CN117278189A

CN117278189A - Electronic device with optical self-injection ring

Info

Publication number: CN117278189A
Application number: CN202310731786.3A
Authority: CN
Inventors: R·卡亚特扎德; N·穆哈雷莫维奇; B·R·贡泽尔曼; Z·布斯
Original assignee: Apple Inc
Current assignee: Apple Inc
Priority date: 2022-06-22
Filing date: 2023-06-20
Publication date: 2023-12-22

Abstract

The present disclosure relates to an electronic device with an optical self-injection ring. An electronic device may include a wireless circuit to transmit a radio frequency signal having a frequency greater than or equal to 100GHz using a first optical Local Oscillator (LO) signal and a second optical LO signal generated by a clock circuit. The clock circuit may include a first laser that generates a first optical LO signal and a second laser that generates a second optical LO signal. The first and second self-injection locking ring paths may be coupled around the first and second lasers, respectively. The first loop path may include a first mixer, an optical reference, and a second mixer. The second ring path may include a photodiode, a first mixer, and an optical reference. The photodiode may provide a radio frequency signal to the mixer. The optical reference may comprise an optical delay line or resonator and may reduce phase noise of optical signals used to self injection lock the first and second lasers.

Description

Electronic device with optical self-injection ring

The present application claims priority from U.S. patent application Ser. No. 18/320,540, filed on day 19 at 5 of 2023, and U.S. provisional patent application Ser. No. 63/354,594, filed on day 22 of 6 of 2022, which are incorporated herein by reference in their entireties.

Technical Field

The present disclosure relates generally to electronic devices, and more particularly to electronic devices having wireless circuitry.

Background

The electronic device may be provided with wireless capabilities. An electronic device with wireless capability has a wireless circuit that includes one or more antennas. The radio circuit is for performing communication using radio frequency signals transmitted by the antenna.

As software applications on electronic devices become more data intensive over time, the need for electronic devices that support wireless communications at higher data rates has increased. However, the maximum data rate supported by the electronic device is limited by the frequency of the radio frequency signal. As the communication frequency increases, it may be difficult to provide a low phase noise clock to the wireless circuit.

Disclosure of Invention

An electronic device may include a wireless circuit to transmit wireless signals at frequencies greater than 100 GHz. The wireless or other circuitry in the device may be clocked using a clock circuit. The clock circuit may include a primary laser that emits a first optical Local Oscillator (LO) signal at a fixed first frequency and a secondary laser that emits a second optical LO signal at a second frequency. The wireless circuit may communicate these wireless signals, for example, using a first optical LO signal and a second optical LO signal.

The clock circuit may include a first self-injection locking ring path around the first laser and a second self-injection locking ring path around the second laser. The clock circuit may include a photodiode forming part of the second self-injection locking ring path. The clock circuit may include a first electro-optical mixer forming part of both the first and second self-injection locked loop paths. The clock circuit may include an optical reference that forms part of both the first self-injection locking loop path and the second self-injection locking loop path. The first self-injection locking ring path may include a second electro-optic mixer. If desired, additional optical references may be provided on the first self-injection locking ring path but not on the second self-injection locking ring path. For example, each optical reference may include an optical delay line or an optical resonator.

The photodiode may generate a radio frequency signal based on the first optical LO signal and the second optical LO signal. The first electro-optical mixer may generate a first optical signal based on the first optical LO signal and the radio frequency signal. The optical reference may reduce phase noise of the first optical signal. The second electro-optical mixer may generate a second optical signal based on the first optical LO signal (e.g., after phase noise reduction by the optical reference) and the radio frequency signal. The first electro-optical mixer and the second electro-optical mixer may, for example, perform single sideband carrier suppression on opposite sidebands of their respective optical signals. The second laser may be self-injection locked using the first optical signal. The first laser may be self-injection locked using the second optical signal. This may be used to minimize phase noise in the clock circuit.

An aspect of the present disclosure provides a clock circuit. The clock circuit may include a first light source configured to generate a first optical Local Oscillator (LO) signal at a first frequency. The clock circuit may include a second light source configured to generate a second optical LO signal at a second frequency. The clock circuit may include a photodiode configured to be illuminated by the first optical LO signal and the second optical LO signal. The clock circuit may include a mixer having a first input coupled to the first light source and a second input coupled to the photodiode. The clock circuit may include an optical path coupling an output of the optical mixer to an input of the second light source. The clock circuit may include an optical reference disposed on the optical path.

An aspect of the present disclosure provides a clock circuit. The clock circuit may include a first laser configured to generate a first optical Local Oscillator (LO) signal. The clock circuit may include a second laser configured to generate a second optical LO signal. The clock circuit may include a first self-injection locking ring path coupled around the first laser and configured to self-injection lock the first laser. The clock circuit may include a second self-injection locking ring path coupled around the second laser and configured to self-injection lock the second laser. The clock circuit may include an optical reference that forms part of both the first self-injection locking loop path and the second self-injection locking loop path.

One aspect of the present disclosure provides an electronic device. The electronic device may include a first laser configured to emit a first optical Local Oscillator (LO) signal. The electronic device may include a second laser configured to emit a second optical LO signal. The electronic device may include an antenna configured to transmit a radio frequency signal based on the first optical LO signal and the second optical LO signal. The electronic device may include a photodiode configured to be illuminated by the first optical LO signal and the second optical LO signal. The electronic device may include a first ring path coupled between an output of the first laser and an input of the first laser. The electronic device may include a second ring path coupled between an output of the second laser and an input of the second laser, the photodiode being disposed on the second ring path. The electronic device may include a first mixer disposed on the first ring path and the second ring path. The electronic device may include a second mixer disposed on the first ring path. The electronic device may include an optical reference disposed on the first ring path between the first mixer and the second mixer and on the second ring path between the first mixer and the second laser.

Drawings

Fig. 1 is a block diagram of an exemplary electronic device having a wireless circuit with at least one antenna that transmits wireless signals at a frequency greater than about 100GHz, according to some embodiments.

Fig. 2 is a top view of an exemplary antenna that transmits wireless signals at frequencies greater than about 100GHz based on an optical Local Oscillator (LO) signal, in accordance with some embodiments.

Fig. 3 is a top view illustrating how an exemplary antenna of the type shown in fig. 2 may convert a received wireless signal at a frequency greater than about 100GHz to an intermediate frequency signal based on an optical LO signal, in accordance with some embodiments.

Fig. 4 is a top view showing how multiple antennas of the type shown in fig. 2 and 3 may be stacked to cover multiple polarizations, according to 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 transmitting wireless signals at frequencies greater than about 100GHz within a corresponding signal beam.

Fig. 6 is a circuit diagram of an exemplary radio circuit with an antenna that transmits wireless signals at a frequency greater than about 100GHz and receives wireless signals at a frequency greater than about 100GHz for conversion to an intermediate frequency and then to the optical domain, according to some embodiments.

Fig. 7 is a circuit diagram of an exemplary phased antenna array transmitting wireless signals at a frequency greater than about 100GHz within a corresponding signal beam, in accordance with some embodiments.

Fig. 8 is a circuit diagram of an exemplary clock circuit with first and second light sources that perform self-injection locking using optical references to minimize phase noise, according to some embodiments.

Fig. 9 is a flowchart of exemplary operations for self-injection locking a first light source and then self-injection locking a second light source in a clock circuit with an optical reference, according to some embodiments.

Fig. 10 is a graph of phase noise as a function of frequency showing how an exemplary clock circuit with optical reference may use self injection locking to minimize phase noise, according to some embodiments.

Fig. 11 is a circuit diagram of an exemplary clock circuit having a first light source and a second light source that perform self injection locking using a first optical reference and a second optical reference to minimize phase noise, in accordance with some embodiments.

Fig. 12 is a flowchart of exemplary operations for self-injection locking a first light source and a second light source simultaneously in a clock circuit having a first optical reference and a second optical reference, according to some embodiments.

Fig. 13 is a graph of phase noise as a function of frequency showing how an exemplary clock circuit having a first optical reference and a second optical reference may use self injection locking to minimize phase noise, according to some embodiments.

Detailed Description

The electronic device 10 of fig. 1 (sometimes referred to herein as an electro-optic device 10) may be: computing devices such as laptop computers, desktop computers, computer monitors including embedded computers, tablet computers, cellular telephones, media players, or other handheld or portable electronic devices; smaller devices such as wristwatch devices, hanging devices, earphone or earpiece devices, devices embedded in eyeglasses, goggles; or other equipment worn on the user's head; or other wearable or miniature devices, televisions, computer displays that do not contain embedded computers, gaming devices, navigation devices, embedded systems (such as systems in which electronic equipment with displays is installed in kiosks or automobiles), voice-controlled speakers connected to the wireless internet, home entertainment devices, remote control devices, game controllers, peripheral user input devices, wireless base stations or access points, 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. The housing 12 (which may sometimes be referred to as a shell) may be formed of plastic, glass, ceramic, fiber composite, metal (e.g., stainless steel, aluminum, metal alloys, etc.), other suitable materials, or a combination of these materials. In some cases, some or all of the housing 12 may be formed of dielectric or other low conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other cases, the housing 12 or at least some of the structures making up the housing 12 may be formed from metal elements.

The device 10 may include a control circuit 14. The control circuit 14 may include a memory device, such as the memory circuit 16. The storage circuitry 16 may include hard drive storage, non-volatile memory (e.g., flash memory or other electrically programmable read-only memory configured to form a solid state drive), volatile memory (e.g., static random access memory or dynamic random access memory), and the like. The storage circuitry 16 may include storage and/or removable storage media integrated within the device 10.

The control circuit 14 may include processing circuitry, such as processing circuitry 18. The processing circuitry 18 may be used to control the operation of the device 10. The processing circuitry 18 may include 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), and the like. Control circuitry 14 may be configured to perform operations in device 10 using hardware (e.g., dedicated hardware or circuitry), firmware, and/or software. The software code for performing operations in the device 10 may be stored on the storage circuitry 16 (e.g., the storage circuitry 16 may comprise a non-transitory (tangible) computer-readable storage medium storing the software code). The software code may sometimes be referred to as program instructions, software, data, instructions, or code. Software code stored on the memory circuit 16 may be executed by the processing circuit 18.

