PATENT DOCUMENT

Publication Number: US-10957978-B2
Application Number: US-201916456856-A
Country: US
Kind Code: B2

Title: Electronic devices having multi-frequency ultra-wideband antennas

Abstract:
An electronic device may be provided with an antenna for receiving signals in first and second ultra-wideband communications bands. The antenna may include a first arm that radiates in the first band and a second arm that radiates in the second band. The antenna may be fed by a stripline. A microstrip may couple the stripline to the first and second arms and may be configured to match the impedance of the stripline to the impedance of the first and second arms in the first and second bands, respectively. Sets of antennas tuned to different frequencies may be fed by the same transmission line and may collectively exhibit a relatively wide bandwidth. A conductive shielding layer or other conductive components may be layered over the antennas to mitigate cross-polarization interference at the antennas.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a dielectric substrate; 
 an antenna having first and second resonating element arms formed from conductive traces on the dielectric substrate, a first positive antenna feed terminal coupled to the first resonating element arm, and a second positive antenna feed terminal coupled to the second resonating element arm, wherein the first resonating element arm is configured to radiate in a first ultra-wideband communications band and the second resonating element arm is configured to radiate in a second ultra-wideband communications band that is higher than the first ultra-wideband communications band; 
 a first radio-frequency transmission line on the dielectric substrate; and 
 a second radio-frequency transmission line on the dielectric substrate, wherein the second radio-frequency transmission line couples the first radio-frequency transmission line to the first and second positive antenna feed terminals and comprises:
 a first signal trace segment configured to match an impedance of the first radio-frequency transmission line to an impedance of the first positive antenna feed terminal in the first ultra-wideband communications band, and 
 a second signal trace segment configured to match the impedance of the first radio-frequency transmission line to an impedance of the second positive antenna feed terminal in the second ultra-wideband communication band. 
 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the first signal trace is configured to form an open circuit in the second ultra-wideband communications band and the second signal trace is configured to form an open circuit in the first ultra-wideband communications band. 
     
     
       3. The electronic device defined in  claim 1 , wherein the first radio-frequency transmission line comprises a signal conductor and the second radio-frequency transmission line comprises a third signal trace segment coupled to the signal conductor, the first and second signal trace segments extending from opposing sides of the third signal trace segment. 
     
     
       4. The electronic device defined in  claim 3 , wherein the first signal trace segment has a first length extending from the third signal trace segment to the first positive antenna feed terminal and a first width perpendicular to the first length, the second signal trace segment has a second length extending from the third signal trace segment to the second positive antenna feed terminal and a second width perpendicular to the second length, the first length and the first width are configured to match the impedance of the first radio-frequency transmission line to the impedance of the first positive antenna feed terminal in the first ultra-wideband communications band, and the second length and the second width are configured to match the impedance of the first radio-frequency transmission line to the impedance of the second positive antenna feed terminal in the second ultra-wideband communications band. 
     
     
       5. The electronic device defined in  claim 3 , further comprising:
 ground traces on the dielectric substrate; and 
 a fence of conductive vias extending from the conductive traces to the ground traces through the dielectric substrate, wherein the fence of conductive vias separates the first resonating element arm from the second resonating element arm. 
 
     
     
       6. The electronic device defined in  claim 5 , wherein the third signal trace segment is aligned with the fence of conductive vias. 
     
     
       7. The electronic device defined in  claim 3 , wherein the first radio-frequency transmission line comprises a stripline transmission line and the second radio-frequency transmission line comprises a microstrip transmission line. 
     
     
       8. The electronic device defined in  claim 3 , the dielectric substrate comprising a flexible printed circuit substrate having a plurality of layers, wherein the first, second, and third signal trace segments and the signal conductor are patterned on the same layer of the plurality of layers. 
     
     
       9. The electronic device defined in  claim 3 , further comprising:
 a grounded shielding ring extending around the first and second resonating element arms. 
 
     
     
       10. The electronic device defined in  claim 1 , wherein the first ultra-wideband communications band comprises a 6.5 GHz ultra-wideband communications band, the second ultra-wideband communications band comprising an 8.0 GHz ultra-wideband communications band. 
     
     
       11. The electronic device defined in  claim 1 , further comprising:
 a display having a display cover layer that forms a front face of the electronic device; 
 a dielectric cover layer that forms a rear face of the electronic device; 
 a conductive support plate overlapping the dielectric cover layer and having an opening, wherein the dielectric substrate and the antenna are mounted within the opening, the antenna being configured to radiate through the dielectric cover layer; and 
 a conductive shielding layer that covers the opening and that is electrically coupled to the conductive support plate. 
 
     
     
       12. The electronic device defined in  claim 1 , further comprising:
 a dielectric cover layer that forms a face of the electronic device; 
 a conductive support plate on the dielectric cover layer and having an opening; and 
 a plastic shim on the dielectric cover layer and in the opening, wherein a surface of the plastic shim lies flush with a surface of the conductive support plate, the dielectric substrate is mounted to the surface of the plastic shim, and the antenna extends across the opening. 
 
     
     
       13. An electronic device having opposing first and second faces, the electronic device comprising:
 a display having a display cover layer at the first face; 
 a housing having peripheral conductive housing structures and a conductive support plate that extends between the peripheral conductive housing structures; 
 a dielectric cover layer at the second face and layered on the conductive support plate; 
 first, second, and third openings in the conductive support plate; 
 a flexible printed circuit substrate; 
 first, second, and third ultra-wideband antennas on the flexible printed circuit substrate and aligned with the first, second, and third openings, respectively, wherein the first, second, and third ultra-wideband antennas are configured to radiate through the dielectric cover layer; and 
 a conductive shielding layer that covers the first opening and the first ultra-wideband antenna, wherein the conductive shielding layer is electrically coupled to the conductive support plate and is configured to mitigate cross-polarization interference at the first ultra-wideband antenna. 
 
     
     
       14. The electronic device defined in  claim 13 , further comprising a battery that covers the second and third openings and the second and third ultra-wideband antennas. 
     
     
       15. The electronic device defined in  claim 13 , wherein the conductive shielding layer covers the second opening and the second ultra-wideband antenna, the electronic device further comprising a conductive component that covers the third opening and the third ultra-wideband antenna. 
     
     
       16. The electronic device defined in  claim 13 , further comprising:
 a dielectric shim on the dielectric cover layer in the second opening, wherein the second ultra-wideband antenna is mounted to the dielectric shim and extends across the second opening.

