a shielding layer that covers the opening and the substrate. 
 
     
     
       14. The electronic device of  claim 11 , further comprising:
 a flexible printed circuit tail extending from the substrate, wherein the flexible printed circuit tail has at least one bend. 
 
     
     
       15. The electronic device of  claim 8 , further comprising:
 a radio-frequency transmission line having a signal conductor on the substrate, wherein the signal conductor includes first and second branches; 
 a first conductive feed via that couples the first branch to a first positive antenna feed terminal on the first antenna arm; and 
 a second conductive feed via that couples the second branch to a second positive antenna feed terminal on the second antenna arm. 
 
     
     
       16. The electronic device of  claim 8 , wherein the first frequency band comprises a 6.5 GHz ultra-wideband communications band and the second frequency band comprises an 8.0 GHz ultra-wideband communications band. 
     
     
       17. An antenna comprising:
 a ring of conductive traces having first and second segments; 
 a first arm having opposing first and second ends, wherein the first end is formed from the first segment of the ring of conductive traces, the first arm being configured to radiate in a first frequency band; 
 a first antenna feed coupled to the first arm; 
 a second arm having opposing third and fourth ends, wherein the fourth end faces the second end of the first arm, the second arm is configured to radiate in a second frequency band that is higher than the first frequency band, and the third end is formed from the second segment of the ring of conductive traces; 
 a second antenna feed coupled to the second arm; 
 a ground plane; and 
 a set of conductive vias that couples the first end of the first arm to the ground plane. 
 
     
     
       18. The antenna of  claim 17 , further comprising:
 an additional set of conductive vias that couples the third end of the second arm to the ground plane. 
 
     
     
       19. The antenna of  claim 18 , wherein the ring of conductive traces is configured to form a grounded shielding ring for the antenna. 
     
     
       20. The antenna of  claim 19 , wherein the first frequency band comprises a 6.5 GHz ultra-wideband communications band and the second frequency band comprises an 8.0 GHz ultra-wideband communications band.

Description:
BACKGROUND 
     This relates to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. Some electronic devices perform location detection operations to detect the location of an external device based on an angle of arrival of signals received from the external device (using multiple antennas). 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components for performing location detection operations using compact structures. At the same time, there is a desire for wireless devices to cover a growing number of frequency 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 the desired 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 may be provided with wireless circuitry and control circuitry. The wireless circuitry may include antennas that are used to determine the position and orientation of the electronic device relative to external wireless equipment. The control circuitry may determine the position and orientation of the electronic device relative to the external wireless equipment at least in part by measuring the angle of arrival of radio-frequency signals from the external wireless equipment. The radio-frequency signals may be received in at least first and second ultra-wideband communications bands. 
     The antennas may be formed on a flexible printed circuit structure. Each antenna may include a dielectric substrate on the flexible printed circuit structure. Ground traces may be patterned on a first surface of the dielectric substrate. Conductive traces may be patterned on a second surface of the dielectric substrate. The conductive traces may include a grounded shielding ring having opposing first and second sides and may include first and second antenna arms. The first arm may extend from the first side of the grounded shielding ring to a first radiating edge. The second arm may extend from the second side of the grounded shielding to a second radiating edge. The second radiating edge may face the first radiating edge and may be separated from the first radiating edge by a gap. The first arm may radiate in a first ultra-wideband communications band. The second arm may radiate in a second ultra-wideband communications band. 
     A first set of conductive vias may couple the first side of the grounded shielding ring to the ground traces. A second set of conductive vias may couple the second side of the grounded shielding ring to the ground traces. Additional conductive vias may couple other portions of the grounded shielding ring to the ground traces. The first set of conductive vias may short the first antenna arm to the ground traces and may thereby form a return path for the first antenna arm. The second set of conductive vias may short the second antenna arm to the ground traces and may thereby form a return path for the second antenna arm (e.g., the antenna may be a dual-band planar inverted-F antenna having antenna arms extending from opposing sides of the grounded shielding ring). At the same time, the first and second sets of conductive vias and the grounded shielding ring may help to isolate the antenna from electromagnetic interference. 
     The electronic device may have a dielectric cover layer and a conductive support plate on the dielectric cover layer. An opening may be formed in the conductive support plate. The dielectric substrate may be mounted within the opening. The first and second arms and the grounded shielding ring may be pressed against the dielectric cover layer. A flexible printed circuit tail may extend from the dielectric substrate. The flexible printed circuit tail may include one or more bends. When configured in this way, the antenna may be relatively immune to impedance discontinuities at the dielectric cover layer and may exhibit a relatively compact lateral footprint, thereby minimizing space consumption within the electronic device without sacrificing radio-frequency performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with some embodiments. 
         FIG. 2  is a schematic diagram of illustrative circuitry in an electronic device in accordance with some embodiments. 
         FIG. 3  is a schematic diagram of illustrative wireless circuitry in accordance with some embodiments. 
         FIG. 4  is a diagram of an illustrative electronic device in wireless communication with an external node in a network in accordance with some embodiments. 
         FIG. 5  is a diagram showing how the location (e.g., range and angle of arrival) of an external node in a network may be determined relative to an electronic device in accordance with some embodiments. 
         FIG. 6  is a diagram showing how illustrative antennas in an electronic device may be used for detecting angle of arrival in accordance with some embodiments. 
         FIG. 7  is a schematic diagram of an illustrative flexible printed circuit structure having antennas for detecting range and angle of arrival in accordance with some embodiments. 
         FIG. 8  is a cross-sectional side view showing how a portion of an illustrative flexible printed circuit structure having an antenna may be mounted within an opening in a conductive support plate in accordance with some embodiments. 
         FIG. 9  is a schematic diagram of illustrative inverted-F antenna structures in accordance with some embodiments. 
         FIG. 10  is a schematic diagram of illustrative dual-band inverted-F antenna structures in accordance with some embodiments. 
         FIG. 11  is a bottom view of an illustrative dual-band planar inverted-F antenna having low band and high band arms that share a return path and that are separated by a fence of conductive vias in accordance with some embodiments. 
         FIG. 12  is a bottom view of an illustrative dual-band planar inverted-F antenna having low band and high band arms that extend from a grounded shielding ring and that have separate return paths formed by respective fences of conductive vias in accordance with some embodiments. 
         FIG. 13  is a cross-sectional side view of an illustrative antenna of the type shown in  FIG. 12  in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless circuitry (sometimes referred to herein as wireless communications circuitry). The wireless circuitry may be used to support wireless communications in multiple wireless communications bands. Communications bands (sometimes referred to herein as frequency bands) handled by the wireless circuitry can include satellite navigation system communications bands, cellular telephone communications bands, wireless local area network communications bands, near-field communications bands, ultra-wideband communications bands, or other wireless communications bands. 
     The wireless circuitry may include one or more antennas. The antennas of the wireless circuitry can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, patch antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. 
     The conductive electronic device structures may include conductive housing structures. The conductive housing structures may include peripheral structures such as peripheral conductive structures that run around the periphery of the electronic device. The peripheral conductive structures may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, may have portions that extend upwards from an integral planar rear housing (e.g., to form vertical planar sidewalls or curved sidewalls), and/or may form other housing structures. 
     Gaps may be formed in the peripheral conductive structures that divide the peripheral conductive structures into peripheral segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . Antennas may also be formed using an antenna ground plane and/or an antenna resonating element formed from conductive housing structures (e.g., internal and/or external structures, support plate structures, etc.). 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Device  10  may also be a set-top box, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, a wireless access point, a wireless base station, an electronic device incorporated into a kiosk, building, or vehicle, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may be mounted on the front face of device  10 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or may be insensitive to touch. The rear face of housing  12  (i.e., the face of device  10  opposing the front face of device  10 ) may have a substantially planar housing wall such as rear housing wall  12 R (e.g., a planar housing wall). Rear housing wall  12 R may have slots that pass entirely through the rear housing wall and that therefore separate portions of housing  12  from each other. Rear housing wall  12 R may include conductive portions and/or dielectric portions. If desired, rear housing wall  12 R may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. Housing  12  may also have shallow grooves that do not pass entirely through housing  12 . The slots and grooves may be filled with plastic or other dielectric. If desired, portions of housing  12  that have been separated from each other (e.g., by a through slot) may be joined by internal conductive structures (e.g., sheet metal or other metal members that bridge the slot). 
     Housing  12  may include peripheral housing structures such as peripheral structures  12 W. Peripheral structures  12 W and conductive portions of rear housing wall  12 R may sometimes be referred to herein collectively as conductive structures of housing  12 . Peripheral structures  12 W may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, peripheral structures  12 W may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges and that extend from rear housing wall  12 R to the front face of device  10  (as an example). Peripheral structures  12 W or part of peripheral structures  12 W may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ) if desired. Peripheral structures  12 W may, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral structures  12 W may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, peripheral conductive sidewalls, peripheral conductive sidewall structures, conductive housing sidewalls, peripheral conductive housing sidewalls, sidewalls, sidewall structures, or a peripheral conductive housing member (as examples). Peripheral conductive housing structures  12 W may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming peripheral conductive housing structures  12 W. 
