PATENT DOCUMENT

Publication Number: US-11404783-B2
Application Number: US-202117147117-A
Country: US
Kind Code: B2

Title: Electronic device having dual-frequency ultra-wideband antennas

Abstract:
An electronic device may be provided with antennas for receiving signals in first and second ultra-wideband communications bands. The antennas may include a resonating element formed from conductive traces on a dielectric substrate. The substrate may be mounted to an underlying flexible printed circuit. A fence of conductive vias may extend from the resonating element, through the substrate and the flexible printed circuit, to a ground plane on the flexible printed circuit. The fence may form a return path for the antenna. A shielding ring may be formed on the substrate. Additional fences of vias may couple the shielding ring to the ground plane. If desired, the resonating element may include a patch that is not shorted to the ground plane. The fences of vias, the conductive traces, and the ground plane may form a continuous antenna cavity for the resonating element.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a printed circuit substrate; 
 a dielectric substrate mounted to the printed circuit substrate; 
 an antenna formed from a conductive trace on the dielectric substrate and configured to convey radio-frequency signals with a first polarization in an ultra-wideband communications band and to convey radio-frequency signals with a second polarization; 
 a radio-frequency transmission line in the printed circuit substrate and having a signal conductor trace coupled to the conductive trace through the printed circuit substrate and the dielectric substrate; and 
 a fence of conductive vias extending through the dielectric substrate and into the printed circuit substrate, and laterally surrounding the conductive trace. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the printed circuit substrate comprises a flexible printed circuit substrate for a flexible printed circuit. 
     
     
       3. The electronic device defined in  claim 2 , wherein the dielectric substrate comprises ceramic. 
     
     
       4. The electronic device defined in  claim 1 , further comprising:
 a ground plane on the printed circuit substrate, wherein the fence of conductive vias is coupled to the ground plane. 
 
     
     
       5. The electronic device defined in  claim 4 , wherein the radio-frequency transmission line has a ground conductor trace coupled to the ground plane. 
     
     
       6. The electronic device defined in  claim 4 , further comprising:
 a ring of conductive traces on the dielectric substrate that laterally surrounds the conductive trace, wherein the fence of conductive vias is coupled to the ring of conductive traces. 
 
     
     
       7. The electronic device defined in  claim 6 , wherein the fence of conductive vias, the ground plane, and the ring of conductive traces at least partly define an antenna cavity for the antenna. 
     
     
       8. The electronic device defined in  claim 7 , wherein the antenna cavity comprises the dielectric substrate and a portion of the printed circuit substrate extending from the dielectric substrate to the ground plane. 
     
     
       9. The electronic device defined in  claim 1 , wherein the radio-frequency signals with the second polarization comprise radio-frequency signals in an additional ultra-wideband communications band. 
     
     
       10. The electronic device defined in  claim 1 , wherein the conductive trace forms a patch element for the antenna. 
     
     
       11. The electronic device defined in  claim 10 , wherein the signal conductor trace is coupled to the conductive trace at a positive antenna feed terminal offset from a center of the patch element. 
     
     
       12. The electronic device defined in  claim 10 , wherein a positive antenna feed terminal at the patch element is configured to convey radio-frequency signals to excite a first radiating mode of the patch element associated with the first polarization and to excite a second radiating mode of the patch element associated with the second polarization. 
     
     
       13. The electronic device defined in  claim 1 , wherein the printed circuit substrate forms a flexible printed circuit, and the antenna has a patch element formed from the conductive trace and is configured to convey the radio-frequency signals with the second polarization in an additional ultra-wideband communications band at higher frequencies than the ultra-wideband communications band, the electronic device further comprising:
 a ground plane on the flexible printed circuit; 
 a ring of conductive traces on the dielectric substrate that laterally surrounds the patch element; and 
 an additional fence of conductive vias, the fence and the additional fence of conductive vias extending from the ring of conductive traces through the dielectric substrate and the flexible printed circuit to the ground plane, wherein the fence and additional fence of conductive vias, the ground plane, and the patch element define an antenna cavity for the antenna, the antenna cavity comprising the dielectric substrate and a portion of the flexible printed circuit extending from the dielectric substrate to the ground plane. 
 
     
     
       14. An electronic device comprising:
 a flexible printed substrate; 
 first and second antennas mounted on the flexible printed substrate and configured to handle ultra-wideband communications; 
 a dielectric substrate mounted to the flexible printed substrate, the first antenna having an antenna resonating element on the dielectric substrate; and 
 a set of conductive vias that extend through the dielectric substrate and are coupled to an antenna ground for the first antenna, the set of conductive vias laterally surrounding the antenna resonating element. 
 