Description:
BACKGROUND 
     This relates to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. Some electronic devices perform location detection operations to detect the location of an external device based on an angle of arrival of signals received from the external device (using multiple antennas). 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components for performing location detection operations using compact structures. At the same time, there is a desire for wireless devices to cover a growing number of frequency bands. 
     Because antennas have the potential to interfere with each other and with components in a wireless device, care must be taken when incorporating antennas into an electronic device. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to exhibit satisfactory performance over the desired range of operating frequencies. 
     It would therefore be desirable to be able to provide improved wireless communications circuitry for wireless electronic devices. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry and control circuitry. The wireless circuitry may include antennas that are used to determine the position and orientation of the electronic device relative to external wireless equipment. The control circuitry may determine the position and orientation of the electronic device relative to the external wireless equipment at least in part by measuring the angle of arrival of radio-frequency signals from the external wireless equipment. The radio-frequency signals may be received in at least first and second ultra-wideband communications bands. 
     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. First and second radio-frequency transmission lines may be formed on the flexible printed circuit substrate. The first radio-frequency transmission line may be a stripline. The second radio-frequency transmission line may be a microstrip that couples the stripline to the low and high band arms. The microstrip may include signal trace segments that are configured to match an impedance of the stripline to the impedance of the low band arm in the 6.5 GHz ultra-wideband communications band while also matching an impedance of the stripline to the impedance of the high band arm in the 8.0 GHz ultra-wideband communications band. 
     If desired, the antennas may include first, second, third, and fourth planar inverted-F antennas coupled to the same radio-frequency transmission line. The first and second antennas may have response peaks at first and second frequencies in the 8.0 GHz ultra-wideband communications band. The third and fourth antennas may have response peaks at third and fourth frequencies in the 6.5 GHz ultra-wideband communications band. Signal traces may be configured to match an impedance of the radio-frequency transmission line to each of the first, second, third, and fourth antennas at the respective frequencies handled by each antenna. 
     If desired, the antennas may be aligned with openings in a conductive support plate. The antennas may radiate through a dielectric cover layer for the device. A conductive shielding layer and/or conductive components such as a battery may cover the antennas and the openings. The conductive shielding layer and the conductive component may mitigate cross-polarization interference associated gaps between the antennas and the conductive support plate. If desired, a plastic shim may be formed in the openings and the antennas may be mounted to the plastic shim. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with some embodiments. 
         FIG. 2  is a schematic diagram of illustrative circuitry in an electronic device in accordance with some embodiments. 
         FIG. 3  is a schematic diagram of illustrative wireless circuitry in accordance with some embodiments. 
         FIG. 4  is a diagram of an illustrative electronic device in wireless communication with an external node in a network in accordance with some embodiments. 
         FIG. 5  is a diagram showing how the location (e.g., range and angle of arrival) of an external node in a network may be determined relative to an electronic device in accordance with some embodiments. 
         FIG. 6  is a diagram showing how illustrative antennas in an electronic device may be used for detecting angle of arrival in accordance with some embodiments. 
         FIG. 7  is a schematic diagram of an illustrative flexible printed circuit 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 bottom view of an illustrative dual-band planar inverted-F antenna that conveys radio-frequency signals and that includes impedance matching transmission line structures in in accordance with some embodiments. 
         FIG. 11  is a cross-sectional side view of an illustrative dual-band planar inverted-F antenna on a flexible printed circuit substrate in accordance with some embodiments. 
         FIG. 12  is a bottom view of an illustrative set of antennas that may convey radio-frequency signals in multiple frequency bands with a relatively wide bandwidth in accordance with some embodiments. 
         FIG. 13  is a plot of antenna performance (antenna efficiency) for an illustrative set of antennas of the type shown in  FIG. 12  in accordance with some embodiments. 
         FIGS. 14 and 15  are top views showing how an illustrative conductive shielding layer may be provided over antennas of the types shown in  FIGS. 2-13  for mitigating cross-polarization interference in accordance with some embodiments. 
         FIG. 16  is a cross-sectional side view showing how an illustrative conductive shielding layer may be provided over antennas of the types shown in  FIGS. 2-13  for mitigating cross-polarization interference in accordance with some embodiments. 
         FIG. 17  is a cross-sectional side view showing how antennas of the types shown in  FIGS. 2-13  may be arranged over a conductive support plate for mitigating cross-polarization interference without a separate conductive shielding layer in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless circuitry (sometimes referred to herein as wireless communications circuitry). The wireless circuitry may be used to support wireless communications in multiple wireless communications bands. Communications bands (sometimes referred to herein as frequency bands) handled by the wireless circuitry can include satellite navigation system communications bands, cellular telephone communications bands, wireless local area network communications bands, near-field communications bands, ultra-wideband communications bands, or other wireless communications bands. 
     The wireless circuitry may include one or more antennas. The antennas of the wireless circuitry can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, patch antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. 
     The conductive electronic device structures may include conductive housing structures. The conductive housing structures may include peripheral structures such as peripheral conductive structures that run around the periphery of the electronic device. The peripheral conductive structures may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, may have portions that extend upwards from an integral planar rear housing (e.g., to form vertical planar sidewalls or curved sidewalls), and/or may form other housing structures. 
     Gaps may be formed in the peripheral conductive structures that divide the peripheral conductive structures into peripheral segments. One or more of the segments may be used in forming one or more antennas for electronic device  10 . Antennas may also be formed using an antenna ground plane and/or an antenna resonating element formed from conductive housing structures (e.g., internal and/or external structures, support plate structures, etc.). 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Device  10  may also be a set-top box, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, a wireless access point, a wireless base station, an electronic device incorporated into a kiosk, building, or vehicle, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may be mounted on the front face of device  10 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or may be insensitive to touch. The rear face of housing  12  (i.e., the face of device  10  opposing the front face of device  10 ) may have a substantially planar housing wall such as rear housing wall  12 R (e.g., a planar housing wall). Rear housing wall  12 R may have slots that pass entirely through the rear housing wall and that therefore separate portions of housing  12  from each other. Rear housing wall  12 R may include conductive portions and/or dielectric portions. If desired, rear housing wall  12 R may include a planar metal layer covered by a thin layer or coating of dielectric such as glass, plastic, sapphire, or ceramic. Housing  12  may also have shallow grooves that do not pass entirely through housing  12 . The slots and grooves may be filled with plastic or other dielectric. If desired, portions of housing  12  that have been separated from each other (e.g., by a through slot) may be joined by internal conductive structures (e.g., sheet metal or other metal members that bridge the slot). 
     Housing  12  may include peripheral housing structures such as peripheral structures  12 W. Peripheral structures  12 W and conductive portions of rear housing wall  12 R may sometimes be referred to herein collectively as conductive structures of housing  12 . Peripheral structures  12 W may run around the periphery of device  10  and display  14 . In configurations in which device  10  and display  14  have a rectangular shape with four edges, peripheral structures  12 W may be implemented using peripheral housing structures that have a rectangular ring shape with four corresponding edges and that extend from rear housing wall  12 R to the front face of device  10  (as an example). Peripheral structures  12 W or part of peripheral structures  12 W may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or that helps hold display  14  to device  10 ) if desired. Peripheral structures  12 W may, if desired, form sidewall structures for device  10  (e.g., by forming a metal band with vertical sidewalls, curved sidewalls, etc.). 
     Peripheral structures  12 W may be formed of a conductive material such as metal and may therefore sometimes be referred to as peripheral conductive housing structures, conductive housing structures, peripheral metal structures, peripheral conductive sidewalls, peripheral conductive sidewall structures, conductive housing sidewalls, peripheral conductive housing sidewalls, sidewalls, sidewall structures, or a peripheral conductive housing member (as examples). Peripheral conductive housing structures  12 W may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming peripheral conductive housing structures  12 W. 
     It is not necessary for peripheral conductive housing structures  12 W to have a uniform cross-section. For example, the top portion of peripheral conductive housing structures  12 W may, if desired, have an inwardly protruding lip that helps hold display  14  in place. The bottom portion of peripheral conductive housing structures  12 W may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). Peripheral conductive housing structures  12 W may have substantially straight vertical sidewalls, may have sidewalls that are curved, or may have other suitable shapes. In some configurations (e.g., when peripheral conductive housing structures  12 W serve as a bezel for display  14 ), peripheral conductive housing structures  12 W may run around the lip of housing  12  (i.e., peripheral conductive housing structures  12 W may cover only the edge of housing  12  that surrounds display  14  and not the rest of the sidewalls of housing  12 ). 