     It is not necessary for peripheral conductive housing structures  12 W to have a uniform cross-section. For example, the top portion of peripheral conductive housing structures  12 W may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral conductive housing structures  12 W may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral conductive housing structures  12 W may have substantially straight vertical sidewalls, may have sidewalls that are curved, or may have other suitable shapes. In some configurations (e.g., when peripheral conductive housing structures  12 W serve as a bezel for display  14 ), peripheral conductive housing structures  12 W may run around the lip of housing  12  (i.e., peripheral conductive housing structures  12 W may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     Rear housing wall  12 R may lie in a plane that is parallel to display  14 . In configurations for device  10  in which some or all of rear housing wall  12 R is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  12 W as integral portions of the housing structures forming rear housing wall  12 R. For example, rear housing wall  12 R of device  10  may include a planar metal structure and portions of peripheral conductive housing structures  12 W on the sides of housing  12  may be formed as flat or curved vertically extending integral metal portions of the planar metal structure (e.g., housing structures  12 R and  12 W may be formed from a continuous piece of metal in a unibody configuration). Housing structures such as these may, if desired, be machined from a block of metal and/or may include multiple metal pieces that are assembled together to form housing  12 . Rear housing wall  12 R may have one or more, two or more, or three or more portions. Peripheral conductive housing structures  12 W and/or conductive portions of rear housing wall  12 R may form one or more exterior surfaces of device  10  (e.g., surfaces that are visible to a user of device  10 ) and/or may be implemented using internal structures that do not form exterior surfaces of device  10  (e.g., conductive housing structures that are not visible to a user of device  10  such as conductive structures that are covered with layers such as thin cosmetic layers, protective coatings, and/or other coating layers that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide peripheral conductive housing structures  12 W and/or conductive portions of rear housing wall  12 R from view of the user). 
     Display  14  may have an array of pixels that form an active area AA that displays images for a user of device  10 . For example, active area AA may include an array of display pixels. The array of pixels may be formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels or other light-emitting diode pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. If desired, active area AA may include touch sensors such as touch sensor capacitive electrodes, force sensors, or other sensors for gathering a user input. 
     Display  14  may have an inactive border region that runs along one or more of the edges of active area AA. Inactive area IA may be free of pixels for displaying images and may overlap circuitry and other internal device structures in housing  12 . To block these structures from view by a user of device  10 , the underside of the display cover layer or other layers in display  14  that overlap inactive area IA may be coated with an opaque masking layer in inactive area IA. The opaque masking layer may have any suitable color. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, transparent ceramic, sapphire, or other transparent crystalline material, or other transparent layer(s). The display cover layer may have a planar shape, a convex curved profile, a shape with planar and curved portions, a layout that includes a planar main area surrounded on one or more edges with a portion that is bent out of the plane of the planar main area, or other suitable shapes. The display cover layer may cover the entire front face of device  10 . In another suitable arrangement, the display cover layer may cover substantially all of the front face of device  10  or only a portion of the front face of device  10 . Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button. An opening may also be formed in the display cover layer to accommodate ports such as speaker port  16  or a microphone port. Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.) and/or audio ports for audio components such as a speaker and/or a microphone if desired. 
     Display  14  may include conductive structures such as an array of capacitive electrodes for a touch sensor, conductive lines for addressing pixels, driver circuits, etc. Housing  12  may include internal conductive structures such as metal frame members and a planar conductive housing member (sometimes referred to as a backplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more metal parts that is welded or otherwise connected between opposing sides of peripheral conductive structures  12 W). The backplate may form an exterior rear surface of device  10  or may be covered by layers such as thin cosmetic layers, protective coatings, and/or other coatings that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide the backplate from view of the user. Device  10  may also include conductive structures such as printed circuit boards, components mounted on printed circuit boards, and other internal conductive structures. These conductive structures, which may be used in forming a ground plane in device  10 , may extend under active area AA of display  14 , for example. 
     In regions  22  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive housing structures  12 W and opposing conductive ground structures such as conductive portions of rear housing wall  12 R, conductive traces on a printed circuit board, conductive electrical components in display  14 , etc.). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and/or other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 , if desired. 
     Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  22  and  20  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, may contribute to the performance of a parasitic antenna resonating element, or may otherwise serve as part of antenna structures formed in regions  22  and  20 . If desired, the ground plane that is under active area AA of display  14  and/or other metal structures in device  10  may have portions that extend into parts of the ends of device  10  (e.g., the ground may extend towards the dielectric-filled openings in regions  22  and  20 ), thereby narrowing the slots in regions  22  and  20 . 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing (e.g., ends at regions  22  and  20  of device  10  of  FIG. 1 ), along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of these locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral conductive housing structures  12 W may be provided with peripheral gap structures. For example, peripheral conductive housing structures  12 W may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps in peripheral conductive housing structures  12 W may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide peripheral conductive housing structures  12 W into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral conductive housing structures  12 W (e.g., in an arrangement with two gaps  18 ), three peripheral conductive segments (e.g., in an arrangement with three gaps  18 ), four peripheral conductive segments (e.g., in an arrangement with four gaps  18 ), six peripheral conductive segments (e.g., in an arrangement with six gaps  18 ), etc. The segments of peripheral conductive housing structures  12 W that are formed in this way may form parts of antennas in device  10  if desired. 
     If desired, openings in housing  12  such as grooves that extend partway or completely through housing  12  may extend across the width of the rear wall of housing  12  and may penetrate through the rear wall of housing  12  to divide the rear wall into different portions. These grooves may also extend into peripheral conductive housing structures  12 W and may form antenna slots, gaps  18 , and other structures in device  10 . Polymer or other dielectric may fill these grooves and other housing openings. In some situations, housing openings that form antenna slots and other structure may be filled with a dielectric such as air. 
     In order to provide an end user of device  10  with as large of a display as possible (e.g., to maximize an area of the device used for displaying media, running applications, etc.), it may be desirable to increase the amount of area at the front face of device  10  that is covered by active area AA of display  14 . Increasing the size of active area AA may reduce the size of inactive area IA within device  10 . This may reduce the area behind display  14  that is available for antennas within device  10 . For example, active area AA of display  14  may include conductive structures that serve to block radio-frequency signals handled by antennas mounted behind active area AA from radiating through the front face of device  10 . It would therefore be desirable to be able to provide antennas that occupy a small amount of space within device  10  (e.g., to allow for as large of a display active area AA as possible) while still allowing the antennas to communicate with wireless equipment external to device  10  with satisfactory efficiency bandwidth. 
     In a typical scenario, device  10  may have one or more upper antennas and one or more lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  20 . A lower antenna may, for example, be formed at the lower end of device  10  in region  22 . Additional antennas may be formed along the edges of housing  12  extending between regions  20  and  22  if desired. The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, near-field communications, ultra-wideband communications, etc. 
     A schematic diagram of 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  28 . Control circuitry  28  may include storage such as storage circuitry  30 . Storage circuitry  30  may include 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. 
     Control circuitry  28  may include processing circuitry such as processing circuitry  32 . Processing circuitry  32  may be used to control the operation of device  10 . Processing circuitry  32  may include on one or more microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application specific integrated circuits, central processing units (CPUs), etc. Control circuitry  28  may be configured to perform operations in device  10  using hardware (e.g., dedicated hardware or circuitry), firmware, and/or software. Software code for performing operations in device  10  may be stored on storage circuitry  30  (e.g., storage circuitry  30  may include non-transitory (tangible) computer readable storage media that stores the software code). The software code may sometimes be referred to as program instructions, software, data, instructions, or code. Software code stored on storage circuitry  30  may be executed by processing circuitry  32 . 
     Control circuitry  28  may be used to run software on device  10  such as external node location applications, 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  28  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other WPAN protocols, IEEE 802.11ad protocols, cellular telephone protocols, MIMO protocols, antenna diversity protocols, satellite navigation system protocols (e.g., global positioning system (GPS) protocols, global navigation satellite system (GLONASS) protocols, etc.), IEEE 802.15.4 ultra-wideband communications protocols or other ultra-wideband communications protocols, etc. Each communications protocol may be associated with a corresponding radio access technology (RAT) that specifies the physical connection methodology used in implementing the protocol. 
     Device  10  may include input-output circuitry  24 . Input-output circuitry  24  may include input-output devices  26 . Input-output devices  26  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  26  may include user interface devices, data port devices, sensors, and other input-output components. For example, input-output devices may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, gyroscopes, accelerometers or other components that can detect motion and device orientation relative to the Earth, capacitance sensors, proximity sensors (e.g., a capacitive proximity sensor and/or an infrared proximity sensor), magnetic sensors, and other sensors and input-output components. 
