PATENT DOCUMENT

Publication Number: US-10553945-B2
Application Number: US-201715710361-A
Country: US
Kind Code: B2

Title: Antenna arrays having surface wave interference mitigation structures

Abstract:
An electronic device may be provided with wireless communications circuitry and control circuitry. The wireless communications circuitry may include centimeter and millimeter wave transceiver circuitry and a phased antenna array. A dielectric cover may be formed over the phased antenna array. The phased antenna array may transmit and receive antenna signals through the dielectric cover. The dielectric cover may have a surface that faces the phased antenna array and may have a curvature. The antenna elements of the phased antenna array may be formed on a dielectric substrate. The dielectric substrate may have one or more thinned regions between antenna elements of the phased antenna array to reduce surface wave interference between adjacent antennas. The dielectric substrate may have a smaller thickness in the thinned region than in the regions under the antenna elements. The dielectric substrate may be totally removed in the thinned region.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a phased antenna array including a plurality of antenna elements on a dielectric substrate, wherein the dielectric substrate comprises surface-wave-mitigating recesses, each surface-wave-mitigating recess is interposed between two respective antenna elements, and each surface-wave-mitigating recess has a width that is equal to a distance between the two respective antenna elements; and transceiver circuitry coupled to the phased antenna array and configured to convey wireless signals at a frequency greater than 10 GHz using the phased antenna array. 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising:
 a grounding layer coupled to the dielectric substrate. 
 
     
     
       3. The electronic device defined in  claim 2 , further comprising:
 a plurality of transmission line structures, wherein each transmission line structure of the plurality of transmission line structures is coupled to a respective antenna element of the plurality of antenna elements through the dielectric substrate. 
 
     
     
       4. The electronic device defined in  claim 3 , wherein each transmission line structure of the plurality of transmission line structures is coupled to the grounding layer. 
     
     
       5. The electronic device defined in  claim 4 , further comprising:
 a dielectric cover having a curved inner surface formed over the plurality of antenna elements, wherein the grounding layer is curved. 
 
     
     
       6. The electronic device defined in  claim 1 , wherein the dielectric substrate has portions having a first thickness under the plurality of antenna elements and portions having a second thickness that is less than the first thickness under the surface-wave-mitigating recesses. 
     
     
       7. An electronic device, comprising:
 a dielectric substrate; and an array of antenna resonating elements arranged in rows and columns on the dielectric substrate, wherein the dielectric substrate is patterned to define a continuous recess having a plurality of horizontal portions and a plurality of vertical portions, each horizontal portion of the continuous recess is interposed between adjacent rows of antenna resonating elements, and each vertical portion of the continuous recess is interposed between adjacent columns of antenna resonating elements. 
 
     
     
       8. The electronic device defined in  claim 7 , further comprising:
 transceiver circuitry coupled to the array of antenna resonating elements and configured to convey wireless signals at a frequency greater than 10 GHz using the array of antenna resonating elements. 
 
     
     
       9. The electronic device defined in  claim 8 , further comprising:
 a grounding layer having a planar upper surface, wherein the planar upper surface of the grounding layer is coupled to the dielectric substrate. 
 
     
     
       10. The electronic device defined in  claim 8 , wherein each antenna resonating element of the array of antenna resonating elements is surrounded by the continuous recess defined by the dielectric substrate. 
     
     
       11. The electronic device defined in  claim 8 , further comprising:
 a plurality of transmission line structures, wherein each transmission line structure of the plurality of transmission line structures is coupled to a respective antenna resonating element of the array of antenna resonating elements through the dielectric substrate. 
 
     
     
       12. The electronic device defined in  claim 11 , wherein each transmission line structure of the plurality of transmission line structures is coupled to the grounding layer. 
     
     
       13. The electronic device defined in  claim 7 , further comprising:
 a dielectric cover having a curved inner surface formed over the array of antenna resonating elements. 
 
     
     
       14. An electronic device, comprising:
 a substrate; an array of antenna resonating elements on the substrate, wherein a first portion of the substrate that is overlapped by the array of antenna resonating elements has a first thickness and a second portion of the substrate that is not overlapped by the array of antenna resonating elements has a second thickness that is less than the first thickness; transceiver circuitry coupled to the array of antenna resonating elements and configured to convey wireless signals at a frequency greater than 10 GHz using the array of antenna resonating elements; a dielectric cover having a curved inner surface formed over the array of antenna resonating elements; and a curved grounding layer coupled to the substrate. 
 
     
     
       15. The electronic device defined in  claim 14 , wherein the first portion of the substrate includes a plurality of substrate portions and each substrate portion of the plurality of substrate portions is formed under a respective antenna resonating element of the array of antenna resonating elements. 
     
     
       16. The electronic device defined in  claim 15 , wherein each substrate portion of the plurality of substrate portions is surrounded by the second portion of the substrate. 
     
     
       17. The electronic device defined in  claim 14 , further comprising:
 a grounding layer coupled to the substrate. 
 
     
     
       18. The electronic device defined in  claim 17 , further comprising:
 a plurality of transmission line structures, wherein each transmission line structure of the plurality of transmission line structures is coupled to a respective antenna resonating element of the plurality of antenna resonating elements through the substrate. 
 
     
     
       19. The electronic device defined in  claim 18 , wherein each transmission line structure of the plurality of transmission line structures is coupled to the grounding layer. 
     