     Rear housing wall  12 R may lie in a plane that is parallel to display  14 . In configurations for device  10  in which some or all of rear housing wall  12 R is formed from metal, it may be desirable to form parts of peripheral conductive housing structures  12 W as integral portions of the housing structures forming rear housing wall  12 R. For example, rear housing wall  12 R of device  10  may include a planar metal structure and portions of peripheral conductive housing structures  12 W on the sides of housing  12  may be formed as flat or curved vertically extending integral metal portions of the planar metal structure (e.g., housing structures  12 R and  12 W may be formed from a continuous piece of metal in a unibody configuration). Housing structures such as these may, if desired, be machined from a block of metal and/or may include multiple metal pieces that are assembled together to form housing  12 . Rear housing wall  12 R may have one or more, two or more, or three or more portions. Peripheral conductive housing structures  12 W and/or conductive portions of rear housing wall  12 R may form one or more exterior surfaces of device  10  (e.g., surfaces that are visible to a user of device  10 ) and/or may be implemented using internal structures that do not form exterior surfaces of device  10  (e.g., conductive housing structures that are not visible to a user of device  10  such as conductive structures that are covered with layers such as thin cosmetic layers, protective coatings, and/or other coating layers that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide peripheral conductive housing structures  12 W and/or conductive portions of rear housing wall  12 R from view of the user). 
     Display  14  may have an array of pixels that form an active area AA that displays images for a user of device  10 . For example, active area AA may include an array of display pixels. The array of pixels may be formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels or other light-emitting diode pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. If desired, active area AA may include touch sensors such as touch sensor capacitive electrodes, force sensors, or other sensors for gathering a user input. 
     Display  14  may have an inactive border region that runs along one or more of the edges of active area AA. Inactive area IA may be free of pixels for displaying images and may overlap circuitry and other internal device structures in housing  12 . To block these structures from view by a user of device  10 , the underside of the display cover layer or other layers in display  14  that overlap inactive area IA may be coated with an opaque masking layer in inactive area IA. The opaque masking layer may have any suitable color. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, transparent ceramic, sapphire, or other transparent crystalline material, or other transparent layer(s). The display cover layer may have a planar shape, a convex curved profile, a shape with planar and curved portions, a layout that includes a planar main area surrounded on one or more edges with a portion that is bent out of the plane of the planar main area, or other suitable shapes. The display cover layer may cover the entire front face of device  10 . In another suitable arrangement, the display cover layer may cover substantially all of the front face of device  10  or only a portion of the front face of device  10 . Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button. An opening may also be formed in the display cover layer to accommodate ports such as speaker port  16  or a microphone port. Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.) and/or audio ports for audio components such as a speaker and/or a microphone if desired. 
     Display  14  may include conductive structures such as an array of capacitive electrodes for a touch sensor, conductive lines for addressing pixels, driver circuits, etc. Housing  12  may include internal conductive structures such as metal frame members and a planar conductive housing member (sometimes referred to as a backplate) that spans the walls of housing  12  (i.e., a substantially rectangular sheet formed from one or more metal parts that is welded or otherwise connected between opposing sides of peripheral conductive structures  12 W). The backplate may form an exterior rear surface of device  10  or may be covered by layers such as thin cosmetic layers, protective coatings, and/or other coatings that may include dielectric materials such as glass, ceramic, plastic, or other structures that form the exterior surfaces of device  10  and/or serve to hide the backplate from view of the user. Device  10  may also include conductive structures such as printed circuit boards, components mounted on printed circuit boards, and other internal conductive structures. These conductive structures, which may be used in forming a ground plane in device  10 , may extend under active area AA of display  14 , for example. 
     In regions  22  and  20 , openings may be formed within the conductive structures of device  10  (e.g., between peripheral conductive housing structures  12 W and opposing conductive ground structures such as conductive portions of rear housing wall  12 R, conductive traces on a printed circuit board, conductive electrical components in display  14 , etc.). These openings, which may sometimes be referred to as gaps, may be filled with air, plastic, and/or other dielectrics and may be used in forming slot antenna resonating elements for one or more antennas in device  10 , if desired. 
     Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  22  and  20  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, may contribute to the performance of a parasitic antenna resonating element, or may otherwise serve as part of antenna structures formed in regions  22  and  20 . If desired, the ground plane that is under active area AA of display  14  and/or other metal structures in device  10  may have portions that extend into parts of the ends of device  10  (e.g., the ground may extend towards the dielectric-filled openings in regions  22  and  20 ), thereby narrowing the slots in regions  22  and  20 . 
     In general, device  10  may include any suitable number of antennas (e.g., one or more, two or more, three or more, four or more, etc.). The antennas in device  10  may be located at opposing first and second ends of an elongated device housing (e.g., ends at regions  22  and  20  of device  10  of  FIG. 1 ), along one or more edges of a device housing, in the center of a device housing, in other suitable locations, or in one or more of these locations. The arrangement of  FIG. 1  is merely illustrative. 
     Portions of peripheral conductive housing structures  12 W may be provided with peripheral gap structures. For example, peripheral conductive housing structures  12 W may be provided with one or more gaps such as gaps  18 , as shown in  FIG. 1 . The gaps in peripheral conductive housing structures  12 W may be filled with dielectric such as polymer, ceramic, glass, air, other dielectric materials, or combinations of these materials. Gaps  18  may divide peripheral conductive housing structures  12 W into one or more peripheral conductive segments. There may be, for example, two peripheral conductive segments in peripheral conductive housing structures  12 W (e.g., in an arrangement with two gaps  18 ), three peripheral conductive segments (e.g., in an arrangement with three gaps  18 ), four peripheral conductive segments (e.g., in an arrangement with four gaps  18 ), six peripheral conductive segments (e.g., in an arrangement with six gaps  18 ), etc. The segments of peripheral conductive housing structures  12 W that are formed in this way may form parts of antennas in device  10  if desired. 
     If desired, openings in housing  12  such as grooves that extend partway or completely through housing  12  may extend across the width of the rear wall of housing  12  and may penetrate through the rear wall of housing  12  to divide the rear wall into different portions. These grooves may also extend into peripheral conductive housing structures  12 W and may form antenna slots, gaps  18 , and other structures in device  10 . Polymer or other dielectric may fill these grooves and other housing openings. In some situations, housing openings that form antenna slots and other structure may be filled with a dielectric such as air. 
     In order to provide an end user of device  10  with as large of a display as possible (e.g., to maximize an area of the device used for displaying media, running applications, etc.), it may be desirable to increase the amount of area at the front face of device  10  that is covered by active area AA of display  14 . Increasing the size of active area AA may reduce the size of inactive area IA within device  10 . This may reduce the area behind display  14  that is available for antennas within device  10 . For example, active area AA of display  14  may include conductive structures that serve to block radio-frequency signals handled by antennas mounted behind active area AA from radiating through the front face of device  10 . It would therefore be desirable to be able to provide antennas that occupy a small amount of space within device  10  (e.g., to allow for as large of a display active area AA as possible) while still allowing the antennas to communicate with wireless equipment external to device  10  with satisfactory efficiency bandwidth. 
     In a typical scenario, device  10  may have one or more upper antennas and one or more lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device  10  in region  20 . A lower antenna may, for example, be formed at the lower end of device  10  in region  22 . Additional antennas may be formed along the edges of housing  12  extending between regions  20  and  22  if desired. The antennas may be used separately to cover identical communications bands, overlapping communications bands, or separate communications bands. The antennas may be used to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, near-field communications, ultra-wideband communications, etc. 
     A schematic diagram of illustrative components that may be used in device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry  28 . Control circuitry  28  may include storage such as storage circuitry  30 . Storage circuitry  30  may include hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. 
     Control circuitry  28  may include processing circuitry such as processing circuitry  32 . Processing circuitry  32  may be used to control the operation of device  10 . Processing circuitry  32  may include on one or more microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application specific integrated circuits, central processing units (CPUs), etc. Control circuitry  28  may be configured to perform operations in device  10  using hardware (e.g., dedicated hardware or circuitry), firmware, and/or software. Software code for performing operations in device  10  may be stored on storage circuitry  30  (e.g., storage circuitry  30  may include non-transitory (tangible) computer readable storage media that stores the software code). The software code may sometimes be referred to as program instructions, software, data, instructions, or code. Software code stored on storage circuitry  30  may be executed by processing circuitry  32 . 
     Control circuitry  28  may be used to run software on device  10  such as external node location applications, satellite navigation applications, internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, control circuitry  28  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  28  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other WPAN protocols, IEEE 802.11ad protocols, cellular telephone protocols, MIMO protocols, antenna diversity protocols, satellite navigation system protocols (e.g., global positioning system (GPS) protocols, global navigation satellite system (GLONASS) protocols, etc.), IEEE 802.15.4 ultra-wideband communications protocols or other ultra-wideband communications protocols, etc. Each communications protocol may be associated with a corresponding radio access technology (RAT) that specifies the physical connection methodology used in implementing the protocol. 
     Device  10  may include input-output circuitry  24 . Input-output circuitry  24  may include input-output devices  26 . Input-output devices  26  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  26  may include user interface devices, data port devices, sensors, and other input-output components. For example, input-output devices may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, gyroscopes, accelerometers or other components that can detect motion and device orientation relative to the Earth, capacitance sensors, proximity sensors (e.g., a capacitive proximity sensor and/or an infrared proximity sensor), magnetic sensors, and other sensors and input-output components. 