     
     
       15. The electronic device defined in  claim 14 , wherein the antenna resonating element comprises a patch element. 
     
     
       16. The electronic device defined in  claim 14 , further comprising:
 a radio-frequency transmission line having a signal conductor on the flexible printed substrate; 
 a first additional conductive via that extends through the dielectric substrate to a positive antenna feed terminal at the antenna resonating element; and 
 a second additional conductive via that couples the first additional conductive via to the signal conductor. 
 
     
     
       17. The electronic device defined in  claim 14 , further comprising:
 a conductive trace on the dielectric substrate and laterally surrounding the antenna resonating element, the conductive trace being coupled to the antenna ground. 
 
     
     
       18. The electronic device defined in  claim 14 , further comprising:
 a first radio-frequency transmission line on the flexible printed substrate that is coupled to the first antenna; 
 a second radio-frequency transmission line on the flexible printed substrate that is coupled to the second antenna; and 
 a third radio-frequency transmission line on the flexible printed substrate that is configured to convey radio-frequency signals in a non-ultra-wideband communications frequency band. 
 
     
     
       19. An electronic device comprising:
 a flexible printed circuit; 
 a dielectric substrate mounted to the flexible printed circuit; 
 a ground plane on the flexible printed circuit; and 
 an antenna resonating element for an antenna formed from a conductive trace on the dielectric substrate and configured to convey radio-frequency signals in a first ultra-wideband communications band and to convey radio-frequency signals in a second ultra-wideband communications band at higher frequencies than the first ultra-wideband communications band; and 
 conductive structures on the dielectric substrate and on the flexible printed circuit that define an antenna cavity for the antenna. 
 
     
     
       20. The electronic device defined in  claim 19 , wherein the antenna cavity comprises a portion of the dielectric substrate and a portion of the flexible printed circuit.

Description:
This application is a divisional of U.S. patent application Ser. No. 16/277,808, filed on Feb. 15, 2019. This application claims priority to U.S. patent application Ser. No. 16/277,808, which is hereby incorporated by reference herein in its entirety. 
    
    
     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. 
     In one suitable arrangement, the antennas may include dual-band planar inverted-F antennas. Each antenna may include an antenna resonating element with a low band arm and a high band arm formed from conductive traces on a dielectric substrate. The high band arm may cover a first ultra-wideband communications band such as an 8.0 GHz ultra-wideband communications band. The low band arm may cover a second ultra-wideband communications band such as a 6.5 GHz ultra-wideband communications band. 
     The dielectric substrate may be a flexible printed circuit substrate formed from polyimide, liquid crystal polymer, or other materials. The dielectric substrate may be surface-mounted to an underlying flexible printed circuit. The antenna may include a first positive antenna feed terminal on the low band arm and a second positive antenna feed terminal on the high band arm. A fence of conductive vias may extend from the antenna resonating element, through the dielectric substrate and the flexible printed circuit, to a ground plane on the flexible printed circuit. The fence of conductive vias may form a return path for the antenna and may separate the low band arm from the high band arm. 
     A grounded shielding ring may be formed on the dielectric substrate. Additional fences of conductive vias may couple the grounded shielding ring to the ground plane through the dielectric substrate and the flexible printed circuit. The antenna may be fed using a stripline transmission line. The stripline may have a signal conductor that is coupled to the first and second positive antenna feed terminals using conductive vias extending through the dielectric substrate and the flexible printed circuit. The dielectric substrate and the flexible printed circuit may form an antenna cavity for the antenna resonating element. 
     In another suitable arrangement, the antennas may include dual-band patch antennas. In this scenario, the antenna may include a patch element formed from conductive traces on the dielectric substrate mounted to the flexible printed circuit. The dielectric substrate may be formed from ceramic when the antenna is implemented as a dual-band patch antenna. The patch element may have first opposing sides that configure the antenna to radiate in the 8.0 GHz ultra-wideband communications band and second opposing sides that configure the antenna to radiate in the 6.5 GHz ultra-wideband communications band. The fences of conductive vias coupled to the grounded shielding ring, the patch element, and the ground plane may form an antenna cavity for the patch element. The antenna cavity may include the dielectric substrate and a portion of the flexible printed circuit extending from the dielectric substrate to the ground plane. 
    