     Input-output circuitry  24  may include wireless circuitry such as wireless circuitry  34  (sometimes referred to herein as wireless communications circuitry  34 ) for wirelessly conveying radio-frequency signals. 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). 
     While control circuitry  28  is shown separately from wireless circuitry  34  in the example of  FIG. 2  for the sake of clarity, wireless circuitry  34  may include processing circuitry that forms a part of processing circuitry  32  and/or storage circuitry that forms a part of storage circuitry  30  of control circuitry  28  (e.g., portions of control circuitry  28  may be implemented on wireless circuitry  34 ). As an example, control circuitry  28  (e.g., processing circuitry  32 ) may include baseband processor circuitry or other control components that form a part of wireless circuitry  34 . 
     Wireless circuitry  34  may include radio-frequency transceiver circuitry for handling various radio-frequency communications bands. For example, wireless circuitry  34  may include ultra-wideband (UWB) transceiver circuitry  36  that supports communications using the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols. Ultra-wideband radio-frequency signals may be based on an impulse radio signaling scheme that uses band-limited data pulses. Ultra-wideband signals may have any desired bandwidths such as bandwidths between 499 MHz and 1331 MHz, bandwidths greater than 500 MHz, etc. The presence of lower frequencies in the baseband may sometimes allow ultra-wideband signals to penetrate through objects such as walls. In an IEEE 802.15.4 system, a pair of electronic devices may exchange wireless time stamped messages. Time stamps in the messages may be analyzed to determine the time of flight of the messages and thereby determine the distance (range) between the devices and/or an angle between the devices (e.g., an angle of arrival of incoming radio-frequency signals). Ultra-wideband transceiver circuitry  36  may operate (i.e., convey radio-frequency signals) in frequency bands such as an ultra-wideband communications band between about 5 GHz and about 8.5 GHz (e.g., a 6.5 GHz UWB communications band, an 8 GHz UWB communications band, and/or at other suitable frequencies). 
     As shown in  FIG. 2 , wireless circuitry  34  may also include non-UWB transceiver circuitry  38 . Non-UWB transceiver circuitry  38  may handle communications bands other than UWB communications bands such as 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications or communications in other wireless local area network (WLAN) bands, the 2.4 GHz Bluetooth® communications band or other wireless personal area network (WPAN) bands, and/or cellular telephone frequency bands such as a cellular low band (LB) from 600 to 960 MHz, a cellular low-midband (LMB) from 1410 to 1510 MHz, a cellular midband (MB) from 1710 to 2170 MHz, a cellular high band (HB) from 2300 to 2700 MHz, a cellular ultra-high band (UHB) from 3300 to 5000 MHz, or other communications bands between 600 MHz and 5000 MHz or other suitable frequencies (as examples). 
     Non-UWB transceiver circuitry  38  may handle voice data and non-voice data. Wireless circuitry  34  may include circuitry for other short-range and long-range wireless links if desired. For example, wireless circuitry  34  may include 60 GHz transceiver circuitry (e.g., millimeter wave transceiver circuitry), circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. 
     Wireless circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable types of antenna structures. 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, dipole antenna structures, monopole antenna structures, hybrids of two or more of these designs, etc. If desired, one or more of antennas  40  may be cavity-backed antennas. 
     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 and another type of antenna may be used in forming a remote wireless link antenna. Dedicated antennas may be used for conveying radio-frequency signals in a UWB communications band or, if desired, antennas  40  can be configured to convey both radio-frequency signals in a UWB communications band and radio-frequency signals in a non-UWB communications band (e.g., wireless local area network signals and/or cellular telephone signals). Antennas  40  can include two or more antennas for handling ultra-wideband wireless communication. In one suitable arrangement that is described herein as an example, antennas  40  include one or more groups of three antennas (sometimes referred to herein as triplets of antennas) for handling ultra-wideband wireless communication. Antennas  40  may include one or more doublets (pairs) of antennas for handling ultra-wideband wireless communication if desired. 
     Space is often at a premium in electronic devices such as device  10 . In order to minimize space consumption within device  10 , the same antenna  40  may be used to cover multiple frequency bands. In one suitable arrangement that is described herein as an example, each antenna  40  that is used to perform ultra-wideband wireless communication may be a multi-band antenna that conveys (e.g., transmits and/or receives) radio-frequency signals in at least two ultra-wideband communications bands (e.g., the 6.5 GHz UWB communications band and the 8.0 GHz UWB communications band). In another suitable arrangement that is described herein as an example, each antenna  40  may convey radio-frequency signals in a single ultra-wideband communications band but antennas  40  may include different antennas that cover different ultra-wideband frequencies. Radio-frequency signals that are conveyed in UWB communications bands (e.g., using a UWB protocol) may sometimes be referred to herein as UWB signals or UWB radio-frequency signals. Radio-frequency signals in frequency bands other than the UWB communications bands (e.g., radio-frequency signals in cellular telephone frequency bands, WPAN frequency bands, WLAN frequency bands, etc.) may sometimes be referred to herein as non-UWB signals or non-UWB radio-frequency signals. 
     A schematic diagram of wireless circuitry  34  is shown in  FIG. 3 . As shown in  FIG. 3 , wireless circuitry  34  may include transceiver circuitry  42  (e.g., UWB transceiver circuitry  36  or non-UWB transceiver circuitry  38  of  FIG. 2 ) that is coupled to a given antenna  40  using a radio-frequency transmission line path such as radio-frequency transmission line path  50 . 
     To provide antenna structures such as antenna  40  with the ability to cover different frequencies of interest, antenna  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  40  may be provided with adjustable circuits such as tunable components that tune the antenna over communications (frequency) bands of interest. The tunable components may be part of a tunable filter or tunable impedance matching network, may be part of an antenna resonating element, may span a gap between an antenna resonating element and antenna ground, etc. 
     Radio-frequency transmission line path  50  may include one or more radio-frequency transmission lines (sometimes referred to herein simply as transmission lines). Radio-frequency transmission line path  50  (e.g., the transmission lines in radio-frequency transmission line path  50 ) may include a positive signal conductor such as positive signal conductor  52  and a ground signal conductor such as ground conductor  54 . 
     The transmission lines in radio-frequency transmission line path  50  may, for example, include coaxial cable transmission lines (e.g., ground conductor  54  may be implemented as a grounded conductive braid surrounding signal conductor  52  along its length), stripline transmission lines (e.g., where ground conductor  54  extends along two sides of signal conductor  52 ), a microstrip transmission line (e.g., where ground conductor  54  extends along one side of signal conductor  52 ), coaxial probes realized by a metalized via, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, waveguide structures (e.g., coplanar waveguides or grounded coplanar waveguides), combinations of these types of transmission lines and/or other transmission line structures, etc. In one suitable arrangement that is sometimes described herein as an example, radio-frequency transmission line path  50  may include a stripline transmission line coupled to transceiver circuitry  42  and a microstrip transmission line coupled between the stripline transmission line and antenna  40 . 
     Transmission lines in radio-frequency transmission line path  50  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, radio-frequency transmission line path  50  may include transmission line conductors (e.g., signal conductors  52  and ground conductors  54 ) integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive). The multilayer laminated structures may, if desired, be folded or bent in multiple dimensions (e.g., two or three dimensions) and may maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). 
     A matching network may include components such as inductors, resistors, and capacitors used in matching the impedance of antenna  40  to the impedance of radio-frequency transmission line path  50 . 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. Components such as these may also be used in forming filter circuitry in antenna(s)  40  and may be tunable and/or fixed components. 
     Radio-frequency transmission line path  50  may be coupled to antenna feed structures associated with antenna  40 . As an example, antenna  40  may form an inverted-F antenna, a planar inverted-F antenna, a patch antenna, or other antenna having an antenna feed  44  with a positive antenna feed terminal such as terminal  46  and a ground antenna feed terminal such as ground antenna feed terminal  48 . Signal conductor  52  may be coupled to positive antenna feed terminal  46  and ground conductor  54  may be coupled to ground antenna feed terminal  48 . Other types of antenna feed arrangements may be used if desired. For example, antenna  40  may be fed using multiple feeds each coupled to a respective port of transceiver circuitry  42  over a corresponding transmission line. If desired, signal conductor  52  may be coupled to multiple locations on antenna  40  (e.g., antenna  40  may include multiple positive antenna feed terminals coupled to signal conductor  52  of the same radio-frequency transmission line path  50 ). Switches may be interposed on the signal conductor between transceiver circuitry  42  and the positive antenna feed terminals if desired (e.g., to selectively activate one or more positive antenna feed terminals at any given time). The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     During operation, device  10  may communicate with external wireless equipment. If desired, device  10  may use radio-frequency signals conveyed between device  10  and the external wireless equipment to identify a location of the external wireless equipment relative to device  10 . Device  10  may identify the relative location of the external wireless equipment by identifying a range to the external wireless equipment (e.g., the distance between the external wireless equipment and device  10 ) and the angle of arrival (AoA) of radio-frequency signals from the external wireless equipment (e.g., the angle at which radio-frequency signals are received by device  10  from the external wireless equipment). 