     Input-output circuitry  24  may include wireless circuitry such as wireless circuitry  34  (sometimes referred to herein as wireless communications circuitry  34 ) for wirelessly conveying radio-frequency signals. To support wireless communications, wireless circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas such as antennas  40 , transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     While control circuitry  28  is shown separately from wireless circuitry  34  in the example of  FIG. 2  for the sake of clarity, wireless circuitry  34  may include processing circuitry that forms a part of processing circuitry  32  and/or storage circuitry that forms a part of storage circuitry  30  of control circuitry  28  (e.g., portions of control circuitry  28  may be implemented on wireless circuitry  34 ). As an example, control circuitry  28  (e.g., processing circuitry  32 ) may include baseband processor circuitry or other control components that form a part of wireless circuitry  34 . 
     Wireless circuitry  34  may include radio-frequency transceiver circuitry for handling various radio-frequency communications bands. For example, wireless circuitry  34  may include ultra-wideband (UWB) transceiver circuitry  36  that supports communications using the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols. Ultra-wideband radio-frequency signals may be based on an impulse radio signaling scheme that uses band-limited data pulses. Ultra-wideband signals may have any desired bandwidths such as bandwidths between 499 MHz and 1331 MHz, bandwidths greater than 500 MHz, etc. The presence of lower frequencies in the baseband may sometimes allow ultra-wideband signals to penetrate through objects such as walls. In an IEEE 802.15.4 system, a pair of electronic devices may exchange wireless time stamped messages. Time stamps in the messages may be analyzed to determine the time of flight of the messages and thereby determine the distance (range) between the devices and/or an angle between the devices (e.g., an angle of arrival of incoming radio-frequency signals). Ultra-wideband transceiver circuitry  36  may operate (i.e., convey radio-frequency signals) in frequency bands such as an ultra-wideband communications band between about 5 GHz and about 8.3 GHz (e.g., a 6.5 GHz UWB communications band, an 8 GHz UWB communications band, and/or at other suitable frequencies). 
     As shown in  FIG. 2 , wireless circuitry  34  may also include non-UWB transceiver circuitry  38 . Non-UWB transceiver circuitry  38  may handle communications bands other than UWB communications bands such as 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications or communications in other wireless local area network (WLAN) bands, the 2.4 GHz Bluetooth® communications band or other wireless personal area network (WPAN) bands, and/or cellular telephone frequency bands such as a cellular low band (LB) from 600 to 960 MHz, a cellular low-midband (LMB) from 1410 to 1510 MHz, a cellular midband (MB) from 1710 to 2170 MHz, a cellular high band (HB) from 2300 to 2700 MHz, a cellular ultra-high band (UHB) from 3300 to 5000 MHz, or other communications bands between 600 MHz and 5000 MHz or other suitable frequencies (as examples). 
     Non-UWB transceiver circuitry  38  may handle voice data and non-voice data. Wireless circuitry  34  may include circuitry for other short-range and long-range wireless links if desired. For example, wireless circuitry  34  may include 60 GHz transceiver circuitry (e.g., millimeter wave transceiver circuitry), circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. 
     Wireless circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable types of antenna structures. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, dipole antenna structures, monopole antenna structures, hybrids of two or more of these designs, etc. If desired, one or more of antennas  40  may be cavity-backed antennas. 
     Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. Dedicated antennas may be used for conveying radio-frequency signals in a UWB communications band or, if desired, antennas  40  can be configured to convey both radio-frequency signals in a UWB communications band and radio-frequency signals in a non-UWB communications band (e.g., wireless local area network signals and/or cellular telephone signals). Antennas  40  can include two or more antennas for handling ultra-wideband wireless communication. In one suitable arrangement that is described herein as an example, antennas  40  include one or more groups of three antennas (sometimes referred to herein as triplets of antennas) for handling ultra-wideband wireless communication. In yet another suitable arrangement, antennas  40  may include a triplet of sets of antennas, where each set of antenna includes four antennas that are tuned to four respective frequencies (e.g., antennas  40  may include three sets of four antennas for handling ultra-wideband wireless communication). Antennas  40  may include one or more doublets of antennas for handling ultra-wideband wireless communication if desired. 
     Space is often at a premium in electronic devices such as device  10 . In order to minimize space consumption within device  10 , the same antenna  40  may be used to cover multiple frequency bands. In one suitable arrangement that is described herein as an example, each antenna  40  that is used to perform ultra-wideband wireless communication may be a multi-band antenna that conveys radio-frequency signals in at least two ultra-wideband communications bands (e.g., the 6.5 GHz UWB communications band and the 8.0 GHz UWB communications band). In another suitable arrangement that is described herein as an example, each antenna  40  may convey radio-frequency signals in a single ultra-wideband communications band but antennas  40  may include different antennas that cover different ultra-wideband frequencies. Radio-frequency signals that are conveyed in UWB communications bands (e.g., using a UWB protocol) may sometimes be referred to herein as UWB signals or UWB radio-frequency signals. Radio-frequency signals in frequency bands other than the UWB communications bands (e.g., radio-frequency signals in cellular telephone frequency bands, WPAN frequency bands, WLAN frequency bands, etc.) may sometimes be referred to herein as non-UWB signals or non-UWB radio-frequency signals. 
     A schematic diagram of wireless circuitry  34  is shown in  FIG. 3 . As shown in  FIG. 3 , wireless circuitry  34  may include transceiver circuitry  42  (e.g., UWB transceiver circuitry  36  or non-UWB transceiver circuitry  38  of  FIG. 2 ) that is coupled to a given antenna  40  using a radio-frequency transmission line path such as radio-frequency transmission line path  50 . 
     To provide antenna structures such as antenna  40  with the ability to cover different frequencies of interest, antenna  40  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna  40  may be provided with adjustable circuits such as tunable components that tune the antenna over communications (frequency) bands of interest. The tunable components may be part of a tunable filter or tunable impedance matching network, may be part of an antenna resonating element, may span a gap between an antenna resonating element and antenna ground, etc. 
     Radio-frequency transmission line path  50  may include one or more radio-frequency transmission lines (sometimes referred to herein simply as transmission lines). Radio-frequency transmission line path  50  (e.g., the transmission lines in radio-frequency transmission line path  50 ) may include a positive signal conductor such as positive signal conductor  52  and a ground signal conductor such as ground conductor  54 . 
     The transmission lines in radio-frequency transmission line path  50  may, for example, include coaxial cable transmission lines (e.g., ground conductor  54  may be implemented as a grounded conductive braid surrounding signal conductor  52  along its length), stripline transmission lines (e.g., where ground conductor  54  extends along two sides of signal conductor  52 ), a microstrip transmission line (e.g., where ground conductor  54  extends along one side of signal conductor  52 ), coaxial probes realized by a metalized via, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, waveguide structures (e.g., coplanar waveguides or grounded coplanar waveguides), combinations of these types of transmission lines and/or other transmission line structures, etc. In one suitable arrangement that is sometimes described herein as an example, radio-frequency transmission line path  50  may include a stripline transmission line coupled to transceiver circuitry  42  and a microstrip transmission line coupled between the stripline transmission line and antenna  40 . 
     Transmission lines in radio-frequency transmission line path  50  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, radio-frequency transmission line path  50  may include transmission line conductors (e.g., signal conductors  52  and ground conductors  54 ) integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive). The multilayer laminated structures may, if desired, be folded or bent in multiple dimensions (e.g., two or three dimensions) and may maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). 
     A matching network may include components such as inductors, resistors, and capacitors used in matching the impedance of antenna  40  to the impedance of radio-frequency transmission line path  50 . Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Components such as these may also be used in forming filter circuitry in antenna(s)  40  and may be tunable and/or fixed components. 
     Radio-frequency transmission line path  50  may be coupled to antenna feed structures associated with antenna  40 . As an example, antenna  40  may form an inverted-F antenna, a planar inverted-F antenna, a patch antenna, or other antenna having an antenna feed  44  with a positive antenna feed terminal such as terminal  46  and a ground antenna feed terminal such as ground antenna feed terminal  48 . Signal conductor  52  may be coupled to positive antenna feed terminal  46  and ground conductor  54  may be coupled to ground antenna feed terminal  48 . Other types of antenna feed arrangements may be used if desired. For example, antenna  40  may be fed using multiple feeds each coupled to a respective port of transceiver circuitry  42  over a corresponding transmission line. If desired, signal conductor  52  may be coupled to multiple locations on antenna  40  (e.g., antenna  40  may include multiple positive antenna feed terminals coupled to signal conductor  52  of the same radio-frequency transmission line path  50 ). Switches may be interposed on the signal conductor between transceiver circuitry  42  and the positive antenna feed terminals if desired (e.g., to selectively activate one or more positive antenna feed terminals at any given time). The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
     During operation, device  10  may communicate with external wireless equipment. If desired, device  10  may use radio-frequency signals conveyed between device  10  and the external wireless equipment to identify a location of the external wireless equipment relative to device  10 . Device  10  may identify the relative location of the external wireless equipment by identifying a range to the external wireless equipment (e.g., the distance between the external wireless equipment and device  10 ) and the angle of arrival (AoA) of radio-frequency signals from the external wireless equipment (e.g., the angle at which radio-frequency signals are received by device  10  from the external wireless equipment). 
       FIG. 4  is a diagram showing how device  10  may determine a distance D between device  10  and external wireless equipment such as wireless network node  60  (sometimes referred to herein as wireless equipment  60 , wireless device  60 , external device  60 , or external equipment  60 ). Node  60  may include devices that are capable of receiving and/or transmitting radio-frequency signals such as radio-frequency signals  56 . Node  60  may include tagged devices (e.g., any suitable object that has been provided with a wireless receiver and/or a wireless transmitter), electronic equipment (e.g., an infrastructure-related device), and/or other electronic devices (e.g., devices of the type described in connection with  FIG. 1 , including some or all of the same wireless communications capabilities as device  10 ). 