    
     
       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 top down view of an illustrative flexible printed circuit having antennas for detecting range and angle of arrival in accordance with some embodiments. 
         FIG. 8  is a schematic diagram of illustrative inverted-F antenna structures in accordance with some embodiments. 
         FIG. 9  is a schematic diagram of illustrative dual-band inverted-F antenna structures in accordance with some embodiments. 
         FIG. 10  is a top view of an illustrative dual-band planar inverted-F antenna that conveys radio-frequency signals in multiple ultra-wideband communications bands in accordance with some embodiments. 
         FIG. 11  is a cross-sectional side view of an illustrative dual-band planar inverted-F antenna formed on a dielectric substrate mounted to a flexible printed circuit in accordance with some embodiments. 
         FIG. 12  is a perspective view of an illustrative dual-band patch antenna that conveys radio-frequency signals in multiple ultra-wideband communications bands in accordance with some embodiments. 
         FIG. 13  is a cross-sectional side view of an illustrative dual-band patch antenna formed on a dielectric substrate mounted to a flexible printed circuit in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications 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 communications 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 communications circuitry may include one or more antennas. The antennas of the wireless communications 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 8.3 GHz (e.g., a 6.5 GHz frequency band, an 8 GHz frequency 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 3400 to 3600 MHz, or other communications bands between 600 MHz and 4000 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 sets of three antennas (sometimes referred to herein as triplets of antennas) for handling ultra-wideband wireless communication. 
     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 radio-frequency signals in at least two ultra-wideband communications bands (e.g., the 6.5 GHz band and the 8.0 GHz band). 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 path such as 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. 
     Path  50  may include one or more transmission lines. As an example, path  50  of  FIG. 3  may be a transmission line having a positive signal conductor such as line  52  and a ground signal conductor such as line  54 . Path  50  may sometimes be referred to herein as transmission line  50  or radio-frequency transmission line  50 . Line  52  may sometimes be referred to herein as positive signal conductor  52 , signal conductor  52 , signal line conductor  52 , signal line  52 , positive signal line  52 , signal path  52 , or positive signal path  52  of transmission line  50 . Line  54  may sometimes be referred to herein as ground signal conductor  54 , ground conductor  54 , ground line conductor  54 , ground line  54 , ground signal line  54 , ground path  54 , or ground signal path  54  of transmission line  50 . 
     Transmission line  50  may, for example, include a coaxial cable transmission line (e.g., ground conductor  54  may be implemented as a grounded conductive braid surrounding signal conductor  52  along its length), a stripline transmission line, a microstrip transmission line, coaxial probes realized by a metalized via, an edge-coupled microstrip transmission line, an edge-coupled stripline transmission line, a waveguide structure (e.g., a coplanar waveguide or grounded coplanar waveguide), combinations of these types of transmission lines and/or other transmission line structures, etc. 
     Transmission lines in device  10  such as transmission line  50  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, transmission lines such as transmission line  50  may also 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 transmission line  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. 
     Transmission line  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 transmission line  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  70  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 transmission lines (e.g., a first transmission line  50 - 1  and a second transmission line  50 - 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 dz.  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 substrate.  FIG. 7  is a top-down view showing how antennas  40  may be mounted to a common substrate such as a flexible printed circuit. 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  72  within region  74 . The antennas in region  74  may be fed using transmission lines  82 - 2  (e.g., a set of three transmission lines such as transmission line  50  of  FIG. 3 ). Transmission lines  82 - 2  may be coupled to UWB transceiver circuitry  36  of  FIG. 2  over radio-frequency connector  80 . Radio-frequency connector  80  may be a coaxial cable connector or any other desired radio-frequency connector. The UWB transceiver circuitry may be formed on a separate substrate such as a main logic board for device  10 . 