Control circuitry 14 may be used to run software on device 10, such as a satellite navigation applicationPrograms, internet browsing applications, voice Over Internet Protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, and the like. To support interaction with external equipment, the control circuit 14 may be used to implement a communication protocol. Communication protocols that may be implemented using control circuitry 14 include Internet protocol, wireless Local Area Network (WLAN) protocol (e.g., IEEE 802.11 protocol, sometimes referred to as) Such as->Protocols or other Wireless Personal Area Network (WPAN) protocols, etc. for other short-range wireless communication links, IEEE 802.11ad protocols (e.g., ultra wideband protocols), cellular telephone protocols (e.g., 3G protocols, 4G (LTE) protocols, 3GPP fifth generation (5G) new air interface (NR) protocols, sixth generation (6G) 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 communication protocols, or any other desired communication protocol. Each communication protocol may be associated with a corresponding Radio Access Technology (RAT) that specifies the physical connection method used to implement the protocol.

The device 10 may include an input-output circuit 20. The input-output circuit 20 may include an input-output device 22. The input-output device 22 may be used to allow data to be supplied to the device 10 and to allow data to be provided from the device 10 to an external device. The input-output devices 22 may include user interface devices, data port devices, and other input-output components. For example, the input-output devices 22 may include touch sensors, displays (e.g., touch-sensitive and/or force-sensitive displays), lighting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), scroll wheels, touch pads, keypads, 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), capacitive sensors, proximity sensors, magnetic sensors, force sensors (e.g., force sensors coupled to the display to detect pressure applied to the display), temperature sensors, and the like. In some configurations, keyboards, headphones, displays, pointing devices such as touch pads, mice, and joysticks, and other input-output devices may be coupled to the device 10 using wired or wireless connections (e.g., some of the input-output devices 22 may be peripheral devices coupled to a main processing unit or other portion of the device 10 via wired or wireless links).

The input-output circuitry 20 may include wireless circuitry 24 to support wireless communications. The wireless circuitry 24 (sometimes referred to herein as wireless communications circuitry 24) may include one or more antennas 30. The 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, clock 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 antenna 30. The components of transceiver circuit 26 may be implemented on one integrated circuit, chip, system on a chip (SOC), die, printed circuit board, substrate, or package, or the components of transceiver circuit 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 illustrative and not limiting. Although, for clarity, in the example of fig. 1, control circuit 14 is shown separate from wireless circuit 24, wireless circuit 24 may include processing circuitry (e.g., one or more processors) that forms part of processing circuit 18 and/or storage circuitry that forms part of storage circuit 16 of control circuit 14 (e.g., portions of control circuit 14 may be implemented on wireless circuit 24). As one example, the control circuitry 14 may include baseband circuitry (e.g., one or more baseband processors), digital control circuits, analog control circuits, and/or other control circuits forming a portion of the wireless circuitry 24. The baseband circuitry may, for example, access a communication protocol stack on the control circuitry 14 (e.g., the memory circuitry 20) to: executing user plane functions in a PHY layer, a MAC layer, an RLC layer, a PDCP layer, an SDAP layer and/or a PDU layer; and/or performing control plane functions at a PHY layer, a MAC layer, an RLC layer, a PDCP layer, an RRC layer, and/or a non-access layer.

The transceiver circuit 26 may be coupled to each antenna 30 in the wireless circuit 24 by 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 line/path for conveying wireless signals between transceiver circuitry 26 and antenna 30. The antenna 30 may be formed using any desired antenna structure for transmitting wireless signals. For example, the antenna 30 may include antennas with resonating elements formed from dipole antenna structures, planar dipole antenna structures (e.g., butterfly antenna structures), slot antenna structures, loop antenna structures, patch antenna structures, inverted-F antenna structures, planar inverted-F antenna structures, spiral antenna structures, monopole antennas, dipoles, hybrids of these designs, and so forth. 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 the antenna 30 over time.

If desired, two or more of the antennas 30 may be integrated into a phased antenna array (sometimes referred to herein as a phased array antenna) in which each of these antennas transmits a wireless signal having a respective phase and magnitude that is adjusted over time, so that the wireless signals constructively and destructively interfere to produce (form) a signal beam in a given pointing direction. As used herein, the term "transmit wireless signal" means the transmission and/or reception of a wireless signal (e.g., for performing unidirectional and/or bidirectional wireless communications with external wireless communication equipment). The antenna 30 may transmit wireless signals by radiating signals into free space (or through intervening device structures such as dielectric cover layers). Additionally or alternatively, antenna 30 may receive wireless signals from free space (e.g., through an intervening device structure such as a dielectric cover layer). The transmission and reception of wireless signals by the antenna 30 each involves the excitation or resonance of antenna currents on antenna resonating (radiating) elements in the antenna by wireless signals within the operating frequency band of the antenna.

Transceiver circuitry 26 may transmit and/or receive wireless signals using antenna 30 that communicate wireless communication data between device 10 and external wireless communication equipment (e.g., one or more other devices, such as device 10, a wireless access point or base station, etc.). Wireless communication data may be transmitted bi-directionally or uni-directionally. The wireless communication data may include, for example, data encoded into corresponding data packets, such as wireless data associated with a telephone call, streaming media content, internet browsing, wireless data associated with a software application running on device 10, email messages, and the like.

In addition or alternatively, the wireless circuitry 24 may perform wireless sensing operations using the antenna 30. The sensing operation may allow the device 10 to detect (e.g., sense or identify) the presence, position, orientation, and/or speed (movement) of an object external to the device 10. Control circuitry 14 may use the detected presence, position, orientation, and/or speed of the external object to perform any desired device operation. As an example, the control circuitry 14 may use the detected presence, position, orientation, and/or velocity of an external object to identify corresponding user inputs for one or more software applications running on the device 10, such as gesture inputs performed by a user's hand or other body part or by an external stylus, game controller, head mounted device, or other peripheral device or accessory, to determine when one or more antennas 30 need to be disabled or set with a reduced maximum transmit power level (e.g., to satisfy regulatory limits on radio frequency exposure), to determine how to steer (form) a radio frequency signal beam generated by the antennas 30 for the wireless circuitry 24 (e.g., where the antennas 30 include a phased array of antennas 30), to map or model an environment surrounding the device 10 (e.g., to generate a software model of a room in which the device 10 is located for use by an augmented reality application, a game application, a mapping application, a home design application, an engineering application, etc.), to detect the presence of obstacles in the vicinity of the device 10 (e.g., the surroundings) or in the direction of motion of the user of the device 10, etc.

The wireless circuitry 24 may transmit and/or receive wireless signals within a corresponding frequency band of the electromagnetic spectrum (sometimes referred to herein as a communications band or simply "band"). The frequency bands handled by communication circuit 26 may include: the Wireless Local Area Network (WLAN) band (e.g.,(IEEE 802.11) or other WLAN communication bands) such as the 2.4GHz WLAN band (e.g., 2400MHz to 2480 MHz), the 5GHz WLAN band (e.g., 5180MHz to 5825 MHz), -, and->6E band (e.g., 5925MHz-7125 MHz) and/or others +.>A band (e.g., 1875MHz-5160 MHz); wireless Personal Area Network (WPAN) bands such asA band or other WPAN communication band; cellular telephone frequency bands (e.g., about 600MHz to about 5GHz band, 3G band, 4G LTE band, 5G new air interface frequency range 1 (FR 1) band below 10GHz, 5G new air interface frequency range 2 (FR 2) band between 20GHz and 60GHz, etc.); other centimeter or millimeter wave bands between 10GHz-100 GHz; near field communication band (e.g., 13.56 MHz); satellite navigation frequency bands (e.g., GPS band 1565MHz to 1610MHz, global navigation satellite System (GLONASS) band, beidou satellite navigation System (BDS) band, etc.); ultra Wideband (UWB) operating under IEEE 802.15.4 protocols and/or other ultra wideband communication protocols) A frequency band; a communication band belonging to the 3GPP wireless communication standard series; a communications band belonging to the IEEE 802.Xx family of standards; and/or any other desired frequency band of interest.

Over time, software applications on electronic devices, such as device 10, have become increasingly data intensive. Thus, wireless circuitry on electronic devices needs to support data transmission at increasingly higher data rates. Generally, the data rate supported by the radio circuit is proportional to the frequency of the radio signal transmitted by the radio circuit (e.g., higher frequencies may support higher data rates than lower frequencies). Wireless circuitry 24 may transmit 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 about 10GHz and 100 GHz). However, the data rates supported by the centimeter and millimeter wave signals may still be insufficient to meet all of the data transmission requirements of device 10. To support even higher data rates, such as data rates up to 5Gbps-10Gbps or higher, wireless circuitry 24 may transmit wireless signals at frequencies greater than 100 GHz.

As shown in fig. 1, the wireless circuitry 24 may transmit wireless signals 32 at frequencies greater than about 100GHz and may receive wireless signals 34 at frequencies greater than about 100 GHz. The wireless signals 32 and 34 may sometimes be referred to herein as very high frequency (THF) signals 32 and 34, sub-THz signals 32 and 34, or sub-millimeter wave signals 32 and 34.THF signals 32 and 34 may be at sub-THz frequencies or frequencies of THz such as between 100GHz and 1THz, between 100GHz and 10THz, between 100GHz and 2THz, between 200GHz and 1THz, between 300GHz and 2THz, between 300GHz and 10THz, between 100GHz and 800GHz, between 200GHz and 1.5THz, etc. (e.g., within sub-THz, THz, THF or sub-millimeter frequency bands such as 6G bands). The high data rates supported by these frequencies may be utilized by device 10 to perform cellular telephone voice and/or data communications (e.g., while supporting spatial multiplexing to provide additional data bandwidth), to perform spatial ranging operations such as radar operations to detect the presence, location, and/or speed of objects external to device 10, to perform automotive sensing (e.g., with enhanced security), to perform health/body monitoring on a user or another person of device 10, 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 displaying 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 signal 32 to another antenna 30 on a second chip in device 10), and/or to perform any other desired high data rate operations.

Within an electronic device, such as device 10, space is at a premium. In some cases, the antenna 30 for transmitting the THF signal 32 is different from the antenna 30 for receiving the THF signal 34. However, using different antennas 30 to handle the transmission of THF signal 32 and the reception of THF signal 34 may consume excessive space and other resources within device 10, as both antennas 30 and signal paths 28 would be required to handle both transmission and reception. To minimize space and resource consumption within the device 10, the same antenna 30 and signal path 28 may be used to transmit THF signals 32 and receive THF signals 34. Multiple antennas 30 in the wireless circuit 24 may transmit THF signals 32 and may receive THF signals 34, if desired. The antennas may be integrated into a phased antenna array that transmits THF signals 32 and receives THF signals 34 within corresponding signal beams oriented in the selected beam pointing direction.

