Patent Publication Number: US-11646501-B2

Title: Electronic devices having antennas with hybrid substrates

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 can support high throughput but may raise significant challenges. For example, if care is not taken, the antennas might exhibit insufficient bandwidth to cover multiple frequency bands of interest and the antennas might occupy excessive space within the electronic device. 
     It would therefore be desirable to be able to provide electronic devices with improved wireless communications circuitry such as communications circuitry that supports millimeter and centimeter wave communications. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry. The wireless circuitry may include a phased antenna array. The phased antenna array may convey radio-frequency signals in a signal beam at a frequency greater than 10 GHz. 
     An antenna in the phased antenna array may be formed on a dielectric substrate. The dielectric substrate may have routing layers, a first set of antenna layers on the routing layers, a second set of antenna layers on the first set of antenna layers, and a third set of antenna layers on the second set of antenna layers. The antenna may include a first layer of conductive traces on an uppermost layer of the first set of antenna layers. A second layer of conductive traces may be patterned on an uppermost layer of the second set of antenna layers. A third layer of conductive traces may be patterned on an uppermost layer of the third set of antenna layers. Ground traces may be patterned on an uppermost layer of the routing layers. Signal traces on the routing layers may be coupled to positive antenna feed terminal(s) on the first and optionally the second layers of conductive traces. 
     The first layer of conductive traces may form a first patch element that radiates in a first frequency band. The second layer of conductive traces may form a second patch element that radiates in a second frequency band that is higher than the first frequency band. The third layer of conductive traces may form a parasitic patch. A conductive via may form a short path that couples the first patch element to ground. The conductive via may be coupled to the center of the first patch element to allow the first patch element to form part of the antenna ground for the second patch element in the second frequency band without affecting performance of the first patch element in the first frequency band. The first set of antenna layers may have a higher dielectric permittivity than the second and third sets of antenna layers to minimize the thickness of the substrate without affecting radio-frequency performance and without requiring a separate dielectric loading layer over the antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a front perspective view of an illustrative electronic device with wireless circuitry in accordance with some embodiments. 
         FIG.  2    is a rear perspective view of an illustrative electronic device with wireless circuitry in accordance with some embodiments. 
         FIG.  3    is a schematic diagram of an illustrative electronic device with wireless circuitry in accordance with some embodiments. 
         FIG.  4    is a diagram of an illustrative phased antenna array in accordance with some embodiments. 
         FIG.  5    is a diagram of illustrative wireless circuitry in accordance with some embodiments. 
         FIG.  6    is a perspective view of an illustrative antenna having stacked patch elements in accordance with some embodiments. 
         FIG.  7    is a cross-sectional side view of an illustrative antenna having three layers of stacked patch elements, a shorting path, and parasitic elements in accordance with some embodiments. 
         FIG.  8    is a cross-sectional side view showing how an illustrative antenna having stacked patch elements, a shorting path, and parasitic elements may be differentially loaded by a dielectric substrate in accordance with some embodiments. 
         FIG.  9    is a plot of antenna performance (antenna efficiency) as a function of frequency for an illustrative antenna 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 and/or spatial ranging operations 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 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, a desktop computer, a portable speaker, a keyboard, a gaming controller, a gaming system, 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. In the illustrative configuration of  FIG.  1   , device  10  is a portable device such as a cellular telephone, media player, tablet computer, portable speaker, or other portable computing device. Other configurations may be used for device  10  if desired. The example of  FIG.  1    is merely illustrative. 
     As shown in  FIG.  1   , device  10  may include a display such as display  8 . Display  8  may be mounted in 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, 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.). 
     Display  8  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 sensor electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  8  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. 
     Display  8  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other transparent dielectrics. Openings may be formed in the display cover layer. For example, openings may be formed in the display cover layer to accommodate one or more buttons, sensor circuitry such as a fingerprint sensor or light sensor, ports such as a speaker port or microphone port, etc. Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, charging port, etc.). Openings in housing  12  may also be formed for audio components such as a speaker and/or a microphone. 
     Antennas may be mounted in housing  12 . If desired, some of the antennas (e.g., antenna arrays that implement beam steering, etc.) may be mounted under an inactive border region of display  8  (see, e.g., illustrative antenna locations  6  of  FIG.  1   ). Display  8  may contain an active area with an array of pixels (e.g., a central rectangular portion). Inactive areas of display  8  are free of pixels and may form borders for the active area. If desired, antennas may also operate through dielectric-filled openings in the rear of housing  12  or elsewhere in device  10 . 
     To avoid disrupting communications when an external object such as a human hand or other body part of a user blocks one or more antennas, antennas may be mounted at multiple locations in housing  12 . Sensor data such as proximity sensor data, real-time antenna impedance measurements, signal quality measurements such as received signal strength information, and other data may be used in determining when one or more antennas is being adversely affected due to the orientation of housing  12 , blockage by a user&#39;s hand or other external object, or other environmental factors. Device  10  can then switch one or more replacement antennas into use in place of the antennas that are being adversely affected. 
     Antennas may be mounted at the corners of housing  12  (e.g., in corner locations  6  of  FIG.  1    and/or in corner locations on the rear of housing  12 ), along the peripheral edges of housing  12 , on the rear of housing  12 , under the display cover glass or other dielectric display cover layer that is used in covering and protecting display  8  on the front of device  10 , over a dielectric window on a rear face of housing  12  or the edge of housing  12 , over a dielectric cover layer such as a dielectric rear housing wall that covers some or all of the rear face of device  10 , or elsewhere in device  10 . 
       FIG.  2    is a rear perspective view of electronic device  10  showing illustrative locations  6  on the rear and sides of housing  12  in which antennas (e.g., single antennas and/or phased antenna arrays) may be mounted in device  10 . The antennas may be mounted at the corners of device  10 , along the edges of housing  12  such as edges formed by sidewalls  12 E, on upper and lower portions of rear housing wall  12 R, in the center of rear housing wall  12 R (e.g., under a dielectric window structure or other antenna window in the center of rear housing wall  12 R), at the corners of rear housing wall  12 R (e.g., on the upper left corner, upper right corner, lower left corner, and lower right corner of the rear of housing  12  and device  10 ), etc. 
