PATENT DOCUMENT

Publication Number: US-11923904-B2
Application Number: US-202217827290-A
Country: US
Kind Code: B2

Title: Electronic devices with high frequency reflective antenna arrays

Abstract:
An electronic device may include a photonics-based phased antenna array that conveys wireless signals at frequencies greater than 100 GHz. In a transmit mode, the array may transmit signals using the first and second optical signals. In a receive mode, the array may receive signals using the optical signals. In a passive mode, the array may reflect incident wireless signals as reflected signals. Photodiodes in the array may be controlled to exhibit output impedances that are mismatched with respect to input impedances of radiating elements in the array. Different mismatches can be used across the array or as a function of time to impart different phase and/or frequency shifts on the reflected signals. The phase shifts may be used to encode information into the reflected signals and/or to form a signal beam of the reflected signals.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 an antenna radiating element having an input impedance; 
 a photodiode coupled to the antenna radiating element and having an output impedance, the photodiode being configured to receive a control signal that places the photodiode into a selected one of a first mode in which the input impedance is mismatched with respect to the output impedance at a frequency greater than or equal to 100 GHz or a second mode in which the input impedance matches the output impedance at the frequency; and 
 an optical signal path configured to illuminate the photodiode using a first optical local oscillator (LO) signal and a second optical LO signal that is offset in wavelength with respect to the first optical LO signal while the photodiode is in the second mode, the antenna radiating element being configured to reflect wireless signals at the frequency while the photodiode is in the first mode. 
 
     
     
       2. The electronic device of  claim 1 , further comprising:
 an optical modulator disposed along the optical signal path and configured to modulate wireless data onto the second optical LO signal while the photodiode is in the second mode, wherein the antenna radiating element is configured to transmit additional wireless signals at an additional frequency greater than or equal to 100 GHz while the photodiode is in the second mode. 
 
     
     
       3. The electronic device of  claim 2 , wherein the optical modulator comprises a Mach-Zehnder modulator (MZM). 
     
     
       4. The electronic device of  claim 2 , wherein the control signal comprises a first bias voltage and a second bias voltage that is different from the first bias voltage, the photodiode is configured to receive the first bias voltage while in the second mode, and the photodiode is configured to receive, using the antenna radiating element while the photodiode receives the second bias voltage, additional wireless signals. 
     
     
       5. The electronic device of  claim 1 , wherein the antenna radiating element is configured to receive additional wireless signals at an additional frequency greater than or equal to 100 GHz while the photodiode is in the second mode. 
     
     
       6. The electronic device of  claim 1 , wherein the photodiode is not illuminated by the first optical LO signal and the second optical LO signal while the photodiode is in the first mode. 
     
     
       7. The electronic device of  claim 1 , wherein the photodiode comprises a uni-travelling-carrier photodiode (UTC PD). 
     
     
       8. The electronic device of  claim 1 , wherein the photodiode comprises a PIN photodiode. 
     
     
       9. The electronic device of  claim 1 , wherein the photodiode comprises a graphene sublayer. 
     
     
       10. The electronic device of  claim 1 , further comprising:
 one or more processors; and 
 a phased antenna array that includes the antenna radiating element and the photodiode, the one or more processors being configured to control the phased antenna array to form a signal beam of the wireless signals reflected by the antenna radiating element at the frequency in a selected beam pointing direction while the photodiode is in the first mode. 
 
     
     
       11. The electronic device of  claim 1 , further comprising:
 one or more processors configured to perform space-time coding on the wireless signals reflected by the antenna radiating element by using the control signal to vary an amount of mismatch between the input impedance and the output impedance over time. 
 
     
     
       12. The electronic device of  claim 1 , further comprising:
 one or more processors configured to use the control signal to impart a selected phase shift, a selected frequency shift, or a selected polarization change on the wireless signals reflected by the antenna radiating element. 
 
     
     
       13. The electronic device of  claim 1 , further comprising a terahertz lens overlapping the antenna radiating element. 
     
     
       14. A method of operating an electronic device having an array of antennas that include antenna radiating elements and photodiodes coupled to the antenna radiating elements, the method comprising:
 generating, using the photodiodes, current on the antenna radiating elements that transmits first wireless signals at a frequency greater than or equal to 100 GHz while the photodiodes are illuminated using a first optical local oscillator (LO) signal and a second optical LO signal that is offset in wavelength with respect to the first optical LO signal; and 
 reflecting, using the antenna radiating elements, second wireless signals at the frequency while the photodiodes are controlled to exhibit one or more output impedances that are mismatched at the frequency with respect to input impedances of the antenna radiating elements. 
 
     
     
       15. The method of  claim 14 , further comprising:
 varying, using one or more processors, the one or more output impedances across the array. 
 
     
     
       16. The method of  claim 14 , further comprising:
 encoding, using one or more processors, information in the second wireless signals reflected by the antenna radiating elements by varying the one or more output impedances. 
 
     
     
       17. The method of  claim 14 , further comprising:
 varying, using one or more processors, the one or more output impedances to form a signal beam of the second wireless signals reflected by the antenna radiating elements that is oriented in a selected beam pointing direction. 
 
     
     
       18. An electronic device comprising:
 a phased antenna array; and 
 one or more processors configured to switch the phased antenna array between a first mode in which the phased antenna array is configured to transmit first wireless signals, a second mode in which the phased antenna array is configured to receive second wireless signals, and a third mode in which the phased antenna array is configured to reflect third wireless signals incident upon the phased antenna array. 
 
     
     
       19. The electronic device of  claim 18  wherein, in the third mode, the phased antenna array is configured to reflect the third wireless signals from an incident angle onto a corresponding output angle. 
     