     If desired, other components may be mounted to flexible printed circuit  72  (e.g., input-output devices  26  or portions of control circuitry  28  of  FIG. 2 , additional antennas, etc.). Flexible printed circuit  72  may include additional radio-frequency transmission lines for routing radio-frequency signals for other antennas in device  10 . For example, flexible printed circuit  72  may include transmission lines  82 - 1  and  82 - 3 . Transmission line  82 - 1  may be coupled to an antenna that covers non-UWB frequency bands such as a WLAN frequency band via radio-frequency connector  76 . Similarly, transmission line  82 - 2  may be coupled to an antenna that covers non-UWB frequency bands such as cellular telephone frequency bands via radio-frequency connector  78 . Integrating different radio-frequency transmission lines for covering different frequency bands into the same flexible printed circuit  72  may serve to minimize space consumption and optimize transmission line routing within device  10 , for example. 
     The example of  FIG. 7  is merely illustrative. In general, flexible printed circuit  72  may have any desired shape and may include any desired number of radio-frequency connectors. If desired, some but not all of the antennas in a given triplet of antennas for conveying UWB signals may be formed in region  74 . One or more of the antennas in the triplet may be located on another substrate if desired. Flexible printed circuit  72  may be replaced with any other desired substrate such as a rigid printed circuit board, plastic substrate, etc. 
     Any desired antenna structures may be used for implementing the antennas in region  74  of  FIG. 7  (e.g., for implementing 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 - 1  and  40 - 2 . Antennas that are implemented using planar inverted-F antenna structures may sometimes be referred to herein as planar inverted-F antennas. 
       FIG. 8  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. 8 , antenna  40  may include an antenna resonating element such as antenna resonating element  86  and an antenna ground such as antenna ground  84 . Antenna resonating element  86  may include a resonating element arm  90  (sometimes referred to herein as an antenna resonating element arm) that is shorted to antenna ground  84  by return path  88 . Antenna  40  may be fed by coupling a radio-frequency transmission line (e.g., transmission line  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  90  and ground antenna feed terminal  48  may be coupled to antenna ground  84 . Return path  88  may be coupled between resonating element arm  90  and antenna ground  84  in parallel with antenna feed  44 . The length of resonating element arm  90  may determine the resonant frequency of the antenna. 
     In the example of  FIG. 8 , antenna  40  is configured to cover only a single frequency band. If desired, antenna resonating element  86  may include multiple resonating element arms  90  that configure antenna  40  to cover multiple frequency bands.  FIG. 9  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. 9 , antenna resonating element  86  includes a first resonating element arm  90 L and a second resonating element arm  90 H extending from opposing sides of return path  88 . 
     The length of first resonating element arm  90 L (sometimes referred to herein as low band arm  90 L) may be selected to radiate in a first frequency band and the length of second resonating element arm  90 H (sometimes referred to herein as high band arm  90 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  90 L may have a length that configures low band arm  90 L to radiate in the 6.5 GHz UWB band whereas high band arm  90 H has a length that configures high band arm  90 H to radiate in the 8.0 GHz UWB band. 
     Antenna  40  of  FIG. 9  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  90 H. Antenna feed  44 L may include a positive antenna feed terminal  46 L coupled to low band arm  90 L. The ground antenna feed terminals of antenna feeds  44 L and  44 H are not shown in the example of  FIG. 9  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 radio-frequency 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  90 L and the frequency band covered by high band arm  90 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  88 ). 
     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  90 H and  90 L may be formed using a conductive structure (e.g., a conductive trace, sheet metal, conductive foil, etc.) that extends across a planar lateral area above antenna ground  84 . 
       FIG. 10  is a top-down 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. 10 , antenna resonating element  86  of antenna  40  (e.g., a dual-band planar inverted-F antenna) may be formed from conductive structures such as conductive traces on the surface of an underlying dielectric substrate  92 . Dielectric 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, dielectric substrate  92  is a flexible printed circuit substrate having stacked layers of flexible printed circuit material (e.g., polyimide, liquid crystal polymer, etc.). Dielectric substrate  92  may therefore sometimes be referred to herein as flexible printed circuit substrate  92 . 
     As shown in  FIG. 10 , antenna resonating element  86  may have a planar shape with a length equal to the sum of the length  94  of high band arm  90 H and the length  96  of low band arm  90 L. Antenna resonating element  86  (e.g., each of resonating element arms  90 H and  90 L) may have a perpendicular width  95  such that antenna resonating element  86  has a planar shape that laterally extends in a given plane (e.g., the X-Y plane of  FIG. 10 ) parallel to the antenna ground (e.g., antenna ground  84  of  FIG. 9 ). In other words, low band arm  90 L has length  96  and width  95  whereas high band arm  90 H has length  94  and width  95 . 