     In configurations in which housing  12  is formed entirely or nearly entirely from a dielectric (e.g., plastic, glass, sapphire, ceramic, fabric, etc.), the antennas may transmit and receive antenna signals through any suitable portion of the dielectric. In configurations in which housing  12  is formed from a conductive material such as metal, regions of the housing such as slots or other openings in the metal may be filled with plastic or other dielectrics. The antennas may be mounted in alignment with the dielectric in the openings. These openings, which may sometimes be referred to as dielectric antenna windows, dielectric gaps, dielectric-filled openings, dielectric-filled slots, elongated dielectric opening regions, etc., may allow antenna signals to be transmitted to external wireless equipment from the antennas mounted within the interior of device  10  and may allow internal antennas to receive antenna signals from external wireless equipment. In another suitable arrangement, the antennas may be mounted on the exterior of conductive portions of housing  12 . 
       FIGS.  1  and  2    are merely illustrative. In general, housing  12  may have any desired shape (e.g., a rectangular shape, a cylindrical shape, a spherical shape, combinations of these, etc.). Display  8  of  FIG.  1    may be omitted if desired. Antennas may be located within housing  12 , on housing  12 , and/or external to housing  12 . 
     A schematic diagram of illustrative components that may be used in device  10  is shown in  FIG.  3   . As shown in  FIG.  3   , device  10  may include control circuitry  14 . Control circuitry  14  may include storage such as storage circuitry  20 . Storage circuitry  20  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  14  may include processing circuitry such as processing circuitry  22 . Processing circuitry  22  may be used to control the operation of device  10 . Processing circuitry  22  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  14  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  20  (e.g., storage circuitry  20  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  20  may be executed by processing circuitry  22 . 
     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, 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  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, 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  16  may include wireless circuitry such as wireless circuitry  24  for wirelessly conveying radio-frequency signals. While control circuitry  14  is shown separately from wireless circuitry  24  in the example of  FIG.  3    for the sake of clarity, wireless circuitry  24  may include processing circuitry that forms a part of processing circuitry  22  and/or storage circuitry that forms a part of storage circuitry  20  of control circuitry  14  (e.g., portions of control circuitry  14  may be implemented on wireless circuitry  24 ). As an example, control circuitry  14  may include baseband processor circuitry or other control components that form a part of wireless circuitry  24 . 
     Wireless circuitry  24  may include millimeter and centimeter wave transceiver circuitry such as millimeter/centimeter wave transceiver circuitry  28 . Millimeter/centimeter wave transceiver circuitry  28  may support communications at frequencies between about 10 GHz and 300 GHz. For example, millimeter/centimeter wave 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, millimeter/centimeter wave 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 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  28  may support IEEE 802.11ad communications at 60 GHz and/or 5 th  generation mobile networks or 5 th  generation wireless systems (5G) New Radio (NR) Frequency Range 2 (FR2) communications bands between about 24 GHz and 90 GHz (e.g., FR2 bands N257, N258, N261, and/or other bands between about 24.25 GHz and 29.5 GHz, FR2 bands N259, N260, and/or other bands between about 37 GHz and 43.5 GHz, etc.). Millimeter/centimeter wave transceiver 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.). 
     Millimeter/centimeter wave transceiver circuitry  28  (sometimes referred to herein simply as transceiver circuitry  28  or millimeter/centimeter wave circuitry  28 ) may perform spatial ranging operations using radio-frequency signals at millimeter and/or centimeter wave frequencies that are transmitted and received by millimeter/centimeter wave transceiver circuitry  28 . 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  14  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  14  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  28  are unidirectional. If desired, millimeter/centimeter wave transceiver circuitry  28  may also perform bidirectional communications with external wireless equipment such as external wireless equipment  10 ′ (e.g., over bi-directional millimeter/centimeter wave wireless communications link  31 ). External wireless equipment  10 ′ may include other electronic devices such as electronic device  10 , a wireless base station, wireless access point, a wireless accessory, or any other desired equipment that transmits and receives millimeter/centimeter wave signals. Bidirectional communications involve both the transmission of wireless data by millimeter/centimeter wave transceiver circuitry  28  and the reception of wireless data that has been transmitted by external wireless equipment  10 ′. 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  24  may include transceiver circuitry for handling communications at frequencies below 10 GHz such as non-millimeter/centimeter wave transceiver circuitry  26 . For example, non-millimeter/centimeter wave transceiver circuitry  26  may handle wireless local area network (WLAN) communications bands such as the 2.4 GHz and 5 GHz Wi-Fi® (IEEE 802.11) bands, wireless personal area network (WPAN) communications bands such as the 2.4 GHz Bluetooth® communications band, cellular telephone communications bands such as a cellular low band (LB) (e.g., 600 to 960 MHz), a cellular low-midband (LMB) (e.g., 1400 to 1550 MHz), a cellular midband (MB) (e.g., from 1700 to 2200 MHz), a cellular high band (HB) (e.g., from 2300 to 2700 MHz), a cellular ultra-high band (UHB) (e.g., from 3300 to 5000 MHz, or other cellular communications bands between about 600 MHz and about 5000 MHz (e.g., 3G bands, 4G LTE bands, 5G New Radio Frequency Range 1 (FR1) bands below 10 GHz, etc.), a near-field communications (NFC) band (e.g., at 13.56 MHz), satellite navigations bands (e.g., an L1 global positioning system (GPS) band at 1575 MHz, an L5 GPS band at 1176 MHz, a Global Navigation Satellite System (GLONASS) band, a BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) communications band(s) supported by the IEEE 802.15.4 protocol and/or other UWB communications protocols (e.g., a first UWB communications band at 6.5 GHz and/or a second UWB communications band at 8.0 GHz), and/or any other desired communications bands. The communications bands handled by the radio-frequency transceiver circuitry may sometimes be referred to herein as frequency bands or simply as “bands,” and may span corresponding ranges of frequencies. Non-millimeter/centimeter wave transceiver circuitry  26  and millimeter/centimeter wave transceiver circuitry  28  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. 
     In general, the transceiver circuitry in wireless circuitry  24  may cover (handle) any desired frequency bands of interest. As shown in  FIG.  3   , wireless circuitry  24  may include antennas  30 . The transceiver circuitry may convey radio-frequency signals using one or more antennas  30  (e.g., antennas  30  may convey the radio-frequency signals for the transceiver circuitry). The term “convey radio-frequency signals” as used herein means the transmission and/or reception of the radio-frequency signals (e.g., for performing unidirectional and/or bidirectional wireless communications with external wireless communications equipment). Antennas  30  may transmit the radio-frequency signals by radiating the radio-frequency signals into free space (or to freespace through intervening device structures such as a dielectric cover layer). Antennas  30  may additionally or alternatively receive the radio-frequency signals from free space (e.g., through intervening devices structures such as a dielectric cover layer). The transmission and reception of radio-frequency signals by antennas  30  each involve the excitation or resonance of antenna currents on an antenna resonating element in the antenna by the radio-frequency signals within the frequency band(s) of operation of the antenna. 