       FIG. 4  is a diagram showing how device  10  may determine a distance D between device  10  and external wireless equipment such as wireless network node  60  (sometimes referred to herein as wireless equipment  60 , wireless device  60 , external device  60 , or external equipment  60 ). Node  60  may include devices that are capable of receiving and/or transmitting radio-frequency signals such as radio-frequency signals  56 . Node  60  may include tagged devices (e.g., any suitable object that has been provided with a wireless receiver and/or a wireless transmitter), electronic equipment (e.g., an infrastructure-related device), and/or other electronic devices (e.g., devices of the type described in connection with  FIG. 1 , including some or all of the same wireless communications capabilities as device  10 ). 
     For example, node  60  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, headset device (e.g., virtual or augmented reality headset devices), or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Node  60  may also be a set-top box, a camera device with wireless communications capabilities, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, or other suitable electronic equipment. Node  60  may also be a key fob, a wallet, a book, a pen, or other object that has been provided with a low-power transmitter (e.g., an RFID transmitter or other transmitter). Node  60  may be electronic equipment such as a thermostat, a smoke detector, a Bluetooth® Low Energy (Bluetooth LE) beacon, a Wi-Fi® wireless access point, a wireless base station, a server, a heating, ventilation, and air conditioning (HVAC) system (sometimes referred to as a temperature-control system), a light source such as a light-emitting diode (LED) bulb, a light switch, a power outlet, an occupancy detector (e.g., an active or passive infrared light detector, a microwave detector, etc.), a door sensor, a moisture sensor, an electronic door lock, a security camera, or other device. Device  10  may also be one of these types of devices if desired. 
     As shown in  FIG. 4 , device  10  may communicate with node  60  using wireless radio-frequency signals  56 . Radio-frequency signals  56  may include Bluetooth® signals, near-field communications signals, wireless local area network signals such as IEEE 802.11 signals, millimeter wave communication signals such as signals at 60 GHz, UWB signals, other radio-frequency wireless signals, infrared signals, etc. In one suitable arrangement that is described herein by example, radio-frequency signals  56  are UWB signals conveyed in multiple UWB communications bands such as the 6.5 GHz and 8 GHz UWB communications bands. Radio-frequency signals  56  may be used to determine and/or convey information such as location and orientation information. For example, control circuitry  28  in device  10  ( FIG. 2 ) may determine the location  58  of node  60  relative to device  10  using radio-frequency signals  56 . 
     In arrangements where node  60  is capable of sending or receiving communications signals, control circuitry  28  ( FIG. 2 ) on device  10  may determine distance D using radio-frequency signals  56  of  FIG. 4 . The control circuitry may determine distance D using signal strength measurement schemes (e.g., measuring the signal strength of radio-frequency signals  56  from node  60 ) or using time-based measurement schemes such as time of flight measurement techniques, time difference of arrival measurement techniques, angle of arrival measurement techniques, triangulation methods, time-of-flight methods, using a crowdsourced location database, and other suitable measurement techniques. This is merely illustrative, however. If desired, the control circuitry may use information from Global Positioning System receiver circuitry, proximity sensors (e.g., infrared proximity sensors or other proximity sensors), image data from a camera, motion sensor data from motion sensors, and/or using other circuitry on device  10  to help determine distance D. In addition to determining the distance D between device  10  and node  60 , the control circuitry may determine the orientation of device  10  relative to node  60 . 
       FIG. 5  illustrates how the position and orientation of device  10  relative to nearby nodes such as node  60  may be determined. In the example of  FIG. 5 , the control circuitry on device  10  (e.g., control circuitry  28  of  FIG. 2 ) uses a horizontal polar coordinate system to determine the location and orientation of device  10  relative to node  60 . In this type of coordinate system, the control circuitry may determine an azimuth angle θ and/or an elevation angle φ to describe the position of nearby nodes  60  relative to device  10 . The control circuitry may define a reference plane such as local horizon  64  and a reference vector such as reference vector  68 . Local horizon  64  may be a plane that intersects device  10  and that is defined relative to a surface of device  10  (e.g., the front or rear face of device  10 ). For example, local horizon  64  may be a plane that is parallel to or coplanar with display  14  of device  10  ( FIG. 1 ). Reference vector  68  (sometimes referred to as the “north” direction) may be a vector in local horizon  64 . If desired, reference vector  68  may be aligned with longitudinal axis  62  of device  10  (e.g., an axis running lengthwise down the center of device  10  and parallel to the longest rectangular dimension of device  10 , parallel to the Y-axis of  FIG. 1 ). When reference vector  68  is aligned with longitudinal axis  62  of device  10 , reference vector  68  may correspond to the direction in which device  10  is being pointed. 
     Azimuth angle θ and elevation angle φ may be measured relative to local horizon  64  and reference vector  68 . As shown in  FIG. 5 , the elevation angle φ (sometimes referred to as altitude) of node  60  is the angle between node  60  and local horizon  64  of device  10  (e.g., the angle between vector  67  extending between device  10  and node  60  and a coplanar vector  66  extending between device  10  and local horizon  64 ). The azimuth angle θ of node  60  is the angle of node  60  around local horizon  64  (e.g., the angle between reference vector  68  and vector  66 ). In the example of  FIG. 5 , the azimuth angle θ and elevation angle φ of node  60  are greater than 0°. 
     If desired, other axes besides longitudinal axis  62  may be used to define reference vector  68 . For example, the control circuitry may use a horizontal axis that is perpendicular to longitudinal axis  62  as reference vector  68 . This may be useful in determining when nodes  60  are located next to a side portion of device  10  (e.g., when device  10  is oriented side-to-side with one of nodes  60 ). 
     After determining the orientation of device  10  relative to node  60 , the control circuitry on device  10  may take suitable action. For example, the control circuitry may send information to node  60 , may request and/or receive information from  60 , may use display  14  ( FIG. 1 ) to display a visual indication of wireless pairing with node  60 , may use speakers to generate an audio indication of wireless pairing with node  60 , may use a vibrator, a haptic actuator, or other mechanical element to generate haptic output indicating wireless pairing with node  60 , may use display  14  to display a visual indication of the location of node  60  relative to device  10 , may use speakers to generate an audio indication of the location of node  60 , may use a vibrator, a haptic actuator, or other mechanical element to generate haptic output indicating the location of node  60 , and/or may take other suitable action. 
     In one suitable arrangement, device  10  may determine the distance between the device  10  and node  60  and the orientation of device  10  relative to node  60  using two or more ultra-wideband antennas. The ultra-wide band antennas may receive radio-frequency signals from node  60  (e.g., radio-frequency signals  56  of  FIG. 4 ). Time stamps in the wireless communication signals may be analyzed to determine the time of flight of the wireless communication signals and thereby determine the distance (range) between device  10  and node  60 . Additionally, angle of arrival (AoA) measurement techniques may be used to determine the orientation of electronic device  10  relative to node  60  (e.g., azimuth angle θ and elevation angle φ). 
     In angle of arrival measurement, node  60  transmits a radio-frequency signal to device  10  (e.g., radio-frequency signals  56  of  FIG. 4 ). Device  10  may measure a delay in arrival time of the radio-frequency signals between the two or more ultra-wideband antennas. The delay in arrival time (e.g., the difference in received phase at each ultra-wideband antenna) can be used to determine the angle of arrival of the radio-frequency signal (and therefore the angle of node  60  relative to device  10 ). Once distance D and the angle of arrival have been determined, device  10  may have knowledge of the precise location of node  60  relative to device  10 . 
       FIG. 6  is a schematic diagram showing how angle of arrival measurement techniques may be used to determine the orientation of device  10  relative to node  60 . As shown in  FIG. 6 , device  10  may include multiple antennas (e.g., a first antenna  40 - 1  and a second antenna  40 - 2 ) coupled to UWB transceiver circuitry  36  over respective radio-frequency transmission line paths (e.g., a first radio-frequency transmission line path  50 - 1  and a second radio-frequency transmission line path  50 - 2 ). UWB transceiver circuitry  36  and antennas  40 - 1  and  40 - 2  may operate at UWB frequencies (e.g., UWB transceiver circuitry  36  may convey (transmit and/or receive) UWB signals using antennas  40 - 1  and  40 - 2 ). 