     Length  94  may be selected to configure high band arm  90 H to radiate in a relatively high frequency band such as the 8.0 GHz UWB band. Length  96  may be selected to configure low band arm  90 L to radiate in a relatively low frequency band such as the 6.5 GHz UWB band. For example, length  94  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 band. Similarly, length  96  may be approximately equal to one-quarter of the effective wavelength corresponding to a frequency in the 6.5 GHz UWB band. These effective wavelengths are modified from free-space wavelengths by a constant value associated with the dielectric material used to form flexible printed circuit 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 flexible printed circuit substrate  92 ). This example is merely illustrative and, in general, any desired frequency bands (e.g., UWB communications bands) may be covered by resonating element arms  90 L and  90 H. 
     Low band arm  90 L may be separated from high band arm  90 H in antenna resonating element  86  by a fence of conductive vias  102 . Conductive vias  102  extend from the surface of flexible printed circuit substrate  92 , through flexible printed circuit substrate  92 , and to an underlying ground plane (e.g., in the direction of the Z-axis of  FIG. 10 ). The fence of conductive vias  102  may form the return path for antenna  40  (e.g., return path  88  of  FIG. 9 ). 
     Each conductive via  102  may be separated from one or more adjacent conductive vias  102  by a sufficiently narrow distance such that the portion of antenna resonating element  86  to the left of the fence of conductive vias  102  appears as an open circuit (infinite impedance) to antenna currents in the 6.5 GHz frequency band and such that the portion of antenna resonating element  86  to the right of the fence of conductive vias  102  appears as an open circuit (infinite impedance) to antenna currents in the 8.0 GHz frequency band. As an example, each conductive via  102  in the fence may be separated from one or more adjacent conductive vias  102  by one-sixth of the wavelength covered by high band arm  90 H, one-eighth of the wavelength covered by high band arm  90 H, one-tenth of the wavelength covered by high band arm  90 H, one-fifteenth of the wavelength covered by high band arm  90 H, less than one-fifteenth of the wavelength covered by high band arm  90 H, less than one-sixth of the wavelength covered by high band arm  90 H, etc. 
     If desired, a grounded shielding ring  98  may laterally surround antenna resonating element  86  at the surface of flexible printed circuit substrate  92 . Grounded shielding ring  98  may be formed from conductive traces on the surface of flexible printed circuit substrate  92 . The conductive traces of grounded shielding ring  98  are shorted to the antenna ground (e.g., an underlying ground plane) by fences of conductive vias  100  extending through flexible printed circuit substrate  92  (e.g., in the direction of the Z-axis of  FIG. 10 ). Grounded shielding ring  98  and conducive vias  100  may serve to isolate and shield antenna  40  from electromagnetic interference. Grounded shielding ring  98 , conductive vias  100 , and the underlying ground plane may collectively form antenna ground  84  of  FIG. 9  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 . 
     Antenna  40  of  FIG. 10  may be fed using a radio-frequency transmission line such as stripline  104  (e.g., a stripline used to form transmission line  50  of  FIG. 3  or one of transmission lines  82 - 2  of  FIG. 7 ). Stripline  104  may be formed on a flexible printed circuit underlying flexible printed circuit substrate  92  (e.g., flexible printed circuit substrate  92  may be mounted to the underlying flexible printed circuit used to form stripline  104 ). Stripline  104  may include grounded conductive traces  106  and fences of conductive vias  108  extending from grounded conductive traces  106  to an underlying ground plane (e.g., in the direction of the Z-axis of  FIG. 10 ). Each conductive via  108  may be separated from one or more adjacent conductive vias  108  and each conductive via  100  may be separated from one or more adjacent conductive vias  100  by one-eighth of the wavelength covered by high band arm  90 H, one-tenth of the wavelength covered by high band arm  90 H, one-fifteenth of the wavelength covered by high band arm  90 H, less than one-fifteenth of the wavelength covered by high band arm  90 H, less than one-sixth of the wavelength covered by high band arm  90 H, etc. 
     Stripline  104  may include signal conductor traces  110  (e.g., signal conductor traces that collectively form signal conductor  52  of  FIG. 3 ). Signal conductor traces  110  may be embedded within the flexible printed circuit underlying flexible printed circuit substrate  92 . Signal conductor traces  110  may include a first branch coupled to positive antenna feed terminal  46 H on high band arm  90 H and a second branch coupled to positive antenna feed terminal  46 L on low band arm  90 L. Conductive vias (not shown) may be used to couple signal conductor traces  110  in the underlying flexible printed circuit to positive antenna feed terminals  46 H and  46 L (e.g., through flexible printed circuit substrate  92 ). In this way, the same radio-frequency transmission line (stripline  104 ) may be used to feed both high band arm  90 H and low band arm  90 L of antenna  40 . 
     In the example of  FIG. 10 , antenna  40  is only capable of conveying radio-frequency signals with a single linear polarization. In other words, high band arm  90 H conveys radio-frequency signals in the 8.0 GHz UWB band with a given linear polarization and low band arm  90 L conveys radio-frequency signals in the 6.5 UWB 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. 10  is merely illustrative. If desired, antenna resonating antenna  40  and/or grounded shielding ring  98  may have other shapes (e.g., shapes having any desired number of straight and/or curved edges). 