     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  28  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 forming (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  30  in wireless circuitry  24  may be formed using any suitable antenna types. For example, antennas  30  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. If desired, one or more of antennas  30  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  26  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  28 . Antennas  30  that are used to convey radio-frequency signals at millimeter and centimeter wave frequencies may be arranged in one or more phased antenna arrays. In one suitable arrangement that is described herein as an example, the antennas  30  that are arranged in a corresponding phased antenna array may be stacked patch antennas having patch antenna resonating elements that overlap and are vertically stacked with respect to one or more parasitic patch elements. 
       FIG.  4    is a diagram showing how antennas  30  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  36  (sometimes referred to herein as array  36 , antenna array  36 , or array  36  of antennas  30 ) may be coupled to radio-frequency transmission line paths  32 . For example, a first antenna  30 - 1  in phased antenna array  36  may be coupled to a first radio-frequency transmission line path  32 - 1 , a second antenna  30 - 2  in phased antenna array  36  may be coupled to a second radio-frequency transmission line path  32 - 2 , an Mth antenna  30 -M in phased antenna array  36  may be coupled to an Mth radio-frequency transmission line path  32 -M, etc. While antennas  30  are described herein as forming a phased antenna array, the antennas  30  in phased antenna array  36  may sometimes also be referred to as collectively forming a single phased array antenna (e.g., where each antenna  30  in the phased array antenna forms an antenna element of the phased array antenna). 
     Radio-frequency transmission line paths  32  may each be coupled to millimeter/centimeter wave transceiver circuitry  28  of  FIG.  3   . Each radio-frequency transmission line path  32  may include one or more radio-frequency transmission lines, a positive signal conductor, and a ground signal conductor. The positive signal conductor may be coupled to a positive antenna feed terminal on an antenna resonating element of the corresponding antenna  30 . The ground signal conductor may be coupled to a ground antenna feed terminal on an antenna ground for the corresponding antenna  30 . 
     Radio-frequency transmission line paths  32  may include stripline transmission lines (sometimes referred to herein simply as striplines), coaxial cables, coaxial probes realized by metalized vias, microstrip transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, waveguide structures, conductive vias, combinations of these, etc. Multiple types of transmission lines may be used to couple the millimeter/centimeter wave transceiver circuitry to phased antenna array  36 . Filter circuitry, switching circuitry, impedance matching circuitry, phase shifter circuitry, amplifier circuitry, and/or other circuitry may be interposed on radio-frequency transmission line path  32 , 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). 
     Antennas  30  in phased antenna array  36  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 line paths  32  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  28  ( FIG.  3   ) to phased antenna array  36  for wireless transmission. During signal reception operations, radio-frequency transmission line paths  32  may be used to convey signals received at phased antenna array  36  (e.g., from external wireless equipment  10 ′ of  FIG.  3   ) to millimeter/centimeter wave transceiver circuitry  28  ( FIG.  3   ). 
     The use of multiple antennas  30  in phased antenna array  36  allows radio-frequency beam forming arrangements (sometimes referred to herein as radio-frequency 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   , the antennas  30  in phased antenna array  36  each have a corresponding radio-frequency phase and magnitude controller  33  (e.g., a first phase and magnitude controller  33 - 1  interposed on radio-frequency transmission line path  32 - 1  may control phase and magnitude for radio-frequency signals handled by antenna  30 - 1 , a second phase and magnitude controller  33 - 2  interposed on radio-frequency transmission line path  32 - 2  may control phase and magnitude for radio-frequency signals handled by antenna  30 - 2 , an Mth phase and magnitude controller  33 -M interposed on radio-frequency transmission line path  32 -M may control phase and magnitude for radio-frequency signals handled by antenna  30 -M, etc.). 
     Phase and magnitude controllers  33  may each include circuitry for adjusting the phase of the radio-frequency signals on radio-frequency transmission line paths  32  (e.g., phase shifter circuits) and/or circuitry for adjusting the magnitude of the radio-frequency signals on radio-frequency transmission line paths  32  (e.g., power amplifier and/or low noise amplifier circuits). Phase and magnitude controllers  33  may sometimes be referred to collectively herein as beam steering or beam forming circuitry (e.g., beam steering circuitry that steers the beam of radio-frequency signals transmitted and/or received by phased antenna array  36 ). 
     Phase and magnitude controllers  33  may adjust the relative phases and/or magnitudes of the transmitted signals that are provided to each of the antennas in phased antenna array  36  and may adjust the relative phases and/or magnitudes of the received signals that are received by phased antenna array  36 . Phase and magnitude controllers  33  may, if desired, include phase detection circuitry for detecting the phases of the received signals that are received by phased antenna array  36 . The term “beam,” “signal beam,” “radio-frequency beam,” or “radio-frequency signal beam” may be used herein to collectively refer to wireless signals that are transmitted and received by phased antenna array  36  in a particular direction. The signal beam may exhibit a peak gain that is oriented in a particular beam pointing direction at a corresponding beam 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  33  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  33  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  33  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  33  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  33  may be controlled to produce a desired phase and/or magnitude based on a corresponding control signal S received from control circuitry  38  of  FIG.  4    over control paths  34  (e.g., the phase and/or magnitude provided by phase and magnitude controller  33 - 1  may be controlled using control signal S 1  on control path  34 - 1 , the phase and/or magnitude provided by phase and magnitude controller  33 - 2  may be controlled using control signal S 2  on control path  34 - 2 , the phase and/or magnitude provided by phase and magnitude controller  33 -M may be controlled using control signal SM on control path  34 -M, etc.). If desired, control circuitry  38  may actively adjust control signals S in real time to steer the transmit or receive beam in different desired directions (e.g., to different desired beam pointing angles) over time. Phase and magnitude controllers  33  may provide information identifying the phase of received signals to control circuitry  38  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  36  and external wireless equipment (e.g., external wireless equipment  10 ′ of  FIG.  3   ). If the external wireless equipment is located at point A of  FIG.  4   , phase and magnitude controllers  33  may be adjusted to steer the signal beam towards point A (e.g., to form a signal beam having a beam pointing angle directed towards point A). Phased antenna array  36  may then transmit and receive radio-frequency signals in the direction of point A. Similarly, if the external wireless equipment is located at point B, phase and magnitude controllers  33  may be adjusted to steer the signal beam towards point B (e.g., to form a signal beam having a beam pointing angle directed towards point B). Phased antenna array  36  may then 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  36  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. 
