PATENT DOCUMENT

Publication Number: US-11728569-B2
Application Number: US-202017111131-A
Country: US
Kind Code: B2

Title: Electronic devices with dielectric resonator antennas

Abstract:
An electronic device may be provided with a phased antenna array and a display cover layer. The phased antenna array may include a dielectric resonator antenna. The dielectric resonator antenna may include a dielectric resonating element embedded in a lower permittivity dielectric substrate. The substrate and the resonating element may be mounted to a flexible printed circuit. A slot may be formed in ground traces on the flexible printed circuit and aligned with the resonating element. The slot may excite resonant modes of the resonating element. The resonating element may convey corresponding radio-frequency signals through the cover layer. A dielectric matching layer may be interposed between the resonating element and the cover layer. If desired, the slot may radiate additional radio-frequency signals and the matching layer may have a tapered shape. Dielectric resonator antennas for covering different polarizations and frequencies may be interleaved across the array.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a printed circuit; 
 ground traces on the printed circuit; 
 a slot in the ground traces; 
 a dielectric column mounted to the printed circuit and overlapping the slot, wherein the dielectric column has a first dielectric constant; 
 a dielectric substrate mounted to the printed circuit and laterally surrounding the dielectric column, wherein the dielectric substrate has a second dielectric constant that is less than the first dielectric constant; 
 a dielectric cover layer overlapping the dielectric column; and 
 a radio-frequency transmission line on the printed circuit and configured to convey radio-frequency signals to the slot at a frequency between 10 GHz and 300 GHz, wherein the slot is configured to excite an electromagnetic resonant mode of the dielectric column, the dielectric column being configured to form a waveguide for the radio-frequency signals that directs the radio-frequency signals through the dielectric cover layer. 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising:
 a phased antenna array, wherein the dielectric column is embedded in the dielectric substrate and forms part of the phased antenna array, the phased antenna array further comprising:
 an additional slot in the ground traces, and 
 an additional dielectric column mounted to the printed circuit, embedded in the dielectric substrate, and overlapping the additional slot, the additional dielectric column being configured to direct additional radio-frequency signals at the frequency through the dielectric cover layer. 
 
 
     
     
       3. The electronic device defined in  claim 2 , further comprising:
 peripheral conductive housing structures that extend around a periphery of the electronic device, wherein the dielectric cover layer is mounted to the peripheral conductive housing structures; and 
 a notch in the peripheral conductive housing structures, wherein the phased antenna array is aligned with the notch and configured to convey the radio-frequency signals and the additional radio-frequency signals through the notch. 
 
     
     
       4. The electronic device defined in  claim 2 , further comprising:
 peripheral conductive housing structures that extend around a periphery of the electronic device, wherein the dielectric cover layer is mounted to the peripheral conductive housing structures; 
 a display module configured to emit light through the dielectric cover layer, wherein the display module comprises a notch, the notch having edges defined by the display module and the peripheral conductive housing structures; 
 an audio speaker aligned with the notch; and 
 an image sensor aligned with the notch, wherein the phased antenna array is aligned with the notch and configured to convey the radio-frequency signals and the additional radio-frequency signals through the notch. 
 
     
     
       5. The electronic device defined in  claim 2 , wherein the slot and the dielectric column are configured to convey the radio-frequency signals with a first linear polarization, the additional slot and the additional dielectric column being configured to convey the additional radio-frequency signals with a second linear polarization orthogonal to the first linear polarization. 
     
     
       6. The electronic device defined in  claim 2 , wherein the dielectric column has a first width and the additional dielectric column has second width that is greater than the first width. 
     
     
       7. The electronic device defined in  claim 6 , wherein the radio-frequency signals are in a first frequency band and the additional radio-frequency signals are in a second frequency band that is lower than the first frequency band. 
     
     
       8. The electronic device defined in  claim 1 , further comprising:
 a housing with a rear housing wall and peripheral conductive housing structures that extend from the rear housing wall to the dielectric cover layer; and 
 a display module that emits light through the dielectric cover layer, wherein the dielectric substrate is mounted against the peripheral conductive housing structures, the printed circuit runs along the rear housing wall, and the dielectric column is configured to convey the radio-frequency signals through a portion of the dielectric cover layer that is interposed between the display module and the peripheral conductive housing structures. 
 
     
     
       9. The electronic device defined in  claim 8 , wherein the display module comprises a notch, the notch having edges defined by the display module and the peripheral conductive housing structures; and
 an image sensor aligned with the notch, wherein the dielectric column is aligned with the notch and is configured to convey the radio-frequency signals through the notch. 
 
     
     
       10. The electronic device defined in  claim 9 , further comprising:
 an audio component aligned with the notch, wherein the audio component is interposed between the dielectric column and the image sensor. 
 
     
     
       11. An electronic device comprising:
 a printed circuit; 
 a display; 
 a dielectric column mounted to the printed circuit, wherein the dielectric column has a first dielectric constant; 
 a dielectric substrate mounted to the printed circuit and laterally surrounding the dielectric column, wherein the dielectric substrate has a second dielectric constant that is less than the first dielectric constant; 
 a dielectric cover layer overlapping the display and the dielectric column; and 
 a radio-frequency transmission line on the printed circuit and configured to convey radio-frequency signals at a frequency between 10 GHz and 300 GHz, wherein the dielectric column is configured to form a waveguide for the radio-frequency signals that directs the radio-frequency signals through the dielectric cover layer. 
 
     
     
       12. The electronic device defined in  claim 11 , wherein the dielectric cover layer has a third dielectric constant that is less than the first dielectric constant. 
     
     
       13. The electronic device defined in  claim 12 , further comprising:
 a dielectric matching layer interposed between the dielectric column and the dielectric cover layer, wherein the dielectric matching layer has a fourth dielectric constant that is greater than the third dielectric constant and less than the first dielectric constant. 
 
     
     
       14. The electronic device defined in  claim 13 , wherein the dielectric matching layer is tapered. 
     
     
       15. The electronic device defined in  claim 11 , wherein the printed circuit has ground traces and wherein the dielectric column overlaps an opening in the ground traces. 
     
     
       16. The electronic device defined in  claim 15 , wherein the radio-frequency transmission line is configured to excite an electromagnetic mode of the dielectric column through the opening. 
     
     
       17. An electronic device comprising:
 a phased antenna array; and 
 a dielectric cover layer overlapping the phased antenna array, wherein the phased antenna array comprises:
 a dielectric substrate; 
 a first set of dielectric columns laterally surrounded by the dielectric substrate and configured to convey first radio-frequency signals with a first linear polarization through the dielectric cover layer, and 
 a second set of dielectric columns laterally surrounded by the dielectric substrate and configured to convey second radio-frequency signals with a second linear polarization orthogonal to the first linear polarization through the dielectric cover layer. 
 
 
     
     
       18. The electronic device defined in  claim 17 , wherein the dielectric columns in the second set are interleaved among the dielectric columns in the first set. 
     
     
       19. The electronic device defined in  claim 17 , wherein the phased antenna array further comprises:
 a first set of slot antenna resonating elements, wherein each slot antenna resonating element in the first set of slot antenna resonating elements is configured to excite a resonant mode of a different respective dielectric column in the first set of dielectric columns and is further configured to radiate third radio-frequency signals with the first linear polarization through the dielectric cover layer; and 
 a second set of slot antenna resonating elements, wherein each slot antenna resonating element in the second set of slot antenna resonating elements is configured to excite a resonant mode of a different respective dielectric column in the second set of dielectric columns and is further configured to radiate fourth radio-frequency signals with the second linear polarization through the dielectric cover layer. 
 
     
     
       20. The electronic device defined in  claim 17 , wherein the first set of dielectric columns is configured to convey the first radio-frequency signals at a first frequency between 10 GHz and 300 GHz, the second set of dielectric columns is configured to convey the second radio-frequency signals at the first frequency, and the phased antenna array further comprises:
 a third set of dielectric columns configured to convey third radio-frequency signals at a second frequency and with the first linear polarization through the dielectric cover layer, wherein the second frequency is greater than 10 GHz and less than the first frequency; 
 a fourth set of dielectric columns configured to convey fourth radio-frequency signals at the second frequency and with the second linear polarization through the dielectric cover layer; 
 a repeating pattern of first antenna unit cells, wherein each of the first antenna unit cells comprises a first dielectric column from the first set, a second dielectric column from the third set, and a third dielectric column from the second set that is interposed between the first and second dielectric columns; and 
 a repeating pattern of second antenna unit cells, wherein each of the second antenna unit cells comprises a fourth dielectric column from the first set, a fifth dielectric column from the fourth set, and a sixth dielectric column from the second set that is interposed between the fourth and fifth dielectric columns.