     
       20. The electronic device of  claim 18 , wherein the first wireless signals, the second wireless signals, and the third wireless signals are at a frequency greater than or equal to 100 GHz.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 63/235,611, filed Aug. 20, 2021, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This disclosure relates generally to electronic devices and, more particularly, to electronic devices with wireless circuitry. 
     BACKGROUND 
     Electronic devices can be provided with wireless capabilities. An electronic device with wireless capabilities has wireless circuitry that includes one or more antennas. The wireless circuitry is used to perform communications using radio-frequency signals conveyed by the antennas. 
     As software applications on electronic devices become more data-intensive over time, demand has grown for electronic devices that support wireless communications at higher data rates. However, the maximum data rate supported by electronic devices is limited by the frequency of the radio-frequency signals. In addition, it can be difficult to implement wireless circuitry for handling high data rates in a resource-efficient and space-efficient manner, particularly when antennas are not always used to actively transmit or receive signals. 
     SUMMARY 
     An electronic device may include wireless circuitry controlled by one or more processors. The wireless circuitry may include transceiver circuitry, one or more antennas, and one or more optical signal paths that couple the transceiver circuitry to each of the antennas. To support extremely high data rates, the antennas may convey wireless signals at frequencies greater than or equal to about 100 GHz. Each antenna may both transmit and receive the wireless signals using a time division duplexing scheme, if desired. 
     The antenna may include an antenna radiating element coupled to a programmable photodiode such as a uni-travelling-carrier photodiode (UTC PD). The optical signal path may illuminate the UTC PD using a first optical local oscillator (LO) signal and a second optical LO signal that is offset in wavelength with respect to the first optical LO signal. If desired, an optical phase shift may be applied to the first optical LO signal. This may allow for signal beam forming in implementations where the antenna is formed in a phased antenna array. 
     The phased antenna array may be operable in one or more of a transmit mode, a receive mode, and a passive reflector mode. In the transmit mode, the phased antenna array transmits wireless signals using the first and second optical LO signals. In the receive mode, the phased antenna array receives wireless signals using the first and second optical LO signals. In the passive reflector mode, the phased antenna array does not transmit or receive wireless signals and the UTC PDs in the array are not illuminated by the first or second optical LO signals. The phased antenna array may receive incident wireless signals and may reflect the incident wireless signals as reflected signals. The UTC PDs may be controlled to exhibit selected output impedances that are mismatched with respect to the input impedances of the antenna radiating elements by one or more amounts. Different mismatches can be used across the array and/or as a function of time to impart different phase shifts and/or frequency shifts on the reflected signals. The phase shifts may be used to encode information into the reflected signals using space-time coding scheme and/or to form a signal beam of the reflected signals oriented in a selected direction. 
     An aspect of the disclosure provides an electronic device. The electronic device can include an antenna radiating element having an input impedance. The electronic device can include a photodiode coupled to the antenna radiating element and having an output impedance. The photodiode can be configured to receive a control signal that places the photodiode into a selected one of a first mode in which the input impedance is mismatched with respect to the output impedance at a frequency greater than or equal to 100 GHz or a second mode in which the input impedance matches the output impedance at the frequency. The electronic device can include an optical signal path configured to illuminate the photodiode using a first optical local oscillator (LO) signal and a second optical LO signal that is offset in wavelength with respect to the first optical LO signal while the photodiode is in the second mode. The antenna radiating element can be configured to reflect wireless signals at the frequency while the photodiode is in the first mode. 
     An aspect of the disclosure provides a method of operating an electronic device having an array of antennas that include antenna radiating elements and photodiodes coupled to the antenna radiating elements. The method can include with the photodiodes, generating currents on the antenna radiating elements that transmit first wireless signals at a frequency greater than or equal to 100 GHz while the photodiodes are illuminated using a first optical local oscillator (LO) signal and a second optical LO signal that is offset in wavelength with respect to the first optical LO signal. The method can include with the antenna radiating elements, reflecting second wireless signals at the frequency while the photodiodes are controlled to exhibit one or more output impedances that are mismatched at the frequency with respect to input impedances of the antenna radiating elements. 
     An aspect of the disclosure provides an electronic device. An electronic device can include an antenna radiating element having an input impedance. The electronic device can include a photodiode that is coupled to the antenna radiating element and that is configured, using a control signal, to exhibit an output impedance that mismatches an input impedance of the antenna radiating element at a frequency greater than or equal to 100 GHz. 
     An aspect of the disclosure provides an electronic device. The electronic device can include a phased antenna array. The electronic device can include one or more processors configured to place the phased antenna array in a first mode in which the phased antenna array is configured to transmit first wireless signals, a second mode in which the phased antenna array is configured to receive second wireless signals, and a third mode in which the phased antenna array is configured to reflect third wireless signals incident upon the phased antenna array. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram of an illustrative electronic device having wireless circuitry with at least one antenna that both transmits and receives wireless signals at frequencies greater than about 100 GHz in accordance with some embodiments. 
         FIG.  2    is a top view of an illustrative antenna that transmits wireless signals at frequencies greater than about 100 GHz based on optical local oscillator (LO) signals in accordance with some embodiments. 
         FIG.  3    is a top view showing how an illustrative antenna of the type shown in  FIG.  2    may convert received wireless signals at frequencies greater than about 100 GHz into intermediate frequency signals based on optical LO signals in accordance with some embodiments. 
         FIG.  4    is a top view showing how multiple antennas of the type shown in  FIGS.  2  and  3    may be stacked to cover multiple polarizations in accordance with some embodiments. 
         FIG.  5    is a top view showing how stacked antennas of the type shown in  FIG.  4    may be integrated into a phased antenna array for conveying wireless signals at frequencies greater than about 100 GHz within a corresponding signal beam. 
         FIG.  6    is a circuit diagram of illustrative wireless circuitry having an antenna that transmits wireless signals at frequencies greater than about 100 GHz and that receives wireless signals at frequencies greater than about 100 GHz for conversion to intermediate frequencies and then to the optical domain in accordance with some embodiments. 
         FIG.  7    is a circuit diagram of an illustrative phased antenna array that conveys wireless signals at frequencies greater than about 100 GHz within a corresponding signal beam in accordance with some embodiments. 
         FIG.  8    is a top view showing how an illustrative antenna of the type shown in  FIGS.  2  and  3    may be controlled to passively reflect wireless signals at frequencies greater than about 100 GHz while imparting the reflected wireless signals with a desired phase and/or frequency change in accordance with some embodiments. 
         FIG.  9    is a cross-sectional side view of an illustrative uni-travelling-carrier photodiode (UTC PD) in an antenna that can be configured to transmit, receive, and/or passively reflect wireless signals at frequencies greater than about 100 GHz in accordance with some embodiments. 
         FIG.  10    is an equivalent circuit diagram of an illustrative UTC PD in an antenna that can be configured to transmit, receive, and/or passively reflect wireless signals at frequencies greater than about 100 GHz in accordance with some embodiments. 
         FIG.  11    is a diagram showing how illustrative antennas on an electronic device may passively reflect wireless signals transmitted by external communications equipment in different directions in accordance with some embodiments. 
         FIG.  12    is a state diagram showing illustrative operating modes for a phased antenna array that can be configured to transmit, receive, and/or passively reflect wireless signals at frequencies greater than about 100 GHz in accordance with some embodiments. 
         FIG.  13    is a perspective view showing how one or more antennas in one or more illustrative phased antenna arrays may be distributed across different locations on an electronic device in accordance with some embodiments. 
         FIG.  14    is a top view of an illustrative phased antenna array having different subsets of antennas for transmitting, receiving, and/or passively reflecting wireless signals in accordance with some embodiments. 
         FIG.  15    is a side view showing how an illustrative THz lens may overlap a phased antenna array for focusing electromagnetic energy in accordance with some embodiments. 
         FIG.  16    is a flow chart of illustrative operations that may be performed by an illustrative electronic device in using a phased antenna array to transmit, receive, and/or passively reflect wireless signals in accordance with some embodiments. 
         FIG.  17    is a circuit schematic diagram of an illustrative phased antenna array that may be configured to passively reflect radio-frequency signals at frequencies less than 100 GHz in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic device  10  of  FIG.  1    (sometimes referred to herein as electro-optical device  10 ) may be a computing device such as a laptop computer, a desktop 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 device embedded in eyeglasses, goggles, 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 internet-connected voice-controlled speaker, a home entertainment device, a remote control device, a gaming controller, a peripheral user input device, a wireless base station or access point, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in the functional block diagram of  FIG.  1   , device  10  may include components located on or within an electronic device housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, metal alloys, etc.), other suitable materials, or a combination of these materials. In some situations, parts or all of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may include control circuitry  14 . Control circuitry  14  may include storage such as storage circuitry  16 . Storage circuitry  16  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. Storage circuitry  16  may include storage that is integrated within device  10  and/or removable storage media. 
     Control circuitry  14  may include processing circuitry such as processing circuitry  18 . Processing circuitry  18  may be used to control the operation of device  10 . Processing circuitry  18  may include on one or more processors, microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application specific integrated circuits, central processing units (CPUs), graphics processing units (GPUs), 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  16  (e.g., storage circuitry  16  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  16  may be executed by processing circuitry  18 . 
     Control circuitry  14  may be used to run software on device  10  such as satellite navigation applications, internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, control circuitry  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 (WLAN) protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other wireless personal area network (WPAN) protocols, IEEE 802.11ad protocols (e.g., ultra-wideband protocols), cellular telephone protocols (e.g., 3G protocols, 4G (LTE) protocols, 3GPP Fifth Generation (5G) New Radio (NR) protocols, Sixth Generation (6G) protocols, sub-THz protocols, THz protocols, etc.), antenna diversity protocols, satellite navigation system protocols (e.g., global positioning system (GPS) protocols, global navigation satellite system (GLONASS) protocols, etc.), antenna-based spatial ranging protocols, optical communications protocols, or any other desired communications protocols. Each communications protocol may be associated with a corresponding radio access technology (RAT) that specifies the physical connection methodology used in implementing the protocol. 