     Control circuitry  38  of  FIG.  4    may form a part of control circuitry  14  of  FIG.  3    or may be separate from control circuitry  14  of  FIG.  3   . Control circuitry  38  of  FIG.  4    may identify a desired beam pointing angle for the signal beam of phased antenna array  36  and may adjust the control signals S provided to phased antenna array  36  to configure phased antenna array  36  to form (steer) the signal beam at that beam pointing angle. Each possible beam pointing angle that can be used by phased antenna array  36  during wireless communications may be identified by a beam steering codebook such as codebook  40 . Codebook  40  may be stored at control circuitry  38 , elsewhere on device  10 , or may be located (offloaded) on external equipment and conveyed to device  10  over a wired or wireless communications link. 
     Codebook  40  may identify each possible beam pointing angle that may be used by phased antenna array  36 . Control circuitry  38  may store or identify phase and magnitude settings for phase and magnitude controllers  33  to use in implementing each of those beam pointing angles (e.g., control circuitry  38  or codebook  40  may include information that maps each beam pointing angle for phased antenna array  36  to a corresponding set of phase and magnitude values for phase and magnitude controllers  33 ). Codebook  40  may be hard-coded or soft-coded into control circuitry  38  or elsewhere in device  10 , may include one or more databases stored at control circuitry  38  or elsewhere in device  10  (e.g., codebook  40  may be stored as software code), may include one or more look-up-tables at control circuitry  38  or elsewhere in device  10 , and/or may include any other desired data structures stored in hardware and/or software on device  10 . Codebook  40  may be generated during calibration of device  10  (e.g., during design, manufacturing, and/or testing of device  10  prior to device  10  being received by an end user) and/or may be dynamically updated over time (e.g., after device  10  has been used by an end user). 
     Control circuitry  38  may generate control signals S based on codebook  40 . For example, control circuitry  38  may identify a beam pointing angle that would be needed to communicate with external wireless equipment  10 ′ of  FIG.  3    (e.g., a beam pointing angle pointing towards external wireless equipment  10 ′). Control circuitry  38  may subsequently identify the beam pointing angle in codebook  40  that is closest to this identified beam pointing angle. Control circuitry  38  may use codebook  40  to generate phase and magnitude values for phase and magnitude controllers  33 . Control circuitry  38  may transmit control signals S identifying these phase and magnitude values to phase and magnitude controllers  33  over control paths  34 . The beam formed by phased antenna array  36  using control signals S will be oriented at the beam pointing angle identified by codebook  40 . If desired, control circuitry  38  may sweep over some or all of the different beam pointing angles identified by codebook  40  until the external wireless equipment is found and may use the corresponding beam pointing angle at which the external wireless equipment was found to communicate with the external wireless equipment (e.g., over communications link  31  of  FIG.  3   ). 
     A schematic diagram of an antenna  30  that may be formed in phased antenna array  36  (e.g., as antenna  30 - 1 ,  30 - 2 ,  30 - 3 , and/or  30 -N in phased antenna array  36  of  FIG.  4   ) is shown in  FIG.  5   . As shown in  FIG.  5   , antenna  30  may be coupled to transceiver circuitry  42  (e.g., millimeter wave transceiver circuitry  28  of  FIG.  3   ). Transceiver circuitry  42  may be coupled to antenna feed  48  of antenna  30  using radio-frequency transmission line path  32 . Antenna feed  48  may include a positive antenna feed terminal such as positive antenna feed terminal  50  and may include a ground antenna feed terminal such as ground antenna feed terminal  52 . Radio-frequency transmission line path  32  may include a positive signal conductor such as signal conductor  44  that is coupled to positive antenna feed terminal  50  and a ground conductor such as ground conductor  46  that is coupled to ground antenna feed terminal  52 . 
     Any desired antenna structures may be used to form antenna  30 . In one suitable arrangement that is sometimes described herein as an example, stacked patch antenna structures may be used to form antenna  30 . Antennas  30  that are formed using stacked patch antenna structures may sometimes be referred to herein as stacked patch antennas or simply as patch antennas.  FIG.  6    is a perspective view of an illustrative patch antenna that may be used in phased antenna array  36 . 
     As shown in  FIG.  6   , antenna  30  may have a patch antenna resonating element  54  that is separated from and parallel to an antenna ground plane such as ground plane  58  (sometimes referred to herein as antenna ground  58 ). Patch antenna resonating element  54  may lie within a plane such as the X-Y plane of  FIG.  6    (e.g., the lateral surface area of element  54  may lie in the X-Y plane). Patch antenna resonating element  54  may sometimes be referred to herein as patch  54 , patch element  54 , patch resonating element  54 , antenna resonating element  54 , or resonating element  54 . Ground plane  58  may lie within a plane that is parallel to the plane of patch element  54 . Patch element  54  and ground plane  58  may therefore lie in separate parallel planes that are separated by a distance  64 . Patch element  54  and ground plane  58  may be formed from conductive traces patterned on a dielectric substrate. 
     The length of the sides of patch element  54  may be selected so that antenna  30  resonates at a desired operating frequency. For example, the sides of patch element  54  may each have a length L that is approximately equal to half of the wavelength of the signals conveyed by antenna  30  (e.g., the effective wavelength given the dielectric properties of the materials surrounding patch element  54 ). In one suitable arrangement, length L may be between 0.8 mm and 1.2 mm (e.g., approximately 1.1 mm) for covering a millimeter wave frequency band between 57 GHz and 70 GHz or between 1.6 mm and 2.2 mm (e.g., approximately 1.85 mm) for covering a millimeter wave frequency band between 37 GHz and 41 GHz, as just two examples. 
     The example of  FIG.  6    is merely illustrative. Patch element  54  may have a square shape in which all of the sides of patch element  54  are the same length or may have a different rectangular shape. Patch element  54  may be formed in other shapes having any desired number of straight and/or curved edges. If desired, patch element  54  and ground plane  58  may have different shapes and relative orientations. 