Description:
This application is a division of patent application Ser. No. 16/289,433, filed Feb. 28, 2019, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless circuitry. 
     Electronic devices often include wireless circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     It may be desirable to support wireless communications in millimeter wave and centimeter wave communications bands. Millimeter wave communications, which are sometimes referred to as extremely high frequency (EHF) communications, and centimeter wave communications involve communications at frequencies of about 10-300 GHz. Operation at these frequencies may support high bandwidths but may raise significant challenges. For example, radio-frequency communications in millimeter and centimeter wave communications bands can be characterized by substantial attenuation and/or distortion during signal propagation through various mediums. In addition, the presence of conductive electronic device components can make it difficult to incorporate circuitry for handling millimeter and centimeter wave communications into the electronic device. 
     It would therefore be desirable to be able to provide electronic devices with improved wireless circuitry such as wireless circuitry that supports millimeter and centimeter wave communications. 
     SUMMARY 
     An electronic device may be provided with a housing, a display, and wireless circuitry. The housing may include peripheral conductive housing structures that run around a periphery of the device. The display may include a display cover layer mounted to the peripheral conductive housing structures. The wireless circuitry may include a phased antenna array that conveys radio-frequency signals in one or more frequency bands between 10 GHz and 300 GHz. The phased antenna array may convey the radio-frequency signals through the display cover layer or other dielectric cover layers in the device. 
     The phased antenna array may include dielectric resonator antennas. Each dielectric resonator antenna may include a dielectric resonating element formed from a column of relatively high dielectric constant material that is embedded within a surrounding dielectric substrate. The dielectric substrate may be formed from a relatively low dielectric constant material. The dielectric substrate and the dielectric resonating element may be mounted to a flexible printed circuit. A radio-frequency transmission line such as a stripline for the dielectric resonator antenna may be formed on the flexible printed circuit. The flexible printed circuit may include ground traces. A slot may be formed in the ground traces and may be aligned with the dielectric resonating element. The stripline may indirectly feed radio-frequency signals for the slot via near-field electromagnetic coupling. The slot may couple the radio-frequency signals into the dielectric resonating element to excite one or more electromagnetic resonant modes of the dielectric resonating element. When excited, the dielectric resonating element may serve as a waveguide that propagates wave fronts of the radio-frequency signals along its length and through the display cover layer. The dielectric resonating element may exhibit a relatively small lateral footprint. This may allow the dielectric resonating elements of the phased antenna array to be mounted within a relatively narrow space between a display module for the display and the peripheral conductive housing structures. 
     A dielectric matching layer may be interposed between the dielectric resonating element and the display cover layer. The dielectric matching layer may help to match the impedance of the dielectric resonating element to the impedance of the display cover layer. If desired, the slot may be configured to form a slot antenna resonating element that radiates additional radio-frequency signals through the dielectric resonating element in addition to exciting the resonant modes of the dielectric resonating element. In this scenario, the dielectric matching layer may be provided with a tapered shape that helps to match the impedance of the display cover layer to the impedance of the dielectric resonating element in both the frequency band covered by the dielectric resonating element and the frequency band covered by the slot antenna resonating element. 
     The phased antenna array may include first and second sets of dielectric resonator antennas. The first set may convey radio-frequency signals in a first frequency band with a first linear polarization. The second set may convey radio-frequency signals in the first frequency band with an orthogonal second linear polarization. If desired, the phased antenna array may include third and fourth sets of dielectric resonator antennas. The third set may convey radio-frequency signals in a second frequency band with the first linear polarization. The fourth set may convey radio-frequency signals in the second frequency band with the second linear polarization. Because dielectric resonator antennas occupy less lateral area than other types of antennas such as patch antennas or slot antennas, the dielectric resonator antennas from the first, second, third, and/or fourth sets may be arranged in an interleaved pattern across the phased antenna array. 
    
    
     