Incorporating components into the wireless circuitry 24 that supports wireless communications at these high frequencies can be challenging. If desired, the transceiver circuitry 26 and the signal path 28 may include optical components that transmit optical signals to support transmission of the THF signal 32 and reception of the THF signal 34 in a space and resource efficient manner. The optical signal may be used to transmit the THF signal 32 at the THF frequency and to receive the THF signal 34 at the THF frequency.

Fig. 2 is a diagram of an exemplary antenna 30 that may be used to transmit THF signals 32 and receive THF signals 34 using optical signals. The antenna 30 may include one or more antenna radiating (resonating) elements, such as radiating (resonating) element arms 36. In the example of fig. 2, the antenna 30 is a planar dipole antenna (sometimes referred to as a "butterfly" antenna) having two opposing radiating element arms 36 (e.g., butterfly arms or dipole arms). This is illustrative and not limiting. In general, the antenna 30 may be any type of antenna having any desired antenna radiating element architecture.

As shown in fig. 2, the antenna 30 includes a Photodiode (PD) 42 coupled between the radiating element arms 36. An electronic device, such as device 10, including an antenna 30 having a photodiode 42 may also sometimes be referred to as an electro-optic device (e.g., electro-optic device 10). Photodiode 42 may be a programmable photodiode. For example, examples are described herein in which photodiode 42 is a programmable single line carrier photodiode (UTC PD). Thus, the photodiode 42 may sometimes be referred to herein as UTC PD 42 or programmable UTC PD 42. This is illustrative and not limiting. Generally, the photodiode 42 may include any desired type of adjustable/programmable photodiode or component that converts electromagnetic energy (e.g., light or optical energy) at an optical frequency (e.g., infrared, visible, and/or ultraviolet frequencies) to current at THF frequency on the radiating element arm 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 butterfly antenna). Other radiating elements may be used if desired.

UTC PD 42 may have the capability to receive one or more control signals V _{Bias of} Is provided for the bias terminal 38. Control signal V _{Bias of} May include bias voltages set at one or more voltage levels and/or other control signals for controlling the operation of the UTC PD 42, such as an impedance adjustment control signal for adjusting the output impedance of the UTC PD 42. The control circuit 14 (fig. 1) may provide (e.g., apply, supply, assert, etc.) the control signal V in different settings (e.g., values, magnitudes, etc.) _{Bias of} To dynamically control (e.g. program or tune) over timeInteger) operation of UTC PD 42. For example, control signal V _{Bias of} May be used to control whether the antenna 30 transmits the THF signal 32 or receives the THF signal 34. When the control signal V _{Bias of} Including a bias voltage asserted at a first level or magnitude, the antenna 30 may be configured to transmit a THF signal 32. When the control signal V _{Bias of} Including a bias voltage asserted at a second level or magnitude, antenna 30 may be configured to receive THF signal 34. In the example of fig. 2, the control signal V _{Bias of} Including a bias voltage asserted at a first level to configure the antenna 30 to transmit the THF signal 32. If necessary, control signal V _{Bias of} May also be adjusted to control the waveform of the THF signal (e.g., as a square function, linear function, etc. that preserves modulation of the incident optical signal), to perform gain control on the signal transmitted by the antenna 30, and/or to adjust the output impedance of the UTC PD 42.

As shown in fig. 2, UTC PD 42 may be optically coupled to optical path 40. The 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) via optical path 40. The optical signals may include a first optical Local Oscillator (LO) signal LO1 and a second optical local oscillator signal LO2. The optical local oscillator signals LO1 and LO2 may be generated by a light source in transceiver circuitry 26 (fig. 1). The optical local oscillator signals LO1 and LO2 may be at an optical wavelength (e.g., between 400nm and 700 nm), an ultraviolet wavelength (e.g., near ultraviolet wavelength or extreme ultraviolet wavelength), and/or an infrared wavelength (e.g., near infrared wavelength, mid infrared wavelength, or far infrared wavelength). The optical local oscillator signal LO2 may be offset in wavelength from the optical local oscillator signal LO1 by a wavelength offset X. The wavelength offset X may be equal to the wavelength of THF signals transmitted by the antenna 30 (e.g., between 100GHz and 1THz (1000 GHz), between 100GHz and 2THz, between 300GHz and 800GHz, between 300GHz and 1THz, between 300GHz and 400GHz, etc.).

During signal transmission, wireless data (e.g., wireless data packets, symbols, frames, etc.) may be modulated onto the optical local oscillator signal LO2 to produce a modulated optical local oscillator signal LO2'. The optical local oscillator signal LO1 may be provided with an optical phase shift S if desired. The optical path 40 may illuminate the UTC PD 42 with an optical local oscillator signal LO1 (plus an optical phase shift S when applied) and a modulated optical local oscillator signal LO2'. If desired, a lens or other optical component may be interposed between the optical path 40 and the UTC PD 42 to help focus the optical local oscillator signal onto the UTC PD 42.

UTC PD 42 may convert optical local oscillator signal LO1 and modulated local oscillator signal LO2' (e.g., the beat between the two optical local oscillator signals) to an antenna current flowing along the perimeter of radiating element arm 36. The frequency of the antenna current is equal to the frequency difference between the local oscillator signal LO1 and the modulated local oscillator signal LO 2'. The antenna current may radiate (emit) THF signal 32 into free space. Control signal V _{Bias of} UTC PD 42 may be controlled to convert the optical local oscillator signal to an antenna current on radiating element arm 36 while preserving the modulation and thus wireless data on modulated local oscillator signal LO2' (e.g., by applying a squaring function to the signal). THF signal 32 will thereby carry the modulated wireless data for reception and demodulation by external wireless communication equipment.

Fig. 3 shows (e.g., when the control signal V is to be _{Bias of} After the setting of fig. 2 changes from the transmit state to the receive state) the antenna 30 may receive the THF signal 34. As shown in fig. 3, THF signal 34 may be incident on antenna radiating element arm 36. The incident THF signal 34 may generate an antenna current that flows around the perimeter of the radiating element arm 36. UTC PD 42 may use optical local oscillator signal LO1 (plus optical phase shift S when applied), optical local oscillator signal LO2 (e.g., without modulation), and control signal V _{Bias of} The received THF signal 34 is converted (e.g., to a bias voltage asserted at a second level) to an intermediate frequency signal SIGIF that is output onto an intermediate frequency signal path 44.

The frequency of the intermediate frequency signal SIGIF may be equal to the frequency of THF signal 34 minus the difference between the frequency of optical local oscillator signal LO1 and the frequency of optical local oscillator signal LO 2. For example, the intermediate frequency signal SIGIF may be at a lower frequency than THF signals 32 and 34, such as a centimeter or millimeter wave frequency between 10GHz and 100GHz, between 30GHz and 80GHz, about 60GHz, and the like. Transceiver circuitry 26 (fig. 1) may change the frequency of optical local oscillator signal LO1 and/or optical local oscillator signal LO2 when switching from transmit to receive or vice versa, if desired. UTC PD 42 may store the data modulation of THF signal 34 in intermediate signal SIGIF. The receiver in transceiver circuit 26 (fig. 1) may demodulate intermediate frequency signal SIGIF (e.g., after further down conversion) to recover wireless data from THF signal 34. As another example, the wireless circuitry 24 may convert the intermediate frequency signal SIGIF to the optical domain prior to recovering the wireless data. As another example, intermediate frequency signal path 44 may be omitted and UTC PD 42 may convert THF signal 34 into the optical domain for subsequent demodulation and data recovery (e.g., in a sideband of the optical signal).

The antenna 30 of fig. 2 and 3 may support transmission of the THF signal 32 and reception of the THF signal 34 with a given polarization (e.g., linear polarization such as vertical polarization). If desired, the wireless circuitry 24 (FIG. 1) may include multiple antennas 30 for covering different polarizations. Fig. 4 is a diagram illustrating one example of how the wireless circuit 24 may include multiple antennas 30 for covering different polarizations.

As shown in fig. 4, the wireless circuit may include a first antenna 30, such as an antenna 30V for covering a first polarization (e.g., a first linear polarization such as vertical polarization), and may include a second antenna 30, such as an antenna 30H for covering a second polarization (e.g., a second linear polarization such as horizontal polarization) that is different from or orthogonal to the first polarization. The antenna 30V may have a UTC PD 42, such as UTC PD 42V coupled between a corresponding pair of radiating element arms 36. The antenna 30H may have a UTC PD 42, such as UTC PD 42H coupled between a corresponding pair of radiating element arms 36 oriented non-parallel (e.g., orthogonal) to the radiating element arms 36 in the antenna 30V. This may allow antennas 30V and 30H to transmit THF signals 32 with respective (orthogonal) polarizations, and may allow antennas 30V and 30H to receive THF signals 32 with respective (orthogonal) polarizations.

To minimize space within the device 10, the antenna 30V may be vertically stacked above or below the antenna 30H (e.g., with the UTC PD 42V partially or fully overlapping the UTC PD 42H). In this example, both antennas 30V and 30H may be formed on the same substrate, such as a rigid or flexible printed circuit board. The substrate may include a plurality of stacked dielectric layers (e.g., layers of ceramic, epoxy, flexible printed circuit board material, rigid printed circuit board material, etc.). The radiating element arm 36 in antenna 30V may be formed on a separate substrate layer from the radiating element arm 36 in antenna 30H, or the radiating element arm 36 in antenna 30V may be formed on the same substrate layer as the radiating element arm 36 in antenna 30H. The UTC PD 42V may be formed on the same substrate layer as the UTC PD 42H, or the UTC PD 42V may be formed on a separate substrate layer from the UTC PD 42H. The UTC PD 42V may be formed on the same substrate layer as the radiating element arm 36 in the antenna 30V, or may be formed on a separate substrate layer from the radiating element arm 36 in the antenna 30V. The UTC PD 42H may be formed on the same substrate layer as the radiating element arm 36 in the antenna 30H, or may be formed on a separate substrate layer from the radiating element arm 36 in the antenna 30H.