     For example, node  60  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, headset device (e.g., virtual or augmented reality headset devices), or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, or other small portable device. Node  60  may also be a set-top box, a camera device with wireless communications capabilities, a desktop computer, a display into which a computer or other processing circuitry has been integrated, a display without an integrated computer, or other suitable electronic equipment. Node  60  may also be a key fob, a wallet, a book, a pen, or other object that has been provided with a low-power transmitter (e.g., an RFID transmitter or other transmitter). Node  60  may be electronic equipment such as a thermostat, a smoke detector, a Bluetooth® Low Energy (Bluetooth LE) beacon, a Wi-Fi® wireless access point, a wireless base station, a server, a heating, ventilation, and air conditioning (HVAC) system (sometimes referred to as a temperature-control system), a light source such as a light-emitting diode (LED) bulb, a light switch, a power outlet, an occupancy detector (e.g., an active or passive infrared light detector, a microwave detector, etc.), a door sensor, a moisture sensor, an electronic door lock, a security camera, or other device. Device  10  may also be one of these types of devices if desired. 
     As shown in  FIG. 4 , device  10  may communicate with node  60  using wireless radio-frequency signals  56 . Radio-frequency signals  56  may include Bluetooth® signals, near-field communications signals, wireless local area network signals such as IEEE 802.11 signals, millimeter wave communication signals such as signals at 60 GHz, UWB signals, other radio-frequency wireless signals, infrared signals, etc. In one suitable arrangement that is described herein by example, radio-frequency signals  56  are UWB signals conveyed in multiple UWB communications bands such as the 6.5 GHz and 8 GHz UWB communications bands. Radio-frequency signals  56  may be used to determine and/or convey information such as location and orientation information. For example, control circuitry  28  in device  10  ( FIG. 2 ) may determine the location  58  of node  60  relative to device  10  using radio-frequency signals  56 . 
     In arrangements where node  60  is capable of sending or receiving communications signals, control circuitry  28  ( FIG. 2 ) on device  10  may determine distance D using radio-frequency signals  56  of  FIG. 4 . The control circuitry may determine distance D using signal strength measurement schemes (e.g., measuring the signal strength of radio-frequency signals  56  from node  60 ) or using time-based measurement schemes such as time of flight measurement techniques, time difference of arrival measurement techniques, angle of arrival measurement techniques, triangulation methods, time-of-flight methods, using a crowdsourced location database, and other suitable measurement techniques. This is merely illustrative, however. If desired, the control circuitry may use information from Global Positioning System receiver circuitry, proximity sensors (e.g., infrared proximity sensors or other proximity sensors), image data from a camera, motion sensor data from motion sensors, and/or using other circuitry on device  10  to help determine distance D. In addition to determining the distance D between device  10  and node  60 , the control circuitry may determine the orientation of device  10  relative to node  60 . 
       FIG. 5  illustrates how the position and orientation of device  10  relative to nearby nodes such as node  60  may be determined. In the example of  FIG. 5 , the control circuitry on device  10  (e.g., control circuitry  28  of  FIG. 2 ) uses a horizontal polar coordinate system to determine the location and orientation of device  10  relative to node  60 . In this type of coordinate system, the control circuitry may determine an azimuth angle θ and/or an elevation angle φ to describe the position of nearby nodes  60  relative to device  10 . The control circuitry may define a reference plane such as local horizon  64  and a reference vector such as reference vector  68 . Local horizon  64  may be a plane that intersects device  10  and that is defined relative to a surface of device  10  (e.g., the front or rear face of device  10 ). For example, local horizon  64  may be a plane that is parallel to or coplanar with display  14  of device  10  ( FIG. 1 ). Reference vector  68  (sometimes referred to as the “north” direction) may be a vector in local horizon  64 . If desired, reference vector  68  may be aligned with longitudinal axis  62  of device  10  (e.g., an axis running lengthwise down the center of device  10  and parallel to the longest rectangular dimension of device  10 , parallel to the Y-axis of  FIG. 1 ). When reference vector  68  is aligned with longitudinal axis  62  of device  10 , reference vector  68  may correspond to the direction in which device  10  is being pointed. 
     Azimuth angle θ and elevation angle φ may be measured relative to local horizon  64  and reference vector  68 . As shown in  FIG. 5 , the elevation angle φ (sometimes referred to as altitude) of node  60  is the angle between node  60  and local horizon  64  of device  10  (e.g., the angle between vector  67  extending between device  10  and node  60  and a coplanar vector  66  extending between device  10  and local horizon  64 ). The azimuth angle θ of node  60  is the angle of node  60  around local horizon  64  (e.g., the angle between reference vector  68  and vector  66 ). In the example of  FIG. 5 , the azimuth angle θ and elevation angle φ of node  60  are greater than 0°. 
     If desired, other axes besides longitudinal axis  62  may be used to define reference vector  68 . For example, the control circuitry may use a horizontal axis that is perpendicular to longitudinal axis  62  as reference vector  68 . This may be useful in determining when nodes  60  are located next to a side portion of device  10  (e.g., when device  10  is oriented side-to-side with one of nodes  60 ). 
     After determining the orientation of device  10  relative to node  60 , the control circuitry on device  10  may take suitable action. For example, the control circuitry may send information to node  60 , may request and/or receive information from  60 , may use display  14  ( FIG. 1 ) to display a visual indication of wireless pairing with node  60 , may use speakers to generate an audio indication of wireless pairing with node  60 , may use a vibrator, a haptic actuator, or other mechanical element to generate haptic output indicating wireless pairing with node  60 , may use display  14  to display a visual indication of the location of node  60  relative to device  10 , may use speakers to generate an audio indication of the location of node  60 , may use a vibrator, a haptic actuator, or other mechanical element to generate haptic output indicating the location of node  60 , and/or may take other suitable action. 
     In one suitable arrangement, device  10  may determine the distance between the device  10  and node  60  and the orientation of device  10  relative to node  60  using two or more ultra-wideband antennas. The ultra-wide band antennas may receive radio-frequency signals from node  60  (e.g., radio-frequency signals  56  of  FIG. 4 ). Time stamps in the wireless communication signals may be analyzed to determine the time of flight of the wireless communication signals and thereby determine the distance (range) between device  10  and node  60 . Additionally, angle of arrival (AoA) measurement techniques may be used to determine the orientation of electronic device  10  relative to node  60  (e.g., azimuth angle θ and elevation angle φ). 
     In angle of arrival measurement, node  60  transmits a radio-frequency signal to device  10  (e.g., radio-frequency signals  56  of  FIG. 4 ). Device  10  may measure a delay in arrival time of the radio-frequency signals between the two or more ultra-wideband antennas. The delay in arrival time (e.g., the difference in received phase at each ultra-wideband antenna) can be used to determine the angle of arrival of the radio-frequency signal (and therefore the angle of node  60  relative to device  10 ). Once distance D and the angle of arrival have been determined, device  10  may have knowledge of the precise location of node  60  relative to device  10 . 
       FIG. 6  is a schematic diagram showing how angle of arrival measurement techniques may be used to determine the orientation of device  10  relative to node  60 . As shown in  FIG. 6 , device  10  may include multiple antennas (e.g., a first antenna  40 - 1  and a second antenna  40 - 2 ) coupled to UWB transceiver circuitry  36  over respective radio-frequency transmission line paths (e.g., a first radio-frequency transmission line path  50 - 1  and a second radio-frequency transmission line path  50 - 2 ). 
     Antennas  40 - 1  and  40 - 2  may each receive radio-frequency signals  56  from node  60  ( FIG. 5 ). Antennas  40 - 1  and  40 - 2  may be laterally separated by a distance d 1 , where antenna  40 - 1  is farther away from node  60  than antenna  40 - 2  (in the example of  FIG. 6 ). Therefore, radio-frequency signals  56  travel a greater distance to reach antenna  40 - 1  than antenna  40 - 2 . The additional distance between node  60  and antenna  40 - 1  is shown in  FIG. 6  as distance d 2 .  FIG. 6  also shows angles a and b (where a+b=90°). 
     Distance d 2  may be determined as a function of angle a or angle b (e.g., d 2 =d 1 *sin(a) or d 2 =d 1 *cos(b)). Distance d 2  may also be determined as a function of the phase difference between the signal received by antenna  40 - 1  and the signal received by antenna  40 - 2  (e.g., d 2 =(PD)*λ/( 2 * 7 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*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  70 . Flexible printed circuit  70  may be bent or folded along one or more axes if desired (e.g., to accommodate the presence of other electronic device components in the vicinity of flexible printed circuit  70 ). 
     Flexible printed circuit  70  may include portions  72  (sometimes referred to herein as stub portions  72  or stubs  72 ). Antennas  40  for performing ultra-wideband communications may be formed within regions  80 ,  78 , and  74  on stubs  72  of flexible printed circuit  70 . For example, a triplet of antennas  40  for performing ultra-wideband communications may include a first antenna in region  74 , a second antenna in region  78 , and a third antenna in region  80 . In another suitable arrangement, antennas  40  may include a triplet of sets of antennas, where each set of antennas includes two or more antennas  40  (e.g., four antennas  40 ) and respective sets are formed in regions  80 ,  78 , and  74 . One or more of stubs  72  on flexible printed circuit  70  may include a non-UWB antenna (e.g., in region  76 ) for conveying non-UWB signals such as a wireless local area network antenna for conveying radio-frequency signals in a wireless local area network communications band. 
     Radio-frequency transmission line paths (e.g., radio-frequency transmission line path  50  of  FIG. 3 ) may be formed on flexible printed circuit  70  and may be coupled to the antennas in regions  80 ,  78 , and  74 . Flexible printed circuit  70  may include one or more radio-frequency connectors  82  (e.g., at one or more of stubs  72  or elsewhere in flexible printed circuit  70 ). Radio-frequency connector  82  may couple the radio-frequency transmission line paths on flexible printed circuit  70  to transceiver circuitry in device  10  (e.g., transceiver circuitry  42  of  FIG. 3 ). The transceiver circuitry may, for example, be mounted to a different substrate such as a main logic board for device  10 . 
     The example of  FIG. 7  is merely illustrative. In general, flexible printed circuit  70  may have any desired shape. Flexible printed circuit  70  need not include stubs  72  (e.g., flexible printed circuit  70  may have a rectangular shape or other shapes). One of regions  80 ,  78 , and  74  may be omitted in scenarios where only a doublet of antennas is formed on flexible printed circuit  70  for performing ultra-wideband communications. In another suitable arrangement, flexible printed circuit  70  of  FIG. 7  may be replaced with a rigid printed circuit board or other substrates for antennas  40 . If desired, other components may be mounted to flexible printed circuit  70  (e.g., input-output devices  26  or portions of control circuitry  28  of  FIG. 2 , additional antennas, etc.). 