       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 phased antenna array that may be adjusted using control circuitry to direct a beam of signals in accordance with some embodiments. 
         FIG.  5    is a cross-sectional side view of an illustrative electronic device having phased antenna arrays for radiating through different sides of the device in accordance with some embodiments. 
         FIG.  6    is a cross-sectional side view of an illustrative dielectric resonator antenna that may be mounted within an electronic device in accordance with some embodiments. 
         FIG.  7    is a perspective view of an illustrative dielectric resonator antenna in accordance with some embodiments. 
         FIG.  8    is a diagram of radiation patterns for an illustrative dielectric resonator antenna in the presence and absence of a dielectric matching layer in accordance with some embodiments. 
         FIG.  9    is a plot of antenna performance (return loss) for an illustrative dielectric resonator antenna in the presence and absence of a dielectric matching layer in accordance with some embodiments. 
         FIG.  10    is a top-down view of illustrative dielectric resonator antennas arranged in a phased antenna array in accordance with some embodiments. 
         FIG.  11    is a plot of antenna performance (return loss) for an illustrative dielectric resonator antenna that is fed by a radiating slot in accordance with some embodiments. 
         FIG.  12    is a cross-sectional side view of an illustrative dielectric resonator antenna that is fed by a radiating slot and that has a tapered dielectric matching layer in accordance with some embodiments. 
         FIG.  13    is a top-down view of an illustrative tapered dielectric matching layer on an underlying dielectric resonator antenna in accordance with some embodiments. 
         FIG.  14    is a plot of antenna performance (return loss) for an illustrative dielectric resonator antenna that is fed by a radiating slot under different tapered dielectric matching layers in accordance with some embodiments. 
         FIG.  15    is a top-down view of an illustrative phased antenna array having interleaved dielectric resonator antennas for handling the same frequencies and different polarizations in accordance with some embodiments. 
         FIG.  16    is a top-down view of an illustrative phased antenna array having interleaved dielectric resonator antennas for handling different frequencies and polarizations in accordance with some embodiments. 
         FIG.  17    is a top-down view of an illustrative electronic device having dielectric resonator antennas aligned with a notch in peripheral conductive housing structures in accordance with some embodiments. 
         FIG.  18    is a top-down view of an illustrative electronic device having dielectric resonator antennas aligned with a notch in a display module in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG.  1    may contain wireless circuitry. The wireless circuitry may include one or more antennas. The antennas may include phased antenna arrays that are used for performing wireless communications using millimeter and centimeter wave signals. Millimeter wave signals, which are sometimes referred to as extremely high frequency (EHF) signals, propagate at frequencies above about 30 GHz (e.g., at 60 GHz or other frequencies between about 30 GHz and 300 GHz). Centimeter wave signals propagate at frequencies between about 10 GHz and 30 GHz. If desired, device  10  may also contain antennas for handling satellite navigation system signals, cellular telephone signals, local wireless area network signals, near-field communications, light-based wireless communications, or other wireless communications. 
     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. Conductive portions of 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 ledge 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 of display  14  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. Inactive area IA may include a recessed region such as notch  8  that extends into active area AA. Active area AA may, for example, be defined by the lateral area of a display module for display  14  (e.g., a display module that includes pixel circuitry, touch sensor circuitry, etc.). The display module may have a recess or notch in upper region  20  of device  10  that is free from active display circuitry (i.e., that forms notch  8  of inactive area IA). Notch  8  may be a substantially rectangular region that is surrounded (defined) on three sides by active area AA and on a fourth side by peripheral conductive housing structures  12 W. 
     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  in notch  8  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. The conductive segments that are formed in this way may form parts of antennas in device  10  if desired. Other dielectric openings may be formed in peripheral conductive housing structures  12 W (e.g., dielectric openings other than gaps  18 ) and may serve as dielectric antenna windows for antennas mounted within the interior of device  10 . Antennas within device  10  may be aligned with the dielectric antenna windows for conveying radio-frequency signals through peripheral conductive housing structures  12 W. Antennas within device  10  may also be aligned with inactive area IA of display  14  for conveying radio-frequency signals through display  14 . 
     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. Other antennas for covering any other desired frequencies may also be mounted at any desired locations within the interior of device  10 . The example of  FIG.  1    is merely illustrative. If desired, housing  12  may have other shapes (e.g., a square shape, cylindrical shape, spherical shape, combinations of these and/or different shapes, 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 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 WiFi®), 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, antenna-based spatial ranging protocols (e.g., radio detection and ranging (RADAR) protocols or other desired range detection protocols for signals conveyed at millimeter and centimeter wave frequencies), etc. Each communication 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  for wirelessly conveying radio-frequency signals. 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  may include baseband processor circuitry or other control components that form a part of wireless circuitry  34 . 
     Wireless circuitry  34  may include millimeter and centimeter wave transceiver circuitry such as millimeter/centimeter wave transceiver circuitry  38 . Millimeter/centimeter wave transceiver circuitry  38  may support communications at frequencies between about 10 GHz and 300 GHz. For example, millimeter/centimeter wave transceiver circuitry  38  may support communications in Extremely High Frequency (EHF) or millimeter wave communications bands between about 30 GHz and 300 GHz and/or in centimeter wave communications bands between about 10 GHz and 30 GHz (sometimes referred to as Super High Frequency (SHF) bands). As examples, millimeter/centimeter wave transceiver circuitry  38  may support communications in an IEEE K communications band between about 18 GHz and 27 GHz, a K a  communications band between about 26.5 GHz and 40 GHz, a K u  communications band between about 12 GHz and 18 GHz, a V communications band between about 40 GHz and 75 GHz, a W communications band between about 75 GHz and 110 GHz, or any other desired frequency band between approximately 10 GHz and 300 GHz. If desired, millimeter/centimeter wave transceiver circuitry  38  may support IEEE 802.11ad communications at 60 GHz and/or 5 th  generation mobile networks or 5 th  generation wireless systems (5G) communications bands between 27 GHz and 90 GHz. Millimeter/centimeter wave transceiver circuitry  38  may be formed from one or more integrated circuits (e.g., multiple integrated circuits mounted on a common printed circuit in a system-in-package device, one or more integrated circuits mounted on different substrates, etc.). 
     If desired, millimeter/centimeter wave transceiver circuitry  38  (sometimes referred to herein simply as transceiver circuitry  38  or millimeter/centimeter wave circuitry  38 ) may perform spatial ranging operations using radio-frequency signals at millimeter and/or centimeter wave signals that are transmitted and received by millimeter/centimeter wave transceiver circuitry  38 . The received signals may be a version of the transmitted signals that have been reflected off of external objects and back towards device  10 . Control circuitry  28  may process the transmitted and received signals to detect or estimate a range between device  10  and one or more external objects in the surroundings of device  10  (e.g., objects external to device  10  such as the body of a user or other persons, other devices, animals, furniture, walls, or other objects or obstacles in the vicinity of device  10 ). If desired, control circuitry  28  may also process the transmitted and received signals to identify a two or three-dimensional spatial location of the external objects relative to device  10 . 
     Spatial ranging operations performed by millimeter/centimeter wave transceiver circuitry  38  are unidirectional. Millimeter/centimeter wave transceiver circuitry  38  may perform bidirectional communications with external wireless equipment. Bidirectional communications involve both the transmission of wireless data by millimeter/centimeter wave transceiver circuitry  38  and the reception of wireless data that has been transmitted by external wireless equipment. The wireless data may, for example, include data that has been encoded into corresponding data packets such as wireless data associated with a telephone call, streaming media content, internet browsing, wireless data associated with software applications running on device  10 , email messages, etc. 
     If desired, wireless circuitry  34  may include transceiver circuitry for handling communications at frequencies below 10 GHz such as non-millimeter/centimeter wave transceiver circuitry  36 . Non-millimeter/centimeter wave transceiver circuitry  36  may include wireless local area network (WLAN) transceiver circuitry that handles 2.4 GHz and 5 GHz bands for Wi-Fi® (IEEE 802.11) communications, wireless personal area network (WPAN) transceiver circuitry that handles the 2.4 GHz Bluetooth® communications band, cellular telephone transceiver circuitry that handles cellular telephone communications bands from 700 to 960 MHz, 1710 to 2170 MHz, 2300 to 2700 MHz, and/or or any other desired cellular telephone communications bands between 600 MHz and 4000 MHz, GPS receiver circuitry that receives GPS signals at 1575 MHz or signals for handling other satellite positioning data (e.g., GLONASS signals at 1609 MHz), television receiver circuitry, AM/FM radio receiver circuitry, paging system transceiver circuitry, near field communications (NFC) circuitry, etc. Non-millimeter/centimeter wave transceiver circuitry  36  and millimeter/centimeter wave transceiver circuitry  38  may each include one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive radio-frequency components, switching circuitry, transmission line structures, and other circuitry for handling radio-frequency signals. 
     Wireless circuitry  34  may include antennas  40 . Non-millimeter/centimeter wave transceiver circuitry  36  may transmit and receive radio-frequency signals below 10 GHz using one or more antennas  40 . Millimeter/centimeter wave transceiver circuitry  38  may transmit and receive radio-frequency signals above 10 GHz (e.g., at millimeter wave and/or centimeter wave frequencies) using antennas  40 . 
     In satellite navigation system links, cellular telephone links, and other long-range links, radio-frequency signals are typically used to convey data over thousands of feet or miles. In Wi-Fi® and Bluetooth® links at 2.4 and 5 GHz and other short-range wireless links, radio-frequency signals are typically used to convey data over tens or hundreds of feet. Millimeter/centimeter wave transceiver circuitry  38  may convey radio-frequency signals over short distances that travel over a line-of-sight path. To enhance signal reception for millimeter and centimeter wave communications, phased antenna arrays and beam steering techniques may be used (e.g., schemes in which antenna signal phase and/or magnitude for each antenna in an array are adjusted to perform beam steering). Antenna diversity schemes may also be used to ensure that the antennas that have become blocked or that are otherwise degraded due to the operating environment of device  10  can be switched out of use and higher-performing antennas used in their place. 
     Antennas  40  in wireless circuitry  34  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from stacked patch antenna structures, loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, monopole antenna structures, dipole antenna structures, helical antenna structures, Yagi (Yagi-Uda) antenna structures, hybrids of these designs, etc. In another suitable arrangement, antennas  40  may include antennas with dielectric resonating elements such as dielectric resonator antennas. 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 non-millimeter/centimeter wave wireless link for non-millimeter/centimeter wave transceiver circuitry  36  and another type of antenna may be used in conveying radio-frequency signals at millimeter and/or centimeter wave frequencies for millimeter/centimeter wave transceiver circuitry  38 . Antennas  40  that are used to convey radio-frequency signals at millimeter and centimeter wave frequencies may be arranged in one or more phased antenna arrays. 