     To enhance the polarizations handled by antenna  30 , antenna  30  may be provided with multiple antenna feeds. As shown in  FIG.  6   , antenna  30  may have a first antenna feed at antenna port P 1  that is coupled to a first radio-frequency transmission line path  32  ( FIG.  5   ) such as transmission line path  32 V. Antenna  30  may also have a second feed at antenna port P 2  that is coupled to a second radio-frequency transmission line path  32  such as transmission line path  32 H. The first antenna feed may have a first ground feed terminal coupled to ground plane  58  (not shown in  FIG.  6    for the sake of clarity) and a first positive antenna feed terminal  50 V coupled to patch element  54 . The second antenna feed may have a second ground feed terminal coupled to ground plane  58  (not shown in  FIG.  6    for the sake of clarity) and a second positive antenna feed terminal  50 H on patch element  54 . 
     Holes or openings such as openings  66  and  68  may be formed in ground plane  58 . Transmission line path  32 V may include a vertical conductor (e.g., a conductive through-via, conductive pin, metal pillar, solder bump, combinations of these, or other vertical conductive interconnect structures) that extends through opening  66  to positive antenna feed terminal  50 V on patch element  54 . Transmission line path  32 H may include a vertical conductor that extends through opening  68  to positive antenna feed terminal  50 H on patch element  54 . This example is merely illustrative and, if desired, other transmission line structures may be used (e.g., coaxial cable structures, stripline transmission line structures, etc.). 
     When using the first antenna feed associated with port P 1 , antenna  30  may transmit and/or receive radio-frequency signals having a first polarization (e.g., the electric field E 1  of antenna signals  60  associated with port P 1  may be oriented parallel to the Y-axis in  FIG.  6   ). When using the antenna feed associated with port P 2 , antenna  30  may transmit and/or receive radio-frequency signals having a second polarization (e.g., the electric field E 2  of antenna signals  60  associated with port P 2  may be oriented parallel to the X-axis of  FIG.  6    so that the polarizations associated with ports P 1  and P 2  are orthogonal to each other). 
     One of ports P 1  and P 2  may be used at a given time so that antenna  30  operates as a single-polarization antenna or both ports may be operated at the same time so that antenna  30  operates with other polarizations (e.g., as a dual-polarization antenna, a circularly-polarized antenna, an elliptically-polarized antenna, etc.). If desired, the active port may be changed over time so that antenna  30  can switch between covering vertical or horizontal polarizations at a given time. Ports P 1  and P 2  may be coupled to different phase and magnitude controllers  33  ( FIG.  4   ) or may both be coupled to the same phase and magnitude controller  33 . If desired, ports P 1  and P 2  may both be operated with the same phase and magnitude at a given time (e.g., when antenna  30  acts as a dual-polarization antenna). If desired, the phases and magnitudes of radio-frequency signals conveyed over ports P 1  and P 2  may be controlled separately and varied over time so that antenna  30  exhibits other polarizations (e.g., circular or elliptical polarizations). 
     If care is not taken, antennas  30  such as dual-polarization patch antennas of the type shown in  FIG.  6    may have insufficient bandwidth for covering an entirety of a frequency band of interest (e.g., a frequency band at frequencies greater than 10 GHz). For example, in scenarios where antenna  30  is configured to cover a millimeter wave communications band between 37 GHz and 40 GHz, patch element  54  as shown in  FIG.  6    may have insufficient bandwidth to cover the entirety of the frequency range between 37 GHz and 40 GHz or 43.5 GHz. If desired, antenna  30  may include one or more parasitic antenna resonating elements that serve to broaden the bandwidth of antenna  30 . 
     As shown in  FIG.  6   , a bandwidth-widening parasitic antenna resonating element such as parasitic antenna resonating element  56  may be formed from conductive structures located at a distance  70  over patch element  54 . Parasitic antenna resonating element  56  may sometimes be referred to herein as parasitic resonating element  56 , parasitic antenna element  56 , parasitic element  56 , parasitic patch  56 , parasitic conductor  56 , parasitic structure  56 , parasitic  56 , or patch  56 . Parasitic element  56  is not directly fed, whereas patch element  54  is directly fed via transmission line paths  32 V and  32 H and positive antenna feed terminals  50 V and  50 H. Parasitic element  56  may create a constructive perturbation of the electromagnetic field generated by patch element  54 , creating a new resonance for antenna  30 . This may serve to broaden the overall bandwidth of antenna  30  (e.g., to cover an entire frequency band from 24 GHz to 31 GHz). 
     At least some or an entirety of parasitic element  56  may overlap patch element  54 . In the example of  FIG.  6   , parasitic element  56  has a cross or “X” shape. In order to form the cross shape, parasitic element  56  may include notches or slots formed by removing conductive material from the corners of a square or rectangular metal patch. Parasitic element  56  may have a rectangular (e.g., square) outline or footprint. Removing conductive material from parasitic element  56  to form a cross shape may serve to adjust the impedance of patch element  54  so that the impedance of patch element  54  is matched to both transmission line paths  32 V and  32 H, for example. The example of  FIG.  6    is merely illustrative. If desired, parasitic element  56  may have other shapes or orientations. 
     If desired, antenna  30  of  FIG.  6    may be formed on a dielectric substrate (not shown in  FIG.  6    for the sake of clarity). The dielectric substrate may be, for example, a rigid or printed circuit board or other dielectric substrate. The dielectric substrate may include multiple stacked dielectric layers (e.g., multiple layers of printed circuit board substrate such as multiple layers of fiberglass-filled epoxy, multiple layers of ceramic substrate, etc.). Ground plane  58 , patch element  54 , and parasitic element  56  may be formed from conductive traces on different layers of the dielectric substrate. 
     When configured in this way, antenna  30  may cover a relatively wide frequency band of interest such as a frequency band between 24.25 GHz and 29.5 GHz or between 37 GHz and 43.5 GHz. The example of  FIG.  6    is merely illustrative. Parasitic element  56  may be omitted if desired. Antenna  30  may have any desired number of feeds. Other feeding arrangements may be used. Antenna  30  may include any desired type of antenna resonating element structures. If desired, antenna  30  may include multiple vertically-stacked patch elements  54 . Each of the vertically-stacked patch elements  54  may radiate in a respective frequency band. By forming each patch element  54  with a respective length L, antenna  30  may be configured to cover multiple frequency bands such as a first frequency band (e.g., a low band) from around 24.25 GHz to 29.5 GHz and a second frequency band (e.g., a high band) from around 37 GHz to 40 GHz. 