     Antennas  40 - 1  and  40 - 2  may each receive radio-frequency signals  56  from node  60  ( FIG. 5 ). Antennas  40 - 1  and  40 - 2  may be laterally separated by a distance d 1 , where antenna  40 - 1  is farther away from node  60  than antenna  40 - 2  (in the example of  FIG. 6 ). Therefore, radio-frequency signals  56  travel a greater distance to reach antenna  40 - 1  than antenna  40 - 2 . The additional distance between node  60  and antenna  40 - 1  is shown in  FIG. 6  as distance d 2 .  FIG. 6  also shows angles a and b (where a+b=90°). 
     Distance d 2  may be determined as a function of angle a or angle b (e.g., d 2 =d 1 *sin(a) or d 2 =d 1 *cos(b)). Distance d 2  may also be determined as a function of the phase difference between the signal received by antenna  40 - 1  and the signal received by antenna  40 - 2  (e.g., d 2 =(PD)*λ/(2*π)), where PD is the phase difference (sometimes written “Δϕ”) between the signal received by antenna  40 - 1  and the signal received by antenna  40 - 2 , and λ is the wavelength of radio-frequency signals  56 . Device  10  may include phase measurement circuitry coupled to each antenna to measure the phase of the received signals and to identify phase difference PD (e.g., by subtracting the phase measured for one antenna from the phase measured for the other antenna). The two equations for d 2  may be set equal to each other (e.g., d 1 *sin(a)=(PD)*λ/(2*π)) and rearranged to solve for the angle a (e.g., a=sin −1 ((PD)*λ/(2*π*d 1 )) or the angle b. Therefore, the angle of arrival may be determined (e.g., by control circuitry  28  of  FIG. 2 ) based on the known (predetermined) distance d 1  between antennas  40 - 1  and  40 - 2 , the detected (measured) phase difference PD between the signal received by antenna  40 - 1  and the signal received by antenna  40 - 2 , and the known wavelength (frequency) of the received radio-frequency signals  56 . Angles a and/or b of  FIG. 6  may be converted to spherical coordinates to obtain azimuth angle θ and elevation angle φ of  FIG. 5 , for example. Control circuitry  28  ( FIG. 2 ) may determine the angle of arrival of radio-frequency signals  56  by calculating one or both of azimuth angle θ and elevation angle φ. 
     Distance d 1  may be selected to ease the calculation for phase difference PD between the signal received by antenna  40 - 1  and the signal received by antenna  40 - 2 . For example, d 1  may be less than or equal to one half of the wavelength (e.g., effective wavelength) of the received radio-frequency signals  56  (e.g., to avoid multiple phase difference solutions). 
     With two antennas for determining angle of arrival (as in  FIG. 6 ), the angle of arrival within a single plane may be determined. For example, antennas  40 - 1  and  40 - 2  in  FIG. 6  may be used to determine azimuth angle θ of  FIG. 5 . A third antenna may be included to enable angle of arrival determination in multiple planes (e.g., azimuth angle θ and elevation angle φ of  FIG. 5  may both be determined). The three antennas in this scenario may form a so-called triplet of antennas, where each antenna in the triplet is arranged to lie on a respective corner of a right triangle (e.g., the triplet may include antennas  40 - 1  and  40 - 2  of  FIG. 6  and a third antenna located at distance d 1  from antenna  40 - 1  in a direction perpendicular to the vector between antennas  40 - 1  and  40 - 2 ). Triplets of antennas  40  may be used to determine angle of arrival in two planes (e.g., to determine both azimuth angle θ and elevation angle φ of  FIG. 5 ). Triplets of antennas  40  and/or doublets of antennas (e.g., a pair of antennas such as antennas  40 - 1  and  40 - 2  of  FIG. 6 ) may be used in device  10  to determine angle of arrival. If desired, different doublets of antennas may be oriented orthogonally with respect to each other in device  10  to recover angle of arrival in two dimensions (e.g., using two or more orthogonal doublets of antennas  40  that each measure angle of arrival in a single respective plane). 
     If desired, each antenna in a triplet or doublet of antennas used by device  10  for performing ultra-wideband communications may be mounted to a common (shared) substrate such as a common flexible printed circuit structure.  FIG. 7  is a top-down view showing how antennas  40  may be mounted to a common flexible printed circuit structure. As shown in  FIG. 7 , two or more antennas for performing ultra-wideband communications (e.g., a triplet of antennas) may be mounted to flexible printed circuit structure  70 . Flexible printed circuit structure  70  may be bent or folded along one or more axes if desired (e.g., to accommodate the presence of other electronic device components in the vicinity of flexible printed circuit structure  70 ). 
     Flexible printed circuit structure  70  may include portions  72  (sometimes referred to herein as stub portions  72  or stubs  72 ). Antennas  40  for performing ultra-wideband communications may be formed within regions  80 ,  78 , and  74  on stubs  72  of flexible printed circuit structure  70 . For example, a triplet of antennas  40  for performing ultra-wideband communications may include a first antenna in region  74 , a second antenna in region  78 , and a third antenna in region  80 . 
     Radio-frequency transmission line paths (e.g., radio-frequency transmission line path  50  of  FIG. 3 ) may be formed on flexible printed circuit structure  70  and may be coupled to the antennas in regions  80 ,  78 , and  74 . Flexible printed circuit structure  70  may include one or more radio-frequency connectors  82  (e.g., at one or more of stubs  72  or elsewhere in flexible printed circuit structure  70 ). Radio-frequency connector  82  may couple the radio-frequency transmission line paths on flexible printed circuit structure  70  to transceiver circuitry in device  10  (e.g., transceiver circuitry  42  of  FIG. 3 ). The transceiver circuitry may, for example, be mounted to a different substrate such as a main logic board for device  10 . 
     Flexible printed circuit structure  70  may include, one, two, three, or more than three flexible printed circuits. Each flexible printed circuit may be mounted (e.g., soldered, surface mounted, adhered, etc.) to at least one other flexible printed circuit in flexible printed circuit structure  70  if desired. In one suitable arrangement, regions  80  and  78  are located on a first flexible printed circuit whereas region  74  is located on a second flexible printed circuit that is surface mounted to the first flexible printed circuit. In another suitable arrangement, each of regions  80 ,  78 , and  74  are located on respective flexible printed circuits that are surface mounted together. Radio-frequency connector  82  may be mounted to any desired location on flexible printed circuit structure  70 . 
     The example of  FIG. 7  is merely illustrative. In general, flexible printed circuit structure  70  may have any desired shape. Flexible printed circuit structure  70  need not include stubs  72  (e.g., flexible printed circuit structure  70  may have a rectangular shape or other shapes). One of regions  80 ,  78 , and  74  may be omitted in scenarios where only a doublet of antennas is formed on flexible printed circuit structure  70  for performing ultra-wideband communications. In another suitable arrangement, flexible printed circuit structure  70  of  FIG. 7  may be replaced with a rigid printed circuit board or other substrates for antennas  40 . If desired, other components may be mounted to flexible printed circuit structure  70  (e.g., input-output devices  26  or portions of control circuitry  28  of  FIG. 2 , additional antennas, etc.). 
       FIG. 8  is a cross-sectional side view showing how flexible printed circuit structure  70  may be mounted within device  10 . As shown in  FIG. 8 , device  10  may include a dielectric cover layer such as dielectric cover layer  84  and a conductive support plate such as conductive support plate  86  layered over (on) dielectric cover layer  84 . Dielectric cover layer  84  and conductive support plate  86  may, for example, form a housing wall for device  10  (e.g., rear housing wall  12 R of  FIG. 1 ). Conductive support plate  86  may be an integral portion of peripheral conductive housing walls  12 W ( FIG. 1 ) or may be welded or otherwise affixed to peripheral conductive housing walls  12 W if desired. Conductive support plate  86  may have an opening such as opening  88 . 
     Flexible printed circuit structure  70  may extend along conductive support plate  86 . Stub  72  of flexible printed circuit structure  70  may extend within opening  88  in conductive support plate  86 . Flexible printed circuit structure  70  may have an antenna substrate such as antenna substrate  92  at stub  72 . Antenna structures  94  may be formed on antenna substrate  92 . Antenna structures  94  may include portions of a given antenna  40  (e.g., antennas  40 - 1  or  40 - 2  of  FIG. 6 ) for conveying ultrawideband signals or other radio-frequency signals through dielectric cover layer  84 . Stub  72  (e.g., antenna structures  94 ) may be pressed within opening  88 , forming a bend such as bend  98  in flexible printed circuit structure  70 . Stub  72  and antenna structures  94  may thereby be located between upper surface  85  of conductive support plate  86  and dielectric cover layer  84 . Antenna structures  94  may be pressed against (e.g., in direct contact with) dielectric cover layer  84  (e.g., bend  98  may allow antenna structures  94  to be pressed against dielectric cover layer  84  despite the remainder of flexible printed circuit structure  70  being formed outside of opening  88 ). If desired, adhesive may be used to help adhere antenna structures  94  to dielectric cover layer  84 . 