     Device  10  may include input-output circuitry  20 . Input-output circuitry  20  may include input-output devices  22 . Input-output devices  22  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  22  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  22  may include touch sensors, displays (e.g., touch-sensitive and/or force-sensitive displays), light-emitting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, audio jacks and other audio port components, digital data port devices, motion sensors (accelerometers, gyroscopes, and/or compasses that detect motion), capacitance sensors, proximity sensors, magnetic sensors, force sensors (e.g., force sensors coupled to a display to detect pressure applied to the display), temperature sensors, etc. In some configurations, keyboards, headphones, displays, pointing devices such as trackpads, mice, and joysticks, and other input-output devices may be coupled to device  10  using wired or wireless connections (e.g., some of input-output devices  22  may be peripherals that are coupled to a main processing unit or other portion of device  10  via a wired or wireless link). 
     Input-output circuitry  20  may include wireless circuitry  24  to support wireless communications. Wireless circuitry  24  (sometimes referred to herein as wireless communications circuitry  24 ) may include one or more antennas  30 . 
     Wireless circuitry  24  may also include transceiver circuitry  26 . Transceiver circuitry  26  may include transmitter circuitry, receiver circuitry, modulator circuitry, demodulator circuitry (e.g., one or more modems), radio-frequency circuitry, one or more radios, intermediate frequency circuitry, optical transmitter circuitry, optical receiver circuitry, optical light sources, other optical components, baseband circuitry (e.g., one or more baseband processors), amplifier circuitry, clocking circuitry such as one or more local oscillators and/or phase-locked loops, memory, one or more registers, filter circuitry, switching circuitry, analog-to-digital converter (ADC) circuitry, digital-to-analog converter (DAC) circuitry, radio-frequency transmission lines, optical fibers, and/or any other circuitry for transmitting and/or receiving wireless signals using antennas  30 . The components of transceiver circuitry  26  may be implemented on one integrated circuit, chip, system-on-chip (SOC), die, printed circuit board, substrate, or package, or the components of transceiver circuitry  26  may be distributed across two or more integrated circuits, chips, SOCs, printed circuit boards, substrates, and/or packages. 
     The example of  FIG.  1    is merely illustrative. While control circuitry  14  is shown separately from wireless circuitry  24  in the example of  FIG.  1    for the sake of clarity, wireless circuitry  24  may include processing circuitry (e.g., one or more processors) that forms a part of processing circuitry  18  and/or storage circuitry that forms a part of storage circuitry  16  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 circuitry (e.g., one or more baseband processors), digital control circuitry, analog control circuitry, and/or other control circuitry that forms part of wireless circuitry  24 . The baseband circuitry may, for example, access a communication protocol stack on control circuitry  14  (e.g., storage circuitry  20 ) to: perform user plane functions at a PHY layer, MAC layer, RLC layer, PDCP layer, SDAP layer, and/or PDU layer, and/or to perform control plane functions at the PHY layer, MAC layer, RLC layer, PDCP layer, RRC, layer, and/or non-access stratum layer. 
     Transceiver circuitry  26  may be coupled to each antenna  30  in wireless circuitry  24  over a respective signal path  28 . Each signal path  28  may include one or more radio-frequency transmission lines, waveguides, optical fibers, and/or any other desired lines/paths for conveying wireless signals between transceiver circuitry  26  and antenna  30 . Antennas  30  may be formed using any desired antenna structures for conveying wireless signals. For example, antennas  30  may include antennas with resonating elements that are formed from dipole antenna structures, planar dipole antenna structures (e.g., bowtie antenna structures), slot antenna structures, loop antenna structures, patch antenna structures, inverted-F antenna structures, planar inverted-F antenna structures, helical antenna structures, monopole antennas, dipoles, hybrids of these designs, etc. Filter circuitry, switching circuitry, impedance matching circuitry, and/or other antenna tuning components may be adjusted to adjust the frequency response and wireless performance of antennas  30  over time. 
     If desired, two or more of antennas  30  may be integrated into a phased antenna array (sometimes referred to herein as a phased array antenna) in which each of the antennas conveys wireless signals with a respective phase and magnitude that is adjusted over time so the wireless signals constructively and destructively interfere to produce (form) a signal beam in a given pointing direction. The term “convey wireless signals” as used herein means the transmission and/or reception of the wireless signals (e.g., for performing unidirectional and/or bidirectional wireless communications with external wireless communications equipment). Antennas  30  may transmit the wireless signals by radiating the signals into free space (or to free space through intervening device structures such as a dielectric cover layer). Antennas  30  may additionally or alternatively receive the wireless signals from free space (e.g., through intervening devices structures such as a dielectric cover layer). The transmission and reception of wireless signals by antennas  30  each involve the excitation or resonance of antenna currents on an antenna resonating (radiating) element in the antenna by the wireless signals within the frequency band(s) of operation of the antenna. 
     Transceiver circuitry  26  may use antenna(s)  30  to transmit and/or receive wireless signals that convey wireless communications data between device  10  and external wireless communications equipment (e.g., one or more other devices such as device  10 , a wireless access point or base station, etc.). The wireless communications data may be conveyed bidirectionally or unidirectionally. The wireless communications 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. 
     Additionally or alternatively, wireless circuitry  24  may use antenna(s)  30  to perform wireless sensing operations. The sensing operations may allow device  10  to detect (e.g., sense or identify) the presence, location, orientation, and/or velocity (motion) of objects external to device  10 . Control circuitry  14  may use the detected presence, location, orientation, and/or velocity of the external objects to perform any desired device operations. As examples, control circuitry  14  may use the detected presence, location, orientation, and/or velocity of the external objects to identify a corresponding user input for one or more software applications running on device  10  such as a gesture input performed by the user&#39;s hand(s) or other body parts or performed by an external stylus, gaming controller, head-mounted device, or other peripheral devices or accessories, to determine when one or more antennas  30  needs to be disabled or provided with a reduced maximum transmit power level (e.g., for satisfying regulatory limits on radio-frequency exposure), to determine how to steer (form) a radio-frequency signal beam produced by antennas  30  for wireless circuitry  24  (e.g., in scenarios where antennas  30  include a phased array of antennas  30 ), to map or model the environment around device  10  (e.g., to produce a software model of the room where device  10  is located for use by an augmented reality application, gaming application, map application, home design application, engineering application, etc.), to detect the presence of obstacles in the vicinity of (e.g., around) device  10  or in the direction of motion of the user of device  10 , etc. 
     Wireless circuitry  24  may transmit and/or receive wireless signals within corresponding frequency bands of the electromagnetic spectrum (sometimes referred to herein as communications bands or simply as “bands”). The frequency bands handled by transceiver circuitry  26  may include wireless local area network (WLAN) frequency bands (e.g., Wi-Fi® (IEEE 802.11) or other WLAN communications bands) such as a 2.4 GHz WLAN band (e.g., from 2400 to 2480 MHz), a 5 GHz WLAN band (e.g., from 5180 to 5825 MHz), a Wi-Fi® 6E band (e.g., from 5925-7125 MHz), and/or other Wi-Fi® bands (e.g., from 1875-5160 MHz), wireless personal area network (WPAN) frequency bands such as the 2.4 GHz Bluetooth® band or other WPAN communications bands, cellular telephone frequency bands (e.g., bands from about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G New Radio Frequency Range 1 (FR1) bands below 10 GHz, 5G New Radio Frequency Range 2 (FR2) bands between 20 and 60 GHz, etc.), other centimeter or millimeter wave frequency bands between 10-100 GHz, near-field communications frequency bands (e.g., at 13.56 MHz), satellite navigation frequency bands (e.g., a GPS band from 1565 to 1610 MHz, a Global Navigation Satellite System (GLONASS) band, a BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) frequency bands that operate under the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols, communications bands under the family of 3GPP wireless communications standards, communications bands under the IEEE 802.XX family of standards, and/or any other desired frequency bands of interest. 
     Over time, software applications on electronic devices such as device  10  have become more and more data intensive. Wireless circuitry on the electronic devices therefore needs to support data transfer at higher and higher data rates. In general, the data rates supported by the wireless circuitry are proportional to the frequency of the wireless signals conveyed by the wireless circuitry (e.g., higher frequencies can support higher data rates than lower frequencies). Wireless circuitry  24  may convey centimeter and millimeter wave signals to support relatively high data rates (e.g., because centimeter and millimeter wave signals are at relatively high frequencies between around 10 GHz and 100 GHz). However, the data rates supported by centimeter and millimeter wave signals may still be insufficient to meet all the data transfer needs of device  10 . To support even higher data rates such as data rates up to 5-10 Gbps or higher, wireless circuitry  24  may convey wireless signals at frequencies greater than 100 GHz. 
     As shown in  FIG.  1   , wireless circuitry  24  may transmit wireless signals  32  and may receive wireless signals  34  at frequencies greater than around 100 GHz. Wireless signals  32  and  34  may sometimes be referred to herein as tremendously high frequency (THF) signals  32  and  34 , sub-THz signals  32  and  34 , THz signals  32  and  34 , or sub-millimeter wave signals  32  and  34 . THF signals  32  and  34  may be at sub-THz or THz frequencies such as frequencies between 100 GHz and 1 THz, between 100 GHz and 10 THz, between 100 GHz and 2 THz, between 200 GHz and 1 THz, between 300 GHz and 1 THz, between 300 GHz and 2 THz, between 300 GHz and 10 THz, between 100 GHz and 800 GHz, between 200 GHz and 1.5 THz, etc. (e.g., within a sub-THz, THz, THF, or sub-millimeter frequency band such as a 6G frequency band). The high data rates supported by these frequencies may be leveraged by device  10  to perform cellular telephone voice and/or data communications (e.g., while supporting spatial multiplexing to provide further data bandwidth), to perform spatial ranging operations such as radar operations to detect the presence, location, and/or velocity of objects external to device  10 , to perform automotive sensing (e.g., with enhanced security), to perform health/body monitoring on a user of device  10  or another person, to perform gas or chemical detection, to form a high data rate wireless connection between device  10  and another device or peripheral device (e.g., to form a high data rate connection between a display driver on device  10  and a display that displays ultra-high resolution video), to form a remote radio head (e.g., a flexible high data rate connection), to form a THF chip-to-chip connection within device  10  that supports high data rates (e.g., where one antenna  30  on a first chip in device  10  transmits THF signals  32  to another antenna  30  on a second chip in device  10 ), and/or to perform any other desired high data rate operations. 
     Space is at a premium within electronic devices such as device  10 . In some scenarios, different antennas  30  are used to transmit THF signals  32  than are used to receive THF signals  34 . However, handling transmission of THF signals  32  and reception of THF signals  34  using different antennas  30  can consume an excessive amount of space and other resources within device  10  because two antennas  30  and signal paths  28  would be required to handle both transmission and reception. To minimize space and resource consumption within device  10 , the same antenna  30  and signal path  28  may be used to both transmit THF signals  32  and to receive THF signals  34 . If desired, multiple antennas  30  in wireless circuitry  24  may transmit THF signals  32  and may receive THF signals  34 . The antennas may be integrated into a phased antenna array that transmits THF signals  32  and that receives THF signals  34  within a corresponding signal beam oriented in a selected beam pointing direction. 
     It can be challenging to incorporate components into wireless circuitry  24  that support wireless communications at these high frequencies. If desired, transceiver circuitry  26  and signal paths  28  may include optical components that convey optical signals to support the transmission of THF signals  32  and the reception of THF signals  34  in a space and resource-efficient manner. The optical signals may be used in transmitting THF signals  32  at THF frequencies and in receiving THF signals  34  at THF frequencies. 
       FIG.  2    is a diagram of an illustrative antenna  30  that may be used to both transmit THY signals  32  and to receive THF signals  34  using optical signals. Antenna  30  may include one or more antenna radiating (resonating) elements such as radiating (resonating) element arms  36 . In the example of  FIG.  2   , antenna  30  is a planar dipole antenna (sometimes referred to as a “bowtie” antenna) having two opposing radiating element arms  36  (e.g., bowtie arms or dipole arms). This is merely illustrative and, in general, antenna  30  may be any type of antenna having any desired antenna radiating element architecture. 