     
       20. The electronic device defined in  claim 7 , further comprising:
 a dielectric cover having a curved inner surface formed over the array of antenna resonating elements.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     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, millimeter wave communications signals generated by antennas can be characterized by substantial attenuation and/or distortion during signal propagation through various mediums. 
     It would therefore be desirable to be able to provide electronic devices with improved wireless communications circuitry such as communications circuitry that supports millimeter wave communications. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry. The wireless circuitry may include one or more antennas and transceiver circuitry such as centimeter and millimeter wave transceiver circuitry (e.g., circuitry that transmits and receives antennas signals at frequencies greater than 10 GHz). The antenna elements may be arranged in a phased antenna array. 
     A dielectric cover (sometimes referred to herein as a radome) may be formed over the antenna elements in the phased antenna array. The phased antenna array may transmit and receive a beam of signals through the dielectric cover and may steer the signals over a corresponding field of view. The dielectric cover may have a first surface and a second opposing surface that faces the phased antenna array. The second surface may be a curved surface (e.g., may include a curve). 
     The antenna elements of the phased antenna array may be formed on a dielectric substrate. The dielectric substrate may have one or more thinned regions between antenna elements of the phased antenna array to reduce surface wave interference between adjacent antennas in the phased antenna array. The thinned regions may include a notch in the dielectric substrate such that the dielectric substrate has a smaller thickness between antenna elements than under the antenna elements. The dielectric substrate may be totally removed in the thinned region. 
     A ground layer may be coupled to the dielectric substrate. The ground layer may be planar or may be bent (e.g., bent at the thinned portions of the dielectric substrate). The phased antenna array may also include transmission line structures. Each transmission line structure may be coupled to a respective antenna element of the phased antenna array through the dielectric substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment. 
         FIGS. 2 and 3  are perspective views of an illustrative electronic device showing locations at which phased antenna arrays for millimeter wave communications may be located in accordance with an embodiment. 
         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 an embodiment. 
         FIG. 5  is a perspective view of an illustrative patch antenna in accordance with an embodiment. 
         FIG. 6  is a side view of an illustrative patch antenna in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative antenna array covered by a planar dielectric cover in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of an illustrative antenna array with a substrate that has etched portions in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative antenna array with a substrate that has partially etched portions in accordance with an embodiment. 
         FIG. 10  is a top view of an illustrative antenna array with etched portions interposed between respective row and columns of antenna resonating elements in accordance with an embodiment. 
         FIG. 11  is a top view of an illustrative antenna array with etched portions that have a width that is less than a distance between adjacent antenna resonating elements in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of an illustrative antenna array with etched portions in a substrate that promote bending in accordance with an embodiment. 
         FIG. 13  is a diagram of illustrative antenna radiation patterns associated with phased antenna arrays such as the phased antenna arrays of  FIGS. 7-12  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may contain wireless circuitry. The wireless circuitry may include one or more antennas. The antennas may include phased antenna arrays that are used for handling millimeter wave and centimeter wave communications. Millimeter wave communications, which are sometimes referred to as extremely high frequency (EHF) communications, involve signals at 60 GHz or other frequencies between about 30 GHz and 300 GHz. Centimeter wave communications involve signals at frequencies between about 10 GHz and 30 GHz. While uses of millimeter wave communications may be described herein as examples, centimeter wave communications, EHF communications, or any other types of communications may be similarly used. If desired, electronic devices may also contain wireless communications circuitry 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 devices (such as device  10  in  FIG. 1 ) may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headphone or earpiece device, a virtual or augmented reality headset device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, a wireless access point or base station (e.g., a wireless router or other equipment for routing communications between other wireless devices and a larger network such as the internet or a cellular telephone network), a desktop computer, a keyboard, a gaming controller, a computer mouse, a mousepad, a trackpad or touchpad, equipment that implements the functionality of two or more of these devices, or other electronic equipment. The above-mentioned examples are merely illustrative. Other configurations may be used for electronic devices if desired. 
     A schematic diagram showing illustrative components that may be used in an electronic device such as electronic device  10  is shown in  FIG. 1 . As shown in  FIG. 1 , device  10  may include storage and processing circuitry such as control circuitry  14 . Control circuitry  14  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  14  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processor integrated circuits, application specific integrated circuits, etc. 
     Control circuitry  14  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  14  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  14  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, etc. 
     Device  10  may include input-output circuitry  16 . Input-output circuitry  16  may include input-output devices  18 . Input-output devices  18  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  18  may include user interface devices, data port devices, 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, 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  16  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas  40 , transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  34  may include transceiver circuitry  20  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  22 ,  24 ,  26 , and  28 . 
     Transceiver circuitry  24  may be wireless local area network transceiver circuitry. Transceiver circuitry  24  may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. 
     Circuitry  34  may use cellular telephone transceiver circuitry  26  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a midband from 1710 to 2170 MHz, a high band from 2300 to 2700 MHz, a ultra-high band from 3400 to 3700 MHz, or other communications bands between 600 MHz and 4000 MHz or other suitable frequencies (as examples). Circuitry  26  may handle voice data and non-voice data. 
     Millimeter wave transceiver circuitry  28  (sometimes referred to as extremely high frequency (EHF) transceiver circuitry  28  or transceiver circuitry  28 ) may support communications at frequencies between about 10 GHz and 300 GHz. For example, transceiver circuitry  28  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, transceiver circuitry  28  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 Ku 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, circuitry  28  may support IEEE 802.11ad communications at 60 GHz and/or 5th generation mobile networks or 5th generation wireless systems (5G) communications bands between 27 GHz and 90 GHz. If desired, circuitry  28  may support communications at multiple frequency bands between 10 GHz and 300 GHz such as a first band from 27.5 GHz to 28.5 GHz, a second band from 37 GHz to 41 GHz, and a third band from 57 GHz to 71 GHz, or other communications bands between 10 GHz and 300 GHz. Circuitry  28  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.). While circuitry  28  is sometimes referred to herein as millimeter wave transceiver circuitry  28 , millimeter wave transceiver circuitry  28  may handle communications at any desired communications bands at frequencies between 10 GHz and 300 GHz (e.g., in millimeter wave communications bands, centimeter wave communications bands, etc.). 