     An electromagnetic shield such as conductive shielding layer  96  may be layered over conductive support plate  86  and flexible printed circuit structure  70 . Conductive shielding layer  96  may completely cover opening  88 . Conductive shielding layer  96  may be galvanically connected to conductive support plate  86  (e.g., using solder, welds, or other conductive adhesives), may be placed into contact with conductive support plate  86 , or may be separated from and capacitively coupled to conductive support plate  86 . Conductive shielding layer  96  may include sheet metal, conductive adhesive (e.g., copper tape having an adhesive layer), conductive traces on a dielectric substrate, conductive portions of the housing for device  10 , conductive foil, ferrite, or any other desired structures that block radio-frequency signals. In the absence of conductive shielding layer  96 , gap  90  may radiate in response to radio-frequency signals from polarizations other than the polarization handled by antenna structures  94 . This may introduce undesirable cross-polarization interference on the radio-frequency signals handled by antenna structures  94 . The presence of conductive shielding layer  96  may serve to block these radio-frequency signals from causing gap  90  to radiate, thereby mitigating cross-polarization interference for antenna structures  94 . The example of  FIG. 8  is merely illustrative. If desired, conductive components may overlap gap  90  to prevent cross-polarization interference. Conductive shielding layer  96  may be omitted if desired. Gap  90  may have a width of zero mm if desired (e.g., stub  72  may completely fill the lateral area of opening  88 ). 
     Pressing antenna structures  94  against dielectric cover layer  84  may help to provide a uniform impedance transition across the entire lateral area of antenna structures  94  from antenna structures  94  to free space at the exterior of device  10  (e.g., without any air gaps or bubbles between antenna structures  94  and dielectric cover layer  84  that would otherwise introduce undesirable impedance discontinuities to the system). However, in practice, the material used to form flexible printed circuit structure  70  may have a tendency to lie in a substantially planar shape. The presence of bend  98  may cause flexible printed circuit structure  70  to exhibit biasing forces  100  in the +Z direction. Biasing forces  100  may be particularly pronounced at the lateral corners of stub  72  and antenna structures  94 . Biasing forces  100  affect the impedance of the antenna structures in a direction parallel to the Z-axis (e.g., by introducing slight discontinuities in impedance between antenna structures  94  and dielectric cover layer  84  at the locations where the biasing forces are the strongest). Impedance discontinuities created by biasing forces  100  may be exacerbated by external forces applied to device  10  such as forces associated with drop events in which the device is dropped onto the floor or other surfaces. If care is not taken, these impedance discontinuities can undesirably limit the overall antenna efficiency for antenna structures  94  in one or more frequency bands. It may also be desirable to be able to reduce the lateral area of antenna structures  94  while still exhibiting satisfactory antenna efficiency across multiple frequency bands. 
     Any desired antenna structures may be used for implementing antennas  40  in regions  74 ,  80 , and  78  of  FIG. 7  (e.g., for implementing at least antennas  40 - 1  and  40 - 2  of  FIG. 6  for conveying UWB signals). In one suitable arrangement that is sometimes described herein as an example, planar inverted-F antenna structures may be used for implementing antennas  40 . Antennas that are implemented using planar inverted-F antenna structures may sometimes be referred to herein as planar inverted-F antennas. 
       FIG. 9  is a schematic diagram of inverted-F antenna structures that may be used to form antenna  40  (e.g., a given one of antennas  40 - 1  and  40 - 2  of  FIG. 6 ). As shown in  FIG. 9 , antenna  40  may include an antenna resonating element such as antenna resonating element  104  and an antenna ground such as antenna ground  108 . Antenna resonating element  104  may include a resonating element arm  102  (sometimes referred to herein as an antenna resonating element arm) that is shorted to antenna ground  108  by return path  106 . Antenna  40  may be fed by coupling a transmission line (e.g., a transmission line in radio-frequency transmission line path  50  of  FIG. 3 ) to positive antenna feed terminal  46  and ground antenna feed terminal  48  of antenna feed  44 . Positive antenna feed terminal  46  may be coupled to resonating element arm  102  and ground antenna feed terminal  48  may be coupled to antenna ground  108 . Return path  106  may be coupled between resonating element arm  102  and antenna ground  108  in parallel with antenna feed  44 . The length of resonating element arm  102  may determine the response (resonant) frequency of the antenna. 
     In the example of  FIG. 9 , antenna  40  is configured to cover only a single frequency band. If desired, antenna resonating element  104  may include multiple resonating element arms  102  that configure antenna  40  to cover multiple frequency bands.  FIG. 10  is a schematic diagram of dual-band inverted-F antenna structures that may be used to form antenna  40  (e.g., a given one of antennas  40 - 1  and  40 - 2  of  FIG. 6 ). As shown in  FIG. 10 , antenna resonating element  104  includes a first resonating element arm  102 L and a second resonating element arm  102 H extending from opposing sides of return path  106 . 
     The length of first resonating element arm  102 L (sometimes referred to herein as low band arm  102 L) may be selected to radiate in a first frequency band and the length of second resonating element arm  102 H (sometimes referred to herein as high band arm  102 H) may be selected to radiate in a second frequency band at higher frequencies than the first frequency band. As an example, low band arm  102 L may have a length that configures low band arm  102 L to radiate in the 6.5 GHz UWB communications band whereas high band arm  102 H has a length that configures high band arm  102 H to radiate in the 8.0 GHz UWB communications band. The term “radiate” as used herein refers to the excitation of an antenna resonating element by radio-frequency signals that are transmitted by the antenna resonating element and/or that are received by the antenna resonating element (e.g., within the frequency band(s) of operation of the antenna resonating element). 
     Antenna  40  of  FIG. 10  may be fed using two antenna feeds such as antenna feed  44 H and antenna feed  44 L. Antenna feed  44 H may include a positive antenna feed terminal  46 H coupled to high band arm  102 H. Antenna feed  44 L may include a positive antenna feed terminal  46 L coupled to low band arm  102 L. The ground antenna feed terminals of antenna feeds  44 L and  44 H are not shown in the example of  FIG. 10  for the sake of clarity. If desired, antenna feeds  44 L and  44 H may share the same ground antenna feed terminal. Positive antenna feed terminals  46 H and  46 L may both be coupled to the same transmission line (e.g., to the same signal conductor  52  as shown in  FIG. 3 ). This may, for example, optimize antenna efficiency of antenna  40  in both the frequency band covered by low band arm  102 L and the frequency band covered by high band arm  102 H (e.g., because antenna current may be conveyed to each resonating element arm over the corresponding positive antenna feed terminal without first shorting to ground over return path  106 ). 
     In one suitable arrangement that is sometimes described herein as an example, antenna  40  may be a dual-band planar inverted-F antenna. When configured as a dual-band planar inverted-F antenna, resonating element arms  102 H and  102 L may be formed using a conductive structure (e.g., a conductive trace or patch, sheet metal, conductive foil, etc.) that extends across a planar lateral area above antenna ground  108 . 
       FIG. 11  is a bottom-up view of dual-band planar inverted-F antenna structures that may be used to form antenna  40  (e.g., a given one of antennas  40 - 1  and  40 - 2  of  FIG. 6 ). As shown in  FIG. 11 , antenna resonating element  104  of antenna  40  (e.g., a dual-band planar inverted-F antenna) may be formed from conductive structures such as conductive traces on a surface of the antenna substrate  92  (e.g., on an upper-most surface of antenna substrate  92 ). Antenna substrate  92  may be formed from any desired dielectric materials such as epoxy, plastic, ceramic, glass, foam, polyimide, liquid crystal polymer, or other materials. In one suitable arrangement that is described herein as an example, antenna substrate  92  is a flexible printed circuit substrate having stacked layers of flexible printed circuit material (e.g., polyimide, liquid crystal polymer, etc.). Antenna substrate  92  may sometimes be referred to herein as dielectric substrate  92 . 
     As shown in  FIG. 11 , antenna resonating element  104  may have a planar shape with a length equal to the sum of the length L 2  of high band arm  102 H and the length L 1  of low band arm  102 L. Antenna resonating element  104  (e.g., each of resonating element arms  102 H and  102 L) may have a perpendicular width  114  such that antenna resonating element  104  has a planar shape that laterally extends in a given plane (e.g., the X-Y plane of  FIG. 11 ) parallel to the antenna ground (e.g., antenna ground  108  of  FIG. 10 ). In other words, low band arm  102 L has length L 1  and width  114  whereas high band arm  102 H has length L 2  and width  114 . The example of  FIG. 11  is merely illustrative and, if desired, low band arm  102 L and/or high band arm  102 H may have other shapes (e.g., shapes with cut-out regions to accommodate other components in the vicinity of antenna  40 , shapes having any desired number of curved and/or straight edges, etc.). In these scenarios, length L 1  may be the greatest lateral dimension of low band arm  102 L and length L 2  may be the greatest lateral dimension of high band arm  102 H, as an example. 