     As shown in  FIG.  2   , antenna  30  includes a photodiode (PD)  42  coupled between radiating element arms  36 . Electronic devices that include antennas  30  with photodiodes  42  such as device  10  may sometimes also be referred to as electro-optical devices (e.g., electro-optical device  10 ). Photodiode  42  may be a programmable photodiode. An example in which photodiode  42  is a programmable uni-travelling-carrier photodiode (UTC PD) is described herein as an example. Photodiode  42  may therefore sometimes be referred to herein as UTC PD  42  or programmable UTC PD  42 . This is merely illustrative and, in general, photodiode  42  may include any desired type of adjustable/programmable photodiode or component that converts electromagnetic energy at optical frequencies to current at THF frequencies on radiating element arms  36  and/or vice versa. Each radiating element arm  36  may, for example, have a first edge at UTC PD  42  and a second edge opposite the first edge that is wider than the first edge (e.g., in implementations where antenna  30  is a bowtie antenna). Other radiating elements may be used if desired. 
     UTC PD  42  may have a bias terminal  38  that receives one or more control signals V BIAS . Control signals V BIAS  may include bias voltages provided at one or more voltage levels and/or other control signals for controlling the operation of UTC PD  42  such as impedance adjustment control signals for adjusting the output impedance of UTC PD  42 . Control circuitry  14  ( FIG.  1   ) may provide (e.g., apply, supply, assert, etc.) control signals V BIAS  at different settings (e.g., values, magnitudes, etc.) to dynamically control (e.g., program or adjust) the operation of UTC PD  42  over time. For example, control signals V BIAS  may be used to control whether antenna  30  transmits THF signals  32  or receives THF signals  34 . When control signals V BIAS  include a bias voltage asserted at a first level or magnitude, antenna  30  may be configured to transmit THF signals  32 . When control signals V BIAS  include a bias voltage asserted at a second level or magnitude, antenna  30  may be configured to receive THF signals  34 . In the example of  FIG.  2   , control signals V BIAS  include the bias voltage asserted at the first level to configure antenna  30  to transmit THF signals  32 . If desired, control signals V BIAS  may also be adjusted to control the waveform of the THF signals (e.g., as a squaring function that preserves the modulation of incident optical signals, a linear function, etc.), to perform gain control on the signals conveyed by antenna  30 , and/or to adjust the output impedance of UTC PD  42 . 
     As shown in  FIG.  2   , UTC PD  42  may be optically coupled to optical path  40 . Optical path  40  may include one or more optical fibers or waveguides. UTC PD  42  may receive optical signals from transceiver circuitry  26  ( FIG.  1   ) over optical path  40 . The optical signals may include a first optical local oscillator (LO) signal LO 1  and a second optical local oscillator signal LO 2 . Optical local oscillator signals LO 1  and LO 2  may be generated by light sources in transceiver circuitry  26  ( FIG.  1   ). Optical local oscillator signals LO 1  and LO 2  may be at optical wavelengths (e.g., between 400 nm and 700 nm), ultra-violet wavelengths (e.g., near-ultra-violet or extreme ultraviolet wavelengths), and/or infrared wavelengths (e.g., near-infrared wavelengths, mid-infrared wavelengths, or far-infrared wavelengths). Optical local oscillator signal LO 2  may be offset in wavelength from optical local oscillator signal LO 1  by a wavelength offset X. Wavelength offset X may be equal to the wavelength of the THF signals conveyed by antenna  30  (e.g., between 100 GHz and 1 THz (1000 GHz), between 100 GHz and 2 THz, between 300 GHz and 800 GHz, between 300 GHz and 1 THz, between 300 and 400 GHz, etc.). 
     During signal transmission, wireless data (e.g., wireless data packets, symbols, frames, etc.) may be modulated onto optical local oscillator signal LO 2  to produce modulated optical local oscillator signal LO 2 ′. If desired, optical local oscillator signal LO 1  may be provided with an optical phase shift S. Optical path  40  may illuminate UTC PD  42  with optical local oscillator signal LO 1  (plus the optical phase shift S when applied) and modulated optical local oscillator signal LO 2 ′. If desired, lenses or other optical components may be interposed between optical path  40  and UTC PD  42  to help focus the optical local oscillator signals onto UTC PD  42 . 
     UTC PD  42  may convert optical local oscillator signal LO 1  and modulated local oscillator signal LO 2 ′ (e.g., beats between the two optical local oscillator signals) into antenna currents that run along the perimeter of radiating element arms  36 . The frequency of the antenna currents is equal to the frequency difference between local oscillator signal LO 1  and modulated local oscillator signal LO 2 ′. The antenna currents may radiate (transmit) THF signals  32  into free space. Control signal V BIAS  may control UTC PD  42  to convert the optical local oscillator signals into antenna currents on radiating element arms  36  while preserving the modulation and thus the wireless data on modulated local oscillator signal LO 2 ′ (e.g., by applying a squaring function to the signals). THF signals  32  will thereby carry the modulated wireless data for reception and demodulation by external wireless communications equipment. 
       FIG.  3    is a diagram showing how antenna  30  may receive THF signals  34  (e.g., after changing the setting of control signals V BIAS  into a reception state from the transmission state of  FIG.  2   ). As shown in  FIG.  3   , THF signals  34  may be incident upon antenna radiating element arms  36 . The incident THF signals  34  may produce antenna currents that flow around the perimeter of radiating element arms  36 . UTC PD  42  may use optical local oscillator signal LO 1  (plus the optical phase shift S when applied), optical local oscillator signal LO 2  (e.g., without modulation), and control signals V BIAS  (e.g., a bias voltage asserted at the second level) to convert the received THF signals  34  into intermediate frequency signals SIGIF that are output onto intermediate frequency signal path  44 . 
     The frequency of intermediate frequency signals SIGIF may be equal to the frequency of THF signals  34  minus the difference between the frequency of optical local oscillator signal LO 1  and the frequency of optical local oscillator signal LO 2 . As an example, intermediate frequency signals SIGIF may be at lower frequencies than THF signals  32  and  34  such as centimeter or millimeter wave frequencies between 10 GHz and 100 GHz, between 30 GHz and 80 GHz, around 60 GHz, etc. If desired, transceiver circuitry  26  ( FIG.  1   ) may change the frequency of optical local oscillator signal LO 1  and/or optical local oscillator signal LO 2  when switching from transmission to reception or vice versa. UTC PD  42  may preserve the data modulation of THF signals  34  in intermediate signals SIGIF. A receiver in transceiver circuitry  26  ( FIG.  1   ) may demodulate intermediate frequency signals SIGIF (e.g., after further down conversion) to recover the wireless data from THF signals  34 . In another example, wireless circuitry  24  may convert intermediate frequency signals SIGIF to the optical domain before recovering the wireless data. In yet another example, intermediate frequency signal path  44  may be omitted and UTC PD  42  may convert THF signals  34  into the optical domain for subsequent demodulation and data recovery (e.g., in a sideband of the optical signal). 
     The antenna  30  of  FIGS.  2  and  3    may support transmission of THF signals  32  and reception of THF signals  34  with a given polarization (e.g., a linear polarization such as a vertical polarization). If desired, wireless circuitry  24  ( FIG.  1   ) may include multiple antennas  30  for covering different polarizations.  FIG.  4    is a diagram showing one example of how wireless circuitry  24  may include multiple antennas  30  for covering different polarizations. 
     As shown in  FIG.  4   , the wireless circuitry may include a first antenna  30  such as antenna  30 V for covering a first polarization (e.g., a first linear polarization such as a vertical polarization) and may include a second antenna  30  such as antenna  30 H for covering a second polarization different from or orthogonal to the first polarization (e.g., a second linear polarization such as a horizontal polarization). Antenna  30 V may have a UTC PD  42  such as UTC PD  42 V coupled between a corresponding pair of radiating element arms  36 . Antenna  30 H may have a UTC PD  42  such as UTC PD  42 H coupled between a corresponding pair of radiating element arms  36  oriented non-parallel (e.g., orthogonal) to the radiating element arms  36  in antenna  30 V. This may allow antennas  30 V and  30 H to transmit THF signals  32  with respective (orthogonal) polarizations and may allow antennas  30 V and  30 H to receive THF signals  32  with respective (orthogonal) polarizations. 
     To minimize space within device  10 , antenna  30 V may be vertically stacked over or under antenna  30 H (e.g., where UTC PD  42 V partially or completely overlaps UTC PD  42 H). In this example, antennas  30 V and  30 H may both be formed on the same substrate such as a rigid or flexible printed circuit board. The substrate may include multiple stacked dielectric layers (e.g., layers of ceramic, epoxy, flexible printed circuit board material, rigid printed circuit board material, etc.). The radiating element arms  36  in antenna  30 V may be formed on a separate layer of the substrate than the radiating element arms  36  in antenna  30 H or the radiating element arms  36  in antenna  30 V may be formed on the same layer of the substrate as the radiating element arms  36  in antenna  30 H. UTC PD  42 V may be formed on the same layer of the substrate as UTC PD  42 H or UTC PD  42 V may be formed on a separate layer of the substrate than UTC PD  42 H. UTC PD  42 V may be formed on the same layer of the substrate as the radiating element arms  36  in antenna  30 V or may be formed on a separate layer of the substrate as the radiating element arms  36  in antenna  30 V. UTC PD  42 H may be formed on the same layer of the substrate as the radiating element arms  36  in antenna  30 H or may be formed on a separate layer of the substrate as the radiating element arms  36  in antenna  30 H. 
     If desired, antennas  30  or antennas  30 H and  30 V of  FIG.  4    may be integrated within a phased antenna array.  FIG.  5    is a diagram showing one example of how antennas  30 H and  30 V may be integrated within a phased antenna array. As shown in  FIG.  5   , device  10  may include a phased antenna array  46  of stacked antennas  30 H and  30 V arranged in a rectangular grid of rows and columns. Each of the antennas in phased antenna array  46  may be formed on the same substrate. This is merely illustrative. In general, phased antenna array  46  (sometimes referred to as a phased array antenna) may include any desired number of antennas  30 V and  30 H (or non-stacked antennas  30 ) arranged in any desired pattern. Each of the antennas in phased antenna array  46  may be provided with a respective optical phase shift S ( FIGS.  2  and  3   ) that configures the antennas to collectively transmit THF signals  32  and/or receive THF signals  34  that sum to form a signal beam of THF signals in a desired beam pointing direction. The beam pointing direction may be selected to point the signal beam towards external communications equipment, towards a desired external object, away from an external object, etc. 
     Phased antenna array  46  may occupy relatively little space within device  10 . For example, each antenna  30 V/ 30 H may have a length  48  (e.g., as measured from the end of one radiating element arm to the opposing end of the opposite radiating element arm). Length  48  may be approximately equal to one-half the wavelength of THF signals  32  and  34 . For example, length  48  may be as small as 0.5 mm or less. Each UTC-PD  42  in phased antenna array  46  may occupy a lateral area of 100 square microns or less. This may allow phased antenna array  46  to occupy very little area within device  10 , thereby allowing the phased antenna array to be integrated within different portions of device  10  while still allowing other space for device components. The examples of  FIGS.  2 - 5    are merely illustrative and, in general, each antenna may have any desired antenna radiating element architecture. 
       FIG.  6    is a circuit diagram showing how a given antenna  30  and signal path  28  ( FIG.  1   ) may be used to both transmit THF signals  32  and receive THF signals  34  based on optical local oscillator signals. In the example of  FIG.  6   , UTC PD  42  converts received THF signals  34  into intermediate frequency signals SIGIF that are then converted to the optical domain for recovering the wireless data from the received THF signals. 
     As shown in  FIG.  6   , wireless circuitry  24  may include transceiver circuitry  26  coupled to antenna  30  over signal path  28  (e.g., an optical signal path sometimes referred to herein as optical signal path  28 ). UTC PD  42  may be coupled between the radiating element arm(s)  36  of antenna  30  and signal path  28 . Transceiver circuitry  26  may include optical components  68 , amplifier circuitry such as power amplifier  76 , and digital-to-analog converter (DAC)  74 . Optical components  68  may include an optical receiver such as optical receiver  72  and optical local oscillator (LO) light sources (emitters)  70 . LO light sources  70  may include two or more light sources such as laser light sources, laser diodes, optical phase locked loops, or other optical emitters that emit light (e.g., optical local oscillator signals LO 1  and LO 2 ) at respective wavelengths. If desired, LO light sources  70  may include a single light source and may include optical components for splitting the light emitted by the light source into different wavelengths. Signal path  28  may be coupled to optical components  68  over optical path  66 . Optical path  66  may include one or more optical fibers and/or waveguides. 