       FIG. 11  is a cross-sectional side view of the dual-band planar inverted-F antenna of  FIG. 10  (e.g., as taken in the direction of arrow  112  of  FIG. 10 ). As shown in  FIG. 11 , antenna resonating element  86  may be formed from conductive traces on surface  116  of flexible printed circuit substrate  92 . Flexible printed circuit substrate  92  may include one or more stacked layers  122  of flexible printed circuit material (e.g., polyimide, liquid crystal polymer, etc.). This example is merely illustrative and, if desired, one or more additional layers  122  of flexible printed circuit substrate  92  may be formed over surface  116  and antenna resonating element  86 . 
     Flexible printed circuit substrate  92  may be mounted to the surface of an underlying flexible printed circuit. In the example of  FIG. 11 , flexible printed circuit substrate  92  is mounted to surface  120  of an underlying flexible printed circuit  124 . Flexible printed circuit  124  may include one or more stacked layers  126  of flexible printed circuit material (e.g., polyimide, liquid crystal polymer, etc.). While flexible printed circuit substrate  92  is shown with a greater thickness (in the direction of the Z-axis) than flexible printed circuit  124  for the sake of clarity, flexible printed circuit  124  may be thicker than flexible printed circuit substrate  92 . In one suitable arrangement, there may be a greater number of layers  126  than layers  122  in device  10 . 
     Flexible printed circuit substrate  92  may be mounted to surface  120  using surface-mount technology, solder, adhesive, screws, pins, clips, springs, and/or any other desired interconnect structures. In the example of  FIG. 11 , conductive interconnect structures  132  are used to couple conductive structures in flexible printed circuit substrate  92  to conductive structures in flexible printed circuit  124 . Conductive interconnect structures  132  may include solder and conductive contact pads in one suitable arrangement. If desired, conductive interconnect structures  132  may include other conductive interconnect structures such as conductive adhesive, screws, pins, clips, springs, etc. 
     Flexible printed circuit  124  may include conductive traces that form a ground plane (layer) such as ground plane  128 . Ground plane  128  may be formed on a surface of flexible printed circuit  124  (as shown in the example of  FIG. 11 ) or may be embedded within layers  126  of flexible printed circuit  124 . Ground plane  128  may form a part of stripline  104  for antenna  40  and may extend under antenna resonating element  86  (e.g., antenna resonating element  86  may overlap ground plane  128 ). Conductive vias  108  may extend through flexible printed circuit  124  to short the grounded traces  106  in stripline  104  to ground plane  128 . 
     Signal conductor traces  110  are interposed between ground plane  128  and grounded traces  106  in stripline  104 . Conductive via  123  may extend from signal conductor traces  110  through flexible printed circuit  124  to conductive interconnect structures  132 . Conductive via  125  may extend from conductive interconnect structures  132  through flexible printed circuit substrate  92  to antenna resonating element  86  (e.g., at a given one of positive antenna feed terminals  46 H and  46 L of  FIG. 10 ). While  FIG. 11  only shows a single conductive via  123  and a single conductive via  125 , antenna  40  may include two conductive vias  123  and two conductive vias  125  for coupling signal conductor traces  110  to both positive antenna feed terminals  46 H and  46 L of  FIG. 10 . 
     Grounded shielding ring  98  may be formed on surface  116  of flexible printed circuit substrate  92 . Grounded shielding ring  98  may surround the periphery of antenna resonating element  86  at surface  116 . Grounded shielding ring  98  may be separated from antenna resonating element  86  by gap  118 . Gap  118  may be large enough to allow for some tolerance in manufacturing antenna  40  while also being small enough to minimize the footprint of antenna  40  within device  10 . As an example, gap  118  may be between 0.4 mm and 0.6 mm (e.g., 0.5 mm) in length. Grounded shielding ring  98  may be shorted to ground plane  128  by conductive vias  100 - 1  and  100 - 2 . Conductive vias  100 - 1  may extend from grounded shielding ring  98  through flexible printed circuit substrate  92  to conductive interconnect structures  132  and/or grounded traces  106  on flexible printed circuit  124 . Conductive vias  100 - 2  may extend from conductive vias  100 - 1  (e.g., at conductive interconnect structures  132  and/or grounded traces  106 ) through flexible printed circuit  124  to ground plane  128 . Conductive vias  100 - 1  and  100 - 2  of  FIG. 11  may collectively form conductive vias  100  of  FIG. 10 . 
     Similarly, conductive vias  102 - 1  may extend from antenna resonating element  86  through flexible printed circuit substrate  92  to conductive interconnect structures  132  on flexible printed circuit  124 . Conductive vias  102 - 2  may extend from conductive vias  102 - 1  (e.g., at conductive interconnect structures  132 ) through flexible printed circuit  124  to ground plane  128 . Conductive vias  102 - 1  and  102 - 2  of  FIG. 11  may collectively form conductive vias  102  of  FIG. 10 . Antenna  40  may include multiple conductive vias  102 - 1  and multiple conductive vias  102 - 2  (e.g., a fence of conductive vias  102  as shown in  FIG. 10 ) to form the return path for antenna  40  (e.g., return path  88  of  FIG. 9 ). 