     Wireless communications circuitry  34  may include satellite navigation system circuitry such as Global Positioning System (GPS) receiver circuitry  22  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data (e.g., GLONASS signals at 1609 MHz). Satellite navigation system signals for receiver  22  are received from a constellation of satellites orbiting the earth. 
     In satellite navigation system links, cellular telephone links, and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. In WiFi® and Bluetooth® links at 2.4 and 5 GHz and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. Extremely high frequency (EHF) wireless transceiver circuitry  28  may convey signals that travel (over short distances) between a transmitter and a receiver 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 is 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. 
     Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. 
     Antennas  40  in wireless communications circuitry  34  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, monopoles, dipoles, helical antenna structures, Yagi (Yagi-Uda) antenna structures, hybrids of these designs, etc. If desired, one or more of antennas  40  may be cavity-backed antennas. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. Dedicated antennas may be used for receiving satellite navigation system signals or, if desired, antennas  40  can be configured to receive both satellite navigation system signals and signals for other communications bands (e.g., wireless local area network signals and/or cellular telephone signals). Antennas  40  can include phased antenna arrays for handling millimeter wave communications. 
     As shown in  FIG. 1 , device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, metallic coatings on a substrate, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). Antennas  40  may be mounted in housing  12 . Dielectric-filled openings such as plastic-filled openings may be formed in metal portions of housing  12  (e.g., to serve as antenna windows and/or to serve as gaps that separate portions of antennas  40  from each other). 
     In scenarios where input-output devices  18  include a display, the display may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. The display may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. The display may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other transparent dielectric. If desired, some of the antennas  40  (e.g., antenna arrays that may implement beam steering, etc.) may be mounted under an inactive border region of the display. The display may contain an active area with an array of pixels (e.g., a central rectangular portion). Inactive areas of the display are free of pixels and may form borders for the active area. If desired, antennas may also operate through dielectric-filled openings elsewhere in device  10 . 
     If desired, housing  12  may include a conductive rear surface. The rear surface of housing  12  may lie in a plane that is parallel to a display of device  10 . In configurations for device  10  in which the rear surface of housing  12  is formed from metal, it may be desirable to form parts of peripheral conductive housing structures as integral portions of the housing structures forming the rear surface of housing  12 . For example, a rear housing wall of device  10  may be formed from a planar metal structure, and portions of peripheral housing structures on the sides of housing  12  may be formed as vertically extending integral metal portions of the planar metal structure. 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 . The planar rear wall of housing  12  may have one or more, two or more, or three or more portions. The peripheral housing structures and/or the conductive rear wall of housing  12  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 internal structures from view of the user). 
     Transmission line paths may be used to route antenna signals within device  10 . For example, transmission line paths may be used to couple antenna structures  40  to transceiver circuitry  20 . Transmission lines in device  10  may include coaxial cable paths, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, waveguide structures for conveying signals at millimeter wave frequencies, transmission lines formed from combinations of transmission lines of these types, etc. Transmission lines in device  10  may be integrated into rigid and/or flexible printed circuit boards. In one suitable arrangement, transmission lines in device  10  may also include transmission line conductors (e.g., signal and ground conductors) 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). Filter circuitry, switching circuitry, impedance matching circuitry, and other circuitry may be interposed within the transmission lines, if desired. 
     Device  10  may contain multiple antennas  40 . The antennas may be used together or one of the antennas may be switched into use while other antenna(s) are switched out of use. If desired, control circuitry  14  may be used to select an optimum antenna to use in device  10  in real time and/or to select an optimum setting for adjustable wireless circuitry associated with one or more of antennas  40 . Antenna adjustments may be made to tune antennas to perform in desired frequency ranges, to perform beam steering with a phased antenna array, and to otherwise optimize antenna performance. Sensors may be incorporated into antennas  40  to gather sensor data in real time that is used in adjusting antennas  40 . 
     In some configurations, antennas  40  may include antenna arrays (e.g., phased antenna arrays to implement beam steering functions). For example, the antennas that are used in handling millimeter wave signals for extremely high frequency wireless transceiver circuits  28  may be implemented as phased antenna arrays. The radiating elements in a phased antenna array for supporting millimeter wave communications may be patch antennas, dipole antennas, Yagi (Yagi-Uda) antennas, or other suitable antenna elements. Transceiver circuitry  28  can be integrated with the phased antenna arrays to form integrated phased antenna array and transceiver circuit modules or packages if desired. 
     In devices such as handheld devices, the presence of an external object such as the hand of a user or a table or other surface on which a device is resting has a potential to block wireless signals such as millimeter wave signals. In addition, millimeter wave communications typically require a line of sight between antennas  40  and the antennas on an external device. Accordingly, it may be desirable to incorporate multiple phased antenna arrays into device  10 , each of which is placed in a different location within or on device  10 . With this type of arrangement, an unblocked phased antenna array may be switched into use and, once switched into use, the phased antenna array may use beam steering to optimize wireless performance. Similarly, if a phased antenna array does not face or have a line of sight to an external device, another phased antenna array that has line of sight to the external device may be switched into use and that phased antenna array may use beam steering to optimize wireless performance. Configurations in which antennas from one or more different locations in device  10  are operated together may also be used (e.g., to form a phased antenna array, etc.). 
       FIG. 2  is a perspective view of electronic device  10  showing illustrative locations  50  at which antennas  40  (e.g., single antennas and/or phased antenna arrays for use with wireless circuitry  34  such as millimeter wave wireless transceiver circuitry  28  in  FIG. 1 ) may be mounted in device  10 . As shown in  FIG. 2 , housing  12  of device  10  may include rear housing wall  12 R (sometimes referred to as wall  12 R, rear housing portion  12 R, or rear housing surface  12 R) and housing sidewalls  12 E. In one suitable arrangement, a display may be mounted to the side of housing  12  opposing rear housing wall  12 R. 