     Length L 2  may be selected to configure high band arm  102 H to radiate in a relatively high frequency band such as the 8.0 GHz UWB communications band. Length L 1  may be selected to configure low band arm  102 L to radiate in a relatively low frequency band such as the 6.5 GHz UWB communications band. For example, length L 2  may be approximately equal to (e.g., within 15% of) one-quarter of the effective wavelength corresponding to a frequency in the 8.0 GHz UWB communications band. Similarly, length L 1  may be approximately equal to one-quarter of the effective wavelength corresponding to a frequency in the 6.5 GHz UWB communications band. These effective wavelengths are modified from free-space wavelengths by a constant value associated with the dielectric material used to form antenna substrate  92  (e.g., the effective wavelengths are found by multiplying the freespace wavelengths by a constant value that is based on the dielectric constant d k  of antenna substrate  92 ). This example is merely illustrative and, in general, any desired frequency bands (e.g., UWB communications bands) may be covered by high band arm  102 H and low band arm  102 L. 
     Low band arm  102 L may be separated from high band arm  102 H in antenna resonating element  104  by a fence of conductive vias  112 . Conductive vias  112  extend from the upper-most surface of antenna substrate  92 , through antenna substrate  92 , and to an underlying ground plane (e.g., in the direction of the Z-axis of  FIG. 11 ). The fence of conductive vias  112  may form the return path for antenna  40  (e.g., return path  106  of  FIG. 10 ). 
     Each conductive via  112  may be separated from one or more adjacent conductive vias  112  by a sufficiently narrow distance such that the portion of antenna resonating element  104  to the left of the fence of conductive vias  112  appears as an open circuit (infinite impedance) to antenna currents in the 8.0 GHz UWB communications band and such that the portion of antenna resonating element  104  to the right of the fence of conductive vias  112  appears as an open circuit (infinite impedance) to antenna currents in the 6.5 GHz UWB communications band. As an example, each conductive via  112  in the fence may be separated from one or more adjacent conductive vias  112  by one-sixth of the wavelength covered by high band arm  102 H, one-eighth of the wavelength covered by high band arm  102 H, one-tenth of the wavelength covered by high band arm  102 H, one-fifteenth of the wavelength covered by high band arm  102 H, less than one-fifteenth of the wavelength covered by high band arm  102 H, less than one-sixth of the wavelength covered by high band arm  102 H, etc. 
     If desired, an electromagnetic shielding (guard) ring such as grounded shielding ring  110  may laterally surround antenna resonating element  104  at the upper-most surface of antenna substrate  92 . Grounded shielding ring  110  may be formed from conductive traces on the surface of antenna substrate  92 . The conductive traces of grounded shielding ring  110  may be shorted to the antenna ground (e.g., underlying planar ground traces) by fences of conductive vias  118  extending through antenna substrate  92 . Each conductive via  118  coupled to grounded shielding ring  110  may be separated from one or more adjacent conductive vias  118  by a sufficiently narrow distance such that the fences of conductive vias appear as a solid wall to radio-frequency signals at the frequency bands handled by antenna resonating element  104 . Grounded shielding ring  110  may serve to isolate and shield antenna  40  from electromagnetic interference. 
     Grounded shielding ring  110 , conductive vias  118 , and the underlying planar ground traces may collectively form antenna ground  108  of  FIG. 10  and may form (define) a conductive antenna cavity for antenna  40  that serves to optimize radio-frequency performance (e.g., antenna efficiency and bandwidth) for antenna  40 . The antenna ground may include ground traces on one or more layers of antenna substrate  92  beneath the upper-most layer of antenna substrate  92 . The ground traces may include planar ground traces extending underneath (e.g., overlapping) substantially all of antenna  40 . If desired, the ground traces may also include a ring of ground traces or ground traces in other shapes overlapping grounded shielding ring  110  but formed on a layer of antenna substrate  92  between the planar ground trace and the upper-most layer of antenna substrate  92 . Each layer of ground traces in antenna  40  may be coupled together using conductive vias if desired (e.g., so that all of the ground traces are held at the same ground potential). 
     Antenna  40  of  FIG. 11  may be fed using a radio-frequency transmission line path (e.g., radio-frequency transmission line path  50  of  FIG. 3 ). The radio-frequency transmission line path may include a transmission line such as stripline or microstrip transmission line. The transmission line may have signal traces  116  (e.g., forming a part of signal conductor  52  of  FIG. 3 ) coupled to antenna resonating element  104 . For example, signal traces  116  may have first and second branches respectively coupled to positive antenna feed terminals  46 L and  46 H on antenna resonating element  104 . 
     In the example of  FIG. 11 , antenna  40  is only capable of conveying radio-frequency signals with a single linear polarization. In other words, high band arm  102 H conveys radio-frequency signals in the 8.0 GHz UWB communications band with a given linear polarization and low band arm  102 L conveys radio-frequency signals in the 6.5 UWB communications band with the same linear polarization. Additional polarizations may be covered in device  10  by providing additional antennas oriented perpendicular to each other if desired. The example of  FIG. 11  is merely illustrative. If desired, antenna resonating antenna  40  and/or grounded shielding ring  110  may have other shapes (e.g., shapes having any desired number of straight and/or curved edges). 
     In the example of  FIG. 11 , antenna resonating element  104  is separated from grounded shielding ring  110  by both a first gap  121  and a second gap  123 . High band arm  102 H has a radiating edge  122  opposite conductive vias  112 . Low band arm has a radiating edge  120  opposite conductive vias  112 . The electric fields produced by antenna currents on antenna resonating element  104  may exhibit peak magnitudes at radiating edges  120  and  122  (e.g., within gaps  121  and  123 ). In general, antenna  40  is particularly susceptible to detuning and decreases in antenna efficiency due to impedance discontinuities at locations where the electric field magnitude is higher than at locations where the electric field magnitude is lower. Antenna  40  may therefore be particularly susceptible to impedance discontinuities at radiating edges  120  and  122  and at gaps  121  and  123 . However, biasing forces in the +Z direction such as biasing forces  100  of  FIG. 8  may create undesirable impedance discontinuities (e.g., in the +Z and −Z directions), particularly at the corners of antenna substrate  92  such as within regions  124  of  FIG. 11 . As shown in  FIG. 11 , regions  124  may at least partially overlap radiating edges  120  and  122  and gaps  121  and  123 , where antenna  40  is most sensitive to impedance discontinuities. These forces may therefore undesirably limit the antenna efficiency of antenna  40  in one or more frequency bands. At the same time, the presence of gaps  121  and  123  and conductive vias  112  may configure antenna  40  to exhibit a relatively large footprint L 3 . This may cause antenna  40  to occupy an excessive amount of space within device  10 . It may therefore be desirable to be able to provide antenna  40  with structures that are relatively immune to impedance discontinuities created by biasing forces  100  ( FIG. 8 ) and that exhibit as compact a footprint as possible. 
       FIG. 12  shows an arrangement for antenna  40  that is relatively immune to impedance discontinuities created by biasing forces  100  ( FIG. 8 ) and that exhibits a relatively compact footprint. As shown in  FIG. 12 , low band arm  102 L and high band arm  102 H may have edges that are defined by respective portions of grounded shielding ring  110  (e.g., low band arm  102 L, high band arm  102 H, and grounded shielding ring  110  may be formed from continuous conductive traces on antenna substrate  92  and may be deposited on antenna substrate  92  at the same time using the same printing/deposition process). In other words, low band arm  102 L and high band arm  102 H may be integral with grounded shielding ring  110 . Low band arm  102 L, high band arm  102 H, and grounded shielding ring  110  may form antenna structures  94  of  FIG. 8 , for example. 
     Low band arm  102 L may extend from a first (left) segment (side)  134  of grounded shielding ring  110  and towards high band arm  102 H (e.g., parallel to the X-axis). High band arm  102 H may extend from a second (right) segment (side)  136  of grounded shielding ring  110  and towards low band arm  102 L (e.g., parallel to the X-axis). Segment  134  of grounded shielding ring  110  may be the segment of grounded shielding ring  110  opposite to segment  136  of grounded shielding ring  110 . Grounded shielding ring  110  may have a third segment that extends perpendicular to segments  134  and  136  and that couples segment  134  to segment  136 . In this arrangement, antenna  40  may include separate return paths for low band arm  102 L and high band arm  102 H (e.g., return paths such as return path  106  of  FIGS. 9 and 10 ). The return paths for low band arm  102 L and high band arm  102 H may be formed from respective sets (fences) of the conductive vias  118  coupled to grounded shielding ring  110 . For example, the return path for low band arm  102 L may be formed from a first set (fence) of conductive vias  118  coupled to first segment  134  of grounded shielding ring  110  (e.g., where the first set of conductive vias shorts low band arm  102 L to the ground traces in the 6.5 GHz UWB communications band), whereas the return path for high band arm  102 H is formed from a second set (fence) of conductive vias  118  coupled to second segment  136  of grounded shielding ring  110  (e.g., where the second set of conductive vias shorts high band arm  102 H to the ground traces in the 8.0 GHz UWB communications band). 