     Conductive vias  100 - 1  and  100 - 2 , antenna resonating element  86 , and ground plane  128  may define a continuous antenna cavity (volume)  130  for antenna  40 . In general, the bandwidth of antenna  40  is proportional to the size of antenna cavity  130 . The portion of surface  120  underlying antenna resonating element  86  may be free from grounded traces  106  to maximize the size of antenna cavity  130  (e.g., allowing antenna cavity  130  to extend downward to ground plane  128 ). This may serve to maximize bandwidth and efficiency for antenna  40 . Grounded shielding ring  98  and conductive vias  100 - 1  and  100 - 2  may also serve to shield antenna  40  from external electromagnetic interference. 
     If desired, flexible printed circuit  124  may be mounted to another substrate such as flexible printed circuit  72  of  FIG. 7  or may be formed from a part of flexible printed circuit  72 . As shown in  FIG. 11 , flexible printed circuit  124  and antenna  40  may be mounted within device  10  adjacent to a dielectric cover layer such as dielectric cover layer  114 . Dielectric cover layer  114  may form a dielectric rear wall for device  10  (e.g., dielectric cover layer  114  of  FIG. 11  may form part of rear housing wall  12 R of  FIG. 1 ) or may form a display cover layer for device  10  (e.g., dielectric cover layer  114  of  FIG. 11  may be a display cover layer for display  14  of  FIG. 1 ), as examples. Dielectric cover layer  114  may be formed from a visually opaque material, may be provided with pigment so that dielectric cover layer  114  is visually opaque, or may be provided with an ink layer that hides antenna  40  from view, if desired. Antenna resonating element  86  may be separated from dielectric cover layer  114  by an air gap, may be adhered to dielectric cover layer  114  using adhesive, or may be pressed against dielectric cover layer  114  if desired. Antenna  40  may convey radio-frequency signals through dielectric cover layer  114 . 
     The example of  FIGS. 10 and 11  in which antenna  40  is implemented as a dual-band planar inverted-F antenna is merely illustrative. In another suitable arrangement, antenna  40  may be implemented as a dual-band patch antenna.  FIG. 12  is a perspective view of dual-band patch 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. 12 , antenna  40  (e.g., a dual-band patch antenna) may have an antenna resonating element  134  that is separated from antenna ground  84 . Antenna resonating element  134  may sometimes be referred to herein as patch element  134 , patch antenna resonating element  134 , patch radiating element  134 , or patch  134 . 
     Patch element  134  may lie within a plane such as the X-Y plane of  FIG. 12 . Antenna ground  84  may lie within a plane that is parallel to the plane of patch element  134 . Patch element  134  and antenna ground  84  may therefore lie in separate parallel planes that are separated by a distance  136 . In general, greater distances (heights)  136  may allow antenna  40  to exhibit a greater bandwidth than shorter distances  136 . However, greater distances  136  may consume more volume within device  10  than shorter distances  136 . 
     The perimeter of patch element  134  may be selected so that antenna  40  radiates in first and second frequency bands (e.g., the 6.5 GHz and 8.0 GHz UWB bands). Opposing edges  138  of patch element  134  may have a length  142  that is selected to radiate in the 8.0 GHz UWB band whereas opposing edges  140  of patch element  134  may have a length  144  that is selected to radiate in the 6.5 GHz UWB band. Length  142  may be, for example, one-half of the effective wavelength corresponding to a frequency in the 8.0 GHz UWB band. Similarly, length  144  may be one-half of the effective wavelength corresponding to a frequency in the 6.5 GHz UWB band. This example is merely illustrative and, in general, antenna  40  may be configured to cover any desired UWB communications bands and patch element  134  may have any desired number of curved and/or straight edges. 
     Patch element  134  may be fed using a single positive antenna feed terminal  46 . Radio-frequency signals conveyed over positive antenna feed terminal  46  may excite a first radiating mode of patch element  134  associated with edges  138  and length  142  and may excite a second radiating mode of patch element  134  associated with edges  140  and length  144 . The radiating mode associated with edges  138  and length  142  may be used to convey the radio-frequency signals with a first linear polarization. The radiating mode associated with edges  140  and length  144  may be used to convey the radio-frequency signals with a second linear polarization. Because edges  140  are perpendicular to edges  138  (in the example of  FIG. 12 ), the first linear polarization is orthogonal to the second linear polarization. In this way, antenna  40  may convey radio-frequency signals with multiple polarizations, whereas the dual-band planar inverted-F antenna of  FIGS. 10 and 11  conveys radio-frequency signals with only a single linear polarization. As shown in  FIG. 12 , positive antenna feed terminal  46  may be offset from the center  146  of patch element  134  by a distance that is selected to match the impedance of antenna  40  for both polarizations to the impedance of the transmission line coupled to positive antenna feed terminal  46 . 