The antenna 30 or the antennas 30H and 30V of fig. 4 may be integrated within a phased antenna array, if desired. Fig. 5 is a diagram showing one example of how antennas 30H and 30V may be integrated within a phased antenna array. As shown in fig. 5, the device 10 may include a phased antenna array 46 of stacked antennas 30H and 30V arranged in a rectangular grid of rows and columns. Each of these antennas in phased antenna array 46 may be formed on the same substrate. This is illustrative and not limiting. In general, the phased antenna array 46 (sometimes referred to as a phased array antenna) may include any desired number of antennas 30V and 30H (or non-stacked antennas 30) arranged in any desired pattern. Each of these antennas in phased antenna array 46 may be provided with a respective optical phase shift S (fig. 2 and 3) that configures the antennas to collectively transmit THF signals 32 and/or receive THF signals 34 that add to form a signal beam of THF signals in the desired beam pointing direction. The beam pointing direction may be selected to point the signal beam toward external communication equipment, toward 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 30V/30H may have a length 48 (e.g., as measured from one radiating element arm end to an opposite radiating element arm end). Length 48 may be approximately equal to half the wavelength of THF signals 32 and 34. For example, the length 48 may be as small as 0.5mm or less. Each UTC-PD 42 in the phased antenna array 46 may occupy a lateral area of 100 square microns or less. This may allow the phased antenna array 46 to occupy a very small area within the device 10, allowing the phased antenna array to be integrated within different portions of the device 10 while still allowing additional space for device components. The examples of fig. 2-5 are illustrative and not limiting. 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 transmit THF signals 32 and receive THF signals 34 based on an optical local oscillator signal. In the example of fig. 6, UTC PD 42 converts the received THF signal 34 to intermediate frequency signals SIGIF, which are then converted to the optical domain for recovering wireless data from the received THF signal.

As shown in fig. 6, the wireless circuit 24 may include a transceiver circuit 26 coupled to an antenna 30 through a signal path 28 (e.g., an optical signal path sometimes referred to herein as an optical signal path 28). UTC PD 42 may be coupled between radiating element arm 36 of antenna 30 and signal path 28. Transceiver circuitry 26 may include optical components 68, amplifier circuitry such as a power amplifier 76 and a digital-to-analog converter (DAC) 74. The optical component 68 may include an optical receiver, such as optical receiver 72, and an optical Local Oscillator (LO) light source (emitter) 70.LO light source 70 may include two or more light sources (e.g., sources of electromagnetic, light, or optical energy) such as laser light sources, laser diodes, optical phase locked loops, or other optical emitters that emit light at respective wavelengths (e.g., electromagnetic, light, or optical energy including optical local oscillator signals LO1 and LO 2) (e.g., visible, infrared, and/or ultraviolet wavelengths). If desired, the LO light source 70 may comprise 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 component 68 through optical path 66. Optical path 66 may include one or more optical fibers and/or waveguides.

Signal path 28 may include optical splitters such as Optical Splitter (OS) 54, optical paths such as optical path 64 and optical path 62, optical combiners such as Optical Combiner (OC) 52, and optical path 40. The optical path 62 may be an optical fiber or waveguide. The optical path 64 may be an optical fiber or waveguide. 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 interposed (optically) on or along optical path 64. An optical modulator, such as optical modulator 56, may be interposed (optically) on or along optical path 62. Optical modulator 56 may be, for example, a Mach-Zehnder modulator (MZM) and, thus, may 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 an optical path 62. Propagating optical local oscillator signal LO2 along arms 60 and 58 of MZM 56 may allow for a different optical phase shift to be imparted to each arm before recombining the signals at the output of the MZM in the presence of a voltage signal applied to one or both arms (e.g., where the optical phase modulation produced on these arms is converted to intensity modulation 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. The phase shift performed at MZM 56 may be used to perform beam forming/steering in addition to or instead of optical phase shifter 80, if desired. MZM 56 may receive one or more bias voltages W applied to one or both arms 58 and 60 _{Bias of} (at the present)Sometimes referred to herein as bias signal W _{Bias of} ). The control circuit 14 (FIG. 1) can provide bias voltages W having different magnitudes _{Bias of} To place MZM 56 in different modes of operation (e.g., an operation mode that suppresses the optical carrier signal, an operation mode that does not suppress the optical carrier signal, 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 signal SIGIF from UTC PD 42 to MZM 56.DAC 74 may have inputs coupled to up-conversion circuitry, modulator circuitry, and/or baseband circuitry in the transmitter of transceiver circuitry 26. DAC 74 may receive digital data for transmission through 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 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.

The LO light source 70 may generate (emit) optical local oscillator signals LO1 and LO2 (e.g., at different wavelengths separated by the wavelength of THF signals 32/34). Optical component 68 may include lenses, waveguides, optical couplers, optical fibers, and/or other optical components that direct the emitted optical local oscillator signals LO1 and LO2 toward splitter 54 via optical path 66. Splitter 54 may split the optical signal (e.g., by wavelength) on optical path 66 to output optical local oscillator signal LO1 onto optical path 64 while outputting optical local oscillator signal LO2 onto optical path 62.

Control circuit 14 (fig. 1) may provide phase control signal CTRL to optical phase shifter 80. The phase control signal CTRL may control the optical phase shifter 80 to apply an optical phase shift S to the optical local oscillator signal LO1 on the optical path 64. The phase shift S may be selected to steer the signal beam of THF signal 32/34 in a desired pointing direction. Optical phase shifter 80 may pass the phase shifted optical local oscillator signal LO1 (referred to as LO1+ 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 those of THF signals 32 and 34. Optical combiner 52 may receive optical local oscillator signal LO2 via optical path 62. The optical combiner 52 may combine the optical local oscillator signals LO1 and LO2 onto an optical path 40 that directs these optical local oscillator signals onto the UTC PD 42 for use during signal transmission or reception.

During transmission of the THF signal 32, the DAC 74 may receive digital wireless data (e.g., data packets, frames, symbols, etc.) for transmission by the THF signal 32. DAC 74 may convert the digital wireless data to the analog domain and may output (transmit) the data as data DAT onto transmit data path 78 (e.g., for transmission via antenna 30). The power amplifier 76 may amplify the data DAT. Transmit data path 78 may communicate data DAT to MZM 56 (e.g., arm 60). MZM 56 may modulate data DAT onto optical local oscillator signal LO2 to produce a modulated optical local oscillator signal LO2' (e.g., an optical local oscillator signal at the frequency/wavelength of optical local oscillator signal LO2 but modulated to include data identified by data DAT). Optical combiner 52 may combine optical local oscillator signal LO1 with modulated optical local oscillator signal LO2' at optical path 40.

The optical path 40 may illuminate the UTC PD 42 with (using) an optical local oscillator signal LO1 (e.g., and a phase shift S applied by an optical phase shifter 80) and a modulated optical local oscillator signal LO 2'. The control circuit 14 (FIG. 1) may apply a control signal V to the UTC PD 42 _{Bias of} The control signal configures the antenna 30 for transmitting the THF signal 32.UTC PD 42 may convert optical local oscillator signal LO1 and modulated optical local oscillator signal LO2' to an antenna current on radiating element arm 36 at the frequency of THF signal 32 (e.g., when programmed for use with control signal V _{Bias of} When transmitting). The antenna current on radiating element arm 36 may radiate THFSignal 32. The frequency of THF signal 32 is given by the frequency difference between optical local oscillator signal LO1 and modulated optical local oscillator signal LO 2'. Control signal V _{Bias of} UTC PD 42 may be controlled to preserve the modulation from modulated optical local oscillator signal LO2' in radiated THF signal 32. The external equipment receiving the THF signal 32 will thus be able to extract the data DAT from the THF signal 32 transmitted by the antenna 30.

During receipt of THF signal 34, MZM 56 does not modulate any data onto optical local oscillator signal LO 2. The optical path 40 thus illuminates the UTC PD 42 with the optical local oscillator signal LO1 (e.g., and phase shift S) and the optical local oscillator signal LO 2. The control circuit 14 (FIG. 1) may apply a control signal V to the UTC PD 42 _{Bias of} (e.g., bias voltage) that configures the antenna 30 to receive the THF signal 32.UTC PD 42 may use optical local oscillator signals LO1 and LO2 to convert received THF signal 34 to an intermediate frequency signal SIGIF that is output onto intermediate frequency signal path 44 (e.g., when programmed for use with bias voltage V _{Bias of} Upon reception). The intermediate frequency signal SIGIF may include modulated data from the received THF signal 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 signal SIGIF as optical signal LOrx to the optical domain (e.g., by modulating data in intermediate frequency signal SIGIF onto one of the optical local oscillator signals) and may pass these optical signals to optical receiver 72 in optical component 68 as indicated by arrow 63 (e.g., via optical paths 62 and 66 or other optical paths). The control circuit 14 (fig. 1) may use the optical receiver 72 to convert the optical signal lor to another format and recover (demodulate) the data carried by the THF signal 34 from the optical signal. In this way, the same antenna 30 and signal path 28 may be used to transmit and receive THF signals while also performing beam steering operations.

The example of fig. 6 in which the intermediate frequency signal SIGIF is converted to the optical domain is illustrative and non-limiting. The transceiver circuit 26 can receive and demodulate the intermediate frequency signal SIGIF, if desired, without the need forThese signals are first passed to the optical domain. For example, transceiver circuit 26 may include an analog-to-digital converter (ADC), intermediate frequency signal path 44 may be coupled to an input of the ADC instead of MZM 56, and the ADC may convert intermediate frequency signal SIGIF to the digital domain. As another example, intermediate frequency signal path 44 may be omitted and control signal V _{Bias of} UTC PD 42 may be controlled to sample THF signal 34 directly into the optical domain along with optical local oscillator signals LO1 and LO 2. For example, UTC PD 42 may use received THF signal 34 and control signal V _{Bias of} An optical signal is generated 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., 30GHz-100GHz, 60GHz, 50GHz-70GHz, 10GHz-100GHz, etc.). The sidebands may be used to carry the modulated data from the received THF signal 34. The signal path 28 may direct (propagate) the optical signal generated by the UTC PD 42 to an optical receiver 72 in the optical component 68 (e.g., via optical paths 40, 64, 62, 66, 63, and/or other optical paths). Control circuit 14 (fig. 1) may use optical receiver 72 to convert the optical signal to other formats and recover (demodulate) the data carried by THF signal 34 from the optical signal (e.g., from sidebands of the optical signal).

If desired, optical component 68 may include a clock circuit, such as a Clock (CLK) circuit 75 (sometimes referred to herein as clock circuit 75 or clock generation circuit 75). Clock circuit 75 may include one or more of an electro-optic phase-locked loop (OPLL), a frequency-locked loop (FLL), and a self-injection locked (locked) loop. As shown in fig. 6, clock circuit 75 may be used to control and clock LO light source 70 and/or to clock any other desired hardware in device 10 (e.g., clock circuit 75 need not be located in transceiver 26 and may generally be located elsewhere in device 10). LO light source 70 may generate optical LO signals (e.g., optical local oscillator signals LO1 and LO 2) that are phase locked, self-injection locked, and/or frequency locked with respect to one another, for example, using a clock circuit 75.