     Any desired antenna structures may be used for implementing the antennas  40  in regions  74 ,  80 , and  78  of  FIG. 7  (e.g., for implementing at least antennas  40 - 1  and  40 - 2  of  FIG. 6  for conveying UWB signals). In one suitable arrangement that is sometimes described herein as an example, planar inverted-F antenna structures may be used for implementing antennas  40 . Antennas that are implemented using planar inverted-F antenna structures may sometimes be referred to herein as planar inverted-F antennas. 
       FIG. 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 transmission line (e.g., a transmission line in radio-frequency transmission line path  50  of  FIG. 3 ) to positive antenna feed terminal  46  and ground antenna feed terminal  48  of antenna feed  44 . Positive antenna feed terminal  46  may be coupled to resonating element arm  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 response (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 communications 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 communications 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 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 or patch, sheet metal, conductive foil, etc.) that extends across a planar lateral area above antenna ground  84 . 
       FIG. 10  is a bottom-up view of dual-band planar inverted-F antenna structures that may be used to form antenna  40  (e.g., a given one of antennas  40 - 1  and  40 - 2  of  FIG. 6 ). As shown in  FIG. 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 a surface of an underlying dielectric substrate  92  (e.g., on an upper-most surface of 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 L 2  of high band arm  90 H and the length L 1  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 L 1  and width  95  whereas high band arm  90 H has length L 2  and width  95 . The example of  FIG. 10  is merely illustrative and, if desired, low band arm  90 L and/or high band arm  90 H may have other shapes (e.g., shapes with cut-out regions to accommodate other components in the vicinity of antenna  40 , shapes having any desired number of curved and/or straight edges, etc.). In these scenarios, length L 1  may be the greatest lateral dimension of low band arm  90 L and length L 2  may be the greatest lateral dimension of high band arm  90 H, as an example. 
     Length L 2  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 communications band. Length L 1  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 communications band. For example, length L 2  may be approximately equal to (e.g., within 15% of) one-quarter of the effective wavelength corresponding to a frequency in the 8.0 GHz UWB communications band. Similarly, length L 1  may be approximately equal to one-quarter of the effective wavelength corresponding to a frequency in the 6.5 GHz UWB communications band. These effective wavelengths are modified from free-space wavelengths by a constant value associated with the dielectric material used to form 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 dk 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 high band arm  90 H and low band arm  90 L. 
     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 upper-most 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 8.0 GHz UWB communications 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 6.5 GHz UWB communications 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 upper-most 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  may be shorted to the antenna ground (e.g., underlying planar ground traces) by fences of conductive vias extending through flexible printed circuit substrate  92  (not shown in  FIG. 10  for the sake of clarity). Grounded shielding ring  98  may serve to isolate and shield antenna  40  from electromagnetic interference. 
     Grounded shielding ring  98 , the conductive vias coupled to grounded shielding ring  98 , and the underlying planar ground traces 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 . The antenna ground may include ground traces on one or more layers of flexible printed circuit substrate  92  beneath the upper-most layer of flexible printed circuit substrate  92 . The ground traces may include a planar ground traces extending underneath (e.g., overlapping) substantially all of antenna  40 . If desired, the ground traces may also include a ring of ground traces or ground traces in other shapes overlapping grounded shielding ring  98  but formed on a layer of flexible printed circuit substrate  92  between the planar ground trace and the upper-most layer of flexible printed circuit substrate  92 . Each layer of ground traces in antenna  40  may be coupled together using conductive vias if desired (e.g., so that all of the ground traces are held at the same ground potential). 
     Antenna  40  of  FIG. 10  may be fed using a radio-frequency transmission line path (e.g., radio-frequency transmission line path  50  of  FIG. 3 ). The radio-frequency transmission line path may include a first transmission line such as stripline transmission line  96  (sometimes referred to herein simply as stripline  96 ) and a second transmission line such as microstrip transmission line  94  (sometimes referred to herein simply as microstrip  94 ). Microstrip  94  may couple stripline  96  to antenna resonating element  86 . 
     For example, stripline  96  may include signal trace  100  (e.g., a conductive trace that forms part of signal conductor  52  of  FIG. 3 ). Stripline  96  may be coupled to positive antenna feed terminals  46 L and  46 H on antenna resonating element  86  through microstrip  94 . The signal conductor for microstrip  94  may include signal trace segments  101 ,  104 , and  106  (e.g., conductive traces that form respective segments of the signal conductor for microstrip  94  and thus signal conductor  52  of  FIG. 3 , and that may therefore sometimes be referred to herein as conductive traces, signal traces, or segments  101 ,  104 , and  106 ). Signal trace segment  101  may be coupled to signal trace  100  of stripline  96 . Signal trace segment  101  may couple signal trace segments  104  and  106  to signal trace  101 . Signal trace segment  104  may be coupled to positive antenna feed terminal  46 L on low band arm  90 L by a conductive via extending through at least one layer of flexible printed circuit substrate  92 . Signal trace segment  106  may be coupled to positive antenna feed terminal  46 H on high band arm  90 H by a conductive via extending through at least one layer of flexible printed circuit substrate  92 . Signal trace  100  and signal trace segments  104 ,  106 , and  101  may each be formed from conductive traces on the same layer of flexible printed circuit substrate  92  (e.g., a layer that is vertically interposed between the planar ground trace for antenna  40  and the uppermost layer in flexible printed circuit substrate  92 ). 
     Stripline  96  may exhibit a corresponding impedance (e.g., a 50 Ohm impedance). In practice, it can be difficult to ensure that the impedance of stripline  96  is matched to both the impedance of low band arm  90 L at positive antenna feed terminal  46 L (e.g., in the 6.5 GHz UWB communications band) and the impedance of high band arm  90 H at positive antenna feed terminal  46 H (e.g., in the 8.0 GHz UWB communications band). If care is not taken, impedance discontinuities between stripline  96  and antenna resonating element  86  may generate undesirable signal reflections that limit the overall antenna efficiency for antenna  40  in one or more frequency bands. 
     In order to help match the impedance of stripline  96  to the impedance of positive antenna feed terminals  46 L and  46 H, signal trace segments  104  and  106  may be configured to form impedance matching structures for antenna  40  (e.g., microstrip  94  may both convey radio-frequency signals for antenna  40  and serve as an impedance matching structure that matches the impedance of stripline  96  to the impedance of antenna resonating element  86 ). Signal trace segments  104  and  106  may therefore sometimes also be referred to herein as impedance matching segments  104  and  106  or impedance matching traces  104  and  106 . 
     Signal trace segment  104  may extend laterally from signal trace segment  101  to the location of positive antenna feed terminal  46 L. Signal trace segment  106  may extend laterally from signal trace segment  101  to the location of positive antenna feed terminal  46 H. The dimensions of signal trace segments  104  and  106  (and the locations of positive antenna feed terminals  46 L and  46 H) may be selected to match the impedance of stripline  96  to the impedance of antenna resonating element  86 . 
     For example, signal trace segment  104  may have a length D 1  extending from signal trace segment  101  to positive antenna feed terminal  46 L and may have a perpendicular width W 1 . Similarly, signal trace segment  106  may have a length D 2  extending from signal trace segment  101  to positive antenna feed terminal  46 H. Adjusting length D 1 , length D 2 , width W 1 , width W 2 , the location of positive antenna feed terminal  46 L, and/or the location of positive antenna feed terminal  46 H may serve to adjust the impedance matching performed by microstrip  94  in the frequency bands handled by low band arm  90 L and high band arm  90 H. 
     For example, width W 1 , length D 1 , and/or the position of positive antenna feed terminal  46 L may selected so that microstrip  94  exhibits a 50 Ohm impedance to the left of signal trace segment  101  (e.g., in the direction of arrow  97 ) in the frequency band of low band arm  90 L (e.g., in the 6.5 GHz UWB communications band) while simultaneously exhibiting an infinite (open circuit) impedance to the left of signal trace segment  101  in the frequency band of high band arm  90 H (e.g., in the 8.0 GHz UWB communications band). Similarly, width W 2 , length D 2 , and/or the position of positive antenna feed terminal  46 H may selected so that microstrip  94  exhibits a 50 Ohm impedance to the right of signal trace segment  101  (e.g., in the direction of arrow  99 ) in the frequency band of high band arm  90 H (e.g., in the 8.0 GHz UWB communications band) while simultaneously exhibiting an infinite (open circuit) impedance to the right of signal trace segment  101  in the frequency band of low band arm  90 L (e.g., in the 6.5 GHz UWB communications band). In this way, microstrip  94  may perform asymmetric impedance matching to either side of signal trace segment  101 , thereby allowing stripline  96  to be impedance matched to positive antenna feed terminal  46 L in the 6.5 GHz UWB communications band while simultaneously being impedance matched to positive antenna feed terminal  46 H in the 8.0 GHz UWB communications band. 
     This example is merely illustrative and, in general, signal trace segments  104  and  106  may have any desired shapes (e.g., shapes having any number of curved and/or straight edges). Width W 1  may be equal to width W 2  or may be different than width W 1 . Length D 1  may be different from length D 2  or may be equal to length D 2 . In one suitable arrangement, signal trace segment  101  is aligned (e.g., along the X-axis of  FIG. 10 ) with the fence of conductive vias  102  forming the return path for antenna resonating element  86 . This is merely illustrative and, in general, signal trace segment  101  may be aligned with other locations on antenna resonating element  86 . Grounded shielding ring  98  may be omitted if desired. 