     Signal path  28  may include an optical splitter such as optical splitter (OS)  54 , optical paths such as optical path  64  and optical path  62 , an optical combiner such as optical combiner (OC)  52 , and optical path  40 . Optical path  62  may be an optical fiber or waveguide. Optical path  64  may be an optical fiber or waveguide. Optical splitter  54  may have a first (e.g., input) port coupled to optical path  66 , a second (e.g., output) port coupled to optical path  62 , and a third (e.g., output) port coupled to optical path  64 . Optical path  64  may couple optical splitter  54  to a first (e.g., input) port of optical combiner  52 . Optical path  62  may couple optical splitter  54  to a second (e.g., input) port of optical combiner  52 . Optical combiner  52  may have a third (e.g., output) port coupled to optical path  40 . 
     An optical phase shifter such as optical phase shifter  80  may be (optically) interposed on or along optical path  64 . An optical modulator such as optical modulator  56  may be (optically) interposed on or along optical path  62 . Optical modulator  56  may be, for example, a Mach-Zehnder modulator (MZM) and may therefore sometimes be referred to herein as MZM  56 . MZM  56  includes a first optical arm (branch)  60  and a second optical arm (branch)  58  interposed in parallel along optical path  62 . Propagating optical local oscillator signal LO 2  along arms  60  and  58  of MZM  56  may, in the presence of a voltage signal applied to one or both arms, allow different optical phase shifts to be imparted on each arm before recombining the signal at the output of the MZM (e.g., where optical phase modulations produced on the arms are converted to intensity modulations at the output of MZM  56 ). When the voltage applied to MZM  56  includes wireless data, MZM  56  may modulate the wireless data onto optical local oscillator signal LO 2 . If desired, the phase shifting performed at MZM  56  may be used to perform beam forming/steering in addition to or instead of optical phase shifter  80 . MZM  56  may receive one or more bias voltages W BIAS  (sometimes referred to herein as bias signals W BIAS ) applied to one or both of arms  58  and  60 . Control circuitry  14  ( FIG.  1   ) may provide bias voltage W BIAS  with different magnitudes to place MZM  56  into different operating modes (e.g., operating modes that suppress optical carrier signals, operating modes that do not suppress optical carrier signals, etc.). 
     Intermediate frequency signal path  44  may couple UTC PD  42  to MZM  56  (e.g., arm  60 ). An amplifier such as low noise amplifier  82  may be interposed on intermediate frequency signal path  44 . Intermediate frequency signal path  44  may be used to pass intermediate frequency signals SIGIF from UTC PD  42  to MZM  56 . DAC  74  may have an input coupled to up-conversion circuitry, modulator circuitry, and/or baseband circuitry in a transmitter of transceiver circuitry  26 . DAC  74  may receive digital data to transmit over antenna  30  and may convert the digital data to the analog domain (e.g., as data DAT). DAC  74  may have an output coupled to transmit data path  78 . Transmit data path  78  may couple DAC  74  to MZM  56  (e.g., arm  60 ). Each of the components along signal path  28  may allow the same antenna  30  to both transmit THF signals  32  and receive THF signals  34  (e.g., using the same components along signal path  28 ), thereby minimizing space and resource consumption within device  10 . 
     LO light sources  70  may produce (emit) optical local oscillator signals LO 1  and LO 2  (e.g., at different wavelengths that are separated by the wavelength of THF signals  32 / 34 ). Optical components  68  may include lenses, waveguides, optical couplers, optical fibers, and/or other optical components that direct the emitted optical local oscillator signals LO 1  and LO 2  towards optical splitter  54  via optical path  66 . Optical splitter  54  may split the optical signals on optical path  66  (e.g., by wavelength) to output optical local oscillator signal LO 1  onto optical path  64  while outputting optical local oscillator signal LO 2  onto optical path  62 . 
     Control circuitry  14  ( FIG.  1   ) may provide phase control signals CTRL to optical phase shifter  80 . Phase control signals CTRL may control optical phase shifter  80  to apply optical phase shift S to the optical local oscillator signal LO 1  on optical path  64 . Phase shift S may be selected to steer a signal beam of THF signals  32 / 34  in a desired pointing direction. Optical phase shifter  80  may pass the phase-shifted optical local oscillator signal LO 1  (denoted as LO 1 +S) to optical combiner  52 . Signal beam steering is performed in the optical domain (e.g., using optical phase shifter  80 ) rather than in the THF domain because there are no satisfactory phase shifting circuit components that operate at frequencies as high as the frequencies of THF signals  32  and  34 . Optical combiner  52  may receive optical local oscillator signal LO 2  over optical path  62 . Optical combiner  52  may combine optical local oscillator signals LO 1  and LO 2  onto optical path  40 , which directs the optical local oscillator signals onto UTC PD  42  for use during signal transmission or reception. 
     During transmission of THF signals  32 , DAC  74  may receive digital wireless data (e.g., data packets, frames, symbols, etc.) for transmission over THF signals  32 . DAC  74  may convert the digital wireless data to the analog domain and may output (transmit) the data onto transmit data path  78  as data DAT (e.g., for transmission via antenna  30 ). Power amplifier  76  may amplify data DAT. Transmit data path  78  may pass data DAT to MZM  56  (e.g., arm  60 ). MZM  56  may modulate data DAT onto optical local oscillator signal LO 2  to produce modulated optical local oscillator signal LO 2 ′ (e.g., an optical local oscillator signal at the frequency/wavelength of optical local oscillator signal LO 2  but that is modulated to include the data identified by data DAT). Optical combiner  52  may combine optical local oscillator signal LO 1  with modulated optical local oscillator signal LO 2 ′ at optical path  40 . 
     Optical path  40  may illuminate UTC PD  42  with (using) optical local oscillator signal LO 1  (e.g., with the phase shift S applied by optical phase shifter  80 ) and modulated optical local oscillator signal LO 2 ′. Control circuitry  14  ( FIG.  1   ) may apply a control signal V BIAS  to UTC PD  42  that configures antenna  30  for the transmission of THF signals  32 . UTC PD  42  may convert optical local oscillator signal LO 1  and modulated optical local oscillator signal LO 2 ′ into antenna currents on radiating element arm(s)  36  at the frequency of THF signals  32  (e.g., while programmed for transmission using control signal V BIAS ). The antenna currents on radiating element arm(s)  36  may radiate THF signals  32 . The frequency of THF signals  32  is given by the difference in frequency between optical local oscillator signal LO 1  and modulated optical local oscillator signal LO 2 ′. Control signals V BIAS  may control UTC PD  42  to preserve the modulation from modulated optical local oscillator signal LO 2 ′ in the radiated THF signals  32 . External equipment that receives THF signals  32  will thereby be able to extract data DAT from the THF signals  32  transmitted by antenna  30 . 
     During reception of THF signals  34 , MZM  56  does not modulate any data onto optical local oscillator signal LO 2 . Optical path  40  therefore illuminates UTC PD  42  with optical local oscillator signal LO 1  (e.g., with phase shift S) and optical local oscillator signal LO 2 . Control circuitry  14  ( FIG.  1   ) may apply a control signal V BIAS  (e.g., a bias voltage) to UTC PD  42  that configures antenna  30  for the receipt of THF signals  32 . UTC PD  42  may use optical local oscillator signals LO 1  and LO 2  to convert the received THF signals  34  into intermediate frequency signals SIGIF output onto intermediate frequency signal path  44  (e.g., while programmed for reception using bias voltage V BIAS ). Intermediate frequency signals SIGIF may include the modulated data from the received THF signals  34 . Low noise amplifier  82  may amplify intermediate frequency signals SIGIF, which are then provided to MZM  56  (e.g., arm  60 ). MZM  56  may convert intermediate frequency signals SIGIF to the optical domain as optical signals LOrx (e.g., by modulating the data in intermediate frequency signals SIGIF onto one of the optical local oscillator signals) and may pass the optical signals to optical receiver  72  in optical components  68 , as shown by arrow  63  (e.g., via optical paths  62  and  66  or other optical paths). Control circuitry  14  ( FIG.  1   ) may use optical receiver  72  to convert optical signals LOrx to other formats and to recover (demodulate) the data carried by THF signals  34  from the optical signals. In this way, the same antenna  30  and signal path  28  may be used for both the transmission and reception of THF signals while also performing beam steering operations. 
     The example of  FIG.  6    in which intermediate frequency signals SIGIF are converted to the optical domain is merely illustrative. If desired, transceiver circuitry  26  may receive and demodulate intermediate frequency signals SIGIF without first passing the signals to the optical domain. For example, transceiver circuitry  26  may include an analog-to-digital converter (ADC), intermediate frequency signal path  44  may be coupled to an input of the ADC rather than to MZM  56 , and the ADC may convert intermediate frequency signals SIGIF to the digital domain. As another example, intermediate frequency signal path  44  may be omitted and control signals V BIAS  may control UTC PD  42  to directly sample THF signals  34  with optical local oscillator signals LO 1  and LO 2  to the optical domain. As an example, UTC PD  42  may use the received THF signals  34  and control signals V BIAS  to produce an optical signal on optical path  40 . The optical signal may have an optical carrier with sidebands that are separated from the optical carrier by a fixed frequency offset (e.g., 30-100 GHz, 60 GHz, 50-70 GHz, 10-100 GHz, etc.). The sidebands may be used to carry the modulated data from the received THF signals  34 . Signal path  28  may direct (propagate) the optical signal produced by UTC PD  42  to optical receiver  72  in optical components  68  (e.g., via optical paths  40 ,  64 ,  62 ,  66 ,  63 , and/or other optical paths). Control circuitry  14  ( FIG.  1   ) may use optical receiver  72  to convert the optical signal to other formats and to recover (demodulate) the data carried by THF signals  34  from the optical signal (e.g., from the sidebands of the optical signal). 
       FIG.  7    is a circuit diagram showing one example of how multiple antennas  30  may be integrated into a phased antenna array  88  that conveys THF signals over a corresponding signal beam. In the example of  FIG.  7   , MZMs  56 , intermediate frequency signal paths  44 , data paths  78 , and optical receiver  72  of  FIG.  6    have been omitted for the sake of clarity. Each of the antennas in phased antenna array  88  may alternatively sample received THF signals directly into the optical domain or may pass intermediate frequency signals SIGIF to ADCs in transceiver circuitry  26 . 
     As shown in  FIG.  7   , phased antenna array  88  includes N antennas  30  such as a first antenna  30 - 0 , a second antenna  30 - 1 , and an Nth antenna  30 -(N−1). Each of the antennas  30  in phased antenna array  88  may be coupled to optical components  68  via a respective optical signal path (e.g., optical signal path  28  of  FIG.  6   ). Each of the N signal paths may include a respective optical combiner  52  coupled to the UTC PD  42  of the corresponding antenna  30  (e.g., the UTC PD  42  in antenna  30 - 0  may be coupled to optical combiner  52 - 0 , the UTC PD  42  in antenna  30 - 1  may be coupled to optical combiner  52 - 1 , the UTC PD  42  in antenna  30 -(N−1) may be coupled to optical combiner  52 -(N−1), etc.). Each of the N signal paths may also include a respective optical path  62  and a respective optical path  64  coupled to the corresponding optical combiner  52  (e.g., optical paths  64 - 0  and  62 - 0  may be coupled to optical combiner  52 - 0 , optical paths  64 - 1  and  62 - 1  may be coupled to optical combiner  52 - 1 , optical paths  64 -(N−1) and  62 -(N−1) may be coupled to optical combiner  52 -(N−1), etc.). 
     Optical components  68  may include LO light sources  70  such as a first LO light source  70 A and a second LO light source  70 B. The optical signal paths for each of the antennas  30  in phased antenna array  88  may share one or more optical splitters  54  such as a first optical splitter  54 A and a second optical splitter  54 B. LO light source  70 A may generate (e.g., produce, emit, transmit, etc.) first optical local oscillator signal LO 1  and may provide first optical local oscillator signal LO 1  to optical splitter  54 A via optical path  66 A. Optical splitter  54 A may distribute first optical local oscillator signal LO 1  to each of the UTC PDs  42  in phased antenna array  88  over optical paths  64  (e.g., optical paths  64 - 0 ,  64 - 1 ,  64 -(N−1), etc.). Similarly, LO light source  70 B may generate (e.g., produce, emit, transmit, etc.) second optical local oscillator signal LO 2  and may provide second optical local oscillator signal LO 2  to optical splitter  54 B via optical path  66 B. Optical splitter  54 B may distribute second optical local oscillator signal LO 2  to each of the UTC PDs  42  in phased antenna array  88  over optical paths  62  (e.g., optical paths  62 - 0 ,  62 - 1 ,  62 -(N−1), etc.). 