     Antennas  40  (e.g., single antennas  40  or arrays of antennas  40 ) may be mounted at locations  50  at the corners of device  10 , along the edges of housing  12  such as on sidewalls  12 E, on the upper and lower portions of rear housing portion  12 R, in the center of rear housing  12  (e.g., under a dielectric window structure such as a plastic logo), etc. In configurations in which housing  12  is formed from a dielectric, antennas  40  may transmit and receive antenna signals through the dielectric, may be formed from conductive structures patterned directly onto the dielectric, or may be formed on dielectric substrates (e.g., flexible printed circuit board substrates) formed on the dielectric. In configurations in which housing  12  is formed from a conductive material such as metal, slots or other openings may be formed in the metal that are filled with plastic or other dielectric. Antennas  40  may be mounted in alignment with the dielectric (i.e., the dielectric in housing  12  may serve as one or more antenna windows for antennas  40 ) or may be formed on dielectric substrates (e.g., flexible printed circuit board substrates) mounted to external surfaces of housing  12 . 
     In the example of  FIG. 2 , rear housing wall  12 R has a rectangular periphery. Housing sidewalls  12 E surround the rectangular periphery of wall  12 R and extend from wall  12 R to the opposing face of device  10 . In another suitable arrangement, device  10  and housing  12  may have a cylindrical shape. As shown in  FIG. 3 , rear housing wall  12 R has a circular or elliptical periphery. Rear housing wall  12 R may oppose surface  52  of device  10 . Surface  52  may be formed from a portion of housing  12 , may be formed from a display or transparent display cover layer, or may be formed using any other desired device structures. Housing sidewall  12 E may extend between surface  52  and rear housing wall  12 R. Antennas  40  may be mounted at locations  50  along housing sidewall  12 E, on surface  52 , and/or on wall  12 R. By forming phased antenna arrays at different locations along wall  12 E, on surface  52  (sometimes referred to herein as housing surface  52 ), and/or on rear housing wall  12 R (e.g., as shown in  FIGS. 2 and 3 ), the different phased antenna arrays on device  10  may collectively provide line of sight coverage to any point on a sphere surrounding device  10  (or on a hemisphere surrounding device  10  in scenarios where phased antenna arrays are only formed on one side of device  10 ). 
     The examples of  FIGS. 2 and 3  are merely illustrative. In general, housing  12  and device  10  may have any desired shape or form factor. For example, rear housing wall  12 R may have a triangular periphery, hexagonal periphery, polygonal periphery, a curved periphery, combinations of these, etc. Housing sidewall  12 E may include straight portions, curved portions, stepped portions, combinations of these, etc. If desired, housing  12  may include other portions having any other desired shapes. The height of sidewall  12 E may be less than, equal to, or greater than the length and/or width of housing rear wall  12 R. 
       FIG. 4  shows how antennas  40  on device  10  may be formed in a phased antenna array. As shown in  FIG. 4 , phased antenna array  60  (sometimes referred to herein as array  60 , antenna array  60 , or array  60  of antennas  40 ) may be coupled to a signal path such as path  64  (e.g., one or more radio-frequency transmission line structures, extremely high frequency waveguide structures or other extremely high frequency transmission line structures, etc.). Phased antenna array  60  may include a number N of antennas  40  (e.g., a first antenna  40 - 1 , a second antenna  40 - 2 , an Nth antenna  40 -N, etc.). Antennas  40  in phased antenna array  60  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, path  64  may be used to supply signals (e.g., millimeter wave signals) from millimeter wave transceiver circuitry  28  ( FIG. 1 ) to phased antenna array  60  for wireless transmission to external wireless equipment. During signal reception operations, path  64  may be used to convey signals received at phased antenna array  60  from external equipment to millimeter wave transceiver circuitry  28  ( FIG. 1 ). 
     The use of multiple antennas  40  in phased antenna array  60  allows beam steering arrangements to be implemented by controlling the relative phases and amplitudes of the signals for the antennas. In the example of  FIG. 4 , antennas  40  each have a corresponding radio-frequency controllers  62  (sometimes referred to as controllers  62  or phase and magnitude controllers  62 ). For example, a first controller  62 - 1  is coupled between signal path  64  and first antenna  40 - 1 , a second controller  62 - 2  is coupled between signal path  64  and second antenna  40 - 2 , an Nth controller  62 -N is coupled between path  64  and Nth antenna  40 -N, etc. Controllers  62  may, for example, include phase adjustment circuitry that is controlled to provide a desired phase shift on the signals conveyed by the corresponding antenna  40  and/or gain (magnitude) adjustment circuitry (e.g., adjustable amplifier circuitry) that is controlled (e.g., biased) to provide a desired gain on signals conveyed by the corresponding antenna  40 . 
     Beam steering circuitry such as control circuitry  70  (sometimes referred to herein as control circuit  70 , circuit  70 , or circuitry  70 ) may use controllers  62  or any other suitable phase and magnitude control circuitry to adjust the relative phases and/or magnitudes of the transmitted signals that are provided to each of the antennas in the antenna array and to adjust the relative phases of the received signals that are received by the antenna array from external equipment. The term “beam” or “signal beam” may be used herein to collectively refer to wireless signals that are transmitted and received by array  60  in a particular direction. The term “transmit beam” may sometimes be used herein to refer to wireless signals that are transmitted in a particular direction whereas the term “receive beam” may sometimes be used herein to refer to wireless signals that are received from a particular direction. 
     If, for example, control circuitry  70  is adjusted to produce a first set of phases and/or magnitudes on transmitted millimeter wave signals, the transmitted signals will form a millimeter wave frequency transmit beam as shown by beam  66  of  FIG. 4  that is oriented in the direction of point A. If, however, control circuitry  70  adjusts controllers  62  to produce a second set of phases and/or magnitudes on the transmitted signals, the transmitted signals will form a millimeter wave frequency transmit beam as shown by beam  68  that is oriented in the direction of point B. Similarly, if control circuitry  70  adjusts controllers  62  to produce the first set of phases and/or magnitudes, wireless signals (e.g., millimeter wave signals in a millimeter wave frequency receive beam) may be received from the direction of point A as shown by beam  66 . If control circuitry  70  adjusts controllers  62  to produce the second set of phases and/or magnitudes, signals may be received from the direction of point B, as shown by beam  68 . Control circuitry  70  may be controlled by control circuitry  14  of  FIG. 1  or by other control and processing circuitry in device  10  if desired. 