     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 communications band with a given linear polarization and low band arm  90 L conveys radio-frequency signals in the 6.5 UWB communications band with the same linear polarization. Additional polarizations may be covered in device  10  by providing additional antennas oriented perpendicular to each other if desired. The example of  FIG. 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 . 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 include a tail  124  that extends beyond the lateral outline of antenna resonating element  86 . Stripline  96  may be formed on tail  124 . Flexible printed circuit  92  may include conductive traces that form a ground plane (layer) such as planar ground traces  128 . Planar ground traces  128  may be formed on a surface of flexible printed circuit substrate  92  (as shown in the example of  FIG. 11 ) or may be embedded within layers  122  of flexible printed circuit substrate  92 . Planar ground traces  128  may form a part of stripline  96  and microstrip  94  for antenna  40  and may extend under antenna resonating element  86  (e.g., antenna resonating element  86  may overlap planar ground traces  128 ). Conductive vias  108  may extend through tail  124  of flexible printed circuit substrate  92  to short the planar ground traces  128  to additional ground traces  110  in stripline  96  (e.g., signal trace  100  of stripline  96  may be interposed between additional ground traces  110  and planar ground traces  128 ). This example is merely illustrative. In another suitable arrangement, signal trace  100  in stripline  96  may be laterally surrounded on two sides (e.g., in the X-Y plane) by additional grounded traces (e.g., additional grounded traces that at least partially overlap grounded shielding ring  98  of  FIG. 10 ). Other transmission line structures may be used if desired. 
     Signal trace  100  may be coupled to signal trace segment  101  in microstrip  94 . Conductive via  123  may extend from the signal conductor in microstrip  94  (e.g., signal trace  106  of  FIG. 11 ) to antenna resonating element  86  (e.g., at positive antenna feed terminal  46 H of  FIG. 10 ). Conductive via  123  may be coupled to conductive contacts such as landing pads  132  at the interfaces between each layer  122  in flexible printed circuit substrate  92 . While  FIG. 11  only shows a single conductive via  123 , antenna  40  may include two conductive vias  123  for coupling both signal trace segments  106  and  104  to positive antenna feed terminals  46 H and  46 L of  FIG. 10 , respectively. 
     Grounded shielding ring  98  may be formed on surface  116  of flexible printed circuit substrate  92 . Grounded shielding ring  98  may surround some or all of 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 planar ground traces  128  by conductive vias such as conductive vias  112 . Similarly, conductive vias  102  may extend from antenna resonating element  86  through flexible printed circuit substrate  92  to planar ground traces  128 . Conductive vias  102  and  112  may be coupled to landing pads  132  at the interfaces between each layer  122  in flexible printed circuit substrate  92 . Antenna  40  may include a fence of conductive vias  102  to form the return path for antenna  40  (e.g., return path  88  of  FIG. 9 ). 
     Conductive vias  112 , antenna resonating element  86 , and planar ground traces  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 to maximize the size of antenna cavity  130  (e.g., allowing antenna cavity  130  to extend downward to planar ground traces  128 ). This may serve to maximize bandwidth and efficiency for antenna  40 . Grounded shielding ring  98  and conductive vias  112  may also serve to shield antenna  40  from external electromagnetic interference. 
     As shown in  FIG. 11 , 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 gap  126 , 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 . 
     If desired, flexible printed circuit substrate  92  may form part of flexible printed circuit  70  or may be mounted to flexible printed circuit  70  of  FIG. 7  (e.g., antenna  40  of  FIG. 11  may be mounted in one of regions  80 ,  78 , or  74  of  FIG. 7 ). In order to further enhance the bandwidth covered by the antennas within each of regions  80 ,  78 , and  74  of  FIG. 7 , each region may include a respective set of antennas  40  that are tuned to slightly different frequencies. The set of antennas may collectively exhibit a bandwidth that is greater than the bandwidth of the dual-band antenna of  FIGS. 10 and 11 . 
       FIG. 12  is a bottom-up view of an illustrative set  134  of antennas that may be formed in one of regions  80 ,  78 , or  74  of  FIG. 7  for performing ultra-wideband communications with a relatively large bandwidth. As shown in  FIG. 12 , set  134  may include four antennas  40  such as a first antenna  40 -A, a second antenna  40 -B, a third antenna  40 -C, and a fourth antenna  40 -D. Each antenna in set  134  may be fed using the same transmission line (e.g., a transmission line such as a stripline or microstrip having signal conductor  138 ). 
     In the example of  FIG. 12 , each of antennas  40 -A,  40 -B,  40 -C, and  40 -D is a planar inverted-F antenna having a corresponding antenna resonating element  86 , a single resonating element arm (e.g., resonating element arm  90  of  FIG. 8 ) with a corresponding width  95 , and a corresponding fence of conductive vias  102  (e.g., for forming a return path for the antenna such as return path  88  of  FIG. 8 ). Each antenna in set  134  may have the same width  95  or the antennas in set  134  may have different lateral widths. 
     Antennas  40 -A,  40 -B,  40 -C, and  40 -D may be configured to cover different frequencies. The response frequencies of antennas  40 -A and  40 -C may be selected to collectively cover the 8.0 GHz UWB communications band (e.g., with a wider bandwidth than in a scenario where only a single antenna is used to cover the 8.0 GHz UWB communications band) whereas the response frequencies of antennas  40 -B and  40 -D may be selected to collectively cover the 6.5 GHz UWB communications band (e.g., with a wider bandwidth than in a scenario where only a single antenna is used to cover the 6.5 GHz UWB communications band). For example, the antenna resonating element  86  in antenna  40 -A may have a length L 3  that configures antenna  40 -A to resonate at a first frequency that is less than 8.0 GHz and greater than 6.5 GHz (e.g., 7.9 GHz, 7.8 GHz, 7.7 GHz, or any other desired frequency that is 300 MHz or less below 8.0 GHz), whereas the antenna resonating element  86  in antenna  40 -C may have a length L 5  that configures antenna  40 -C to resonate at a second frequency that is greater than 8.0 GHz (e.g., 8.1 GHz, 8.2 GHz, 8.3 GHz, or any other desired frequency that 300 MHz or less greater than 8.0 GHz). Similarly, the antenna resonating element  86  in antenna  40 -B may have a length L 4  that configures antenna  40 -B to resonate at a third frequency that is less than 6.5 GHz (e.g., 6.4 GHz, 6.3 GHz, 6.2 GHz, or any other desired frequency that is 300 MHz or less below 6.5 GHz), whereas the antenna resonating element  86  in antenna  40 -D may have a length L 6  that configures antenna  40 -D to resonate at a fourth frequency that is greater than 6.5 GHz and less than 8.0 GHz (e.g., 6.6 GHz, 6.7 GHz, 6.8 GHz, or any other desired frequency that is 300 MHz or less greater than 6.5 GHz). Lengths L 3 , L 4 , L 5 , and L 6  may, for example, be approximately equal to one-quarter of the effective wavelengths of operation of antennas  40 -A,  40 -B,  40 -C, and  40 -D, respectively. Collectively, the antennas in set  134  may cover both ultra-wideband communications bands with greater bandwidth than in scenarios where a signal dual-band antenna is used. 
     Signal trace  138  may be coupled to the positive antenna feed terminal  46  on antenna  40 -C by signal trace  142  and may be coupled to the positive antenna feed terminal  46  on antenna  40 -D by signal trace  140 . Conductive vias may be used to couple signal traces  142  and  140  to positive antenna feed terminals  46  (e.g., conductive vias extending through the underlying flexible printed circuit substrate such as flexible printed circuit substrate  92  of  FIGS. 10 and 11 ). Signal traces  142  and  140  may, for example, form the signal conductor of a microstrip transmission line that couples signal conductor  138  to antennas  40 -C and  40 -D. 
     Signal trace  142  may also be an impedance matching trace that is configured to match the impedance of signal trace  138  to the impedance of antenna  40 -C at the second frequency. For example, the length D 3  of signal trace  142 , the width W 3  of signal trace  142 , and/or the position of the positive antenna feed terminal  46  for antenna  40 -C may be selected to form a 50 Ohm impedance to the left of signal trace  138  (e.g., in the direction of arrow  152 ) at the second frequency while forming an infinite impedance at the fourth frequency (e.g., at the response frequency of antenna  40 -D). Similarly, signal trace  140  may also be an impedance matching trace that is configured to match the impedance of signal trace  138  to the impedance of antenna  40 -D at the fourth frequency. For example, the length D 4  of signal trace  140 , the width W 4  of signal trace  140 , and/or the position of the positive antenna feed terminal  46  for antenna  40 -D may be selected to form a 50 Ohm impedance to the right of signal trace  138  (e.g., in the direction of arrow  154 ) at the fourth frequency while forming an infinite impedance at the second frequency (e.g., at the response frequency of antenna  40 -C). This may serve to match the impedance of signal trace  138  to both antennas  40 -C and  40 -D in their respective frequency bands, thereby maximizing the antenna efficiency for antennas  40 -C and  40 -D. 
     The positive antenna feed terminal  46  on antenna  40 -A may be coupled to signal trace  148  and the positive antenna feed terminal  46  on antenna  40 -B may be coupled to signal trace  150  (e.g., using respective conductive vias). Signal traces  150  and  148  may extend from opposing sides of signal trace  144 . Signal trace  144  may couple signal traces  150  and  148  to signal traces  142 ,  140 , and  138 . Signal traces  144 ,  148 , and  150  may, for example, form the signal conductor of a microstrip transmission line that couples signal conductor  138  to antennas  40 -A and  40 -B. 
     Signal trace  148  may also be an impedance matching trace that is configured to match the impedance of signal trace  138  to the impedance of antenna  40 -A at the first frequency. For example, the length D 5  of signal trace  148 , the width W 5  of signal trace  148 , and/or the position of the positive antenna feed terminal  46  for antenna  40 -A may be selected to form a 50 Ohm impedance to the left of signal trace  144  (e.g., in the direction of arrow  152 ) at the first frequency while forming an infinite impedance at the third frequency (e.g., at the response frequency of antenna  40 -B). Similarly, signal trace  150  may also be an impedance matching trace that is configured to match the impedance of signal trace  138  to the impedance of antenna  40 -B at the third frequency. For example, the length D 6  of signal trace  150 , the width W 6  of signal trace  150 , and/or the position of the positive antenna feed terminal  46  for antenna  40 -B may be selected to form a 50 Ohm impedance to the right of signal trace  144  (e.g., in the direction of arrow  154 ) at the third frequency while forming an infinite impedance at the first frequency (e.g., at the response frequency of antenna  40 -A). This may serve to match the impedance of signal trace  138  to both antennas  40 -A and  40 -B in their respective frequency bands, thereby maximizing the antenna efficiency for antennas  40 -A and  40 -B. If desired, the dimensions of signal trace  144  may also contribute to the impedance matching for antennas  40 -A and  40 -B. 
     If desired, signal trace  144  may have a length  146  that is selected so that the radio-frequency signals at the positive antenna feed terminal  46  for antenna  40 -C are in phase with the radio-frequency signals at the positive antenna feed terminal  46  for antenna  40 -A and so that the radio-frequency signals at the positive antenna feed terminal  46  for antenna  40 -B are in phase with the radio-frequency signals at the positive antenna feed terminal  46  for antenna  40 -D. This may serve to maximize antenna efficiency for antennas  40 -A and  40 -C (e.g., in the 8.0 GHz UWB communications band) and to maximize antenna efficiency for antennas  40 -B and  40 -D (e.g., in the 6.5 GHz UWB communications band). 