Fig. 7 is a circuit diagram showing one example of how multiple antennas 30 may be integrated into a phased antenna array 88 that transmits THF signals through corresponding signal beams. In the example of fig. 7, MZM 56, intermediate frequency signal path 44, data path 78, and optical receiver 72 of fig. 6 have been omitted for clarity. Each of these antennas in phased antenna array 88 may alternatively sample the received THF signal directly into the optical domain, or may pass the intermediate frequency signal SIGIF to an ADC in transceiver circuitry 26.

As shown in FIG. 7, the phased antenna array 88 includes N antennas 30, such as a first antenna 30-0, a second antenna 30-1, and an N antenna 30- (N-1). Each of the antennas 30 in the phased antenna array 88 may be coupled to the optical component 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, which respective optical combiner 52 is 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, which are 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.).

The optical component 68 may include LO light sources 70, such as a first LO light source 70A and a second LO light source 70B. The optical signal paths for each of the antennas 30 in the phased antenna array 88 may share one or more splitters 54, such as a first splitter 54A and a second splitter 54B. LO light source 70A may generate (e.g., generate, emit, etc.) a first optical local oscillator signal LO1 and may provide first optical local oscillator signal LO1 to splitter 54A via optical path 66A. Splitter 54A may distribute first optical local oscillator signal LO1 to each UTC PD of UTC PDs 42 in phased antenna array 88 via optical path 64 (e.g., optical paths 64-0, 64-1, 64- (N-1), etc.). Similarly, LO light source 70B may generate (e.g., generate, emit, etc.) a second optical local oscillator signal LO2 and may provide second optical local oscillator signal LO2 to splitter 54B via optical path 66B. Splitter 54B may distribute second optical local oscillator signal LO2 to each UTC PD of UTC PDs 42 in phased antenna array 88 via optical path 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 a phase S imparted by the optical phase shifter to the optical local oscillator signal LO1 (e.g., a first optical phase shifter 80-0 may impart an optical phase shift of zero degrees/radian to the optical local oscillator signal LO1 provided to the antenna 30-0), a second optical phase shifter 80-1 may impart an optical phase shift of ΔΦ to the optical local oscillator signal LO1 provided to the antenna 30-1, an nth optical phase shifter 80- (N-1) may impart an optical phase shift of (N-1) ΔΦ to the optical local oscillator signal LO1 provided to the antenna 30- (N-1), by adjusting the phase S imparted by each of the N optical phase shifters 80, the control circuit 14 (fig. 1) may control each of the antennas in the phased antenna array 88 to transmit THF signals 32 and/or receive THF signals 34 within the formed signal beam 83.

Phased antenna array 88 may be capable of operating in an active mode in which the array transmits and/or receives THF signals using optical local oscillator signals LO1 and LO2 (e.g., using phase shifted pilot signal beam 83 provided to each antenna element). The phased antenna array 88 may also be capable of operating in a passive mode, if desired, in which the array does not transmit or receive THF signals. Conversely, in the passive mode, the phased antenna array 88 may be configured to form a passive reflector that reflects THF signals or other electromagnetic waves incident on the device 10. In the passive mode, UTC PD 42 in phased antenna array 88 is not illuminated by optical local oscillator signals LO1 and LO2, and transceiver circuitry 26 does not perform modulation/demodulation, mixing, filtering, detection, modulation, and/or amplification on the incident THF signal.

The device with processing capability includes a clock circuit that generates a clock signal. Devices with THF signaling capability, such as device 10, are particularly sensitive to jitter (deviation from perfect periodicity) and phase noise frequency generation in the clock signal (e.g., because for THF frequencies, the clock circuit consumes a relatively large amount of power and chip area). To minimize clock jitter and phase noise, the processing operations in device 10 may be clocked using clock circuit 75. For example, examples are described herein in which THF communications using transceiver 26 (fig. 1) are clocked using clock circuit 75. This is illustrative and not limiting. In general, clock circuit 75 may be used to time any desired processing operation in device 10 (e.g., high-speed digital interface operation, processor computing, sensing, automotive, input/output operation, communication at frequencies below 100GHz, such as millimeter/centimeter wave frequencies or frequencies below 10GHz, etc.).

Fig. 8 is a circuit diagram of the clock circuit 75. As shown in fig. 8, clock circuit 75 may include a photodiode such as UTC PD 96, a first light source such as primary laser 90 (e.g., LO light source 70 from fig. 6), a second light source such as secondary laser 92 (e.g., LO light source 70 from fig. 6), a first mixer such as optical mixer 102, a second mixer such as optical mixer 110, and an optical reference such as optical reference 106. The UTC PD 96 need not be a UTC PD, and may generally include other types of photodiodes.

For example, the first optical mixer 102 may be an electro-optical mixer such as an MZM. The first optical mixer 102 may modulate (mix) the received optical signal with the received electrical signal. For example, the second optical mixer 110 may also be an electro-optical mixer such as a MZM. The second optical mixer 110 may modulate (mix) the received optical signal with the received electrical signal. These electro-optic modulations may produce output signals having a carrier at the optical signal frequency, a first (left) sideband at the optical signal frequency minus the electrical signal frequency, and a second (right) sideband at the optical signal frequency plus the electrical signal frequency. If desired, the optical mixer may filter or reject one of the carrier and sidebands when generating its corresponding output signal in a process sometimes referred to as single sideband modulated carrier rejection (SSB-CS).

Secondary laser 92 may have an output coupled to optical path 118. The output terminal 122 of the clock circuit 75 may be coupled to the optical path 118. Primary laser 90 may have an output coupled to optical path 94. The output terminal 120 of the clock circuit 75 may be coupled to the optical path 94. The optical path 94 may be coupled to a first input of the optical mixer 102. Optical paths 94 and 118 may be coupled to one or more inputs of UTC PD 96 (e.g., optical paths 94 and 118 illuminate UTC PD, respectively, or may be coupled to an optical combiner that illuminates UTC PD 96 with two optical local oscillator signals). UTC PD 96 may have an output coupled to a second input of optical mixer 102 (e.g., an electrical input of optical mixer 102) via radio frequency path 100 and to a first input of optical mixer 110 (e.g., an electrical input of optical mixer 110) via radio frequency path 98.

The optical mixer 102 may have an output coupled to the optical path 104. The optical path 104 may be coupled to an input of the secondary laser 92 (e.g., a control input of the secondary laser 92) and to a second input of the optical mixer 110. The output of the optical mixer 110 may be coupled to an input of the primary laser 90 (e.g., a control input of the primary laser 90) via an optical path 116. The optical paths 118, 94, 104, and 116 may each include one or more optical fibers, optical waveguides, splitters, optical combiners, optical switches, optical lenses, optical prisms, optical beam splitters, and/or optical couplers. The radio frequency paths 100 and 98 may include radio frequency transmission line structures, conductive traces, conductive wiring, radio frequency waveguides, and the like.

An optical reference, such as optical reference 106, may be disposed (e.g., interposed) on optical path 104 between the output of optical mixer 102 and the input of secondary laser 92 and optical mixer 110. In other words, the output of optical mixer 102 may be coupled to the input of optical reference 106 through a first portion of optical path 104, and the output of optical reference 106 may be coupled to secondary laser 92 and optical mixer 110 through a second portion of optical path 104. The optical reference 106 may include optical components that remove, clean up, and/or reduce phase noise of optical signals (photons) received at its input through the optical path 104. The optical reference 106 may thereby output an optical signal (photon) onto the optical path 104 having reduced phase noise relative to photons received by the optical reference 106. The optical components in optical reference 106 may be configured such that photons traveling along optical path 104 within optical reference 106 are longer than photons within optical path 104 without optical reference 106. This photon retention allows the photons to circulate within the optical reference, increasing the photon lifetime and figure of merit in a manner that reduces the phase noise of the photons. The optical components may be passive components to help prevent the introduction of additional noise to the optical signal along the optical path 104. If desired, the optical reference 106 may be controlled by a temperature controller to further stabilize photons within the optical reference 106.

The optical reference 106 may comprise, for example, an optical delay line. The optical delay line may comprise one or more long optical fibers (e.g., optical fibers having a length of several meters or kilometers). Additionally or alternatively, the optical reference 106 may include an optical resonator. The optical resonator resonantly circulates received photons within the optical resonator with a high Q factor (e.g., where the Q factor varies with how long the photons remain within the optical resonator). Generally, the optical delay line is not frequency selective, but the optical resonator is frequency selective (e.g., functions similar to an optical filter for received photons). At the same time, the optical resonator is significantly smaller than the optical delay line and is therefore easier to integrate into a compact device such as device 10. Additionally or alternatively, the optical reference 106 may include any other desired optical component for reducing phase noise of photons received from the output of the optical mixer 102.

During operation, primary laser 90 may emit a first optical local oscillator signal LO1 on optical path 94. The secondary laser 92 may emit a second optical local oscillator signal LO2 on an optical path 118. Output terminals 120 and 122 may transmit optical local oscillator signals LO1 and LO2, respectively, to clock other components in device 10. For example, in implementations in which clock circuit 75 is used to clock THF communications using transceiver 26 (fig. 1), terminal 122 may be coupled to optical path 62 and terminal 120 may be coupled to optical path 64 of fig. 6.

Clock circuit 75 may include a plurality of control/feedback loops for minimizing phase noise and jitter in the optical LO signals provided to output terminals 120 and 122. As shown in fig. 8, the clock circuit 75 may include at least a first self-injection locking ring (e.g., an outer ring) around the primary laser 90 and a second self-injection locking ring (e.g., an inner ring) around the secondary laser 92. At least a portion of the second self-injection locking ring may form a portion of the first self-injection locking ring.

For example, the output of the primary laser 90, the optical path 94, the optical mixer 102, the optical path 104, the optical mixer 110, and the optical path 116 may form a first self-injection locking loop, as shown by path 114 (sometimes referred to herein as a self-injection locking loop 114, a self-injection locking loop path 114, or a loop path 114). The output of the secondary laser 92, the optical path 118, the UTC PD 96, the radio frequency path 100, the optical mixer 102, and a portion of the optical path 104 extending from the optical mixer 102 to the input of the secondary laser 92 may form a second self-injection locking loop, as shown by path 112 (sometimes referred to herein as a self-injection locking loop 112, a self-injection locking loop path 112, or a loop path 112). The optical reference 106 may be disposed on (e.g., may form part of) the two self-injection locking rings 112 and 114.