     In one suitable arrangement, controllers  62  may each include radio-frequency mixing circuitry. The mixing circuitry of controllers  62  may receive signals from path  64  at a first input and may receive a corresponding signal weight value W at a second input (e.g., mixing circuitry of controller  62 - 1  may receive a first weight W 1 , mixing circuitry of controller  62 - 2  may receive a second weight W 2 , mixing circuitry of controller  62 -N may receive an Nth weight W N , etc.). Weight values W may, for example, be provided by control circuitry  14  (e.g., using corresponding control signals) or from other control circuitry. The mixing circuitry may mix (e.g., multiply) the signals received over path  64  with the corresponding signal weight value to produce an output signal that is transmitted on the corresponding antenna. For example, a signal S may be provided to controllers  62  over path  64 . Controller  62 - 1  may output a first output signal S*W 1  that is transmitted on first antenna  40 - 1 , controller  62 - 2  may output a second output signal S*W 2  that is transmitted on second antenna  40 - 2 , etc. The output signals transmitted by each antenna may constructively and destructively interfere to generate a beam of signals in a particular direction (e.g., in a direction as shown by beam  66  or a direction as shown by beam  68 ). Similarly, adjusting weights W may allow for millimeter wave signals to be received from a particular direction and provided to path  64 . Different combinations of weights W provided to each mixer will steer the signal beam in different desired directions. If desired, control circuitry  70  may actively adjust weights W provided to controllers  62  in real time to steer the transmit or receive beam in desired directions. 
     When performing millimeter wave communications, millimeter wave signals are conveyed over a line of sight path between phased antenna array  60  and external equipment. If the external equipment is located at location A of  FIG. 4 , circuit  70  may be adjusted to steer the signal beam towards direction A. If the external equipment is located at location B, circuit  70  may be adjusted to steer the signal beam towards direction 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 is steered over two 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 ). 
     Any desired antenna structures may be used for implementing antenna  40 . For example, patch antenna structures may be used for implementing antenna  40 . Antennas  40  may therefore sometimes be referred to herein as patch antennas  40 . An illustrative patch antenna is shown in  FIG. 5 . As shown in  FIG. 5 , patch antenna  40  may have a patch antenna resonating element such as patch element  110  that is separated from a ground plane structure such as ground  112  (sometimes referred to as ground layer  112  or grounding layer  112 ). Patch antenna resonating element  110  and ground  112  may be formed from metal foil, machined metal structures, metal traces on a printed circuit or a molded plastic carrier, electronic device housing structures, or other conductive structures in an electronic device such as device  10 . 
     Patch antenna resonating element  110  may lie within a plane such as the X-Y plane of  FIG. 5 . Ground  112  may lie within a plane that is parallel to the plane of patch antenna resonating element (patch)  110 . Patch  110  and ground  112  may therefore lie in separate parallel planes that are separated by a distance H. Conductive path  114  may be used to couple terminal  98 ′ to terminal  98 . Antenna  40  may be fed using a transmission line with a positive conductor coupled to terminal  98 ′ (and thus terminal  98 ) and with a ground conductor coupled to terminal  100 . Other feeding arrangements may be used if desired. Moreover, patch  110  and ground  112  may have different shapes and orientations (e.g., planar shapes, curved patch shapes, patch element shapes with non-rectangular outlines, shapes with straight edges such as squares, shapes with curved edges such as ovals and circles, shapes with combinations of curved and straight edges, etc.). 
     A side view of a patch antenna such as patch antenna  40  of  FIG. 5  is shown in  FIG. 6 . As shown in  FIG. 6 , antenna  40  may be fed using an antenna feed (with terminals  98  and  100 ) that is coupled to a transmission line such as transmission line  92 . Patch antenna resonating element  110  of antenna  40  may lie in a plane parallel to the X-Y plane of  FIG. 6  and the surface of the structures that form ground (e.g., ground  112 ) may lie in a plane that is separated by vertical distance H from the plane of patch antenna resonating element  110 . With the illustrative feeding arrangement of  FIG. 6 , a ground conductor of transmission line  92  is coupled to antenna feed terminal  100  on ground  112  and a positive conductor of transmission line  92  is coupled to antenna feed terminal  98  via an opening in ground  112  and conductive path  114  (which may be an extended portion of the transmission line&#39;s positive conductor). Other feeding arrangements may be used if desired (e.g., feeding arrangements in which a microstrip transmission line in a printed circuit or other transmission line that lies in a plane parallel to the X-Y plane is coupled to terminals  98  and  100 , etc.). To enhance the frequency coverage and polarizations handled by antenna  40 , antenna  40  may be provided with multiple feeds (e.g., two feeds) if desired. These examples are merely illustrative and, in general, the patch antenna resonating elements may have any desired shape. Other types of antennas may be used if desired. 
     Antennas of the types shown in  FIGS. 5 and 6  and/or other types of antennas such as dipole antennas and Yagi antennas may be arranged in a phased antenna array such as phased antenna array  60  of  FIG. 4 .  FIG. 7  is a cross-sectional side view of an illustrative patch antenna array  60  formed from a pattern of patch antennas (e.g., antennas of the types shown in  FIGS. 5 and 6 ). As shown in  FIG. 7 , multiple patch antennas  40  may be arranged in antenna array  60 . Antenna resonating elements  110  (sometimes referred to herein as antenna elements  110 , elements  110 , patch antenna resonating elements  110 , patch elements  110 , or resonating elements  110 ) of respective antennas  40  may be formed at different locations over ground plane  112 . While  FIG. 7  shows a side view of array  60 , array  60  may have patch antennas arranged in a two-dimensional grid pattern (e.g., arranged in a rectangular array pattern of rows and columns, arranged in a 5×5 array, etc.) or any other desired pattern. While  FIG. 7  shows five patch antennas, this is merely illustrative. If desired, any number of patch antennas may be formed in array  60 . The example of antenna elements  110  being patch antenna elements is merely illustrative. Antenna resonating elements  110  may be dipole antenna resonating elements, Yagi antenna resonating elements, or antenna resonating elements of any other desired type. 
     Respective transmission lines  92  may couple a corresponding antenna resonating element  110  to transceiver circuitry  28  (e.g., transceiver circuitry  28  of  FIG. 1 ) through substrate  120 . Transmission lines  92  may also couple transceiver circuitry  28  to ground  112 . As an example, ground  112  may be shared between multiple antenna elements  110  in  FIG. 7 . Elements  110  may be formed on a dielectric substrate such as substrate  120 . Substrate  120  may be a printed circuit, dielectric (e.g., plastic ceramic, foam, glass, etc.) support structure, or any other suitable structure on which elements  110  may be formed. 
     As previously described, array  60  may be located at any desired location (e.g., locations  50  in  FIGS. 2 and 3 ). In order to protect array  60  from damage, dust, water, and other contaminants and for the purposes of mechanical reliability of the antenna assembly, a dielectric cover layer such as cover layer  122  (sometimes referred to as cover  122 , dielectric cover  122 , or radome  122 ) may be formed over array  60 . The dielectric properties and the geometry of cover layer  122  may affect the radiation characteristics of array  60 . 
     As shown in  FIG. 7 , cover layer  122  may be separated from antenna elements  110  of array  60  by a gap such as gap G. Gap G may be filled with a dielectric material such as plastic, foam, air, etc. Cover  122  may be formed from any desired dielectric material. As examples, cover  122  may be formed from plastic, glass, ceramics, fiber composites, a combination of two or more of these materials, or any other suitable materials. Cover  122  may be formed from a portion of housing  12  (e.g., from a dielectric antenna window portion of housing  12  or other dielectric portions of housing  12 ) or any other dielectric structures of device  10 . If desired, some or all of cover  122  may be formed from internal structures within device  10  (e.g., internal printed circuits, dielectric support structures, etc.). 