     A respective optical phase shifter  80  may be interposed along (on) each optical path  64  (e.g., a first optical phase shifter  80 - 0  may be interposed along optical path  64 - 0 , a second optical phase shifter  80 - 1  may be interposed along optical path  64 - 1 , an Nth optical phase shifter  80 -(N−1) may be interposed along optical path  64 -(N−1), etc.). Each optical phase shifter  80  may receive a control signal CTRL that controls the phase S provided to optical local oscillator signal LO 1  by that optical phase shifter (e.g., first optical phase shifter  80 - 0  may impart an optical phase shift of zero degrees/radians to the optical local oscillator signal LO 1  provided to antenna  30 - 0 , second optical phase shifter  80 - 1  may impart an optical phase shift of Δϕ to the optical local oscillator signal LO 1  provided to antenna  30 - 1 , Nth optical phase shifter  80 -(N−1) may impart an optical phase shift of (N−1)Δϕ to the optical local oscillator signal LO 1  provided to antenna  30 -(N−1), etc.). By adjusting the phase S imparted by each of the N optical phase shifters  80 , control circuitry  14  ( FIG.  1   ) may control each of the antennas  30  in phased antenna array  88  to transmit THF signals  32  and/or to receive THF signals  34  within a formed signal beam  83 . Signal beam  83  may be oriented in a particular beam pointing direction (angle)  84  (e.g., the direction of peak gain of signal beam  83 ). The THF signals conveyed by phased antenna array  88  may have wavefronts  86  that are orthogonal to beam pointing direction  84 . Control circuitry  14  may adjust beam pointing direction  84  over time to point towards external communications equipment or an external object or to point away from external objects, as examples. 
     Phased antenna array  88  may be operable in an active mode in which the array transmits and/or receives THF signals using optical local oscillator signals LO 1  and LO 2  (e.g., using phase shifts provided to each antenna element to steer signal beam  83 ). If desired, phased antenna array  88  may also be operable in a passive mode in which the array does not transmit or receive THF signals. Instead, in the passive mode, phased antenna array  88  may be configured to form a passive reflector that reflects THF signals or other electromagnetic waves incident upon device  10 . In the passive mode, the UTC PDs  42  in phased antenna array  88  are not illuminated by optical local oscillator signals LO 1  and LO 2  and transceiver circuitry  26  performs no modulation/demodulation, mixing, filtering, detection, modulation, and/or amplifying of the incident THF signals. While in the passive mode, control signals V BIAS  may be used to control each antenna  30  to impart one or more selected phase shifts, carrier frequency shifts, and/or polarization changes in the process of reflecting the incident electromagnetic waves. Phased antenna array  88  may sometimes be referred to as an intelligent reflecting surface (IRS) when placed in the passive mode and when controlled/programmed to apply one or more phase shifts, carrier frequency shifts, and/or polarization changes to the reflected electromagnetic waves. The carrier frequency shifts may be from a given carrier frequency f c  to 2*f c  or other frequencies or vice versa, for example. The polarization changes may be changes from vertical to horizontal linear polarizations, from horizontal to vertical linear polarizations, to or from orbital-angular-momentum (OAM) configurations, etc. Any desired combination of polarization, frequency, and phase changes may be used. 
       FIG.  8    is a diagram of a given antenna  30  in phased antenna array  88  that may be configured to reflect electromagnetic waves while phased antenna array  88  is placed in the passive mode. As shown in  FIG.  8   , in the passive mode, UTC PD  42  is not supplied with optical local oscillator signals. Control signals V BIAS  may include a bias voltage and/or other control signals that configure UTC PD  42  to exhibit a selected output impedance. The selected output impedance may be mismatched with respect to the input impedance of antenna radiating element arms  36  (e.g., at the frequencies of THF signals  34 ). This impedance mismatch may cause antenna  30  to reflect (scatter) incident THF signals  34  as reflected THF signals  34 R (sometimes referred to herein simply as reflected signals  34 R). 
     The selected impedance mismatch may also configure antenna  30  to impart a selected phase shift and/or carrier frequency shift on reflected signals  34 R relative to the incident THF signals  34  (e.g., where reflected signals  34 R are phase-shifted with respect to THF signals  34  by the selected phase shift, are frequency-shifted with respect to THF signals  34  by the selected carrier frequency shift, etc.). Additionally or alternatively, the system may be adapted to configure antenna(s)  30  to impart polarization changes on reflected signals  34 R relative to the incident THF signals  34 . Control signals V BIAS  may change, adjust, or alter the output impedance of UTC PD  42  over time to change the amount of mismatch between the output impedance of UTC PD  42  and the input impedance of antenna radiating element arms  36  to impart reflected signals  34 R with different phase shifts and/or carrier frequency shifts. In other words, control circuitry  14  may program the phase, frequency, and/or polarization characteristics of reflected signals  34 R (e.g., using the control signals V BIAS  applied to UTC PD  42 ). 
     The same impedance mismatch may be applied to all the antennas  30  in phased antenna array  88  or different impedance mismatches may be applied for different antennas  30  in phased antenna array  88  at any given time. Applying different impedance mismatches across phased antenna array  88  may, for example, allow control circuitry  14  to perform space-time coding on the reflected signals  34 R (e.g., in which the spatial response and/or the temporal response of reflected signals  34 R are encoded to convey information to external equipment that receives reflected signals  34 R) and/or to form a signal beam of reflected signals  34 R that points in one or more desired beam pointing directions. When phased antenna array  88  is operated in the active mode, control circuitry  14  may control LO light sources  70  to illuminate the UTC PDs  42  in phased antenna array  88  using optical local oscillator signals LO 1  and LO 2  and control signals V BIAS  may be adjusted to configure UTC PD  42  to cause antenna radiating element arms  36  to radiate THF signals  32  or to receive THF signals  34  (e.g., as shown in  FIGS.  2  and  3   ). 
       FIG.  9    is a cross-sectional side view of a given UTC PD  42  in phased antenna array  88 . As shown in  FIG.  9   , UTC PD  42  may include multiple stacked layers (e.g., in a semiconductor substrate). The stacked layers of UTC PD  42  may include an n-type contact layer  104  and a p-type contact layer  90  (e.g., on opposing sides of the stack). N-type contact layer  104  may include n-type doped indium phosphide (InP), as an example. A waveguide layer such as waveguide  102  may be stacked (layered) on n-type contact layer  104 . A depletion layer such as depletion layer  100  may be stacked on waveguide  102 . Depletion layer  100  may include n-type doped InP, as an example. One or more spacer layers such as spacer layers  96  and  98  may be stacked on depletion layer  100 . An absorber layer such as absorber layer  94  may be stacked on spacer layer  96 . Absorber layer  94  may include p-type doped indium gallium arsenide (InGaAs), as an example. A ridge layer such as ridge layer  92  may be stacked on absorber layer  94 . Ridge layer  92  may include p-type doped InP, as an example. P-type contact layer  90  may be stacked on ridge layer  92 . P-type contact layer  90  may include InGaAs, as an example. Control signals V BIAS  may be applied to (across) p-type contact layer  90  and n-type contact layer  104  to control the operation of UTC PD  42 . Control signals V BIAS  may adjust the output impedance of UTC PD  42  and/or may configure UTC PD  42  to transmit THF signals  32  and/or receive THF signals  34 . 
     The example of  FIG.  9    is merely illustrative. Antennas  30  need not include UTC PDs and, if desired, UTC PD  42  may be replaced by a PIN diode (e.g., a PIN photodiode) or any other desired programmable diode structure. The layers of UTC PD  42  may be stacked in other orders (e.g., waveguide  102  may be interposed between other layers, etc.). Additional layers may be included in the stack. For example, a graphene layer such as graphene sublayer  105  may be layered onto waveguide  102  or may otherwise be layered under antenna radiating element arms  36  ( FIG.  8   ). Graphene sublayer  105  may, for example, serve to extend the frequency range of antenna  30  for the transmission/reception of THF signals and/or for the passive reflection of THF signals  34  as reflected signals  34 R. 
       FIG.  10    is an equivalent circuit diagram of UTC PD  42 . As shown in  FIG.  10   , UTC PD  42  may include an impedance matching portion (region)  106  coupled between lines  110  and  112 . Impedance matching portion  106  may be formed from layers  94 - 100  of  FIG.  9   , for example. Line  110  may couple terminal  111  to a first terminal of current source  108 . Line  112  may couple terminal  113  to a second terminal of current source  108 . Antenna radiating element arms  36  ( FIG.  8   ) may be coupled between terminals  111  and  113 . 
     A first resistance R 1  may be interposed on line  110  between impedance matching portion  106  and terminal  111 . A parasitic inductance L P  may be interposed on line  110  in series between resistance R 1  and terminal  111 . A parasitic capacitance C P  may be coupled between a node on line  110  between resistance R 1  and parasitic inductance L P  and a node on line  112  between impedance matching portion  106  and terminal  113 . 
     Impedance matching portion  106  may include resistances R 2 , R 3 , and R 4  coupled in series between lines  110  and  112 . Impedance matching portion  106  may include capacitances C 1 , C 2 , and C 3  coupled in series between lines  110  and  112  (and in parallel with resistances R 2 , R 3 , and R 4 ). A path  114  in impedance matching portion  106  may couple a node between resistances R 2  and R 3  to a node between capacitances C 1  and C 2 . A path  116  in impedance matching portion  106  may couple a node between resistances R 3  and R 4  to a node between capacitances C 2  and C 3 . Impedance matching portion  106  may also be simplified as a single capacitance coupled between lines  110  and  112  or as a single capacitance and a single resistance (e.g., a resistance across depletion layer  100 ) coupled in parallel between lines  110  and  112 . 
     Current source  108  may produce a photocurrent I PH  between lines  110  and  112  in response to illumination from optical local oscillator signals LO 1  and LO 2 . Photocurrent I PH  may run along the antenna radiating element arms (e.g., between terminals  111  and  113 ) to radiate THF signals  32 . Impedance matching portion  106  may be configured to exhibit the output impedance Z of UTC PD  42 . Control signals V BIAS  (e.g., one or more bias voltages and/or other control signals) may be applied to P-type contact layer  90  and N-type contact layer  104  ( FIG.  9   ) to vary one or more of resistances R 2 , R 3 , and/or R 4  and/or to vary one or more of capacitances C 1 , C 2 , and/or C 3 , thereby serving to adjust the output impedance Z of UTC PD  42 . 
     For example, when the antenna is transmitting or receiving THF signals in the active mode, control signals V BIAS  may configure impedance matching portion  106  to match output impedance Z to the input impedance of the antenna radiating element arms coupled across terminals  111  and  113 . However, when the antenna is in the passive mode, control signals V BIAS  may configure impedance matching portion  106  to exhibit an output impedance Z that differs from (mismatches) the input impedance of the antenna radiating element arms by a selected amount. The amount of mismatch may be selected to impart a selected phase shift and/or carrier frequency shift (e.g., by antenna  30  on its own or in conjunction with other antennas  30  in the phased antenna array) when reflecting incident THF signals  34  as reflected signals  34 R. Control signals V BIAS  may adjust output impedance Z to adjust the (selected) amount of mismatch between output impedance Z and the input impedance of the antenna radiating element arms over time (e.g., to adjust the phase shift and/or carrier frequency shift imparted by antenna  30  on its own or in conjunction with other antennas  30  when reflecting incident THF signals  34  as reflected signals  34 R). 
       FIG.  11    is a diagram showing how one or more antennas  30  on device  10  (e.g., phased antenna array  88 ) may reflect incident THF signals. As shown in  FIG.  11   , a communications network or system  96  may include device  10  and external communications equipment such as external equipment  114 . External equipment  114  may be another device such as device  10 , a wireless base station, a wireless access point, a peripheral device, an accessory device, a user input device, etc. 
     As shown in  FIG.  11   , external equipment  114  may transmit THF signals  34 . THF signals  34  may be incident upon device  10  at incident angle θ i . When configured in the passive mode, one or more of the antennas  30  in phased antenna array  88  may reflect the THF signals  34  at incident angle  9  as reflected signals  34 R. Control signals V BIAS  may be varied (e.g., thereby varying imparted phase shift) across phased antenna array  88  to configure array  88  to collectively reflect THF signals  34  from incident angle θ i  onto a corresponding output (scattered) angle θ R  (e.g., as a reflected signal beam with a beam pointing direction in the direction of output angle θ R ). 