     A schematic diagram of an antenna  40  that may be formed in a phased antenna array for conveying radio-frequency signals at millimeter and centimeter wave frequencies is shown in  FIG.  3   . As shown in  FIG.  3   , antenna  40  may be coupled to millimeter/centimeter (MM/CM) wave transceiver circuitry  38 . Millimeter/centimeter wave transceiver circuitry  38  may be coupled to antenna feed  44  of antenna  40  using a transmission line path that includes radio-frequency transmission line  42 . Radio-frequency transmission line  42  may include a positive signal conductor such as signal conductor  46  and may include a ground conductor such as ground conductor  48 . Ground conductor  48  may be coupled to the antenna ground for antenna  40  (e.g., over a ground antenna feed terminal of antenna feed  44  located on the antenna ground). Signal conductor  46  may be coupled to the antenna resonating element for antenna  40 . For example, signal conductor  46  may be coupled to a positive antenna feed terminal of antenna feed  44  located on the antenna resonating element. In another suitable arrangement, antenna  40  may be indirectly fed. For example, signal conductor  46  may indirectly feed radio-frequency signals to a portion of antenna  40  via near-field electromagnetic coupling and the antenna resonating element for antenna  40  may radiate the indirectly-fed radio-frequency signals. 
     Radio-frequency transmission line  42  may include a stripline transmission line (sometimes referred to herein simply as a stripline), a coaxial cable, a coaxial probe realized by metalized vias, a microstrip transmission line, an edge-coupled microstrip transmission line, an edge-coupled stripline transmission lines, a waveguide structure, combinations of these, etc. Multiple types of transmission lines may be used to form the transmission line path that couples millimeter/centimeter wave transceiver circuitry  38  to antenna feed  44 . Filter circuitry, switching circuitry, impedance matching circuitry, phase shifter circuitry, amplifier circuitry, and/or other circuitry may be interposed on radio-frequency transmission line  42 , if desired. 
     Radio-frequency transmission lines in device  10  may be integrated into ceramic substrates, rigid printed circuit boards, and/or flexible printed circuits. In one suitable arrangement, radio-frequency transmission lines in device  10  may be 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) that may be folded or bent in multiple dimensions (e.g., two or three dimensions) and that 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). 
       FIG.  4    shows how antennas  40  for handling radio-frequency signals at millimeter and centimeter wave frequencies may be formed in a phased antenna array. As shown in  FIG.  4   , phased antenna array  54  (sometimes referred to herein as array  54 , antenna array  54 , or array  54  of antennas  40 ) may be coupled to radio-frequency transmission lines  42 . For example, a first antenna  40 - 1  in phased antenna array  54  may be coupled to a first radio-frequency transmission line  42 - 1 , a second antenna  40 - 2  in phased antenna array  54  may be coupled to a second radio-frequency transmission line  42 - 2 , an Nth antenna  40 -N in phased antenna array  54  may be coupled to an Nth radio-frequency transmission line  42 -N, etc. While antennas  40  are described herein as forming a phased antenna array, the antennas  40  in phased antenna array  54  may sometimes also be referred to as collectively forming a single phased array antenna. 
     Antennas  40  in phased antenna array  54  may be arranged in any desired number of rows and columns or in any other desired pattern (e.g., the antennas need not be arranged in a grid pattern having rows and columns). During signal transmission operations, radio-frequency transmission lines  42  may be used to supply signals (e.g., radio-frequency signals such as millimeter wave and/or centimeter wave signals) from millimeter/centimeter wave transceiver circuitry  38  ( FIG.  3   ) to phased antenna array  54  for wireless transmission. During signal reception operations, radio-frequency transmission lines  42  may be used to convey signals received at phased antenna array  54  (e.g., from external wireless equipment or transmitted signals that have been reflected off of external objects) to millimeter/centimeter wave transceiver circuitry  38  ( FIG.  3   ). 
     The use of multiple antennas  40  in phased antenna array  54  allows beam steering arrangements to be implemented by controlling the relative phases and magnitudes (amplitudes) of the radio-frequency signals conveyed by the antennas. In the example of  FIG.  4   , antennas  40  each have a corresponding radio-frequency phase and magnitude controller  50  (e.g., a first phase and magnitude controller  50 - 1  interposed on radio-frequency transmission line  42 - 1  may control phase and magnitude for radio-frequency signals handled by antenna  40 - 1 , a second phase and magnitude controller  50 - 2  interposed on radio-frequency transmission line  42 - 2  may control phase and magnitude for radio-frequency signals handled by antenna  40 - 2 , an Nth phase and magnitude controller  50 -N interposed on radio-frequency transmission line  42 -N may control phase and magnitude for radio-frequency signals handled by antenna  40 -N, etc.). 
     Phase and magnitude controllers  50  may each include circuitry for adjusting the phase of the radio-frequency signals on radio-frequency transmission lines  42  (e.g., phase shifter circuits) and/or circuitry for adjusting the magnitude of the radio-frequency signals on radio-frequency transmission lines  42  (e.g., power amplifier and/or low noise amplifier circuits). Phase and magnitude controllers  50  may sometimes be referred to collectively herein as beam steering circuitry (e.g., beam steering circuitry that steers the beam of radio-frequency signals transmitted and/or received by phased antenna array  54 ). 
     Phase and magnitude controllers  50  may adjust the relative phases and/or magnitudes of the transmitted signals that are provided to each of the antennas in phased antenna array  54  and may adjust the relative phases and/or magnitudes of the received signals that are received by phased antenna array  54 . Phase and magnitude controllers  50  may, if desired, include phase detection circuitry for detecting the phases of the received signals that are received by phased antenna array  54 . The term “beam” or “signal beam” may be used herein to collectively refer to wireless signals that are transmitted and received by phased antenna array  54  in a particular direction. The signal beam may exhibit a peak gain that is oriented in a particular pointing direction at a corresponding pointing angle (e.g., based on constructive and destructive interference from the combination of signals from each antenna in the phased antenna array). The term “transmit beam” may sometimes be used herein to refer to radio-frequency signals that are transmitted in a particular direction whereas the term “receive beam” may sometimes be used herein to refer to radio-frequency signals that are received from a particular direction. 
     If, for example, phase and magnitude controllers  50  are adjusted to produce a first set of phases and/or magnitudes for transmitted radio-frequency signals, the transmitted signals will form a transmit beam as shown by beam B 1  of  FIG.  4    that is oriented in the direction of point A. If, however, phase and magnitude controllers  50  are adjusted to produce a second set of phases and/or magnitudes for the transmitted signals, the transmitted signals will form a transmit beam as shown by beam B 2  that is oriented in the direction of point B. Similarly, if phase and magnitude controllers  50  are adjusted to produce the first set of phases and/or magnitudes, radio-frequency signals (e.g., radio-frequency signals in a receive beam) may be received from the direction of point A, as shown by beam B 1 . If phase and magnitude controllers  50  are adjusted to produce the second set of phases and/or magnitudes, radio-frequency signals may be received from the direction of point B, as shown by beam B 2 . 
     Each phase and magnitude controller  50  may be controlled to produce a desired phase and/or magnitude based on a corresponding control signal  52  received from control circuitry  28  of  FIG.  2    (e.g., the phase and/or magnitude provided by phase and magnitude controller  50 - 1  may be controlled using control signal  52 - 1 , the phase and/or magnitude provided by phase and magnitude controller  50 - 2  may be controlled using control signal  52 - 2 , etc.). If desired, the control circuitry may actively adjust control signals  52  in real time to steer the transmit or receive beam in different desired directions over time. Phase and magnitude controllers  50  may provide information identifying the phase of received signals to control circuitry  28  if desired. 
     When performing wireless communications using radio-frequency signals at millimeter and centimeter wave frequencies, the radio-frequency signals are conveyed over a line of sight path between phased antenna array  54  and external communications equipment. If the external object is located at point A of  FIG.  4   , phase and magnitude controllers  50  may be adjusted to steer the signal beam towards point A (e.g., to steer the pointing direction of the signal beam towards point A). Phased antenna array  54  may transmit and receive radio-frequency signals in the direction of point A. Similarly, if the external communications equipment is located at point B, phase and magnitude controllers  50  may be adjusted to steer the signal beam towards point B (e.g., to steer the pointing direction of the signal beam towards point B). Phased antenna array  54  may transmit and receive radio-frequency signals in the direction of point B. In the example of  FIG.  4   , beam steering is shown as being performed over a single degree of freedom for the sake of simplicity (e.g., towards the left and right on the page of  FIG.  4   ). However, in practice, the beam may be steered over two or more degrees of freedom (e.g., in three dimensions, into and out of the page and to the left and right on the page of  FIG.  4   ). Phased antenna array  54  may have a corresponding field of view over which beam steering can be performed (e.g., in a hemisphere or a segment of a hemisphere over the phased antenna array). If desired, device  10  may include multiple phased antenna arrays that each face a different direction to provide coverage from multiple sides of the device. 
       FIG.  5    is a cross-sectional side view of device  10  in an example where device  10  has multiple phased antenna arrays. As shown in  FIG.  5   , peripheral conductive housing structures  12 W may extend around the (lateral) periphery of device  10  and may extend from rear housing wall  12 R to display  14 . Display  14  may have a display module such as display module  68  (sometimes referred to as a display panel). Display module  68  may include pixel circuitry, touch sensor circuitry, force sensor circuitry, and/or any other desired circuitry for forming active area AA of display  14 . Display  14  may include a dielectric cover layer such as display cover layer  56  that overlaps display module  68 . Display module  68  may emit image light and may receive sensor input through display cover layer  56 . Display cover layer  56  and display  14  may be mounted to peripheral conductive housing structures  12 W. The lateral area of display  14  that does not overlap display module  68  may form inactive area IA of display  14 . 
     Device  10  may include multiple phased antenna arrays  54  such as a rear-facing phased antenna array  54 - 1 . As shown in  FIG.  5   , phased antenna array  54 - 1  may transmit and receive radio-frequency signals  60  at millimeter and centimeter wave frequencies through rear housing wall  12 R. In scenarios where rear housing wall  12 R includes metal portions, radio-frequency signals  60  may be conveyed through an aperture or opening in the metal portions of rear housing wall  12 R or may be conveyed through other dielectric portions of rear housing wall  12 R. The aperture may be overlapped by a dielectric cover layer or dielectric coating that extends across the lateral area of rear housing wall  12 R (e.g., between peripheral conductive housing structures  12 W). Phased antenna array  54 - 1  may perform beam steering for radio-frequency signals  60  across the hemisphere below device  10 , as shown by arrow  62 . 
     Phased antenna array  54 - 1  may be mounted to a substrate such as substrate  64 . Substrate  64  may be an integrated circuit chip, a flexible printed circuit, a rigid printed circuit board, or other substrate. Substrate  64  may sometimes be referred to herein as antenna module  64 . If desired, transceiver circuitry (e.g., millimeter/centimeter wave transceiver circuitry  38  of  FIG.  2   ) may be mounted to antenna module  64 . Phased antenna array  54 - 1  may be adhered to rear housing wall  12 R using adhesive, may be pressed against (e.g., in contact with) rear housing wall  12 R, or may be spaced apart from rear housing wall  12 R. 