The primary laser 90 may emit a first optical local oscillator signal LO1 at a first optical frequency F1 (e.g., 200,000 ghz). The secondary laser 92 may emit a second optical local oscillator signal LO2 at a second optical frequency F2 (e.g., 200,300 ghz). The second optical frequency F2 may be offset from the first optical frequency F1 by a frequency offset Y (e.g., y=200, 300GHz-200,000 ghz=300 GHz). The optical frequencies F1 and F2, and thus the frequency offset Y, may be selected such that the frequency offset Y is a radio frequency, such as the frequency of the THF signal 32 to be transmitted by the antenna 36 and/or the THF signal 34 to be received by the antenna (e.g., 300GHz, 100GHz to 1000GHz, etc.) fed using the optical local oscillator signals LO1 and LO2.

The optical path 94 may illuminate the UTC PD 96 with an optical local oscillator signal LO1. The optical path 118 may simultaneously illuminate the UTC PD 96 using the optical local oscillator signal LO2. UTC PD 96 may generate radio frequency signal RFSIG in response to illumination by optical local oscillator signals LO1 and LO2 (e.g., by heterodyning optical local oscillator signals LO1 and LO2 on UTC PD 96). UTC PD 96 may transmit radiofrequency signal RFSIG to a first input of optical mixer 110 via radiofrequency path 98, and radiofrequency signal RFSIG to a second input of optical mixer 102 via radiofrequency path 100. The radiofrequency signal RFSIG may have a frequency equal to the frequency offset Y (e.g., 300 GHz).

The optical mixer 102 may generate the self-injection locking signal SILS based on the first optical local oscillator signal LO1 and the radio frequency signal RFSIG (e.g., by mixing, multiplying, or modulating the first optical local oscillator signal LO1 with the radio frequency signal RFSIG). The optical mixer 102 may output a self injection locking signal SILS on an optical path 104. The self-injection locking signal SILS may be an optical signal having a frequency equal to the sum of the first optical frequency F1 of the first optical local oscillator signal LO1 and the frequency of the radio frequency signal RFSIG (e.g., the self-injection locking signal SILS may have a frequency equal to f1+y=200,000 ghz+300ghz=200,300 ghz, which is the same as the second optical frequency F2 of the secondary laser 92).

The optical reference 106 may be received from the optical mixer 102 via the optical path 104 from the injection locking signal SILS. The optical reference 106 may clear, reduce, and/or remove phase noise in the self-injection locking signal SILS to produce a phase noise reduced self-injection locking signal SILS' (e.g., by cycling, resonating, or retaining photons in the self-injection locking signal SILS within the optical reference 106 for an extended period of time). The optical reference 106 may output a phase noise reduced self injection locking signal SILS' via the optical path 104 and transmit it to the input of the secondary laser 92 and to a second input of the optical mixer 110.

The optical mixer 110 may generate a modified self-injection locking signal SILS "based on the phase noise reduced self-injection locking signal SILS' and the radio frequency signal RFSIG received via the radio frequency path 98 (e.g., by mixing, multiplying, or modulating the first optical local oscillator signal LO1 with the radio frequency signal RFSIG) by outputting the modified self-injection locking signal SILS at a desired optical frequency of the primary laser 90 (e.g., at a first optical frequency F1 of the first optical local oscillator LO1, such as 200,000 ghz).

In some implementations described herein as examples, the optical mixer 102 and the optical mixer 110 may perform opposite single sideband modulated carrier rejection (SSB-CS) operations on their respective inputs to generate both a modified self injection locking signal SILS "and a self injection locking signal SILS at their respective frequencies based on the same radio frequency signal RFSIG output by the UTC PD 96. For example, the right sideband modulated carrier suppression (+ssb-CS) performed by the optical mixer 102 may include mixing the first optical local oscillator LO1 with the radio frequency signal RFSIG while filtering out both the carrier (at the first optical frequency F1 or 200,000 GHz) and the left sideband (at the frequency F1-Y or 200,000GHz-300 GHz), leaving the right sideband to form the self-injection locking signal SILS at the frequency f1+y or 200,000ghz+300 ghz=200,300 GHz. On the other hand, the left sideband modulated carrier rejection (-SSB-CS) performed by the optical mixer 110 may include mixing the phase noise reduced self-injection locking signal SILS 'with the radio frequency signal RFSIG while filtering out the carrier (e.g., f1+y or 200,300 ghz) and the right sideband (at frequency (f1+y) +y or 200,300ghz+300 ghz=200,600 ghz) at the frequency of the phase noise reduced self-injection locking signal SILS', leaving the left sideband to form the modified self-injection locking signal SILS at the first optical frequency F1 (200,000 ghz).

In this way, the optical mixer 110 may shift the phase noise reduced self-injection locking signal SILS' back to the frequency of the primary laser 90 (as a modified self-injection locking signal SILS "). The optical path 116 may provide a modified self-injection locking signal SILS to the primary laser 90. The primary laser 90 may be self-injection locked (e.g., in one or more iterations or loops around the self-injection locking loop 114) using the modified self-injection locking signal SILS ". Once the primary laser 90 has been self injection locked, the phase noise reduced self injection locking signal SILS' may be used to self injection lock the secondary laser 92. This may configure the ripple (e.g., phase change) in the secondary laser 92, and thus the second optical local oscillator signal LO2, to closely follow any ripple (e.g., phase change) in the primary laser 90, and thus the primary optical local oscillator signal LO1, thereby configuring the frequency and phase separation between the primary optical local oscillator signal LO1 and the secondary optical local oscillator signal LO2 to be constant over time. This may be used to allow components clocked using optical local oscillator signals LO1 and LO2 to exhibit extremely stable performance over time (e.g., insensitive to phase noise and jitter) without using an external reference oscillator.

The example of fig. 8 is illustrative and not limiting. If desired, one or more Phase Locked Loops (PLLs) and/or Frequency Locked Loops (FLLs) (not shown) may be coupled around one or both lasers to further lock the optical local oscillator signals LO1 and LO2 together (e.g., to perform coarse and then fine laser tuning until the clock circuit is locked). Although described herein as lasers, primary laser 90 and secondary laser 92 may be any desired light source/emitter. For example, lasers 90 and 92 may form LO light source 70 of fig. 7, and/or may form LO light sources 70A and 70B of fig. 7, respectively. Primary laser 90 may sometimes be referred to as a leading laser and secondary laser 92 may sometimes be referred to as a trailing laser.

Fig. 9 is a flowchart of exemplary operations involved in generating phase noise free optical local oscillator signals LO1 and LO2 (e.g., for clocking one or more components in device 10, such as wireless circuit 24 of fig. 1) using clock circuit 75.

At operation 130, the primary laser 90 may begin illuminating the UTC PD 96 through the optical path 94 using the first optical local oscillator signal LO 1. The secondary laser 92 may begin to simultaneously illuminate the UTC PD 96 through the optical path 118 using the second optical local oscillator signal LO 2.

At operation 132, UTC PD 96 may generate (generate) a radio frequency signal RFSIG using (based on) optical local oscillator signals LO1 and LO2 (e.g., by heterodyning the optical local oscillator signals). UTC PD 96 may transmit an rf signal RFSIG to optical mixer 110 via rf path 98 and to optical mixer 102 via rf path 100.

At operation 134, the optical mixer 102 may generate the self injection locking signal SILS using (based on) the first optical local oscillator signal LO1 and the radio frequency signal RFSIG (e.g., by electrically modulating or mixing the first optical local oscillator signal LO1 with the radio frequency signal RFSIG). If desired, the optical mixer 102 may perform a first SSB-CS operation, such as right side band modulated carrier rejection (+SSB-CS), on the optical local oscillator signal LO1 and the radio frequency signal RFSIG. This can be used to filter out the carrier wave (at the first optical frequency F1 of the optical local oscillator signal LO 1) and the left sideband (at a frequency equal to F1 minus the frequency Y of the radiofrequency signal RFSIG) so as to form the self-injection locking signal SILS from the remaining right sideband (at a frequency equal to F1 plus the frequency Y of the radiofrequency signal RFSIG). The optical mixer 102 may transmit the self-injection locking signal SILS to the optical reference 106 via the optical path 104.

At operation 136, the optical reference 106 may reduce the phase noise of the self-injection locking signal SILS to generate a phase noise reduced self-injection locking signal SILS' (e.g., by allowing photons of the self-injection locking signal SILS to circulate, resonate, or remain within the optical reference 106 in a manner that increases photon lifetime, increases quality factor, and/or reduces the phase noise of the photons). The optical reference 106 may transmit a phase noise reduced self injection locking signal SILS' to the secondary laser 92 and the optical mixer 110 via the optical path 104.

At operation 138, the optical mixer 110 may shift the frequency of the phase noise reduced self-injection locking signal SILS 'back to the frequency of the primary laser LO1 based on (using) the radio frequency signal RFSIG (e.g., by electrically modulating or mixing the phase noise reduced self-injection locking signal SILS' with the radio frequency signal RFSIG) to generate a modified self-injection locking signal SILS for the self-injection locking primary laser 90. If desired, the optical mixer 110 may perform a second SSB-CS operation on the noise-reduced self-injection locking signal SILS' and the radio frequency signal RFSIG (e.g., as opposed to the first SSB-CS operation performed by the optical mixer 102). For example, the second SSB-CS operation may be left side band modulated carrier rejection (-SSB-CS). This may be used to filter out both the carrier (at frequency f1+y) and the right sideband (at frequency (f1+y) +y) to form a modified self-injection locking signal SILS from the remaining left sideband (at a frequency equal to (f1+y) -y=f1, which is the first optical frequency of the primary laser 90). The optical mixer 110 may emit the modified self-injection locking signal SILS "to the primary laser 90 via an optical path 116.

At operation 140, the optical path 116 may be from the injection primary laser 90 using the modified self injection locking signal SILS ". The primary laser 90 may, for example, include a laser cavity between two mirrors that hold photons within the laser cavity. If no self-injection is performed, both mirrors are 100% reflective. However, when self-injection is performed, one of the mirrors is less than 100% reflective, allowing a modified self-injection locking signal SILS "(e.g. an optical signal at the same frequency as the first optical local oscillator signal LO1 on the surface) to be launched from the optical path 116 through the mirror into the laser cavity. The self-injected photons from the modified self-injection locking signal SILS "have been cleared (de-correlated) of phase noise by the optical reference 106 and thus may help the primary laser 90 output the phase noise reduced first optical local oscillator signal LO1. Processing may loop back to operation 132 via path 142 to perform multiple iterations of self-injection locking on primary laser 90 until primary laser 90 is locked (e.g., exhibits sufficiently low phase noise).