     Control signals V BIAS  may configure output angle θ R  to be any desired angle. For example, output angle θ R  may be oriented towards external equipment  114  so external equipment  114  receives reflected signals  34 R. This may allow external equipment  114  to locate the position of device  10  (e.g., in situations where external equipment  114  has no a priori knowledge of the location of device  10 ) and/or to receive information from device  10  that has been encoded in the reflected signals. In scenarios where external equipment  114  locates the position of device  10  based on the receipt of reflected signals  34 R, external equipment  114  may use the known position of device  10  to perform further wireless communications with device  10  using THF signals (e.g., by steering a signal beam of THF signals  34  towards the known location of device  10  for subsequent communications). 
     If desired, control circuitry  14  ( FIG.  1   ) may further adjust the phase shifts and/or frequency shifts imparted by one or more of the antennas in phased antenna array  88  as a function of space and/or as a function of time to perform space-time coding that encodes information to be received by external equipment  114  within reflected signals  34 R. Such space-time coding may involve control signals V BIAS  provided to each of the antennas  30  in phased antenna array  88  that configure each antenna  30  to produce, by reflecting/scattering incident THF signals  34 , reflected signals  34 R having respective phase shifts (e.g., with a range from −180 degrees to 180 degrees or some subset thereof), amplitudes, and/or frequency shifts, at each antenna  30  in the array at different times. Control circuitry  14  may, for example, switch the UTC PD control signals V BIAS  at a sufficiently high rate such as at a rate that matches or exceeds the sample rate and/or that matches or exceeds the symbol rate of external equipment  114 . Collectively, over time and space, the reflected signals  34 R may encode any desired information for receipt and decoding by external equipment  114  and/or any other desired external communications equipment. The information may include, for example, information identifying the portion or subset of device  10  that reflected THF signals  34 , a device identifier that identifies device  10  and/or a user of device  10 , application data, messages, control data, configuration data, etc. 
     If desired, control circuitry  14  may control output angle θ R  to point in other directions, as shown by arrows  118 . Arrows  118  may be oriented towards other external communications equipment if desired. The other external communications equipment may identify a location of device  10  based on receipt of reflected signals  34 R and/or may identify any other information transmitted via the reflected signals (e.g., using space-time coding). If desired, control circuitry  14  may sweep reflected signals  34 R over a number of different output angles θ R  as a function of time, as shown by arrows  116 . This may, for example, help device  10  to find other external communications equipment for performing subsequent THF communications (e.g., to identify the location of other external communications equipment for performing further THF communications). 
     If desired, control circuitry  14  may spread the reflected signals  34 R as much as possible across all available directions (e.g., as shown by arrows  118 ) in any desired sequence (e.g., a random or pseudorandom sequence) to reduce the radar cross section of device  10 . This may, for example, help to preserve the privacy of device  10  by hiding the presence or precise location of device  10  relative to the rest of system  96 . If desired, control circuitry  14  may adjust control signals V BIAS  to maximize the amount of electromagnetic energy from THF signals  34  that are absorbed at device  10  rather than reflected as reflected signals  34 R. Such absorption may be used to thermally heat device  10 , for example. If desired, phased antenna array  88  may configure device  10  to form a cooperative device in a radar system. When acting as a cooperative device, THF signals  34  are spatial ranging signals such as radar signals and control circuitry  14  may use reflected signals  34 R to inform the transmitter of THF signals  34  that a user is present at or adjacent to device  10 . This may, for example, help the transmitter of THF signals  34  to be aware of a potential hazard due to the presence of the user (e.g., in scenarios where the transmitter is implemented on an automotive vehicle or other potential hazard to pedestrians or users of device  10 ). 
       FIG.  12    shows a state diagram  120  of illustrative operating modes (states) for device  10  and one or more antennas  30  on device  10  such as antennas  30  that are integrated into a phased antenna array such as phased antenna array  88 . Control circuitry  14  ( FIG.  1   ) can adjust/transition device  10  between the states of state diagram  120  by adjusting LO light sources  70  and the control signals V BIAS  provided to antenna(s)  30 . 
     In transmit mode (state)  122 , control circuitry  14  may provide (assert/supply) control signals V BIAS  to antenna(s)  30  with a first setting. This may, for example, include providing antenna(s)  30  with a first bias voltage. Control signals V BIAS  may configure impedance matching portion  106  of the UTC PD  42  in antenna(s)  30  to exhibit an output impedance that matches the input impedance of the antenna radiating element arms  36  in the antennas. This may serve to maximize the power transfer and the efficiency with which the antennas transmit THF signals. At the same time, LO light sources  70  may produce optical local oscillator signals LO 1  and LO 2 . MZM  56  may modulate wireless data DAT ( FIG.  6   ) onto optical local oscillator signal LO 2  to produce modulated optical local oscillator signal LO 2 ′. The UTC PD  42  in antenna(s)  30  may be illuminated using optical local oscillator signal LO 1  and modulated optical local oscillator signal LO 2 ′. Antenna(s)  30  may radiate (transmit) corresponding THF signals  32  ( FIG.  6   ). If desired, optical phase shifters  80  may apply phase shifts to first optical local oscillator LO 1  to cause the antennas to transmit THF signals  32  within a signal beam  83  oriented (formed) in a selected beam pointing direction  84  ( FIG.  7   ). 
     In receive mode (state)  126 , control circuitry  14  may provide (assert/supply) control signals V BIAS  to antenna(s)  30  with a second setting. This may, for example, include providing antenna(s)  30  with a second bias voltage. Control signals V BIAS  may configure impedance matching portion  106  of the UTC PD  42  in antenna(s)  30  to exhibit an output impedance that matches the input impedance of the antenna radiating element arms  36  in the antennas. This may serve to maximize the power transfer and the efficiency with which the antennas receive THF signals. At the same time, LO light sources  70  may illuminate the UTC PD  42  in antenna(s)  30  using optical local oscillator signals LO 1  and LO 2 . Antenna(s)  30  may receive THF signals  34  and may convert the THF signals into intermediate frequency signals SIGIF ( FIG.  6   ) (e.g., for conversion to the optical domain by MZM  56  or for passing to an ADC) or may sample the THF signals directly into the optical domain. A receiver in transceiver circuitry  26  may demodulate wireless data in the received signals and may pass the demodulated data up a protocol stack for further processing. 
     In a passive mode such as reflective mode  124  (sometimes referred to herein as passive mode  124 , passive reflective mode  124 , passive reflector mode  124 , passive reflection mode  124 , or reflection mode  124 ), optical local oscillator signals LO 1  and LO 2  do not illuminate the UTC PD  42  in antenna(s)  30  (e.g., LO light sources  70  may be disabled, inactive, or powered off, or optical switching or absorption may be used to prevent the optical local oscillator signals from illuminating UTC PD(s)  42 ). Antenna(s)  30  may receive incident THF signals  34  while the UTC PD(s)  42  are unilluminated. At the same time, control circuitry  14  may provide (assert/supply) control signals V BIAS  to antenna(s)  30  with one or more settings other than the first and second settings. Control signals V BIAS  may configure impedance matching portion  106  of the UTC PD  42  in antenna(s)  30  to exhibit one or more output impedances that do not match (i.e., that mismatch) the input impedance of the antenna radiating element arms  36  in the antennas. This may serve to reflect the THF signals  34  incident on antenna(s)  30  as reflected signals  34 R. 
     If desired, control circuitry  14  may use control signals V BIAS  to provide different amounts of impedance mismatch for the incident THF signals  34  at different antennas  30  and/or at different times. This may serve to impart one or more phase shifts and/or carrier frequency shifts to reflected signals  34 R as a function of space and/or time. For example, different phase shifts may be produced in reflected signals  34 R at different antennas  30  to form a signal beam at a selected output angle θ R  ( FIG.  11   ), to perform space-time coding that conveys information to external communications equipment such as the transmitter of THF signals  34  or other external equipment, to scatter the reflected signals over as many directions as possible, to absorb as much of the incident THF signals  34  at device  10  as possible, to allow device  10  to form a cooperative device for a radar system, to inform the transmitter of THF signals  34  and/or other external equipment of the location and/or identity of device  10  (e.g., for use in performing subsequent communications), etc. 
     Control circuitry  14  may place device  10  in transmit mode  122  when device  10  has wireless data DAT to transmit. Control circuitry  14  may place device  10  in receive mode  126  when device  10  is scheduled to receive wireless data in THF signals  34 , for example. Control circuitry  14  may place device  10  in reflective mode  124  when not actively transmitting or receiving THF signals. Reflective mode  124  may, for example, be a default mode for device  10 . Device  10  may consume less power in reflective mode  124  than in transmit mode  122  or receive mode  126  while still being able to passively convey information to external communications equipment via reflected signals  34 R. 
       FIG.  13    is a perspective view showing an example of how different antennas  30  may be located at different locations on device  10 . In the example of  FIG.  13   , device  10  has a front face  127 F (e.g., a front face from a display or display cover layer for device  10 ), a rear face  127 R (e.g., a rear housing wall opposite the front face), and side faces  127 S (e.g., peripheral housing structures extending from rear face  127 R to front face  127 F). This is merely illustrative and, in general, device  10  may have other form factors (e.g., cylindrical form factors, composite form factors, a laptop computer form factor, a desktop computer form factor, a wearable form factor such as a wristwatch form factor or a head-mounted device form factor, etc.). 
     As shown in  FIG.  13   , one or more antenna(s) may be located in one or more regions (locations)  128  on front face  127 F, rear face  127 R, and/or one or more side faces  127 S. If desired, the antennas in different regions  128  may be integrated into one or more phased antenna arrays  88  and/or a single phased antenna array  88  may be located in one or more of regions  128 . There may be zero, one, or more than one region  128  on front face  127 F, rear face  127 R, and side faces  127 S. 
     If desired, device  10  may include one or more antennas  30  (e.g., one or more phased antenna arrays  88 ) that are operable only in transmit mode  122  and reflective mode  124  of  FIG.  12    (e.g., to only transmit or reflect THF signals), that are operable only in receive mode  126  and reflective mode  124  (e.g., to only receive or reflect THF signals), that are operable in all three of transmit mode  122 , receive mode  126 , and reflective mode  124  (e.g., to transmit, receive, or reflect THF signals at different times), and/or that are operable only in reflective mode  124 . Antennas  30  that are operable only in reflective mode  124  may be dedicated passive antennas in device  10  and need not receive optical local oscillator signals LO 1  and LO 2 . If desired, a single array of antennas  30  may include different subsets of antennas that are operable in one, two, or all three of modes  122 - 126 . 
       FIG.  14    is a top-down view showing how a single array of antennas  30  may include different subsets of antennas that are operable in one, two, or all three of modes  122 - 126 . As shown in  FIG.  14   , device  10  may include an array  130  of antennas  30 . The antennas  30  in array  130  may be integrated into a single substrate (e.g., a printed circuit board or other substrate) or may be distributed across multiple substrates. Array  130  may be located within a single region  128  or may be distributed across multiple regions  128  ( FIG.  13   ). 
     Array  130  may include different subsets of antennas  30  such as subsets  132  and  134 . Subsets  132  and  134  may be operable in a different number of modes  122 - 126 . For example, one or more subsets  130  may be operable only in reflective mode  124  (e.g., subsets  130  may include passive antennas  30 ) or may be operable in all three of reflective modes  122 - 126 , whereas a first subset  134  is only operable in transmit mode  122  and second subset  134  is only operable in receive mode, or subsets  134  may be operable in transmit mode  122  and receive mode  126  but not in reflective mode  124 , or subsets  134  may be operable only in transmit mode  124 , or subsets  134  may be operable only in receive mode  126 , etc. Any desired number of antennas  30  in array  130  may form part or all of a corresponding phased antenna array  88  if desired. 