       FIG.  7    is a cross-sectional side view showing how antenna  30  may include two vertically-stacked patch elements  54 . As shown in  FIG.  7   , antenna  30  may include multiple patch elements  54  such as a first patch element  54 - 1  and a second patch element  54 - 2 . Patch element  54 - 2  may be vertically stacked over patch element  54 - 1 . Patch element  54 - 2  may completely or partially overlap patch element  54 - 1 . Patch element  54 - 2  may have different dimensions than patch element  54 - 1  (e.g., for creating additional resonances to cover additional frequencies) or may have similar (e.g., identical) dimensions to patch element  54 - 1 . Parasitic element  56  may be vertically stacked over patch element  54 - 2  and may overlap both patch elements  54 - 1  and  54 - 2 . 
     Antenna  30  may be formed on a dielectric substrate such as substrate  84 . If desired, each of the antennas in the phased antenna array may be formed on the same dielectric substrate (e.g., in an integrated antenna module having a radio-frequency integrated circuit mounted to substrate  84 ). Substrate  84  may be, for example, a rigid or printed circuit board or another dielectric substrate. Substrate  84  may include multiple stacked dielectric layers  86  (e.g., layers of printed circuit board substrate, layers of fiberglass-filled epoxy, layers of polyimide, layers of ceramic substrate, or layers of other dielectric materials). 
     With this type of arrangement, antenna  30  may be embedded within the layers of substrate  84 . For example, antenna  30  may have an antenna ground (e.g., a ground plane for antenna  30  such as ground plane  58  of  FIG.  6   ) that includes ground traces  72 . The same ground traces  72  may be used to form the antenna ground for each antenna in the phased antenna array if desired. Ground traces  72  may be patterned onto a first layer  86  of substrate  84 . 
     Patch element  54 - 1  may be formed from a first layer of conductive traces  74  patterned onto a second layer  86  of substrate  84 . Patch element  54 - 2  may be formed from a second layer of conductive traces  76  patterned onto a third layer  86  of substrate  84 . Parasitic element  56  may be formed from a third layer of conductive traces  78  patterned onto a fourth layer  86  of substrate  84  (e.g., where the second layer is interposed between the first and third layers and the third layer is interposed between the second and fourth layers). In the example of  FIG.  7   , conductive traces  78  are patterned onto an exterior surface of substrate  84 . This is merely illustrative and, if desired, one or more dielectric layers  86  may be disposed over conductive traces  78 . 
     One or more layers  86  of substrate  84  may be vertically interposed between ground traces  72  and the first layer of conductive traces  74 . One or more layers  86  of substrate  84  may be vertically interposed between the first layer of conductive traces  74  and the second layer of conductive traces  76 . One or more layers  86  of substrate  84  may be vertically interposed between the second layer of conductive traces  76  and the third layer of conductive traces  78 . Zero, one, or more than one layer  86  in substrate  84  may be vertically interposed between the third layer of conductive traces  78  and the exterior of substrate  84 . 
     Signal traces  88  and  90  may be patterned onto one or more of the layers  86  in substrate  84  (e.g., ground traces  72  may be vertically interposed between signal traces  88 / 90  and patch element  54 - 1 ). Signal traces  88  may, for example, form the signal conductor of a radio-frequency transmission line path for patch element  54 - 1  (e.g., signal conductor  44  in radio-frequency transmission line path  32  of  FIG.  5   ). A conductive via such as conductive via  80  may couple signal traces  88  to patch element  54 - 1  (e.g., at a positive antenna feed terminal for patch element  54 - 1  such as positive antenna feed terminals  50 V or  5011  of  FIG.  6   ). Similarly, signal traces  90  may form the signal conductor of a radio-frequency transmission line path for patch element  54 - 2 . A conductive via such as conductive via  82  may couple signal traces  90  to patch element  54 - 2  (e.g., at a positive antenna feed terminal for patch element  54 - 2  such as positive antenna feed terminals  50 V or  5011  of  FIG.  6   ). 
     The example of  FIG.  7    shows only a single positive antenna feed terminal on patch element  54 - 1  and only a single positive antenna feed terminal on patch element  54 - 2  for the sake of clarity. If desired, patch element  54 - 1  and/or patch element  54 - 2  may have two positive antenna feed terminals (e.g., positive antenna feed terminals  50 H and  50 V of  FIG.  6   ) for covering multiple polarizations. 
     The layers  86  in substrate  84  that include patch elements  54  and parasitic element  56  may sometimes be referred to collectively herein as antenna layers  92 . The layers  86  in substrate  84  that include signal traces  88  and  90  may sometimes be referred to herein as routing layers  94 , transmission line routing layers  94 , or transmission line layers  94 . Ground traces  72  may separate routing layers  94  from antenna layers  92 . 
     Patch element  54 - 1  may be configured to radiate in a first frequency band such as a low band between around 24.25 GHz and 29.5 GHz. Patch element  54 - 1  may therefore sometimes be referred to herein as low band patch element  54 - 1 . Patch element  54 - 2  may be configured to radiate in a second frequency band such as a high band between around 37 GHz and 40 GHz or 43.5 GHz. Patch element  54 - 2  may therefore sometimes be referred to herein as high band patch element  54 - 2 . Co-locating patch elements  54 - 1  and  54 - 2  in this way (e.g., within antenna  30 ) may minimize the amount of lateral area required for phased antenna array  36  to cover both the low band and the high band. Patch elements  54 - 1  and  54 - 2  may therefore configure antenna  30  to be a dual-band antenna that covers both the low band and the high band. Parasitic element  56  may help to widen the bandwidth of patch element  54 - 2  to help patch element  54 - 2  to cover the entirety of the high band. 
     If desired, additional parasitic elements  77  (e.g., conductive patches that are not directly fed) may be disposed adjacent to patch element  54 - 1  to help the patch element to cover the entirety of the low band. Each patch element  77  may have a length that extends across the some, substantially all, or all of the length of patch element  54 - 1  (e.g., in a direction parallel to the Y-axis) and may have a width that is less than the length (e.g., each parasitic element  77  may be a rectangular patch). Each parasitic element  77  may be separated from patch element  54 - 1  by a respective gap. If desired, patch element  54 - 1  may be provided with four parasitic elements  77 , each extending along a respective side (edge) of the rectangular lateral outline of patch element  54 - 1  (e.g., as viewed in the X-Y plane). Parasitic elements  77  may be formed from conductive traces patterned onto the same layer  86  as the conductive traces  74  in patch element  54 - 1 . If desired, parasitic elements  77  may be patterned onto the layer  86  layered over conductive traces  74  (e.g., at locations  81 ) or may be patterned onto the layer  86  layered under the layer  86  that supports conductive traces  74  (e.g., at locations  79 ). 