     In the example of  FIG. 12 , the conductive vias  102  forming the return path for antenna  40 -A are formed on the side (edge) of antenna resonating element  86  facing away from antenna  40 -B and the conductive vias  102  forming the return path for antenna  40 -B are formed on the side (edge) of antenna resonating element  86  facing away from antenna  40 -A. In addition, the conductive vias  102  forming the return path for antenna  40 -C are formed on the side of antenna resonating element  86  facing antenna  40 -D and the conductive vias  102  forming the return path for antenna  40 -D are formed on the side of antenna resonating element  86  facing antenna  40 -C. This may serve to maximize antenna efficiency for set  134 . This is merely illustrative and, in general, vias  102  may be formed on any desired side of the antenna resonating element  86  in each antenna  40 -A,  40 -B,  40 -C, and  40 -D. Signal trace segments  148 ,  150 ,  142 , and  140  may have any desired shapes having any desired number of straight and/or curved edges. Lengths D 5 , D 6 , D 3 , and D 4  may all be the same or two or more of these lengths may be different. Widths W 5 , W 6 , W 3 , and W 4  may all be the same or two or more of these widths may be different. Antennas  40 -A,  40 -B,  40 -C, and  40 -D may have other shapes if desired (e.g., shapes having any desired number of curved and/or straight edges). Signal traces  148 ,  150 ,  144 ,  142 , and  140  may sometimes be referred to herein as signal trace segments of the signal conductor for the same microstrip transmission line (e.g., a microstrip transmission line that couples signal trace  138  to each of the antennas in set  134 ). 
       FIG. 13  is a plot of antenna performance (antenna efficiency) as a function of frequency for the set  134  of antennas  40 -A,  40 -B,  40 -C, and  40 -D of  FIG. 12 . As shown in  FIG. 13 , curve  156  plots the collective efficiency of each of antennas  40 -A,  40 -B,  40 -C, and  40 -D. The set  134  of antennas may be configured to cover a first ultra-wideband communications band at frequency FL (e.g., 6.5 GHz) and a second ultra-wideband communications band at frequency FH (e.g., 8.0 GHz). As shown by curve  156 , antenna  40 -A may exhibit response peak  164  at the first frequency (e.g., frequency F 1 ), antenna  40 -C may exhibit response peak  166  at the second frequency (e.g., frequency F 2 ), antenna  40 -B may exhibit response peak  160  at the third frequency (e.g., frequency F 3 ), and antenna  40 -D may exhibit response peak  162  at the fourth frequency (e.g., frequency F 4 ). First frequency F 1  may be 0-300 MHz less than frequency FH, second frequency F 2  may be 0-300 greater than frequency FH, third frequency F 3  may be 0-300 less than frequency FL, and frequency F 4  may be 0-300 MHz greater than frequency FL. 
     In scenarios where the dual-band antenna of  FIGS. 10 and 11  is used, low band arm  90 L may cover a relatively narrow bandwidth about frequency FL and high band arm  90 H may cover a relatively narrow bandwidth about frequency FH. In scenarios where set  134  of  FIG. 12  is used, the relatively narrow bandwidths of antennas  40 -A and  40 -C may combine to provide set  134  with an expanded bandwidth about frequency FH. Similarly, the relatively narrow bandwidths of antennas  40 -B and  40 -D may combine to provide set  134  with an expanded bandwidth about frequency FL. For example, antennas  40 -A and  40 -C may exhibit an antenna efficiency PK at frequency FH that is within margin  158  greater than the antenna efficiency at which antennas  40 -A and  40 -C collectively exhibit fixed bandwidth BW (e.g., 500 MHz). Similarly, antennas  40 -B and  40 -D may exhibit an antenna efficiency PK at frequency FL that is within margin  158  greater than the antenna efficiency at which antennas  40 -B and  40 -D collectively exhibit fixed bandwidth BW (e.g., 500 MHz). Margin  158  may be less than or equal to 10 dB, for example. In this way, the antennas in device  10  may cover relatively wide bandwidths for performing ultra-wideband communications. 
       FIG. 14  is a top-down view showing how flexible printed circuit  70  of  FIG. 7  may be mounted within device  10 . As shown in  FIG. 14 , device  10  may include a conductive layer such as conductive support plate  168 . Conductive support plate  168  may form a part of rear housing wall  12 R of  FIG. 1 , may provide mechanical support to device  10 , and may extend across some or all of the length and width of device  10 . Conductive support plate  168  may be held at a ground potential and may form a part of the antenna ground for the antennas in device  10 . A dielectric layer such as dielectric cover layer  114  of  FIG. 11  may be layered under conductive support plate  168 , if desired (not shown in  FIG. 14  for the sake of clarity). 
     Conductive support plate  168  may have openings such as openings  170  (sometimes referred to herein as slots  170 ). Stubs  72  of flexible printed circuit  70  (e.g., the portions of flexible printed circuit  70  where regions  80 ,  78 , and  74  of  FIG. 7  and thus the antennas are located on the flexible printed circuit) may be aligned with openings  170 . Stubs  72  may be inserted within openings  170  or may otherwise overlap openings  170 . Each stub  72  may include a corresponding dual-band antenna such as the dual-band antenna shown in  FIGS. 10 and 11  or may include a corresponding set of antennas such as set  134  of  FIG. 12  (e.g., a triplet of dual-band antennas or a triplet of sets of single band antennas may be aligned with the openings in conductive support plate  168 ). In another suitable arrangement, two of stubs  72  (e.g., the upper-most stubs  72  shown in  FIG. 14 ) may be aligned with a single opening in conductive support plate  168 , as shown by dashed region  174 . 
     In practice, there may be one or more gaps  172  between the antenna structures on each stub  72  and the edges of the opening  170  with which that stub has been aligned. Gaps  172  may be, for example 0.4 mm, 0.2-0.5 mm, 0.1-0.6 mm, or other sizes. The antennas on each stub  72  may be configured to convey radio-frequency signals with a single linear polarization. However, the presence of gaps  172  may introduce cross-polarization interference in which radio-frequency signals of other polarizations are undesirably conveyed by the antennas on stub  72 . In order to mitigate this cross-polarization interference, a conductive shielding layer such as conductive shielding layer  176  may be provided over openings  170 . If desired, other conductive components  178  (e.g., a battery for device  10  or other components in device  10  having conductive structures) may overlap one or more openings  170  instead of conductive shielding layer  176 . In the example of  FIG. 14 , a single conductive shielding layer  176  has been provided over the upper-most openings  170  in conductive support plate  168  whereas conductive component  178  covers the bottom-most opening  170 . Conductive shielding layer  176  and conductive component  178  may prevent radio-frequency signals of other polarizations from interfering with the radio-frequency signals conveyed by the antennas on stubs  72 . 
     The example of  FIG. 14  is merely illustrative. If desired, different conductive shielding layers  176  may be provided over different openings  170 . In another suitable arrangement, conductive component  178  may cover two openings  170  whereas conductive shielding layer  176  only covers a single opening  170 , as shown in the top-down view of  FIG. 15 . These examples are merely illustrative and, in general, any desired combination of zero, one, or more than one conductive layer  176  and zero, one, or more than one conductive component  178  may be used to cover any desired openings  170  in conductive support plate  168 . 
       FIG. 16  is a cross-sectional side view showing how conductive shielding layer  176  may cover a given opening  170  in conductive support plate  168 . As shown in  FIG. 16 , dielectric cover layer  114  may be layered under conductive support plate  168 . Flexible printed circuit  70  may extend along conductive support plate  168 . Stub  72  of flexible printed circuit  70  may extend within opening  170  in conductive support plate  168 . Antenna structures  180  may be formed on flexible printed circuit substrate  92  at stub  72 . Antenna structures  180  may include the dual-band antenna of  FIGS. 10 and 11  or the set  134  of antennas  40 -A,  40 -B,  40 -C, and  40 -D of  FIG. 12 . Stub  72  (e.g., antenna structures  180 ) may be located within opening  170  between upper surface  182  of conductive support plate  168  and dielectric cover layer  114 . 
     Conductive shielding layer  176  may be layered over conductive support plate  168  and flexible printed circuit  176 . Conductive shielding layer  176  may completely cover opening  170 . Conductive shielding layer  176  may be galvanically connected to conductive support plate  168  (e.g., using solder, welds, or other conductive adhesives), may be placed into contact with conductive support plate  168 , or may be separated from and capacitively coupled to conductive support plate  168 . Conductive shielding layer  176  may include sheet metal, conductive adhesive (e.g., copper tape having an adhesive layer), conductive traces on a dielectric substrate, conductive portions of the housing for device  10 , conductive foil, ferrite, or any other desired structures that block radio-frequency signals. In the absence of conductive shielding layer  176 , gap  172  may radiate in response to radio-frequency signals from polarizations other than the polarization handled by antenna structures  180 . This may introduce undesirable cross-polarization interference on the radio-frequency signals handled by antenna structures  180 . The presence of conductive shielding layer  176  may block these radio-frequency signals from causing gap  172  to radiate, thereby mitigating cross-polarization interference for antenna structures  180 . 
     The example of  FIG. 16  is merely illustrative. If desired, conductive components such as conductive component  178  of  FIGS. 14 and 15  may overlap gap  170  to prevent cross-polarization interference.  FIG. 17  is a cross-sectional side view showing how flexible printed circuit  70  may be configured to mitigate cross-polarization interference without conductive shielding layer  176 . As shown in  FIG. 17 , a dielectric substrate such as dielectric shim  184  may be placed on dielectric cover layer  114  within opening  170 . Dielectric shim  184  may, for example, be formed from plastic or other dielectric materials. The upper surface of dielectric shim  184  may lie flush with upper surface  182  of conductive support plate  168 . Stub  72  of flexible printed circuit  70  may be placed on and aligned with dielectric shim  184  in opening  170 . Antenna structures  180  may completely fill the lateral area of opening  170  (e.g., the outer perimeter of antennas  40 -A,  40 -B,  40 -C, and  40 -D of  FIG. 12 , the outer perimeter of antenna resonating element  86  of  FIG. 10 , or grounded shielding ring  98  of  FIG. 10  may be equal to the lateral perimeter of plastic shim  184 ). This may align antenna structures  180  with gap  170  without introducing any gap between the antenna structures and conductive support plate  168 . Because no gaps are formed between antenna structures  180  and conductive support plate  168  in this example, no structures exist on stub  72  that radiate in response to radio-frequency signals of other polarizations, and cross-polarization interference is prevented. The presence of plastic shim  184  may prevent antenna structures  180  from undesirably shorting to conductive support plate  168 . 
     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: 20190628
Publication Date: 20210323
Grant Date: 20210323
Priority Date: 20190628
Inventors: COOPER, AARON J.
TAYEBI, AMIN
DI NALLO, CARLO
LE, VINH T.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q5/335", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/25", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q19/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/25", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/521", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q5/25", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/25", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 73747281