     The field of view of phased antenna array  54 - 1  is limited to the hemisphere under the rear face of device  10 . Display module  68  and other components  58  (e.g., portions of input-output circuitry  24  or control circuitry  28  of  FIG.  2   , a battery for device  10 , etc.) in device  10  include conductive structures. If care is not taken, these conductive structures may block radio-frequency signals from being conveyed by a phased antenna array within device  10  across the hemisphere over the front face of device  10 . While an additional phased antenna array for covering the hemisphere over the front face of device  10  may be mounted against display cover layer  56  within inactive area IA, there may be insufficient space between the lateral periphery of display module  68  and peripheral conductive housing structures  12 W to form all of the circuitry and radio-frequency transmission lines necessary to fully support the phased antenna array. In order to mitigate these issues and provide coverage through the front face of device  10 , a front-facing phased antenna array may be mounted within peripheral region  66  of device  10 . The antennas in the front-facing phased antenna array may include dielectric resonator antennas. Dielectric resonator antennas may occupy less area in the X-Y plane of  FIG.  5    than other types of antennas such as patch antennas and slot antennas. Implementing the antennas as dielectric resonator antennas may allow the radiating elements of the front-facing phased antenna array to fit within inactive area IA between display module  68  and peripheral conductive housing structures  12 W. At the same time, the radio-frequency transmission lines and other components for the phased antenna array may be located behind (under) display module  68 . 
       FIG.  6    is a cross-sectional side view of an illustrative dielectric resonator antenna in a front-facing phased antenna array for device  10 . As shown in  FIG.  6   , device  10  may include a front-facing phased antenna array having a given antenna  40  (e.g., mounted within peripheral region  66  of  FIG.  5   ). Antenna  40  of  FIG.  6    may be a dielectric resonator antenna. In this example, antenna  40  may include a dielectric resonating element  92  mounted to an underlying substrate such as flexible printed circuit  72 . This example is merely illustrative and, if desired, flexible printed circuit  72  may be replaced with a rigid printed circuit board, a plastic substrate, or any other desired substrate. 
     Flexible printed circuit  72  has a lateral area (e.g., in the X-Y plane of  FIG.  6   ) that extends along rear housing wall  12 R. Flexible printed circuit  72  may be adhered to rear housing wall  12 R using adhesive, may be pressed against (e.g., placed in contact with) rear housing wall  12 R, or may be separated from rear housing wall  12 R. Flexible printed circuit  72  may have a first end at antenna  40  and an opposing second end coupled to the millimeter/centimeter wave transceiver circuitry in device  10  (e.g., millimeter/centimeter wave transceiver circuitry  38  of  FIG.  2   ). In one suitable arrangement, the second end of flexible printed circuit  72  may be coupled to antenna module  64  of  FIG.  5   . 
     As shown in  FIG.  6   , flexible printed circuit  72  may include stacked dielectric layers  70 . Dielectric layers  70  may include polyimide, ceramic, liquid crystal polymer, plastic, and/or any other desired dielectric materials. Conductive traces such as conductive traces  78  may be patterned on a top surface  76  of flexible printed circuit  72 . Conductive traces such as conductive traces  82  may be patterned on an opposing bottom surface  80  of flexible printed circuit  72 . Conductive traces  78  and  82  may be held at a ground potential and may therefore sometimes be referred to herein as ground traces  78  and  82 . Ground traces  78  may be shorted to ground traces  82  using conducive vias that extend through flexible printed circuit  72  (not shown in  FIG.  6    for the sake of clarity). Ground traces  78  and  82  may form part of the antenna ground for antenna  40 , for example. Ground traces  78  and  82  may be coupled to a system ground in device  10  (e.g., using solder, welds, conductive adhesive, conductive tape, conductive brackets, conductive pins, conductive screws, conductive clips, combinations of these, etc.). For example, ground traces  78  and  82  may be coupled to peripheral conductive housing structures  12 W, conductive portions of rear housing wall  12 R, or other grounded structures in device  10 . The example of  FIG.  6    in which ground traces  78  are formed on top surface  76  and ground traces  82  are formed on bottom surface  80  of flexible printed circuit  72  is merely illustrative. If desired, one or more dielectric layers  70  may be layered over ground traces  78  and/or one or more dielectric layers  70  may be layered under ground traces  82 . 
     Antenna  40  may be fed using a radio-frequency transmission line (e.g., radio-frequency transmission line  42  of  FIG.  3   ) that is embedded within flexible printed circuit  72  such as stripline  74 . Stripline  74  may include ground traces  78  and  82  and conductive traces  84  extending between ground traces  78  and  82 . Conductive traces  84  may be patterned onto a dielectric layer  70  between ground traces  78  and  82  in flexible printed circuit  72 . The portion of ground traces  78  and  82  overlapping conductive traces  84  may form the ground conductor for stripline  74  (e.g., ground conductor  48  of  FIG.  3   ). Conductive traces  84  may form the signal conductor for stripline  74  (e.g., signal conductor  46  of  FIG.  3   ) and may therefore sometimes be referred to herein as signal traces  84 . Stripline  74  may convey radio-frequency signals between antenna  40  and the millimeter/centimeter wave transceiver circuitry. The example of  FIG.  6    in which antenna  40  is fed using a stripline is merely illustrative. In general, antenna  40  may be fed using any desired transmission line structures in flexible printed circuit  72 . 
     Dielectric resonating element  92  of antenna  40  may be formed from a column (pillar) of dielectric material mounted to top surface  76  of flexible printed circuit  72 . Dielectric resonating element  92  may be embedded within (e.g., laterally surrounded by) a dielectric substrate mounted to top surface  76  of flexible printed circuit  72  such as dielectric substrate  90 . Dielectric substrate  90  and dielectric resonating element  92  extend from a bottom surface  100  at flexible printed circuit  72  to an opposing top surface  98  at display  14 . 
     The radiating frequency of antenna  40  may be selected by adjusting the dimensions of dielectric resonating element  92  (e.g., in the direction of the X, Y, and/or Z axes of  FIG.  6   ). Dielectric resonating element  92  may be formed from a column of dielectric material having dielectric constant d k3 . Dielectric constant d k3  may be relatively high (e.g., greater than 10.0, greater than 12.0, greater than 15.0, greater than 20.0, between 15.0 and 40.0, between 10.0 and 50.0, between 18.0 and 30.0, between 12.0 and 45.0, etc.). In one suitable arrangement, dielectric resonating element  92  may be formed from zirconia or a ceramic material. Other dielectric materials may be used to form dielectric resonating element  92  if desired. 
     Dielectric substrate  90  may be formed from a material having dielectric constant d k4 . Dielectric constant d k4  may be less than dielectric constant d k3  of dielectric resonating element  92  (e.g., less than 18.0, less than 15.0, less than 10.0, between 3.0 and 4.0, less than 5.0, between 2.0 and 5.0, etc.). Dielectric constant d k4  may be greater than dielectric constant d k3  by at least 10.0, 5.0, 15.0, 12.0, 6.0, etc. In one suitable arrangement, dielectric substrate  90  may be formed from molded plastic. Other dielectric materials may be used to form dielectric substrate  90  if desired. The difference in dielectric constant between dielectric resonating element  92  and dielectric substrate  90  may establish a radio-frequency boundary condition between dielectric resonating element  92  and dielectric substrate  90  from bottom surface  100  to top surface  98 . This may configure dielectric resonating element  92  to serve as a waveguide for propagating radio-frequency signals at millimeter and centimeter wave frequencies. 
     Dielectric substrate  90  may have a width (thickness)  106  on each side of dielectric resonating element  92 . Width  106  may be selected to isolate dielectric resonating element  92  from peripheral conductive housing structures  12 W and to minimize signal reflections in dielectric substrate  90 . Width  106  may be, for example, at least one-tenth of the effective wavelength of the radio-frequency signals in a dielectric material of dielectric constant d k4 . Width  106  may be 0.4-0.5 mm, 0.3-0.5 mm, 0.2-0.6 mm, greater than 0.1 mm, greater than 0.3 mm, 0.2-2.0 mm, 0.3-1.0 mm, or greater than between 0.4 and 0.5 mm, as examples. 
     As shown in  FIG.  6   , ground traces  78  may include a slot or opening such as slot  88 . Signal traces  84  in stripline  74  may indirectly feed radio-frequency signals for slot  88  via near-field electromagnetic coupling  86  (e.g., the end of signal traces  84  and slot  88  may form antenna feed  44  of  FIG.  3   ). Slot  88  may electromagnetically couple the radio-frequency signals on stripline  74  into dielectric resonating element  92  (e.g., slot  88  may couple the electric field produced by signal traces  84  to the electric field in the volume of dielectric resonating element  92 ). This may serve to excite one or more electromagnetic modes (e.g., radio-frequency cavity or waveguide modes) of dielectric resonating element  92 . When excited by slot  88 , the electromagnetic modes of dielectric resonating element  92  may configure the dielectric resonating element to serve as a waveguide that propagates the wavefronts of radio-frequency signals  104  along the length of dielectric resonating element  92  (e.g., in the direction of the Z-axis of  FIG.  6   ), through top surface  98 , and through display  14 . 
     For example, during signal transmission, stripline  74  may convey radio-frequency signals from the millimeter/centimeter wave transceiver circuitry to antenna  40 . Slot  88  may couple the radio-frequency signals on signal traces  84  into dielectric resonating element  92 . This may serve to excite one or more electromagnetic modes of dielectric resonating element  92 , resulting in the propagation of radio-frequency signals  104  up the length of dielectric resonating element  92  and to the exterior of device  10  through display cover layer  56 . Similarly, during signal reception, radio-frequency signals  104  may be received through display cover layer  56 . The received radio-frequency signals may excite the electromagnetic modes of dielectric resonating element  92 , resulting in the propagation of the radio-frequency signals down the length of dielectric resonating element  92 . Slot  88  may couple the received radio-frequency signals into stripline  74 , which conveys the radio-frequency signals to the millimeter/centimeter wave transceiver circuitry. The relatively large difference in dielectric constant between dielectric resonating element  92  and dielectric substrate  90  may allow dielectric resonating element  92  to radiate radio-frequency signals  104  with a relatively high antenna efficiency (e.g., by establishing a strong boundary between dielectric resonating element  92  and dielectric substrate  90  for the radio-frequency signals). The relatively high dielectric constant of dielectric resonating element  92  may also allow the dielectric resonating element  92  to occupy a relatively small volume compared to scenarios where materials with a lower dielectric constant are used. 
     The length of slot  88  (e.g., in the direction of the X-axis of  FIG.  6   ) may be selected to optimize electromagnetic coupling between stripline  74  and dielectric resonating element  92 . If desired, slot  88  may feed (excite) dielectric resonating element  92  without radiating the radio-frequency signals itself. The orientation of slot  88  relative to dielectric resonating element  92  may be selected to provide antenna  40  with a desired linear polarization (e.g., a vertical or horizontal polarization). Slot  88  may sometimes be referred to herein as coupling slot  88 , feed slot  88 , or slot element  88 . Dielectric resonating element  92  may sometimes be referred to herein as a dielectric radiating element, dielectric radiator, dielectric resonator, dielectric antenna resonating element, dielectric column, dielectric pillar, radiating element, or resonating element. 
     Display cover layer  56  may be formed from a dielectric material having dielectric constant d k1  that is less than dielectric constant d k3 . For example, dielectric constant may be between about 3.0 and 10.0 (e.g., between 4.0 and 9.0, between 5.0 and 8.0, between 5.5 and 7.0, between 5.0 and 7.0, etc.). In one suitable arrangement, display cover layer  56  may be formed from glass, plastic, or sapphire. If care is not taken, the relatively large difference in dielectric constant between display cover layer  56  and dielectric resonating element  92  may cause undesirable signal reflections at the boundary between the display cover layer and the dielectric resonating element. These reflections may result in destructive interference between the transmitted and reflected signals and in stray signal loss that undesirably limits the antenna efficiency of antenna  40 . 