Once the primary laser 90 has been locked (e.g., self-injection locked), processing may proceed from operation 140 to operation 146 via path 144. At this point, the phase noise of the first optical local oscillator signal LO1 has been cleaned, and the self injection locking signal SILS (and thus the phase noise reduced self injection locking signal SILS') generated using the phase noise cleaned first optical local oscillator signal LO1 is locked to the primary laser 90. The optical path 104 may then self-inject the secondary laser 92 using the phase noise reduced self-injection locking signal SILS'. The secondary laser 92 may, for example, include a laser cavity between two mirrors that hold photons within the laser cavity. If no self-injection is performed, both mirrors are 100% reflective. However, when self-injection is performed, one of the mirrors is less than 100% reflective, allowing a phase noise reduced self-injection locking signal SILS' (e.g. an optical signal at the same frequency (f2=f1+y) as the second optical local oscillator signal LO 2) to be emitted from the optical path 104 through the mirror into the laser cavity. The self-injected photons from the phase-noise reduced self-injection locking signal SILS' have been cleared (de-correlated) of phase noise by the optical reference 106 and have been locked to the primary laser 90, which thus helps the second laser 92 to output the phase-noise reduced second optical local oscillator signal LO2 in a locked manner with the first optical local oscillator signal LO1. Processing may loop back to operation 132 via path 148 to perform multiple iterations of self-injection locking on secondary laser 92 until secondary laser 92 is locked (e.g., exhibits sufficiently low phase noise).

Once secondary laser 92 is locked, secondary laser 92 is locked to primary laser 90 and clock circuit 75 is itself locked. Processing may then proceed via path 150 to operation 152. Clock circuit 75 may use optical local oscillator signals LO1 and LO2 to clock one or more processing operations in device 10 (e.g., device 10 may perform subsequent processing operations as clocked by optical local oscillator signals LO1 and LO 2). For example, UTC PD 42 in device 10 may transmit and/or receive a THF signal with minimal phase noise and jitter using optical local oscillator signals LO1 and LO2 generated by clock circuit 75. Since the optical local oscillator signals LO1 and LO2 have been locked together, any subsequent phase change in the first optical local oscillator signal LO1 will match a corresponding phase change in the second optical local oscillator signal LO2, thereby minimizing phase noise and allowing the optical local oscillator signals LO1 and LO2 to be used for stable and consistent timing purposes over time (e.g., allowing the optical local oscillator signals to heterodyne on the UTC PD for transmission and/or reception of THF signals such that the phase of THF signals remains stable over time).

Fig. 10 is a graph showing how clock circuit 75 may use self-injection locking loops 114 and 112 with optical reference 106 to reduce phase noise. The horizontal axis of fig. 10 plots frequency (e.g., in Hz on a logarithmic scale). The vertical axis of FIG. 10 plots phase noise (e.g., in dBc/Hz). Curve 160 depicts a general (abstract) trend of phase noise of clock circuit 75 (e.g., phase noise of two optical local oscillator signals LO1 and LO2, which may particularly have separate values located on opposite sides of curve 160) prior to any iteration of the self-injection locking operation of fig. 9. Curve 162 depicts the general (abstract) trend of the phase noise of clock circuit 75 after one iteration of the self-injection locking operation of fig. 9. Curve 164 depicts the general (abstract) trend of the phase noise of clock circuit 75 after two iterations of the self-injection locking operation of fig. 9. Curve 166 depicts the general (abstract) trend of the phase noise of clock circuit 75 after three iterations of the self-injection locking operation of fig. 9. As shown by curves 160-166, the self-injection locking operation is used to reduce phase noise after a sufficient number of iterations, as indicated by arrow 168. Curves 160-166 may have other shapes in practice.

In the example of fig. 9, clock circuit 75 includes a single optical reference 106. The clock circuit 75 may include two optical references (e.g., dual optical references), if desired. Fig. 11 is a circuit diagram showing one example of how clock circuit 75 may include two optical references. As shown in fig. 11, clock circuit 75 may include a first optical reference 170 disposed on optical path 94. Thus, in this example, the optical reference 106 on the optical path 104 forms a second optical reference of the clock circuit 75.

Optical reference 170 may receive a first optical local oscillator signal LO1 from primary laser 90 (e.g., through a first portion of optical path 94 coupled to output terminal 120). The optical reference 170 may use (based on) the first optical local oscillator signal LO1 to generate a phase noise reduced first optical local oscillator signal LO1'. Optical reference 170 may transmit phase noise reduced first optical local oscillator signal LO1' to first optical mixer 102 and UTC PD 96 through a second portion of optical path 94. Optical reference 170 may include optical components that remove, clean up, and/or reduce phase noise of optical signals (photons) received at its input via optical path 94. Optical reference 170 may include, for example, an optical delay line, an optical resonator, and/or other optical components.

This example is illustrative, and in other implementations, the optical reference 170 may be disposed on the optical path 116 (e.g., at location 172) and may reduce the phase noise of the modified self-injection locking signal SILS "prior to self-injection of the primary laser 90. In general, optical reference 106 may be disposed on (form a part of) self-injection locking rings 112 and 114, while optical reference 170 is disposed only on (form a part of) self-injection locking ring 114 (but not on self-injection locking ring 112). This may, for example, allow primary laser 90 and secondary laser 92 to be self-injection locked simultaneously, rather than first self-injection locking primary laser 90 and then self-injection locking secondary laser 92.

Fig. 12 is a flowchart of exemplary operations involved in generating phase noise free optical local oscillator signals LO1 and LO2 using clock circuit 75 with optical references 106 and 170 (fig. 11).

At operation 180, the primary laser 90 may begin to emit a first optical local oscillator signal LO1 on the optical path 94. Secondary laser 92 may begin to emit a second optical local oscillator signal LO2 on optical path 118.

At operation 182, optical reference 170 may reduce the phase noise of first optical local oscillator signal LO1 to generate a phase noise reduced first optical local oscillator signal LO1' (e.g., by allowing photons of first optical local oscillator signal LO1 to circulate, resonate, or remain within optical reference 106 in a manner that increases photon lifetime, increases quality factor, and/or reduces the phase noise of the photons). Optical reference 170 may transmit phase noise reduced first optical local oscillator signal LO1' to UTC PD 96 and optical mixer 102 via optical path 94.

At operation 184, the optical path 94 may illuminate the UTC PD 96 with a phase noise reduced first optical local oscillator signal LO 1'. The optical path 118 may simultaneously illuminate the UTC PD 96 with the second optical local oscillator signal LO 2.

At operation 186, UTC PD 96 may generate (generate) a radio frequency signal RFSIG using (based on) the phase noise reduced first and second optical local oscillator signals LO1 and LO2 (e.g., by heterodyning the optical local oscillator signals). UTC PD 96 may transmit an rf signal RFSIG to optical mixer 110 via rf path 98 and to optical mixer 102 via rf path 100.

At operation 188, the optical mixer 102 may generate the self-injection locking signal SILS using (based on) the phase noise reduced first optical local oscillator signal LO1 and the radio frequency signal RFSIG (e.g., by electrically modulating or mixing the phase noise reduced first optical local oscillator signal LO1' with the radio frequency signal RFSIG). If desired, the optical mixer 102 may perform a first SSB-CS operation, such as right side band modulated carrier rejection (+SSB-CS), on the phase noise reduced optical local oscillator signal LO1' and the radio frequency signal RFSIG. The optical mixer 102 may transmit the self-injection locking signal SILS to the optical reference 106 via the optical path 104.

At operation 190, the optical reference 106 may reduce the phase noise of the self-injection locking signal SILS to generate a phase noise reduced self-injection locking signal SILS' (e.g., by allowing photons of the self-injection locking signal SILS to circulate, resonate, or remain within the optical reference 106 in a manner that increases photon lifetime, increases quality factor, and/or reduces the phase noise of the photons). The optical reference 106 may transmit a phase noise reduced self injection locking signal SILS' to the secondary laser 92 and the optical mixer 110 via the optical path 104.

At operation 192, the optical mixer 110 may shift the frequency of the phase noise reduced self-injection locking signal SILS 'back to the frequency of the primary laser LO1 based on (using) the radio frequency signal RFSIG (e.g., by electrically modulating or mixing the phase noise reduced self-injection locking signal SILS' with the radio frequency signal RFSIG) to generate a modified self-injection locking signal SILS for the self-injection locking primary laser 90. If desired, the optical mixer 110 may perform a second SSB-CS operation on the noise-reduced self-injection locking signal SILS' and the radio frequency signal RFSIG (e.g., as opposed to the first SSB-CS operation performed by the optical mixer 102). For example, the second SSB-CS operation may be left side band modulated carrier rejection (-SSB-CS). The optical mixer 110 may emit the modified self-injection locking signal SILS "to the primary laser 90 via an optical path 116.

At operation 194, the optical path 116 may be from the injection primary laser 90 using the modified self injection locking signal SILS ". The optical path 104 may use a phase noise reduced self-injection locking signal SILS' to simultaneously self-inject the secondary laser 92. Since in this example both the first optical local oscillator signal LO1 and the second optical local oscillator signal LO2 reduce phase noise during each iteration of the self-injection locking loops 112 and 114, the primary laser 90 and the secondary laser 92 may be self-injection locked simultaneously and thus to each other without requiring the primary laser 90 to be self-injection locked before the secondary laser 92 is subsequently self-injection locked. Processing may loop back to operation 186 via path 196 to perform multiple iterations of self-injection locking of primary laser 90 and secondary laser 92 until primary laser 90 and secondary laser 92 are locked and thus each other.

Once primary laser 90 has been locked and secondary laser 92 has been locked, processing may proceed from operation 194 to operation 200 via path 198. Clock circuit 75 may use optical local oscillator signals LO1 and LO2 to clock one or more processing operations in device 10 (e.g., device 10 may perform subsequent processing operations as clocked by optical local oscillator signals LO1 and LO 2). For example, UTC PD 42 in device 10 may transmit and/or receive a THF signal with minimal phase noise and jitter using optical local oscillator signals LO1 and LO2 generated by clock circuit 75. Since the optical local oscillator signals LO1 and LO2 have been locked together, any subsequent phase change in the first optical local oscillator signal LO1 will match a corresponding phase change in the second optical local oscillator signal LO2, allowing the optical local oscillator signals LO1 and LO2 to be used for timing purposes that are stable and consistent over time (e.g., allowing the optical local oscillator signals to heterodyne on the UTC PD for transmission and/or reception of the THF signals such that the phase of the THF signals remains stable over time). In implementations where optical reference 170 is disposed at location 172 of FIG. 11, the operations of FIG. 12 may be modified accordingly.