     In the example of  FIG. 7 , dielectric cover  122  has a uniform thickness T across the lateral area of array  60 . Thickness T may be defined by planar lower surface  124  and planar upper surface  126 . Surfaces  124  and  126  may lie in parallel planes with respect to a surface of elements  110 , a surface of substrate  120 , and/or a surface of ground  112 . As an example, cover  122  may completely encapsulate elements  110  and/or a top surface of substrate  120 . In other words, cover  122  and substrate  120  may form a closed cavity in which elements  110  are located. Surface  124  may sometimes be referred to herein as an inner surface, whereas surface  126  may sometimes be referred to herein as an outer surface (e.g., because inner surface  124  faces antennas  40  whereas outer surface  126  may, in some scenarios, be formed at the exterior of device  10 ). 
     During operation of antennas  40  in array  60 , the transmission and reception of signals such as millimeter wave signals may be affected by the presence of cover  122  (e.g., by the geometry of cover  122  with respect to elements  40  and by the dielectric properties of cover  122 ). In particular, signals generated by array  60  may be reflected at the air-solid interfaces of cover  122  (e.g., at surfaces  124  and  126  which may be referred to as interfacial surfaces  124  and  126  or interfaces  124  and  126 ). As a result, only a portion of signals generated by array  60  may be transmitted through cover  122 . Additionally, the reflected portion of the transmit signals of array  60  may distort other transmit signals of array  60  (e.g., reflected signals that are 180 degrees out of phase with transmitted signals may destructively interfere with the transmitted signals). For example, if care is not taken, in the presence of flat cover  122  in  FIG. 7  the peak gain of the signals transmitted by array  60  may be deteriorated, the radiation pattern of the signals generated by array  60  may be narrowed (e.g., to provide an excessively small wireless coverage area), the radiation pattern of the signals generated by array  60  may be otherwise distorted, etc. It may therefore be desirable to provide dielectric covers that can mitigate these adverse effects. 
     In the example of  FIG. 7 , the size of gap G may be selected, the thickness T of cover  122  may be selected, and/or the dielectric material used to form cover  122  may be selected to minimize these adverse effects. In particular, thickness T of cover  122  may be an optimal thickness such that the respective reflected signals generated at surfaces  124  and  126  interfere with each other destructively (e.g., cancel each other out). In other words, out-of-phase reflected signals (e.g., signals that have an approximately 180-degree phase difference with respect to each other) generated at surface  124  and  126  may cancel each other out. The optimal thickness in this example may be determined by the wavelength of the signals propagating through cover  122  and the dielectric constant of cover  122 . As an example, an optimal thickness of cover  122  may be the wavelength of operation of array  60  divided by two, or any other desired thickness that minimizes distortion of the radiation pattern. 
     Other factors may affect the efficiency of antennas  40  in phased antenna array  60 . Two possible sources of losses for antennas  40  (that accordingly decrease efficiency of the antennas) are substrate losses (e.g., losses associated with the material of substrate  120 ) and surface wave losses. Surface wave losses may, for example, be directly proportional to the thickness  128  of substrate  120 . To mitigate surface wave losses, it may therefore be desirable to decrease the thickness of substrate  120 . However, at the same time, the bandwidth of antennas  40  is directly proportional to the volume of antennas  40  (and thus the thickness of substrate  120 ). If care is not taken, it can be difficult to mitigate surface wave losses while also providing the antennas with satisfactory bandwidth. 
     Isolating antennas  40  in phased antenna array  60  may also be important in improving antenna performance. As discussed previously, beam steering techniques may be used (e.g., schemes in which antenna signal phase and/or magnitude for each antenna in an array is adjusted to perform beam steering) to achieve high throughput with phased antenna array  60  using millimeter and centimeter wave communications. Poor isolation between antennas  40  in phased antenna array  60  may make it difficult to accurately implement beamforming algorithms and may negatively affect the transmitted antenna patterns. 
     When an antenna  40  in phased antenna array  60  is used to convey radio-frequency signals, surface waves may be generated by the antenna. For example, antenna element  110 - 1  may be used to convey extremely high frequency (EHF) signals or other wireless signals at frequencies greater than 10 GHz. Conveying the EHF signals may excite electromagnetic surface waves such as surface waves  130 - 1  and  130 - 2  in the volume between elements  110  and ground  112 . For example surface waves may propagate in a lateral direction away from element  110 - 1  (e.g., in the X-Y plane of  FIG. 7 ) such as in direction  131 - 1  towards antenna element  110 - 2 , as shown by surface wave  130 - 1 , and in direction  131 - 2  towards antenna element  110 - 3 , as shown by surface wave  130 - 2 . The surface waves may electromagnetically couple with the adjacent antenna elements and thereby interfere with signals conveyed using the adjacent antenna elements (e.g., antenna elements  110 - 2  and  110 - 3 ). 
     To mitigate interference between adjacent antennas due to surface waves and to decrease substrate losses, surface wave mitigation structures may be formed in array  60 . The surface wave mitigation structures may be formed by removing portions of substrate  120  that are not covered by antennas, for example. An arrangement of this type is shown in  FIG. 8 . 
       FIG. 8  is a cross-sectional side view of a phased antenna array showing how substrate  120  may be etched (e.g., patterned) to improve isolation between adjacent antennas. As shown in  FIG. 8 , substrate  120  for antenna array  60  may be etched in regions (e.g., regions  136 , sometimes referred to as etched regions  136 ) between resonating elements  110 . Portions of the substrate  120  underneath resonating elements  110  (e.g., portions (regions)  138 , sometimes referred to as islands or remaining portions) may not be etched. If desired, as shown in  FIG. 8 , the upper surface  132  and/or the lower surface  134  of substrate  120  may be planar. 
     In general, the generation of surface waves at EHF frequencies may be dependent upon a relatively continuous dielectric permittivity of substrate  120 . However, removing portions of substrate  120  between adjacent antenna elements may create discontinuities in the permittivity of substrate  120 . These discontinuities may serve to prevent surface wave generation and thus interference by the surface waves on adjacent antennas. Removing portions of substrate  120  between adjacent antenna elements may also reduce substrate losses. 
     In  FIG. 8 , substrate  120  is totally removed in regions  136  between antenna resonating elements  110  (e.g., no portions of the dielectric material of substrate  120  may remain in regions that are not overlapped by resonating elements  110 ). However, this example is merely illustrative. If desired, substrate  120  may be partially removed or thinned (e.g., etched) in regions  136  between resonating elements  110 . An arrangement of this type is shown in  FIG. 9 . As shown in  FIG. 9 , substrate  120  has a thickness  144  in etched regions  136  and a thickness  146  in portions  138  that have not been etched. Thickness  146  may be greater than thickness  144 . Thickness  144  of each etched portion of substrate  120  may be the same across the substrate or may vary across the substrate. For example, the thickness of the substrate between first and second resonating elements  110  may be different or the same as the thickness of the substrate between second and third resonating elements  110 . Etching regions  136  of substrate  120  in this way may improve isolation between the antennas in phased antenna array  60  due to decreased surface wave interference. 