     In order to mitigate effects, antenna  40  may be provided with an impedance matching layer such as dielectric matching layer  94 . Dielectric matching layer  94  may be mounted to top surface  98  of dielectric resonating element  92  between dielectric resonating element  92  and display cover layer  56 . If desired, dielectric matching layer  94  may be adhered to dielectric resonating element  92  using a layer of adhesive  96 . Adhesive may also or alternatively be used to adhere dielectric matching layer  94  to display cover layer  56  if desired. Adhesive  96  may be relatively thin so as not to significantly affect the propagation of radio-frequency signals  104 . 
     Dielectric matching layer  94  may be formed from a dielectric material having dielectric constant d k2 . Dielectric constant d k2  may be greater than dielectric constant d k1  and less than dielectric constant d k3 . As an example, dielectric constant d k2  may be equal to SQRT(d k1 *d k3 ), where SQRT( ) is the square root operator and “*” is the multiplication operator. The presence of dielectric matching layer  94  may allow radio-frequency signals to propagate without facing a sharp boundary between the material of dielectric constant d k1  and the material of dielectric constant d k3 , thereby helping to reduce signal reflections. 
     Dielectric matching layer  94  may be provided with thickness  102 . Thickness  102  may be selected to be approximately equal to (e.g., within 15% of) one-quarter of the effective wavelength of radio-frequency signals  104  in dielectric matching layer  94 . The effective wavelength is given by dividing the free space wavelength of radio-frequency signals  104  (e.g., a centimeter or millimeter wavelength corresponding to a frequency between 10 GHz and 300 GHz) by a constant factor (e.g., the square root of d k3 ). When provided with thickness  102 , dielectric matching layer  94  may form a quarter wave impedance transformer that mitigates any destructive interference associated with the reflection of radio-frequency signals  104  at the boundaries between display cover layer  56 , dielectric matching layer  94 , and dielectric resonating element  92 . 
     When configured in this way, antenna  40  may radiate radio-frequency signals  104  through the front face of device  10  despite being coupled to the millimeter/centimeter wave transceiver circuitry over a flexible printed circuit located at the rear of device  10 . The relatively narrow width of dielectric resonating element  92  may allow antenna  40  to fit in the volume between display module  68 , other components  58 , and peripheral conductive housing structures  12 W. Antenna  40  of  FIG.  6    may be formed in a front-facing phased antenna array that conveys radio-frequency signals across at least a portion of the hemisphere above the front face of device  10 . 
       FIG.  7    is a perspective view of the dielectric resonator antenna of  FIG.  6   . Peripheral conductive housing structures  12 W, dielectric substrate  90 , dielectric matching layer  94 , adhesive  96 , rear housing wall  12 R, display  14 , and other components  58  of  FIG.  6    are omitted from  FIG.  7    for the sake of clarity. 
     As shown in  FIG.  7   , dielectric resonating element  92  of antenna  40  is mounted to flexible printed circuit  72 . Slot  88  in ground traces  78  may be aligned with longitudinal (central) axis  108  of dielectric resonating element  92 . Slot  88  may extend along a longitudinal axis  118  parallel to the X-axis of  FIG.  7   . Signal traces  84  of stripline  74  may extend along a longitudinal axis  120  that is perpendicular to longitudinal axis  118 . Longitudinal axes  118  and  120  are perpendicular to longitudinal axis  108  of dielectric resonating element  92 . When oriented in this way, antenna  40  may convey radio-frequency signals (e.g., radio-frequency signals  104  of  FIG.  6   ) with a desired linear polarization (e.g., the electric field of the radio-frequency signals may be aligned with the Y-axis of  FIG.  7   ). In another suitable arrangement, signal traces  84  may extend along longitudinal axis  118  and slot  88  may extend along longitudinal axis  120  to configure antenna  40  to convey radio-frequency signals with an orthogonal linear polarization (e.g., where the electric field of the radio-frequency signals is aligned with the X-axis of  FIG.  7   ). 
     Dielectric resonating element  92  may have a length  110 , width  112 , and height  114 . Length  110 , width  112 , and height  114  may be selected to provide dielectric resonating element  92  with a corresponding mix of electromagnetic cavity/waveguide modes that, when excited by slot  88 , configure antenna  40  to radiate at desired frequencies. For example, height  114  may be 2-10 mm, 4-6 mm, 3-7 mm, 4.5-5.5 mm, or greater than 2 mm. Width  112  and length  110  may each be 0.5-1.0 mm, 0.4-1.2 mm, 0.7-0.9 mm, 0.5-2.0 mm, 1.5 mm-2.5 mm, 1.7 mm-1.9 mm, 1.0 mm-3.0 mm, etc. Width  112  may be equal to length  110  or, in other arrangements, may be different than length  110 . Dielectric resonating element  92  may have sidewalls  116 . Sidewalls  116  may contact the surrounding dielectric substrate (e.g., dielectric substrate  90  of  FIG.  6   ). The example of  FIG.  7    is merely illustrative and, if desired, dielectric resonating element  92  may have other shapes (e.g., shapes with any desired number of straight and/or curved sidewalls  116 ). 
       FIG.  8    shows a cross-sectional side view of an illustrative radiation pattern for antenna  40  in the presence and absence of dielectric matching layer  94  of  FIG.  6   . As shown in  FIG.  8   , curve  122  illustrates a radiation pattern of antenna  40  in scenarios where the dielectric matching layer is omitted. As shown by curve  122 , the radiation pattern may exhibit lobes of peak gain separated by a gain minimum at boresight. This minimum may be the result of signal reflections and destructive interference between the dielectric resonating element and the display cover layer. 
     When antenna  40  is provided with dielectric matching layer  94  of  FIG.  6   , antenna  40  may exhibit a radiation pattern as illustrated by curve  124 . As shown by curve  124 , the dielectric matching layer may serve to merge the gain peaks of curve  122  together to create a more uniform radiation pattern with greater gain at boresight. In other words, the dielectric matching layer may optimize the radiation pattern for antenna  40  by providing a smooth transition between the dielectric material of the dielectric resonating element and the dielectric material of the display cover layer. 
     The example of  FIG.  8    is merely illustrative. In general, curve  124  may exhibit other shapes. The radiation pattern shown in  FIG.  8    illustrate a two-dimensional cross-sectional side view of the radiation pattern. In general, the radiation pattern for antenna  40  is three-dimensional. 
       FIG.  9    is a plot of antenna performance as a function of frequency for antenna  40  in the presence and absence of dielectric matching layer  94  of  FIG.  6   . As shown in  FIG.  9   , curve  126  plots the return loss (e.g., scattering coefficient S 11 ) of antenna  40  in the absence of dielectric matching layer  94 . As shown by curve  126 , antenna  40  may exhibit response peaks at multiple frequencies such as frequencies F 1 , F 2 , and F 3 . Each response peak may be associated with a corresponding electromagnetic mode of dielectric resonating element  92  (e.g., an electromagnetic mode excited by slot  88  of  FIG.  6   ). The dimensions of dielectric resonating element  92  (e.g., length  110 , width  112 , and height  114  of  FIG.  7   ) may be selected to tune the response peaks to different desired frequencies. 
     Curve  128  plots the return loss of antenna  40  in the presence of dielectric matching layer  94 . As shown by curve  128 , antenna  40  may exhibit stronger responses at frequencies F 1 , F 2 , and F 3  as well as at other frequencies between frequencies F 1  and F 3  (e.g., antenna  40  may exhibit satisfactory antenna efficiency over a wider bandwidth) relative to scenarios where the dielectric matching layer is omitted. In this way, dielectric matching layer  94  may configure antenna  40  to exhibit a uniform radiation pattern (e.g., as shown by curve  124  of  FIG.  8   ) over a wider range of frequencies (e.g., from frequency F 1  to F 3 ) relative to scenarios where the dielectric matching layer is omitted. The example of  FIG.  9    is merely illustrative. In general, curve  128  may have other shapes and may exhibit any desired number of response peaks at any desired frequencies. 
       FIG.  10    is a top-down view showing how multiple dielectric resonator antennas may be integrated into a front-facing phased antenna array in device  10  (e.g., as taken in the direction of arrow  105  of  FIG.  6   ). As shown in  FIG.  10   , multiple antennas  40  (e.g., dielectric resonator antennas of the type shown in  FIGS.  6  and  7   ) may be arranged in a corresponding phased antenna array such as front-facing phased antenna array  54 - 2 . As shown in  FIG.  10   , phased antenna array  54 - 2  may include at least three antennas  40  each fed using a corresponding stripline  74  and slot  88  in flexible printed circuit  72 . Each antenna  40  in phased antenna array  54 - 2  includes a corresponding dielectric resonating element  92 . In the example of  FIG.  10   , each dielectric resonating element  92  in phased antenna array  54 - 2  is embedded within the same dielectric substrate  90 . This is merely illustrative and, if desired, two or more dielectric resonating elements  92  may be embedded in different substrates. 
     Each antenna  40  in phased antenna array  54 - 2  may be laterally separated from one or two adjacent antennas  40  in the phased antenna array by distance  131 . Distance  131  may be selected to allow the antennas in phased antenna array  54 - 2  to collectively convey radio-frequency signals over a corresponding signal beam. For example, distance  131  may be approximately one-half of the free-space wavelength of operation of phased antenna array  54 - 2  (e.g., a free-space wavelength corresponding to a frequency in a frequency band of operation for phased antenna array  54 - 2 ). Distance  131  may be 3-5 mm, 2-6 mm, 3.5-4.5 mm, or 1-4 mm, as examples. 
     In the example of  FIG.  10   , each antenna  40  in phased antenna array  54 - 2  is provided with the same linear polarization. If desired, one or more antennas  40  in phased antenna array  54 - 2  may be provided with an orthogonal linear polarization. For example, a first set of antennas  40  in phased antenna array  54 - 2  may convey radio-frequency signals with a vertical polarization whereas a second set of antennas  40  in phased antenna array  54 - 2  may convey radio-frequency signals with a horizontal polarization. The antennas in the first set may be interleaved among the antennas in the second set if desired. 
     In the example of  FIG.  10   , slots  88  have a length  130  and width  132  that are selected to maximize electromagnetic coupling between the corresponding stripline  74  (e.g., signal traces  84 ) and the corresponding dielectric resonating element  92 . In another suitable arrangement, length  130  and width  132  may be selected so that the slots also radiate radio-frequency signals for antennas  40  in addition to exciting dielectric resonating elements  92 . The slots may radiate when length  130  is approximately equal to one-half of the effective wavelength of operation for antennas  40 , for example. When the slots are configured to radiate in this way, the slots may form a slot antenna resonating element for antennas  40  (e.g., antennas  40  may by hybrid slot and dielectric resonator antennas). The slot antenna resonating elements may contribute to the overall frequency response of antennas  40 . 
       FIG.  11    is a plot of antenna performance (return loss) as a function of frequency for antenna  40  in an arrangement where the slot that feeds the dielectric resonating element is also configured to radiate radio-frequency signals as a slot antenna resonating element. As shown by curve  133  of  FIG.  11   , antenna  40  may exhibit a first response peak (mode) at frequency F 4  and a second response peak (mode) at frequency F 5 . The response peak at frequency F 5  may be produced by dielectric resonating element  92  (e.g., frequency F 5  may be determined by length  110 , width  112 , and height  114  of dielectric resonating element  92  as shown in  FIG.  7   ). The response peak at frequency F 4  may be produced by the slot antenna resonating element (e.g., frequency F 4  may be determined by the perimeter of the slot antenna resonating element). In this way, the antenna may perform radio-frequency communications at both frequencies F 4  and F 5  (e.g., in two frequency bands that include frequencies F 4  and F 5 ). As an example, frequency F 4  may be a frequency between 24 GHz and 28 GHz whereas frequency F 5  is a frequency between 30 GHz and 34 GHz. 
     This example is merely illustrative. In another suitable arrangement, the response peak at frequency F 5  may be produced by the slot antenna resonating element whereas the response peak at frequency F 4  is produced by the dielectric resonating element. Curve  133  may have other shapes and may exhibit more than two response peaks if desired. Frequencies F 4  and F 5  may include any desired frequencies between 10 GHz and 300 GHz. 