     In order to further optimize the radio-frequency performance of patch element  54 - 2  in the high band, a short path such as short path  75  may couple patch element  54 - 1  to ground traces  72 . Short path  75  (sometimes referred to herein as shorting pin  75 ) may be formed from one or more conductive vias extending through layers  86  of substrate  84  to ground traces  72 . Short path  75  may be soldered to conductive traces  74  and/or ground traces  72  if desired. Short path  75  may help to optimize the radio-frequency performance of patch element  54 - 2  in the high band without affecting the radio-frequency performance of patch element  54 - 1  in the low band. For example, short path  75  may be coupled to a location on patch element  54 - 1  (conductive traces  74 ) that overlaps a node in the electric field produced by patch element  54 - 1 . 
     Curve  83  is shown in  FIG.  7    to illustrate an exemplary standing wave mode of patch element  54 - 1  (e.g., a λ/2 mode). Curve  83  plots the magnitude of the electric field E 0  produced by patch element  54 - 1  at different points X along its length L. As shown by curve  83 , electric field E 0  exhibits a node (e.g., zero magnitude) at distance X=L/2 from its edge (e.g., at the center of patch element  54 - 1  or halfway along length L). Short path  75  may therefore be coupled to patch element  54 - 1  at the center of patch element  54 - 1  (e.g., at distance X=L/2 from the edge of patch element  54 - 1 ) to align with the node (minimum magnitude) in the electric field produced by the patch element. This may allow short path  75  to appear invisible to patch element  54 - 1  at frequencies in the low band (e.g., by exhibiting an infinite impedance in the −Z direction at frequencies in the low band), such that short path  75  does not affect the radio-frequency performance of patch element  54 - 1 . This example is merely illustrative and, in general, short path  75  may be coupled to any desired location along patch element  54 - 1  where the electric field produced by the patch element exhibits a node in any desired electromagnetic standing wave mode of the patch element. Multiple short paths  75  may couple multiple points on patch element  54 - 1  to ground traces  72  if desired. 
     At the same time, short path  75  remains visible to radio-frequency signals in the high band (e.g., by exhibiting a zero or short circuit impedance in the −Z direction at frequencies in the high band). Short path  75  therefore forms a short path from patch element  54 - 1  to ground traces  72  at frequencies in the high band, allowing patch element  54 - 1  to form a part of the antenna ground for patch element  54 - 2  in the high band (e.g., ground plane  58  of  FIG.  6   ). Extending the antenna ground for patch element  54 - 2  to also include patch element  54 - 1  at frequencies in the high band may serve to maximize the antenna efficiency for patch element  54 - 2 . Coupling short path  75  to patch element  54 - 1  at the center of patch element  54 - 1  allows for high band ground plane extension in this way without impacting the antenna efficiency of patch element  54 - 1  in the low band. 
     The example of  FIG.  7    is merely illustrative. In general, antenna  30  may include any desired number of layers of conductive traces that are vertically stacked over ground traces  72  (e.g., three layers of conductive traces  74 ,  76 , and  78  as shown in  FIG.  7   , only two layers of conductive traces, four or more layers of conductive traces, etc.). Each layer of conductive traces may be used to form a corresponding patch element  54  and/or one or more parasitic elements  56  in antenna  30 . For example, the second layer of conductive traces  76  may form an additional parasitic element  56 . In another example, the third layer of conductive traces  78  may form a third patch element  54  for antenna  30  (e.g., a patch element that is directly fed using one or two positive antenna feed terminals coupled to the patch element). 
     If desired, additional layers of conductive traces may be stacked over the third layer of conductive traces  78  and may form additional patch elements  54  and/or parasitic elements  56  for antenna  30 . Antenna  30  need not be fed using conductive vias such as conductive vias  80  and  82 . If desired, antenna  30  may be capacitively fed or slot-fed. The layers of conductive traces in antenna layers  92  need not be used to form patch antenna resonating elements and may, in general, be used to form antenna resonating elements of any type for antenna  30 . The layers of conductive traces in antenna layers  92  (e.g., the first layer of conductive traces  74 , the second layer of conductive traces  76 , and the third layer of conductive traces  78 ) may sometimes be referred to herein as layers of antenna traces or simply as conductive antenna layers. 
     In some scenarios, the same material is used to form each of the antenna layers  92  and each of the routing layers  94  in substrate  84 . In these scenarios, a high-permittivity dielectric loading layer may be layered over parasitic element  78  (e.g., a dielectric layer that has a higher dielectric permittivity than substrate  84 ) to help reduce the required thickness of substrate  84  (in the direction of the Z-axis). However, adding an additional dielectric loading layer over substrate  84  may increase the cost to design, assemble, and manufacture device  10 , and can occupy excessive space within device  10 . In order to reduce the thickness of substrate  84  without sacrificing radio-frequency performance across the low band and the high band and without using a separate dielectric loading layer, antenna  30  may be differentially loaded by providing dielectric layers having different dielectric permittivities across antenna layers  92 .  FIG.  8    is a cross-sectional side view showing how antenna  30  may be differentially loaded. 
     As shown in  FIG.  8   , the layers  86  in substrate  84  may include one or more relatively low dielectric permittivity layers  86 L (sometimes referred to herein as low dielectric permittivity layers  86 L or low permittivity layers  86 L) and one or more relatively high dielectric permittivity layers  86 H (sometimes referred to herein as high dielectric permittivity layers  86 H or high permittivity layers  86 H). High dielectric permittivity layers  8611  may have relatively high dielectric permittivity DK 2 . Relatively high dielectric permittivity DK 2  may be defined by the particular material used to form the high dielectric permittivity layer. Relatively high dielectric permittivity DK 2  may be, for example, between 6.0 and 8.0, between 6.5 and 7.5, between 5.0 and 9.0, greater than 4.5, greater than 9.0, greater than 10.0, or any other desired permittivity greater than 4.0. As an example, high dielectric permittivity layers  86 H may be formed using low-temperature co-fired ceramics (LTCC) or other ceramics/dielectrics having dielectric permittivity DK 2 . 