     The dual-band patch antenna of  FIG. 12  may be formed on a dielectric substrate that is mounted to an underlying flexible printed circuit, as shown in  FIG. 13 .  FIG. 13  is a cross-sectional side view showing how antenna  40  (e.g., the dual-band patch antenna of  FIG. 12 ) may be formed on a dielectric substrate mounted to an underlying flexible printed circuit such as flexible printed circuit  124 . 
     As shown in  FIG. 13 , patch element  134  may be mounted to surface  154  of dielectric substrate  150 . Dielectric substrate  150  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, dielectric substrate  150  is a ceramic substrate having stacked layers  152  of ceramic material. Dielectric substrate  150  may therefore sometimes be referred to herein as ceramic substrate  150 . This example is merely illustrative and, if desired, one or more additional layers  152  of ceramic substrate  150  may be formed over surface  154  and patch element  134 . 
     Ceramic substrate  150  may be mounted to surface  120  of flexible printed circuit  124 . While ceramic substrate  150  is shown with a greater thickness (in the direction of the Z-axis) than flexible printed circuit  124  for the sake of clarity, flexible printed circuit  124  may be thicker than ceramic substrate  150 . In one suitable arrangement, there may be a greater number of layers  126  than layers  152  in device  10 . Ceramic substrate  150  may be mounted to surface  120  using surface-mount technology, solder, adhesive, screws, pins, clips, springs, and/or any other desired interconnect structures. In the example of  FIG. 13 , conductive interconnect structures  132  are used to couple conductive structures in ceramic substrate  150  to conductive structures in flexible printed circuit  124 . 
     Conductive via  149  may extend from signal conductor traces  110  through flexible printed circuit  124  to conductive interconnect structures  132 . Conductive via  148  may extend from conductive interconnect structures  132  through ceramic substrate  150  to patch element  134  (e.g., at positive antenna feed terminal  46  of  FIG. 12 ). Grounded shielding ring  98  may be formed on surface  154  of ceramic substrate  150  and may surround the periphery of patch element  134  (e.g., in the X-Y plane of  FIG. 13 ). Grounded shielding ring  98  may be shorted to ground plane  128  by conductive vias  100 - 1  and  100 - 2 . Conductive vias  100 - 1  may extend from grounded shielding ring  98  through ceramic substrate  150  to conductive interconnect structures  132  and/or grounded traces  106  on flexible printed circuit  124 . Conductive vias  100 - 2  may extend from conductive vias  100 - 1  through flexible printed circuit  124  to ground plane  128 . 
     Conductive vias  100 - 1  and  100 - 2 , patch element  134 , and ground plane  128  may define a continuous antenna cavity (volume)  156  for antenna  40 . The portion of surface  120  underlying patch element  134  may be free from grounded traces  106  to maximize the size of antenna cavity  156  (e.g., allowing antenna cavity  156  to extend downward to ground plane  128 ). In this way, antenna  40  may radiate within both the higher dielectric permittivity material of ceramic substrate  150  and the lower permittivity material of flexible printed circuit  124 . This may serve to maximize bandwidth and efficiency for antenna  40 . Flexible printed circuit  124  and antenna  40  may be mounted within device  10  adjacent to a dielectric cover layer such as dielectric cover layer  114 . 
     The dual-band patch antenna of  FIGS. 12 and 13  may support a greater number of polarizations than the dual-band planar inverted-F antenna of  FIGS. 10 and 11 . However, ceramic substrates such as ceramic substrate  150  of  FIG. 13  may be more brittle and subject to tighter manufacturing tolerances than flexible printed circuit substrate  92  of  FIGS. 10 and 11 . The ceramic material used to form ceramic substrate  150  typically exhibits a greater dielectric constant (e.g., d k ˜7-10) than the flexible printed circuit material used to form flexible printed circuit substrate  92  and flexible printed circuit  124  (e.g., d k ˜3). Utilizing ceramic material to form ceramic substrate  150  may reduce the area occupied by antenna  40  of  FIGS. 12 and 13  by as much as 33% or more relative to scenarios where flexible printed circuit material is used. This may help to compensate for the greater area required to implement patch antenna structures (which have dimensions on the order of half the wavelength of operation) than planer inverted-F antenna structures (which have dimensions on the order of one-quarter the wavelength of operation). 
     The examples of  FIGS. 8-13  are merely illustrative. In general, antenna  40  may be formed using any desired antenna structures. Stripline  104  may be replaced with any desired radio-frequency transmission line structures. Multiple antennas  40  may be formed on the same flexible printed circuit  124 . 
     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: 20210112
Publication Date: 20220802
Grant Date: 20220802
Priority Date: 20190215
Inventors: COOPER, AARON J.
TAYEBI, AMIN
DI NALLO, CARLO
WANG, ZHEYU
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q5/25", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/241", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/35", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/25", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/085", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/085", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/241", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/25", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 72043353