     In scenarios where antenna  40  covers multiple frequency bands (e.g., scenarios where antenna  40  is provided with a radiating slot antenna element in addition to dielectric resonating element  92  for covering frequencies F 4  and F 5  of  FIG.  11   ), dielectric matching layer  94  of  FIG.  6    may not be capable of performing impedance matching between the dielectric resonator antenna and the display cover layer with sufficient bandwidth to cover each frequency band handled by antenna  40 . If desired, antenna  40  may be provided with a tapered dielectric matching layer. The tapered dielectric matching layer may perform impedance matching between the dielectric resonator antenna and the display cover layer over a sufficiently wide bandwidth to cover each frequency band handled by antenna  40 . 
       FIG.  12    is a cross-sectional side view of device  10  in a scenario where antenna  40  is provided with a radiating slot and a tapered dielectric matching layer. In the example of  FIG.  12   , other components  58 , display module  68 , dielectric substrate  90 , rear housing wall  12 R, adhesive  96 , and peripheral conductive housing structures  12 W of  FIG.  6    are omitted from  FIG.  12    for the sake of clarity. 
     As shown in  FIG.  12   , a radiating slot such as radiating slot  135  may be formed in ground traces  78  on flexible printed circuit  72 . Radiating slot  135  (e.g., a slot  88  of  FIG.  6    that has been provided with a perimeter that configures the slot element to radiate radio-frequency as a slot antenna resonating element) may be indirectly fed by signal traces  84  of stripline  74  via near-field electromagnetic coupling  86 . A tapered dielectric matching layer such as tapered dielectric matching layer  138  may be mounted to dielectric resonating element  92  (e.g., bottom surface  142  of tapered dielectric matching layer  138  may be mounted to top surface  98  of dielectric resonating element  92 ). Display cover layer  56  may be mounted over top surface  144  of tapered dielectric matching layer  138 . A layer of adhesive (not shown for the sake of clarity) may be used to adhere top surface  144  to display cover layer  56  and/or to adhere bottom surface  142  to dielectric resonating element  92 . Adhesive may be omitted if desired. 
     Stripline  74  may convey radio-frequency signals in a first frequency band (e.g., a frequency band at frequency F 4  of  FIG.  11   ) and a second frequency band (e.g., a frequency band at frequency F 5  of  FIG.  11   ). The radio-frequency signals may induce antenna currents in the first frequency band to flow through ground traces  78  and around the perimeter of radiating slot  135  (e.g., in the X-Y plane of  FIG.  12   ). Radiating slot  135  may radiate corresponding radio-frequency signals in the first frequency band through dielectric resonating element  92 , tapered dielectric matching layer  138 , and display cover layer  56 . At the same time, radiating slot  135  may excite the resonant modes (e.g., cavity/waveguide modes) of dielectric resonating element  92  in the second frequency band. Corresponding radio-frequency signals in the second frequency band may propagate down the length of dielectric resonating element  92 , through tapered dielectric matching layer  138 , and through display cover layer  56 . 
     If desired, tapered dielectric matching layer  138  may be formed from the same material as dielectric matching layer  94  of  FIG.  6    (e.g., a dielectric material having dielectric constant d k2 ). The presence of tapered dielectric matching layer  138  may allow radio-frequency signals in both the first and second frequency bands to propagate without facing a sharp impedance discontinuity between dielectric resonating element  92  and display cover layer  56 , thereby helping to reduce signal reflections and maximize antenna efficiency in both frequency bands. The dimensions of tapered dielectric matching element  138  may be selected to tune the matching characteristics of tapered dielectric matching layer  138  as a function of frequency, which in turn serves to tune the antenna efficiency of antenna  40  as a function of frequency. 
     Bottom surface  142  of tapered dielectric matching layer  138  may have width  112  (e.g., the same width as dielectric resonating element  92 ). Top surface  144  of tapered dielectric matching layer  138  may have width  136 . Width  136  is less than width  112 . Tapered dielectric matching layer  138  may have height  134  extending from bottom surface  142  to top surface  144 . Width  136 , width  112 , and height  134  may determine the taper angle  140  of tapered dielectric matching layer  138 . Width  136 , height  134 , and/or taper angle  140  may be selected to tune the matching characteristics of dielectric matching layer  138  and thus the frequency response of antenna  40  in the presence of display cover layer  56 . As an example, width  136  may be between 0.8 mm and 1.2 mm, between 0.7 mm and 1.3 mm, between 0.9 mm and 1.1 mm, greater than 1.3 mm, less than 0.7 mm, or other lengths that are less than width  112  of dielectric resonating element  92 . Height  134  may be 0.5-3.5 mm, 1.0 mm-3.0 mm, 1.5-2.5 mm, or other heights. For a fixed width  112 , height  134  and width  136  may determine taper angle  140 . 
       FIG.  13    is a top-down view of tapered dielectric matching layer  138  on antenna  40 . As shown in  FIG.  13   , tapered dielectric matching layer  138  may be mounted to an underlying dielectric resonating element that is laterally surrounded by dielectric substrate  90  (e.g., tapered dielectric matching layer  138  may protrude above dielectric substrate  90  in the direction of the Z-axis of  FIG.  13   ). Tapered dielectric matching layer  138  has a tapered shape extending from bottom surface  142  at the underlying dielectric resonating element to top surface  144 . Tapered dielectric matching layer  138  may overlap the underlying radiating slot  135 , which is fed by signal traces  84  of the corresponding stripline. 
     The example of  FIGS.  12  and  13    are merely illustrative. If desired, tapered dielectric matching layer  138  may have other shapes (e.g., shapes having any desired number of curved and/or straight edges, cylindrical shapes, conical shapes, combinations of these, etc.). The underlying radiating slot may be oriented at other angles with respect to tapered dielectric matching layer  138  if desired. 
       FIG.  14    is a plot of antenna performance (return loss) as a function of frequency for an antenna having a radiating slot and a dielectric resonating element such as antenna  40  of  FIGS.  12  and  13   . As shown in  FIG.  14   , curves  146 ,  148 , and  150  plot the return loss of antenna  40  when provided with tapered dielectric matching layers  138  having different taper angles (e.g., having fixed widths  136  and  112  but different taper angles  140  and thus different heights  134  as shown in  FIG.  12   ). For example, curve  146  of  FIG.  14    may correspond to the performance of antenna  40  when the tapered dielectric matching layer is provided with a first taper angle (e.g., a first height), curve  148  may correspond to the performance of antenna  40  when the tapered dielectric matching layer is provided with a second taper angle (e.g., a second height), and curve  150  may correspond to the performance of antenna  40  when the tapered dielectric matching layer is provided with a third taper angle (e.g., a third height). The first taper angle may be less than the second and third taper angles and the first height may be less than the second and third heights. Similarly, the second taper angle may be less than the third taper angle and the second height may be less than the third height. 
     As shown by curves  146 ,  148 , and  150 , each configuration of the tapered dielectric matching layer may produce a first response peak within frequency band  152  at frequency F 4 . This response peak may be produced by the slot antenna mode of antenna  40  (e.g., radiating slot  135  of  FIGS.  12  and  13    may support a response peak at frequency F 4  regardless of taper angle). As shown by curve  146 , the first taper angle and first height may configure the tapered dielectric matching layer to provide the antenna with a second response peak in a second frequency band at frequency F 6 . As shown by curve  148 , the second taper angle and second height may configure the tapered dielectric matching layer to provide the antenna with a second response peak in a second frequency band at frequency F 7 . As shown by curve  150 , the third taper angle and third height may configure the tapered dielectric matching layer to provide the antenna with a second response peak in a second frequency band at frequency F 8 . The response peaks at frequencies F 6 , F 7 , and F 8  may be produced by the dielectric resonating element mode of antenna  40  (e.g., frequencies F 6 , F 7 , and F 8  may each be frequency F 5  of  FIG.  11    depending upon the configuration of the tapered dielectric matching layer). In other words, increasing height  134  and thus taper angle  140  (for fixed widths  136  and  112 ) may serve to adjust the matching characteristics of the tapered dielectric matching layer to push the frequency response of antenna  40  in the second frequency band higher, as shown by arrow  154 . By providing the tapered dielectric matching layer with a suitable shape, the antenna may be configured to radiate with satisfactory antenna efficiency in any two desired frequency bands using both the radiating slot and the dielectric resonating element of the antenna. 
     The example of  FIG.  14    is merely illustrative. If desired, other dimensions of the tapered dielectric matching layer may be adjusted to tune the frequency response of antenna  40 . Curves  146 ,  148 , and  150  may have any desired shapes and may exhibit response peaks at any desired frequencies. If the response peak in the second frequency band (e.g., at frequencies F 6 , F 7 , or F 8 ) is sufficiently close to the response peak in the first frequency band (e.g., at frequency F 4 ), the antenna may exhibit a continuous response peak with satisfactory antenna efficiency (e.g., an antenna efficiency that exceeds a minimum threshold efficiency) from the lower limit of the first frequency band to the upper limit of the second frequency band. 
     If desired, a given phased antenna array in device  10  may include different antennas that cover different polarizations (e.g., to provide the phased antenna array with polarization diversity). For example, a given phased antenna array may include a first set of antennas that cover a horizontal polarization and a second set of antennas that cover a vertical polarization. In order to optimize space consumption within the device, the first set of antennas may be interleaved among the second set of antennas in the phased antenna array. 
       FIG.  15    is a top-down view of a given phased antenna array  54 - 2  having antennas for covering both horizontal and vertical polarizations. As shown in  FIG.  15   , phased antenna array  54 - 2  may include a first set of antennas  40 V that convey radio-frequency signals with a first linear polarization (e.g., a vertical polarization) and a second set of antennas  40 H that convey radio-frequency signals with an orthogonal second linear polarization (e.g., a horizontal polarization). 
     Antennas  40 H and  40 V may each include a corresponding dielectric resonating element  92  mounted over an underlying slot element  160 . Each dielectric resonating element  92  in phased antenna array  54 - 2  may be mounted within the same dielectric substrate (e.g., dielectric substrate  90  of  FIGS.  6  and  10   ) or may be mounted within two or more dielectric substrates. Slot elements  160  may be non-radiating slots that excite dielectric resonating elements  92  using radio-frequency signals conveyed over the corresponding stripline signal traces  84  (e.g., slot elements  160  may form slots  88  of  FIGS.  6 ,  7 , and  10   ). In this scenario, antennas  40 H and  40 V may cover frequencies within a single frequency band (e.g., a frequency band from frequency F 1  to frequency F 3  of  FIG.  9   ), for example. In another suitable arrangement, slot elements  160  may be radiating slots that radiate radio-frequency signals and excite dielectric resonating elements  92  to radiate (e.g., slot elements  160  may form radiating slots  135  of  FIGS.  12  and  13   ). In this scenario, antennas  40 H and  40 V may cover frequencies in multiple frequency bands (e.g., a first frequency band at frequency F 4  and a second frequency band at frequency F 5  of  FIG.  11   ). The slot elements  160  and signal traces  84  for antennas  40 V may be oriented perpendicular to the slot elements  160  and signal traces  84  for antennas  40 H. 
     Phased antenna array  54 - 2  may include a repeating pattern of two or more unit cells  156  of antennas (sometimes referred to herein as antenna unit cells  156 ). Each unit cell  156  may include a corresponding antenna  40 V and a corresponding antenna  40 H. In the example of  FIG.  15   , phased antenna array  54 - 2  has four unit cells  156 . This is merely illustrative and, if desired, phased antenna array  54 - 2  may have more than four unit cells  156  or fewer than four unit cells  156 . 