     Low dielectric permittivity layers  86 L may have relatively low dielectric permittivity DK 1 . Relatively low dielectric permittivity DK 1  is less than relatively high dielectric permittivity DK 2  and may be, for example, between 3.0 and 4.0, between 2.0 and 5.0, between 3.3 and 3.7, less than 4.0, less than 4.5, or any other desired permittivity less than relatively high dielectric permittivity DK 2 . As an example, low dielectric permittivity layers  86 L may be formed using low-temperature co-fired ceramics (LTCC) or other ceramics/dielectrics having dielectric permittivity DK 1 . 
     As shown in  FIG.  8   , routing layers  94  may include two or more low dielectric permittivity layers  86 L. Forming routing layers  94  using low dielectric permittivity layers  86 L may, for example, minimize transmission line losses for antenna  30 . Ground traces  72  may be patterned onto the upper-most routing layer  94 . 
     Antenna layers  92  may include a first set of antenna layers  96 , a second set of antenna layers  98 , and a third set of antenna layers  100 . The first set of antenna layers  96  may be vertically interposed between ground traces  72  and the first layer of conductive traces  74 . The second set of antenna layers  98  may be vertically interposed between the first layer of conductive traces  74  and the second layer of conductive traces  76 . The third set of antenna layers  100  may be vertically interposed between the second layer of conductive traces  76  and the third layer of conductive traces  78 . 
     The first set of antenna layers  96  may include one, two, or more than two layers  86 . The first layer of conductive traces  74  in antenna  30  may be patterned onto the uppermost layer  86  in the first set of antenna layers  96 . The second set of antenna layers  98  may include one, two, or more than two layers  86 . The second layer of conductive traces  76  in antenna  30  may be patterned onto the uppermost layer  86  in the second set of antenna layers  98 . The third set of antenna layers  100  may include one, two, or more than two layers  86 . The third layer of conductive traces  78  in antenna  30  may be patterned onto the uppermost layer  86  in the third set of antenna layers  100 . 
     The first layer of conductive traces  74  may be used to form a patch element  54  (e.g., patch element  54 - 1  of  FIG.  7   ) and optionally one or more parasitic elements  77  for antenna  30 . The second layer of conductive traces  76  may be used to form a patch element  54  (e.g., patch element  54 - 2  of  FIG.  7   ) and optionally one or more parasitic elements for antenna  30 . The third layer of conductive traces  78  may be used to form a patch element  54  and/or one or more parasitic elements  56  for antenna  30  (e.g., the third layer of conductive traces  78  may include only parasitic elements  56  in the arrangement of  FIG.  7   ). 
     Each layer in the first set of antenna layers  96  may have relatively high dielectric permittivity DK 2  (e.g., each layer in the first set of antenna layers  96  may be a high dielectric permittivity layer  86 H). Each layer in the second set of antenna layers  98  may have relatively low dielectric permittivity DK 1  (e.g., each layer in the second set of antenna layers  98  may be a low dielectric permittivity layer  86 L). Each layer in the third set of antenna layers  100  may also have relatively low dielectric permittivity DK 1  (e.g., each layer in the third set of antenna layers  100  may be a low dielectric permittivity layer  86 L). In this way, antenna  30  may be differentially loaded across antenna layers  92 . Increasing the dielectric permittivity of substrate  84  between conductive traces  74  and ground traces  72  (e.g., using the first set of antenna layers  96 ) may serve to maintain the effective thickness of the first set of antenna layers  96  at frequencies in the low band (to provide patch element  54 - 1  with a desired bandwidth sufficient to cover all of the low band) while actually reducing the physical thickness of the first set of antenna layers  96 , thereby reducing the overall physical thickness of substrate  84 . 
     The example of  FIG.  8    is merely illustrative. If desired, the second set of antenna layers  98  may be provided with relatively high dielectric permittivity DK 2  whereas the first set of antenna layers  96  are provided with relatively low dielectric permittivity DK 1 . If desired, the first set of antenna layers  96  may include a combination of low dielectric permittivity layers  86 L and high dielectric permittivity layers  86 H that configures the first set of antenna layers  96  to exhibit a bulk dielectric permittivity that is greater than the relatively low dielectric permittivity DK 1  of the second set of antenna layers  98  and the third set of antenna layers  100 . Similarly, if desired, the second set of antenna layers  98  and/or the third set of antenna layers  100  may include one or more high dielectric permittivity layers  86 H (e.g., so long as the bulk dielectric permittivity of the second set of antenna layers  98  and the third set of antenna layers  100  is less than the bulk dielectric permittivity of the first set of antenna layers  96 ). If desired, substrate  84  may include additional layers  86  having other dielectric permittivities (e.g., substrate  84  may include low dielectric permittivity layers  86 L, high dielectric permittivity layers  86 H, and additional layers having other dielectric permittivities such as a dielectric permittivity DK 3  that is greater than dielectric permittivity DK 2 ). The ratio of each of the layers may be varied between the sets of antenna layers to differentially load antenna  30 . 
     Curve  102  of  FIG.  9    plots the antenna performance (return loss) of antenna  30  as a function of frequency. As shown by curve  102 , antenna  30  exhibits a first response peak in low band B 1  (e.g., at frequencies from around 24.25 GHz to around 29.5 GHz) and a second response peak in high band B 2  (e.g., at frequencies from around 37 GHz to around 43.5 GHz). Patch element  54 - 1  ( FIG.  7   ) may produce the response peak in low band B 1 . Parasitic elements  77  may help to expand this response peak to cover an entirety of low band B 1 . The presence of short path  75  does not affect the response peak in low band B 1 . Providing the layers  86  between patch element  54 - 1  and ground traces  72  (e.g., the first set of antenna layers  96  of  FIG.  8   ) with a higher dielectric permittivity than the layers  86  above patch element  54 - 1  may allow patch element  54 - 1  and parasitic elements  77  to support this wide bandwidth while also allowing for a reduction in the thickness of substrate  84 . 
     Patch element  54 - 2  may produce the response peak in high band B 2 . Parasitic element  56  may help to expand this response peak to cover an entirety of high band B 2 . Extending the antenna ground at frequencies in high band B 2  to include low band patch  54 - 1  (e.g., using short path  75  of  FIG.  7   ) may also help patch element  54 - 2  to cover an entirety of high band B 2 . The example of  FIG.  9    is merely illustrative. Low band B 1  and high band B 2  may cover any desired centimeter and/or millimeter wave frequencies. In practice, curve  102  may have other shapes. Antenna  30  may convey radio-frequency signals in more than two frequency bands if desired. 
     Device  10  may gather and/or use personally identifiable information. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     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.