       FIGS. 10 and 11  are top views of illustrative phased antenna arrays with etched substrates. As shown in  FIG. 10 , substrate  120  may support an array of antenna resonating elements  110 . Substrate  120  has etched regions  136  between antenna resonating elements  110 . Etched regions  136  of substrate  120  have a smaller thickness than regions of substrate  120  that have not been etched (e.g., portions  138  in  FIGS. 8 and 9 ). In some cases, the substrate  120  may be completely removed in etched regions  136  (e.g., the thickness of the substrate may be 0). An arrangement of this type is also shown in  FIG. 8 , as an example. In other cases, substrate  120  may not be completely removed in etched regions  136  (e.g., the thickness of the substrate in etched regions  136  may be greater than 0 but less than the thickness of the substrate in regions  138 ). An arrangement of this type is shown in  FIG. 9 , as an example. 
     In  FIG. 10 , there are etched regions  136  between each set of adjacent columns of antenna resonating elements  110  and between each set of adjacent rows of antenna resonating elements  110 . An etched region may be interposed between each pair of antenna elements in phased antenna array  60 . The etched regions may totally surround each antenna resonating element (e.g., may totally laterally surround each antenna resonating element in the X-Y plane). Accordingly, the antennas may sometimes be referred to as island antennas. In the embodiment of  FIG. 10 , each etched region  136  may include all portions of substrate  120  between antenna resonating elements  110 . In other words, the distance ( 142 ) between adjacent antenna resonating elements  110  may be the same as the width of each etched region  136 . The example of  FIG. 10  is merely illustrative, and substrate  120  may include one or more etched regions of any desired depth, thickness, and shape. If desired, the etched regions may be along one, two, three, or four sides of one more of the patches in the array. 
     In another possible arrangement, shown in  FIG. 11 , the width of etched regions  136  may be less than the distance between adjacent antenna resonating elements. As shown in  FIG. 11 , etched region  136  may have a width  140  that is less than the distance  142  between adjacent resonating elements. Width  140  may be any desired percentage (e.g., 90%, 80%, 50%, greater than 50%, less than 50%, between 20 and 80%, greater than 10%, less than 90%) of distance  142 . In general, the etched region between each pair of antenna resonating element may have any desired width. The etched regions also do not have to be centered between adjacent antenna elements. For example, an etched region may be formed closer to a first antenna resonating element than a second, adjacent, antenna resonating element. 
     The examples of  FIGS. 10 and 11  are merely illustrative. If desired, substrate  120  may include any desired number of etched regions. Each etched region may have any desired width (e.g., equal to the distance between adjacent resonating elements or less than the distance between adjacent resonating elements) and any desired thickness (e.g., the thickness of the substrate may be 0 in the etched regions or the thickness of the substrate in the etched regions may be greater than 0 but less than the thickness of the substrate in the regions that are not etched). The examples of  FIGS. 10 and 11  show arrangements where the etched regions extend completely across the substrate. However, the etched regions may have a shorter length such that the etched regions extend only partially across the substrate. Furthermore, the etched regions may extend in any desired direction. The example of  FIGS. 10 and 11  where antenna resonating elements  110  are arranged in a grid with rows and columns of resonating elements is merely illustrative. Each resonating element  110  may have any desired location. Additionally, each antenna resonating element  110  may have any desired shape (e.g., antenna resonating elements  110  may have different shapes) and the antenna resonating elements may be arranged in any desired pattern. 
     In the examples of  FIGS. 10 and 11 , etched regions  136  run vertically between adjacent columns of antenna resonating elements  110  (e.g., parallel to the Y-axis as shown in  FIG. 11 ) and horizontally between adjacent rows of antenna resonating element  110  (e.g., parallel to the X-axis as shown in  FIG. 11 ). These examples are merely illustrative. The etched regions of the substrate may extend vertically, horizontally, or diagonally through the substrate. Additionally, the etched regions of the substrate may be curved or follow a meandering path if desired. Moreover, in  FIGS. 10 and 11  the etched regions extend both horizontally and vertically. These examples are merely illustrative. If desired, the substrate may only include etched regions that extend vertically (e.g., between adjacent columns of antenna elements) or may only include etched regions that extend horizontally (e.g., between adjacent rows of antenna elements). These types of arrangements may still improve isolation due to decreased surface wave coupling between antenna elements in one direction. Including etched regions that extend vertically and horizontally may further improve isolation due to decreased surface wave coupling between antenna elements in two directions. In general, any desired number of etched regions may be included in substrate  120 . 
     Referring to regions  136  in  FIGS. 8-11  as etched regions is merely illustrative. Regions  136  may be formed by etching substrate  120  (e.g., using photolithography techniques) or any other desired method. For example, the regions may be formed by using a mask during a deposition of substrate material or using a cutting tool. The regions may therefore sometimes be referred to as thinned regions (e.g., thinned regions  136 ), removed regions (e.g., removed regions  136 ), cavities (e.g., cavities  136 ), notches (e.g., notches  136 ), recesses (e.g., recesses  136 ), slots (e.g., slots  136 ), grooves (e.g., grooves  136 ), dielectric-free regions (portions) (e.g., dielectric-free regions  136 ), and/or empty regions (portions) (e.g., empty regions  136 ). The regions may sometimes be referred to as air gaps that are interposed between substrate portions (e.g., air gaps  136  between substrate portions  138 ) that are underneath corresponding antenna elements. The recesses  136  may be filled with air or any other dielectric material(s) having a permittivity that is sufficiently different than the permittivity of substrate  120  (e.g., where a difference between the permittivity of the substrate and the permittivity of the dielectric material is greater than a threshold). Moreover, etched regions  136  may sometimes be referred to as a collective singular etched region (e.g., etched region  136  with different portions such as vertically extending portions and horizontally extending portions). Substrate  120  may be considered patterned to define recesses (or a collective singular recess with different portions) between each pair of antenna elements (e.g., un-etched portions  138  may define recesses in regions  136  between each pair of antenna elements). Because the recesses may mitigate surface waves in substrate  120 , recesses  136  may sometimes be referred to as surface-wave-mitigating recesses. Substrate  120  may also be described as including surface-wave-mitigating structures (e.g., recesses  136 ). 
     In some of the aforementioned embodiments, the un-etched portions of the dielectric substrate (e.g., portions  138  in  FIG. 9 ) have a width (and/or shape) that matches the respective antenna resonating element supported by the portion of the dielectric substrate. However, this example is merely illustrative. The un-etched portions of the dielectric substrate (sometimes referred to as islands) do not have to follow the shape of the supported antenna resonating element. For example, the antenna resonating element can take up any desired amount of lateral area on the island (e.g., 90%, greater than 90%, greater than 95%, greater than 75%, greater than 50%, greater than 25%, between 60 and 95%, less than 100%, less than 90%, less than 60%, etc.). 