     In order to allow for satisfactory beam forming, each antenna  40 H in phased antenna array  54 - 2  may be located at approximately one-half of the effective wavelength of operation of antenna  40 H from each adjacent antenna  40 H in phased antenna array  54 - 2 . Similarly, each antenna  40 V may be located at approximately one-half of the effective wavelength of operation of antenna  40 V from each adjacent antenna  40 V. As shown in  FIG.  15   , each antenna  40 V is separated from one or two adjacent antennas  40 V in phased antenna array  54 - 2  by distance  158 . Similarly, each antenna  40 H is separated from one or two adjacent antennas  40 H by distance  158  (e.g., unit cell  156  may have a width equal to distance  158 ). Distance  158  may be between 4 mm and 6 mm, between 3 mm and 7 mm, between 3.5 mm and 4.5 mm, approximately 4 mm, etc. Each antenna  40 V may be located within the space between adjacent antennas  40 H and each antenna  40 H may be located in the space between adjacent antennas  40 V in phased antenna array  54 - 2 . In general, dielectric resonator antennas such as antennas  40 H and  40 L may occupy less lateral area than other types of antennas such as slot antennas or patch antennas. By forming antennas  40 H and  40 L as dielectric resonator antennas, there may be sufficient space between adjacent antennas  40 H and between adjacent antennas  40 L to allow the antennas  40 V to be interleaved in this way among the antennas  40 H in phased antenna array  54 - 2 . When arranged in this way, phased antenna array  54 - 2  may be provided with polarization diversity in as small an area as possible while still allowing for satisfactory beam forming for each polarization. 
     In the example of  FIG.  15   , each antenna in phased antenna array  54 - 2  covers the same frequency band(s). If desired, phased antenna array  54 - 2  may include different antennas that cover different frequency bands and/or different polarizations.  FIG.  16    is a top-down view of a given phased antenna array  54 - 2  having different antennas for covering different frequency bands using both horizontal and vertical polarizations. 
     As shown in  FIG.  16   , phased antenna array  54 - 2  may include a first set of antennas  40 VH, a second set of antennas  40 HH, a third set of antennas  40 VL, and a fourth set of antennas  40 HL. Antennas  40 VH and antennas  40 HH may each convey radio-frequency signals in the same relatively high frequency band. Antennas  40 VL and antennas  40 HL may each convey radio-frequency signals in the same relatively low frequency band. The dimensions of dielectric resonating element  92  and/or slot element  160  in antennas  40 VL and  40 HL may be larger than the dimensions of dielectric resonating element  92  and/or slot element  160  in antennas  40 VH and  40 HH in order to support lower frequencies. The relatively low frequency band may, for example, include frequencies between 24 GHz and 31 GHz (e.g., a 28 GHz band), frequencies between 26 GHz and 30 GHz, or any other desired frequencies that are lower than the relatively high frequency band. The relatively high frequency band may, for example, include frequencies between 37 GHz and 41 GHz (e.g., a 39 GHz band), frequencies between 38 GHz and 40 GHz, or any other desired frequencies that are higher than the relatively low frequency band. 
     Antennas  40 VH and  40 VL may both convey radio-frequency signals with a first linear polarization (e.g., a vertical polarization). Antennas  40 HH and  40 HL may both convey radio-frequency signals with an orthogonal second polarization (e.g., a horizontal polarization). Phased antenna array  54 - 2  of  FIG.  16    may include a repeating pattern of one or more unit cells  162  and one or more unit cells  164  of antennas (sometimes referred to herein as antenna unit cells  162  and  164 ). Each unit cell  162  may include a corresponding antenna  40 VH, antenna  40 HH, and antenna  40 VL. Each unit cell  164  may include a corresponding antenna  40 VH, antenna  40 HH, and antenna  40 HL. In the example of  FIG.  16   , phased antenna array  54 - 2  has two unit cells  162  and two unit cells  164 . This is merely illustrative and, if desired, phased antenna array  54 - 2  may have any desired number of two or more unit cells  162  and two or more unit cells  164 . 
     In order to allow for satisfactory beam forming, each antenna  40 VH in phased antenna array  54 - 2  may be located at approximately one-half of the effective wavelength corresponding to a frequency in the relatively high frequency band from one or more adjacent antennas  40 VH in phased antenna array  54 - 2 . Similarly, each antenna  40 HH may be located at approximately one-half of the effective wavelength corresponding to the frequency in the relatively high frequency band from one or more adjacent antennas  40 HH in phased antenna array  54 - 2 . At the same time, each antenna  40 VL in phased antenna array  54 - 2  may be located at approximately one-half of the effective wavelength corresponding to a frequency in the relatively low frequency band from one or more adjacent antennas  40 VL in phased antenna array  54 - 2 . Similarly, each antenna  40 HL may be located at approximately one-half of the effective wavelength corresponding to the frequency in the relatively low frequency band from one or more adjacent antennas  40 HL in phased antenna array  54 - 2 . 
     As shown in  FIG.  16   , each antenna  40 VH is separated from one or two adjacent antennas  40 VH by distance  166 , each antenna  40 HH is separated from one or two adjacent antennas  40 HH by distance  166 , each antenna  40 VL is separated from one or two adjacent antennas  40 VL by distance  166 , and each antenna  40 HL is separated from one or two adjacent antennas  40 HL by distance  166  (e.g., unit cells  162  and  164  may each have a width equal to distance  166 ). Distance  166  may, for example, be approximately equal to one-half of the wavelength of operation of antennas  40 VH and  40 HH (e.g., the effective wavelength corresponding to a frequency in the relatively high frequency band of phased antenna array  54 - 2 ). As some examples, distance  166  may be between 4 mm and 6 mm, between 4.5 mm and 5.5 mm, between 3 mm and 7 mm, approximately 5 mm, etc. By forming antennas  40 VH,  40 HH,  40 VL, and  40 HL as dielectric resonator antennas (rather than as patch or slot antennas), there may be sufficient space to form both an antenna  40 HH and one of antennas  40 VL or  40 HL between each pair of adjacent antennas  40 VH. By interleaving the antennas in this way, phased antenna array  54 - 2  may be provided with polarization diversity for both the first and second frequency bands while occupying as small an area as possible in device  10 . 
     The examples of  FIGS.  15  and  16    are merely illustrative. If desired, phased antenna array  54 - 2  may include antennas arranged in a two-dimensional pattern. When arranged in this way, similar spacing may be provided between antennas of the same polarization and frequency band in the vertical direction as in the horizontal direction shown in  FIGS.  15  and  16   . For example, adjacent rows of antennas in the phased antenna array may be staggered with respect to each other (e.g., to ensure that vertically-adjacent antennas do not cover the same frequency band and polarization). 
     One or more phased antenna arrays  54 - 2  may be mounted at any desired locations in device  10  along the periphery of display  14  for radiating through the display (e.g., within inactive area IA of display  14  of  FIG.  1   ).  FIG.  17    is a top-down view of device  10  showing how a given phased antenna array  54 - 2  may be aligned with a notch in peripheral conductive housing structures  12 W. 
     As shown in  FIG.  17   , peripheral conductive housing structures  12 W may run around the periphery of display module  68  in device  10 . Display cover layer  56  of  FIGS.  5 ,  6 , and  12    has been omitted from  FIG.  17    for the sake of clarity. Peripheral conductive housing structures  12 W may include an inwardly protruding lip  170  (sometimes referred to herein as a ledge or datum) and a raised portion  168 . Raised portion  168  may run around the peripheral edge of the display cover layer. Lip  170  of peripheral conductive housing structures  12 W may include an opening such as notch  172 . Phased antenna array  54 - 2  (e.g., a phased antenna array that covers a single polarization, a phased antenna array that covers multiple polarizations in the same frequency band(s) as shown in  FIG.  15   , or a phased antenna array that covers multiple polarizations and multiple frequency bands as shown in  FIG.  16   ) may be mounted below lip  170  and aligned with notch  172 . 
     The antennas  40  in phased antenna array  54 - 2  may each include a dielectric resonating element  92  surrounded by one or more dielectric substrates  90 . Each antenna  40  in phased antenna array  54 - 2  may be fed using a corresponding stripline in the same flexible printed circuit  72 . This example is merely illustrative and, if desired, two or more antennas  40  in phased antenna array  54 - 2  may be fed using radio-frequency transmission lines in separate flexible printed circuits. The antennas  40  in phased antenna array  54 - 2  may convey radio-frequency signals through notch  172  and the display cover layer (not shown). Phased antenna array  54 - 2  may perform beam steering within the hemisphere above the front face of device  10 . The example of  FIG.  17    is merely illustrative. If desired, the antennas  40  in phased antenna array  54 - 2  may be arranged in a two-dimensional pattern having multiple rows and columns of antennas or in may be arranged in other patterns. 
     If desired, phased antenna array  54 - 2  may be located elsewhere within device  10 . In one suitable arrangement, phased antenna array  54 - 2  may be located within notch  8  in active area AA of display  14  ( FIG.  1   ).  FIG.  18    is a top-down view showing how phased antenna array  54 - 2  may be aligned with notch  8  in active area AA of display  14 . 
     As shown in  FIG.  18   , display module  68  of display  14  may include notch  8 . Display cover layer  56  of  FIGS.  5 ,  6 , and  12    has been omitted from  FIG.  18    for the sake of clarity. Display module  68  may form active area AA of display  14  whereas notch  8  forms part of inactive area IA of display  14  ( FIG.  1   ). The edges of notch  8  may be defined by peripheral conductive housing structures  12 W and display module  68 . For example, notch  8  may have two or more edges (e.g., three edges) defined by display module  68  and one or more edges defined by peripheral conductive housing structures  12 W. 
     Device  10  may include speaker port  16  (e.g., an ear speaker) within notch  8 . If desired, device  10  may include other components  174  within notch  10 . Other components  174  may include one or more image sensors such as one or more cameras, an infrared image sensor, an infrared light emitter (e.g., an infrared dot projector and/or flood illuminator), an ambient light sensor, a fingerprint sensor, a capacitive proximity sensor, a thermal sensor, a moisture sensor, or any other desired input/output components (e.g., input/output devices  26  of  FIG.  2   ). One or more phased antenna arrays  54 - 2  may be aligned with the portion(s) of notch  8  that are not occupied by other components  174  or speaker port  16 . Phased antenna arrays  54 - 2  that are aligned with notch  8  may include one-dimensional phased antenna arrays such as one-dimensional phased antenna array  54 - 2 ′ and/or two-dimensional phased antenna arrays such as two-dimensional phased antenna array  54 - 2 ″. Because dielectric resonating elements  92  occupy less lateral area than patch antennas or slot antennas that cover the same frequencies, phased antenna arrays  54 - 2 ′ and  54 - 2 ″ may fit within notch  8  and may still exhibit satisfactory antenna efficiency despite the presence of speaker port  16  and other components  174 . 
     If desired, multiple phased antenna arrays  54 - 2  may be aligned with multiple notches in peripheral conductive housing structures  12 W (e.g., multiple notches  172  of  FIG.  17   ) and/or may be aligned with notch  8  in display module  68 . Phased antenna arrays  54 - 2  may provide beam steering in one or more frequency bands between 10 GHz and 300 GHz within some or all of the hemisphere over the front face of device  10 . When combined with the operation of phased antenna array  54 - 1  at the rear of device  10  ( FIG.  5   ), the phased antenna arrays in device  10  may collectively provide coverage within approximately a full sphere around device  10 . 
     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: 20201203
Publication Date: 20230815
Grant Date: 20230815
Priority Date: 20190228
Inventors: AVSER, BILGEHAN
RAJAGOPALAN, HARISH
PAULOTTO, Simone
EDWARDS, JENNIFER M.
XU, HAO
GOMEZ ANGULO, RODNEY A.
HILL, MATTHEW D.
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q9/0485", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/0075", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/0485", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/0485", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q21/0075", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/0075", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 72235967