     The example of  FIG.  14    is merely illustrative. Array  130  may include any desired number of antennas  30 . There may be any desired number of subsets  134  and any desired number of subsets  132 . Subsets  134  and  132  may each include any desired number of antennas  30 . Each subset  134  may include the same number of antennas  30  or different subsets  134  may include different numbers of antennas  30 . Each subset  132  may include the same number of antennas  30  or different subsets  132  may include different numbers of antennas  30 . There may be more than two types of subsets in array  130 . In the example of  FIG.  14   , the antennas  30  in subsets  132  are adjacent to each other and the antennas  30  in subsets  134  are adjacent to each other within array  130 . In general, the antennas  30  in each subset  132  and the antennas in each subset  134  may be distributed across array  130  in any desired manner. The antennas  30  in array  130  need not be arranged in a rectangular grid pattern of rows and columns and may, in general, be arranged in any desired pattern. 
     If desired, additional material can be provided to antenna(s)  30  to help antenna(s)  30  to focus the transmitted, reflected, and/or reflected THF signals. For example, a THz lens may be provided in device  10  to help antenna(s)  30  to focus the transmitted, received, and/or reflected THF signals.  FIG.  15    is a cross-sectional side view showing one example of how device  10  may include a THz lens to help antenna(s)  30  to focus transmitted, received, and/or reflected THF signals. 
     As shown in  FIG.  15   , one or more antennas  30  (e.g., integrated within an array  130 ) may be disposed on or within a substrate  138 . A THz lens such as THz lens  142  may be mounted on or over substrate  138 . THz lens  142  may overlap at least some (e.g., all) of the antennas  30  on substrate  138 . THz lens  142  may serve to focus THz signals  34  onto antennas  30 , to focus transmitted THF signals  32  in a particular direction (e.g., within a corresponding signal beam), and/or to focus reflected signals  34 R in a particular direction (e.g., within a corresponding signal beam). This example is merely illustrative. Multiple THz lenses may be used to focus THz signals for different antennas and/or multiple THz lenses may be used to focus THz signals for one or more antennas. THz lens  142  may have any desired shape. 
       FIG.  16    is a flow chart of illustrative operations that may be performed by control circuitry  14  ( FIG.  1   ) in operating antenna(s)  30  to transmit, receive, and/or passively reflect THF signals. At optional operation  144 , control circuitry  14  may use control signals V BIAS  to place antenna(s)  30  into reflective mode  124  (e.g., while also controlling LO light sources  70  to stop providing optical local oscillator signals LO 1  and LO 2  to the antennas). Operation  144  may be omitted in examples where the antenna(s)  30  are only operable in reflective mode  124  (e.g., where the antennas are passive antennas). 
     At operation  146  (in reflective mode  124 ), control circuitry  14  may use control signals V BIAS  to control the UTC PDs  42  in antenna(s)  30  to create one or more mismatches (e.g., a series of impedance mismatches over time) between the output impedance of the UTC PDs and the input impedance of the antenna radiating element arms  36  in antenna(s)  30 . This may configure antenna(s)  30  to reflect incident THF signals  34  as reflected signals  34 R. If desired, the impedance mismatch(es) may be selected and/or varied to impart one or more phase shifts and/or frequency shifts in reflected signals  34 R relative to the incident THF signals  34 . 
     If desired, control circuitry  14  may adjust the UTC PDs using control signals V BIAS  as a function of time and/or space (e.g., across an array of antennas  30 ) to perform space-time coding in reflected signals  34 R (at operation  148 ). Control circuitry  14  may, for example, encode reflected signals  34 R with a device identifier that identifies device  10  and/or a user of device  10  to external communications equipment, an identifier that identifies the portion of device  10  where the reflection of THF signals  34  occurred, information that informs external communications equipment that a user of device  10  is present at the location of device  10  (e.g., for forming a cooperative device in a radar system), etc. 
     If desired, control circuitry  14  may adjust the operation of one or more antennas  30  that are used to transmit and/or receive THF signals based on configuration and/or status information from the antenna(s)  30  in reflective mode  124  (at operation  150 ). The transmitting and/or receiving antennas may include one or more of the same antennas in reflective mode  124  (e.g., antennas that will later be switched into use for THF signal transmission and/or reception) or may be different antennas from the antennas in reflective mode  124 . As an example, control circuitry  14  may identify incident angle θ i  and/or output angle θ R  based on the configuration or status of the antenna(s) in reflective mode  124  that produced reflected signals  34 R. The antenna(s)  30  that are subsequently used for transmission and/or reception may use the identified incident angle θ i  and/or output angle θ R  as a priori information of the location of external communications equipment for performing THF communications. Control circuitry  14  may then steer the signal beam(s) produced by those antennas to point towards the identified incident angle θ i  and/or output angle θ R . Conversely, control circuitry  14  may use information about the location of external communications equipment that is in communication with the transmitting and/or receiving antenna(s)  30  to adjust the phases produced by the antenna(s)  30  in reflective mode  124  to point towards the known location of the external communications equipment (e.g., to reflect subsequently-transmitted THF signals  34  incident from the direction of the external communications equipment). This may serve to minimize the time required to establish a THF communications link between device  10  and the external equipment. 
     If desired, control circuitry  14  may adjust the UTC PDs using control signals V BIAS  as a function of time and/or space (e.g., across an array of antennas  30 ) to perform privacy protection operations using reflected signals  34 R (at operation  152 ). Control circuitry  14  may, for example, adjust the phases of the UTC PDs  42  of the antenna(s)  30  in the reflective mode to spread the output angle θ R  of reflected signals  34 R over as many angles as possible. This may serve to minimize the radar cross section of device  10  to THF signals, for example. Additionally or alternatively, the UTC PDs  42  may be configured to absorb as much of the incident THF signals  34  as possible (e.g., to heat device  10  using THF signals  34 ). 
     If desired, control circuitry  14  may adjust the UTC PDs using control signals V BIAS  as a function of time and/or space (e.g., across an array of antennas  30 ) to form a signal beam of reflected signals  34 R that is oriented in a selected output angle θ R  (at operation  154 ). Output angle θ R  may be selected to point towards the external communications equipment that transmitted THF signals  34  or towards other external communications equipment. This may allow device  10  to convey information in reflected signals  34 R to the external communications equipment and/or may allow the external communications equipment to locate device  10  (e.g., for directing THF signals towards device  10  for subsequent THF communications). 
     If desired, control circuitry  14  may adjust the UTC PDs  42  using control signals V BIAS  as a function of time and/or space (e.g., across an array of antennas  30 ) to sweep the signal beam of reflected signals  34 R over several different output angles θ R  (at operation  156 ). This may, for example, allow external communications equipment to receive reflected signals  34 R even if device  10  has no a priori knowledge of the location of the external communications equipment (e.g., to allow the external communications equipment to direct THF signals towards device  10  and/or to allow device  10  to direct THF signals towards the external communications equipment during subsequent THF communications). Control circuitry  14  may perform one or more (e.g., all) of operations  148 - 156 . If desired, control circuitry  14  may perform two or more of operations  148 - 156  concurrently. 
     At optional operation  158 , control circuitry  14  may use control signals V BIAS  to place antenna(s)  30  into transmit mode  122  and/or receive mode  126  for performing THF communications with external communications equipment. Operation  158  may be omitted in examples where the antenna(s)  30  are only operable in reflective mode  124  (e.g., where the antennas are passive antennas). Control circuitry  14  may perform operation  146  for some of the antennas  30  in device  10  while concurrently performing operation  158  for other antennas  30  in device  10  if desired. 
     The examples of  FIGS.  6 - 16    in which the antennas that are operable in reflective mode  124  convey THF signals is merely illustrative. If desired, device  10  may include one or more arrays of antennas that operate at lower frequencies and that are operable in reflective mode  124  (e.g., in addition to or instead of the antennas  30  that are operable in reflective mode  124  for THF signals).  FIG.  17    is a circuit diagram showing how device  10  may include antennas  30  that are operable in reflective mode  124  but at frequencies less than around 100 GHz. 
     As shown in  FIG.  17   , device  10  may include one or more phased antenna arrays  172 . Phased antenna array  172  may include M antennas  30  (e.g., antennas  30 - 0 ,  30 -(M−1), etc.). Antennas  30  may be coupled to phase and magnitude controller block  164  via output amplifier stage  166 . Output amplifier stage  166  may include output amplifiers  168  coupled to each antenna  30 . Phase and magnitude controller block  164  may include phase controllers  176  and magnitude controllers  174  that adjust the phase and magnitude (respectively) of the signals conveyed over antennas  30 . Phase and magnitude controller block  164  may map M radio-frequency (RF) multiple-input and multiple-output (MIMO) streams  162  (e.g., a first MIMO stream  162 - 0 , an Mth MIMO stream  162 -(M−1), etc.) onto the M antennas  30  in phased antenna array  172 . Each MIMO stream  162  may be mapped to each antenna  30  or may be mapped to only a subset of antennas  30  by phase and magnitude controller block  164 . 
     Phased antenna array  172  of  FIG.  17    may convey radio-frequency signals at frequencies less than around 100 GHz. These signals may include millimeter wave and/or centimeter wave signals and/or may include signals below 10 GHz, for example. Phased antenna array  172  may be operable in reflective mode  124 . In the reflective mode, control circuitry  14  may provide control signals CTRL′ to output amplifier stage  168 . Control signals CTRL′ may adjust the output impedance of output amplifiers  168  to form one or more impedance mismatches between the output impedance of output amplifiers  168  and the input impedance of antennas  30 . If desired, control circuitry  14  may use control signals CTRL′ to adjust the output impedance of output amplifiers  168  to match the input impedance of antennas  30  during transmission and reception of radio-frequency signals. During reflection of radio-frequency signals (in the reflective mode), the impedance mismatches may cause phased antenna array  172  to reflect incident radio-frequency signals  170  as reflected radio-frequency signals  170 R (sometimes referred to herein as reflected signals  170 R). Control circuitry  14  may control the output impedances of output amplifiers  168  as a function of time and/or space to impart any desired phase and/or frequency shifts in reflected signals  170 R relative to incident signals  170 . 
     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 optical components described herein (e.g., MZM modulator(s), waveguide(s), phase shifter(s), UTC PD(s), etc.) may be implemented in plasmonics technology if desired. 
     The methods and operations described above in connection with  FIGS.  1 - 17    (e.g., the operations of  FIGS.  12  and  16   ) may be performed by the components of device  10  using software, firmware, and/or hardware (e.g., dedicated circuitry or hardware). Software code for performing these operations may be stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) stored on one or more of the components of device  10  (e.g., storage circuitry  16  of  FIG.  1   ). The software code may sometimes be referred to as software, data, instructions, program instructions, or code. The non-transitory computer readable storage media may include drives, non-volatile memory such as non-volatile random-access memory (NVRAM), removable flash drives or other removable media, other types of random-access memory, etc. Software stored on the non-transitory computer readable storage media may be executed by processing circuitry on one or more of the components of device  10  (e.g., processing circuitry  18  of  FIG.  1   , etc.). The processing circuitry may include microprocessors, central processing units (CPUs), application-specific integrated circuits with processing circuitry, or other processing circuitry. 
     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: 20220527
Publication Date: 20240305
Grant Date: 20240305
Priority Date: 20210820
Inventors: GUNZELMANN, Bertram R
BOOS, ZDRAVKO
Assignee: APPLE INC
CPC Classifications: [{"code": "H10F30/223", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B10/116", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W28/0215", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/2676", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q3/2676", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B10/116", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q19/062", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q21/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W28/0215", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 82058206