     As discussed in connection with  FIG. 7 , the dimensions of dielectric cover  122  (in  FIG. 7 ) may be selected to mitigate adverse effects caused by reflections of incident signals off the dielectric cover (e.g., the peak gain of the signals transmitted by array  60  may be deteriorated, the radiation pattern of the signals generated by array  60  may be narrowed, the radiation pattern of the signals generated by array  60  may be otherwise distorted, etc.). In the examples of  FIGS. 7-9 , dielectric cover  122  has a planer upper surface and planar lower surface. However, this example is merely illustrative. In order to mitigate the distortion of the radiation pattern for antenna signals by the dielectric cover, the dielectric cover may include one or more curved inner surfaces. The curved inner surfaces may help to reduce the incident angle of the signal beam generated by steering array  60 . This consequently lowers interfacial reflection of the incident signals, resulting in the transmission of more of the antenna signals through the dielectric cover relative to scenarios where the dielectric cover has a planar inner surface (e.g., cover  122  in  FIG. 7 ). 
       FIG. 12  shows a cross-sectional side view of an illustrative dielectric cover  122  for array  60  that has a curved inner surface such as curved inner surface  124  and planar outer surface  126 . Curved inner surface  124  may, for example, have a spherical curvature, an elliptical curvature, or any other desired type of curvature. Because inner surface  124  is curved, cover  122  may exhibit a variable thickness across its lateral area if desired (as shown in the example of  FIG. 12 ). For example, the edge portions of cover  122  around the periphery of array  60  may be thicker than a center portion of cover  122  over the center of array  60 . This is merely illustrative. If desired, curved inner surface  124  may have a convex curve or any other suitable curvature. 
     Curved inner surface  124  of cover  122  in  FIG. 12  may help to lower the incident angles at which signals transmitted by antenna resonating elements  110  reach surface  124 . By lowering the incident angle of the transmit signals, interface reflection at surface  124  may be decreased and consequently a larger portion of the millimeter wave signals generated by array  60  may be transmitted through cover  122  than if a dielectric cover having a planar inner surface was used. Additionally, concave surface  124  of cover  122  may function as a concave lens for antennas  40  in array  60  and help broaden the radiation pattern of the signal beam transmitted by array  60 . 
     The dielectric cover and antenna array may be placed at various locations within or on electronic device  10  that are adjacent to other internal structures or device housing structures. In order to adapt to the confines of the adjacent internal structures and/or housing structures (e.g., to the form factor of device  10 ) while minimizing high incident-angle reflections at the surfaces of the cover, both the inner surface and the outer surface of a dielectric cover may have curved surfaces. In one illustrative example, dielectric cover  122  may have a uniform thickness with curved upper and lower surfaces. In another illustrative example, dielectric cover  122  may have curved upper and lower surfaces and a non-uniform thickness (the degrees of curvature of the upper and lower surfaces may be different). If desired, the dielectric cover may include multiple discrete cavities (e.g., a corresponding cavity or curved lower surface for each respective antenna element  110  in array  60 ). 
     Curving one or more portions of inner surface  124  may mitigate distortions in the radiation pattern for the antenna signals by the dielectric cover. To further reduce the incident angle of the signal beam generated by steering array  60  and further lower interfacial reflection of the incident signals, array  60  (and substrate  120 ) may be curved in addition to dielectric cover  122  (resulting in the transmission of more of the antenna signals through the dielectric cover relative to scenarios where the array is planar).  FIG. 12  shows an arrangement of this type. 
     Removing portions of substrate  120  to reduce substrate losses and interference due to surface waves (as discussed in connection with  FIGS. 7-11 ) may have the additional benefit of promoting bending of substrate  120 . For the reasons discussed above, bending substrate  120  of phased antenna array  60  may be desirable to improve antenna performance. However, in some configurations substrate  120  may be formed from a fairly rigid material, thus making it difficult to bend substrate  120  as desired. Etching portions of substrate  120  (e.g., to reduce substrate losses and/or interference due to surface waves) may also promote bending of substrate  120  for improved antenna performance. 
     As shown in  FIG. 12 , substrate  120  with antenna resonating elements  110  and underlying ground layer  112  may be curved (bent). Substrate  120  may have an upper surface  132  that is curved. If desired, the curvature of upper surface  132  may be the same as the curvature of lower surface  124  of the dielectric cover (e.g., lower surface  124  of the dielectric cover may be parallel to upper surface  132  of the substrate  120 ). In  FIG. 12 , lower surface  134  of substrate  120  is shown as being curved (e.g., lower surface  134  may have curvature that matches the curvature of upper surface  132 ). However, this example is merely illustrative and lower surface  134  may instead be planar. If desired, the upper surface  132  and/or the lower surface  134  of substrate  120  may be planar (with the curvature of the underling ground layer  112  resulting in the signals from resonating elements  110  having a low incident angle on lower surface  124 ). 
     Etching substrate  120  may therefore reduce substrate losses, mitigate interference between adjacent antennas due to surface wave coupling, and promote bending of substrate  120  and ground layer  112  (thus improving antenna performance). 
       FIG. 13  shows a diagram of illustrative radiation patterns (e.g., radiation pattern envelopes) of phased antenna array  60  with and without surface-mitigating structures such as surface-wave-mitigating recesses  136  in  FIG. 8 . In the perspective of  FIG. 13 , antenna array  60  may lie in the X-Y plane of  FIG. 13 . As shown in  FIG. 13 , curve  200  illustrates a radiation pattern envelope of phased antenna array  60  without any surface-wave-mitigating structures (e.g., the phased antenna array of  FIG. 7 ) placed in the X-Y plane and radiating in the Z-direction. However, when surface-wave-mitigating structures such as recesses in the substrate of the phased antenna array (e.g., the phased antenna array of  FIG. 8 ), the radiation pattern envelope widens from curve  200  to curve  202 . In other words, the presence of surface-wave-mitigation structures may increase the antenna signal coverage area of phased antenna array  60 . These curves are merely illustrative. The radiation pattern of phased antenna arrays with or without surface-wave-mitigation structures may have any other desired shapes. The radiation pattern shown in  FIG. 13  illustrates a two-dimensional view of radiation patterns. In general, radiation patterns generated by antenna arrays are three-dimensional. As an example, the radiation patterns shown by curves  200  and  202  may be rotationally symmetrical about the z-axis in a three-dimensional representation of  FIG. 13 . 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20170920
Publication Date: 20200204
Grant Date: 20200204
Priority Date: 20170920
Inventors: YONG, Siwen
JIANG, YI
WU, JIANGFENG
ZHANG, LIJUN
PASCOLINI, MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q21/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/34", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/34", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/2266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/26", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 65721108