     The edge of low band arm  102 L opposite the first set of conductive vias (segment  134  of grounded shielding ring  110 ) may form radiating edge  120  of low band arm  102 L (e.g., low band arm  102 L may have a first end defined by or formed from segment  134  of grounded shielding ring  110  and may have an opposing second end that forms radiating edge  120 ). The edge of high band arm  102 H opposite the second set of conductive vias (segment  136  of grounded shielding ring  110 ) may form radiating edge  122  of high band arm  102 H (e.g., high band arm  102 H may have a third end defined by or formed from segment  136  of grounded shielding ring  110  and may have an opposing fourth end that forms radiating edge  122 ). When arranged in this way, radiating edge  120  of low band arm  102 L faces radiating edge  122  of high band arm  102 H. 
     Radiating edge  120  is separated from radiating edge  122  by gap  138 . Gap  138 , low band arm  102 L, and high band arm  102 H may have width  114  parallel to the Y-axis. The length of low band arm  102 L from radiating edge  120  to the first set of conductive vias  118  may define the length L 1  of low band arm  102 L. The length of high band arm  102 H from radiating edge  122  to the second set of conductive vias  118  may define the length L 2  of high band arm  102 H. Length L 1  may be selected to configure low band arm  102 L to radiate in a relatively low frequency band such as the 6.5 GHz UWB communications band. Length L 1  may, for example, be approximately equal to one-quarter of the effective wavelength corresponding to a frequency in the 6.5 GHz UWB communications band. Similarly, length L 2  may, for example, be approximately equal to (e.g., within 15% of) one-quarter of the effective wavelength corresponding to a frequency in the 8.0 GHz UWB communications band. 
     As shown in  FIG. 12 , signal traces  116  may include a first branch  128  coupled to positive antenna feed terminal  46 L on low band arm  102 L (e.g., using a conductive feed via extending through antenna substrate  92 ). Signal traces  116  may also include a second branch  126  coupled to positive antenna feed terminal  46 H on high band arm  102 H (e.g., using a conductive feed via extending through antenna substrate  92 ). The length  132  of first branch  128  and/or the width of first branch  128  (as measured perpendicular to length  132 ) may be selected to help match the impedance of signal traces  116  to the impedance of low band arm  102 L (e.g., within the frequency band handled by low band arm  109 L). The length  130  of second branch  126  and/or the width of second branch  126  (as measured perpendicular to length  130 ) may be selected to help match the impedance of signal traces  116  to the impedance of high band arm  102 H (e.g., within the frequency band handled by high band arm  102 H). First branch  128  and/or second branch  126  may additionally or alternatively include one or more transmission line stubs and/or meandering segments to help match the impedance of signal traces  116  to the impedance of antenna resonating element  104  in one or more frequency bands. First branch  128  may be configured to form an open circuit (infinite) impedance in the frequency band handled by high band arm  102 H and second branch  126  may be configured to form an open circuit impedance in the frequency band handled by low band arm  102 L, if desired. 
     In the arrangement of  FIG. 12 , the radiating edges of antenna resonating element  104  (e.g., radiating edges  120  and  122 ) are located at or near the center of antenna substrate  92 . Antenna currents on low band arm  102 L may produce peak electric field magnitudes at radiating edge  120  and within gap  138 . Similarly, antenna currents on high band arm  102 H may produce peak electric field magnitudes at radiating edge  122  and within gap  138 . Because radiating edges  120  and  122  and gap  138  are located relatively far from the corners of antenna substrate  92  (e.g., radiating edges  120  and  122  and gap  138  do not overlap regions  124 ), any relatively strong biasing forces such as biasing forces  100  of  FIG. 8  will have little or no impact on the performance of antenna  40  (e.g., because the impedance discontinuities created by the biasing forces are concentrated within regions  124 , which are relatively far away from radiating edges  120  and  122  and gap  138 ). Antenna  40  of  FIG. 12  will therefore be able to operate with satisfactory antenna efficiency in both the 8.0 GHz and 6.5 GHz UWB frequency bands regardless of any impedance discontinuities created by biasing forces  100  of  FIG. 8 . At the same time, because antenna  40  only has a single gap  138  (as opposed to a pair of gaps such as gaps  121  and  123  of  FIG. 11 ) and because antenna  40  need not include an additional fence of conductive vias to separate low band arm  102 L and high band arm  102 H (e.g., conductive vias  112  of  FIG. 11 ), antenna  40  may exhibit a relatively compact lateral footprint L 4  that is less than lateral footprint L 3  of  FIG. 11 . The example of  FIG. 12  is merely illustrative. Low band arm  102 L, high band arm  102 H, and radiating edges  120  and  122  may have other shapes if desired. 
       FIG. 13  is a cross-sectional side view of antenna  40  of  FIG. 12  (e.g., as taken along line AA′ of  FIG. 12 ). As shown in  FIG. 13 , low band arm  102 L, high band arm  102 H, and grounded shielding ring  110  may be formed from conductive traces on surface  159  of antenna substrate  92  (e.g., may form antenna structures  94 ). Antenna substrate  92  may include one or more stacked layers  162  of dielectric material (e.g., flexible printed circuit material such as polyimide or liquid crystal polymer, ceramic, etc.). This example is merely illustrative and, if desired, one or more additional layers  162  of antenna substrate  92  may be formed over surface  159 . 
     Antenna substrate  92  may include a tail such as tail  142  (e.g., a flexible printed circuit tail) that extends beyond the lateral outline of antenna resonating element  104  (antenna  40 , antenna substrate  40 , and tail  142  may all form part of flexible printed circuit structure  70 ). Tail  142  may, for example, include one or more bends such as bend  98  of  FIG. 8  (e.g., tail  142  may form portions of flexible printed circuit structure  70  of  FIG. 7  outside of stubs  72 ). A radio-frequency transmission line for antenna  40  may be formed on tail  142  and may extend into antenna substrate  92 . Antenna substrate  92  may include conductive traces that form a ground plane (layer) such as planar ground traces  148 . Planar ground traces  148  may be formed on a surface of antenna substrate  92  or may be embedded within layers  162  of antenna substrate  92 . Planar ground traces  148  may form a part of the radio-frequency transmission line for antenna  40  and may extend under antenna resonating element  104  (e.g., antenna resonating element  104  may overlap planar ground traces  148 ). Conductive vias  144  may extend through tail  142  of flexible printed circuit substrate  92  to short the planar ground traces  148  to additional ground traces  150 . 
     The signal traces of the radio-frequency transmission line (e.g., signal traces  116  of  FIG. 12 ) may include first branch  128  and second branch  126  embedded in the layers  162  of antenna substrate  92 . Conductive feed via  154  may extend from first branch  128  to low band arm  102 L at positive antenna feed terminal  46 L. Conductive feed via  156  may extend from second branch  126  to high band arm  102 H at positive antenna feed terminal  46 H. Conductive feed vias  156  and  154  may be coupled to conductive contacts such as landing pads  146  at the interfaces between each layer  162  of antenna substrate  92  (only a single layer of landing pads  146  is shown in  FIG. 13  for the sake of clarity). 
     As shown in  FIG. 13 , grounded shielding ring  110  may be formed on surface  159  of antenna substrate  92 . Radiating edge  120  of low band arm  102 L may be separated from radiating edge  122  of high band arm  102 H at surface  159  by gap  138 . Grounded shielding ring  110  may be shorted to planar ground traces  148  by conductive vias  118  extending through antenna substrate  92 . Conductive vias  118  may be coupled to landing pads  146  at the interfaces between each layer  162  in antenna substrate  92 . 
     Conductive vias  118 , low band arm  102 L, high band arm  102 H, grounded shielding ring  110 , and planar ground traces  148  may define a continuous antenna cavity (volume)  158  for antenna  40 . In general, the bandwidth of antenna  40  is proportional to the size of antenna cavity  158 . The portion of surface  152  underlying antenna resonating element  104  may be free from grounded traces to maximize the size of antenna cavity  158  (e.g., allowing antenna cavity  158  to extend downward to planar ground traces  148 ). This may serve to maximize bandwidth and efficiency for antenna  40 . Grounded shielding ring  110  and conductive vias  118  may also serve to shield antenna  40  from external electromagnetic interference. 
     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: 20200415
Publication Date: 20220201
Grant Date: 20220201
Priority Date: 20200415
Inventors: COOPER, AARON J.
TAYEBI, AMIN
DI NALLO, CARLO
PAPIO TODA, ANA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/273", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/242", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/526", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/50", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/2258", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/526", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/526", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/446", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/422", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/526", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/446", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/422", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 78082572