Fig. 13 is a graph showing how clock circuit 75 may reduce phase noise when self-injection locking ring 114 includes optical references 170 and 106 and self-injection locking ring 112 includes optical reference 106 but does not include optical reference 170 (e.g., as shown in fig. 11). The horizontal axis of fig. 13 plots frequency (e.g., in Hz on a logarithmic scale). The vertical axis of FIG. 13 plots phase noise (e.g., in dBc/Hz). Curve 202 depicts the general (abstract) trend of the phase noise of clock circuit 75 (e.g., the phase noise of the two optical local oscillator signals LO1 and LO2, which may in particular have separate values located on opposite sides of curve 160) prior to any iteration of the self-injection locking operation of fig. 12. Curve 204 depicts the general (abstract) trend of the phase noise of clock circuit 75 after one or more iterations of the self-injection locking operation of fig. 12. As shown by curves 202 and 204, the self-injection locking operation is used to reduce phase noise, as indicated by arrow 206. Curves 202 and 204 may have other shapes in practice.

The optical components described herein (e.g., MZM modulator, waveguide, phase shifter, UTC PD, etc.) may be implemented in or using plasmonic technology, if desired. For example, the optical mixers described herein (e.g., MZM 58 of fig. 6, optical mixer 102 of fig. 8 and 11, optical mixer 110 of fig. 8 and 11, etc.) may be plasmon-based optical modulators.

As used herein, the term "concurrent" refers to at least partial overlap in time. In other words, a first event and a second event are referred to herein as "concurrent" with each other if at least some of the first event occurs concurrently with at least some of the second event (e.g., if at least some of the first event occurs during, concurrently with, or upon at least some of the second event). The first event and the second event may occur simultaneously if they are simultaneous (e.g., if the entire duration of the first event overlaps in time with the entire duration of the second event), but the first event and the second event may also occur simultaneously if they are non-simultaneous (e.g., if the first event begins before or after the second event begins, if the first event ends before or after the second event ends, or if the first event and the second event are partially non-overlapping in time). As used herein, the term "when …" is synonymous with "concurrent".

The device 10 may collect and/or use personally identifiable information. It is well known that the use of personally identifiable information should follow privacy policies and practices that are recognized as meeting or exceeding industry or government requirements for maintaining user privacy. In particular, personally identifiable information data should be managed and processed to minimize the risk of inadvertent or unauthorized access or use, and the nature of authorized use should be specified to the user.

The methods and operations described above in connection with fig. 1-13 (e.g., the operations of fig. 9 and 12) may be performed by components of device 10 using software, firmware, and/or hardware (e.g., dedicated circuitry or hardware). The software code for performing these operations may be stored on a non-transitory computer readable storage medium (e.g., a tangible computer readable storage medium) stored on one or more of the components of the device 10 (e.g., the 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 medium may include a drive, non-volatile memory such as non-volatile random access memory (NVRAM), a removable flash drive or other removable medium, other types of random access memory, and the like. Software stored on the non-transitory computer readable storage medium may be executed by processing circuitry (e.g., processing circuitry 18 of fig. 1, etc.) on one or more of the components of device 10. The processing circuitry may include a microprocessor, a Central Processing Unit (CPU), an application-specific integrated circuit with processing circuitry, or other processing circuitry.

According to one embodiment, there is provided a clock circuit including: a first light source configured to generate a first optical Local Oscillator (LO) signal at a first frequency; a second light source configured to generate a second optical LO signal at a second frequency; a photodiode configured to be illuminated by the first optical LO signal and the second optical LO signal; a mixer having a first input coupled to the first light source and a second input coupled to the photodiode; an optical path coupling an output of the optical mixer to an input of the second light source; and an optical reference disposed on the optical path.

According to another embodiment, the optical reference comprises an optical delay line.

According to another embodiment, the optical reference comprises an optical resonator.

According to another embodiment, the clock circuit includes an additional mixer having a third input coupled to the optical path, a fourth input coupled to the photodiode, and an output coupled to an input of the first light source.

According to another embodiment, the photodiode is configured to generate a radio frequency signal based on the first and second optical LO signals and to transmit the radio frequency signal to the second input of the mixer and the fourth input of the additional mixer.

According to another embodiment, the mixer comprises a first electro-optical mixer and the additional mixer comprises a second electro-optical mixer.

According to another embodiment, the first electro-optical mixer comprises a first mach-zehnder modulator (MZM), and the second electro-optical mixer comprises a second MZM.

According to another embodiment, the first electro-optical mixer is configured to generate a first optical signal on the optical path by mixing the radio frequency signal with the first optical LO signal while filtering out a first carrier and a left sideband of the first carrier.

According to another embodiment, the second electro-optical mixer is configured to generate a second optical signal at its output by mixing the radio frequency signal with the first optical signal while filtering out a second carrier and a right sideband of the second carrier.

According to another embodiment, the second frequency is separated from the first frequency by a frequency offset, the radio frequency signal has a frequency equal to the frequency offset, the first optical signal has the second frequency, and the second optical signal has the first frequency.

According to another embodiment, the optical path is configured to self-injection lock the second light source using the first optical signal, and the second electro-optical mixer is configured to self-injection lock the first light source using the second optical signal.

According to another embodiment, the clock circuit includes an additional optical path coupling an output of the additional optical reference to the input of the first light source and an additional optical reference disposed on the additional optical path.

According to another embodiment, the clock circuit comprises an additional optical path coupling the output of the first light source to the first input of the mixer and an additional optical reference arranged on the additional optical path.

According to one embodiment, there is provided a clock circuit including: a first laser configured to generate a first optical Local Oscillator (LO) signal; a second laser configured to generate a second optical LO signal; a first self-injection locking ring path coupled around the first laser and configured to self-injection lock the first laser; a second self-injection locking ring path coupled around the second laser and configured to self-injection lock the second laser; and an optical reference forming a portion of both the first self-injection locking loop path and the second self-injection locking loop path.

According to a further embodiment, the clock circuit comprises an additional optical reference forming part of the first self-injection locking ring path but not forming part of the second self-injection locking ring path.

According to another embodiment, the clock circuit comprises: a photodiode configured to generate a radio frequency signal based on the first optical LO signal and the second optical LO signal; a first mixer having a first input coupled to the first laser and a second input coupled to the photodiode, the first mixer configured to generate a first optical signal based on the radio frequency signal and the first optical LO signal; a second mixer having a first input coupled to the photodiode, an output coupled to an input of the first laser, and a second input; and an optical path coupling an output of the first optical mixer to the second input of the second mixer, the second mixer configured to generate a second optical signal based on the radio frequency signal and the first optical signal, the optical reference disposed on the optical path, the first self-injection locking loop path including the first mixer, the optical path, the optical reference, and the second mixer, and the second self-injection locking loop path including the photodiode, the first mixer, the optical reference, and a portion of the optical path.

According to one embodiment, there is provided an electronic device including: a first laser configured to emit a first optical Local Oscillator (LO) signal; a second laser configured to emit a second optical LO signal; an antenna configured to communicate a radio frequency signal based on the first and second optical LO signals; a photodiode configured to be illuminated by the first optical LO signal and the second optical LO signal; a first ring path coupled between an output of the first laser and an input of the first laser; a second ring path coupled between an output of the second laser and an input of the second laser, the photodiode disposed on the second ring path; a first mixer disposed on the first loop path and the second loop path; a second mixer disposed on the first ring path; and an optical reference disposed on the first ring path between the first mixer and the second mixer and on the second ring path between the first mixer and the second laser.

According to another embodiment, the first mixer has a first input coupled to the output of the first laser, a second input coupled to the photodiode, and an output coupled to the input of the optical reference, the second mixer has a third input coupled to the output of the optical reference, a fourth input coupled to the photodiode, and an output coupled to the input of the first laser, and the output of the optical reference is coupled to the input of the second laser.

The foregoing is merely exemplary and various modifications may be made to the embodiments described. The foregoing embodiments may be implemented independently or may be implemented in any combination.

Claims

1. A clock circuit, the clock circuit comprising:

a first light source configured to generate a first optical Local Oscillator (LO) signal at a first frequency;

a second light source configured to generate a second optical LO signal at a second frequency;

a photodiode configured to be illuminated by the first optical LO signal and the second optical LO signal;

A mixer having a first input coupled to the first light source and a second input coupled to the photodiode;

an optical path coupling an output of the optical mixer to an input of the second light source; and

an optical reference disposed on the optical path.

2. The clock circuit of claim 1, wherein the optical reference comprises an optical delay line.

3. The clock circuit of claim 1, wherein the optical reference comprises an optical resonator.

4. The clock circuit of claim 1, further comprising:

an additional mixer having a third input coupled to the optical path, a fourth input coupled to the photodiode, and an output coupled to an input of the first light source.

5. The clock circuit of claim 4, wherein the photodiode is configured to generate a radio frequency signal based on the first and second optical LO signals and to transmit the radio frequency signal to the second input of the mixer and the fourth input of the additional mixer.

6. The clock circuit of claim 5, wherein the mixer comprises a first electro-optic mixer and the additional mixer comprises a second electro-optic mixer.

7. The clock circuit of claim 6, wherein the first electro-optical mixer comprises a first mach-zehnder modulator (MZM) and the second electro-optical mixer comprises a second MZM.

8. The clock circuit of claim 6, wherein the first electro-optical mixer is configured to generate a first optical signal on the optical path by mixing the radio frequency signal with the first optical LO signal while filtering out a first carrier and a left sideband of the first carrier.

9. The clock circuit of claim 8, wherein the second electro-optical mixer is configured to generate a second optical signal at its output by mixing the radio frequency signal with the first optical signal while filtering out a second carrier and a right sideband of the second carrier.

10. The clock circuit of claim 9, wherein the second frequency is separated from the first frequency by a frequency offset, the radio frequency signal has a frequency equal to the frequency offset, the first optical signal has the second frequency, and the second optical signal has the first frequency.

11. The clock circuit of claim 10, wherein the optical path is configured to self-injection lock the second light source using the first optical signal and the second electro-optical mixer is configured to self-injection lock the first light source using the second optical signal.

12. The clock circuit of claim 4, further comprising:

an additional optical path coupling the output of the additional optical reference to the input of the first light source; and

an additional optical reference disposed on the additional optical path.

13. The clock circuit of claim 1, further comprising:

an additional optical path coupling an output of the first light source to the first input of the mixer; and

an additional optical reference disposed on the additional optical path.

14. A clock circuit, the clock circuit comprising:

a first laser configured to generate a first optical Local Oscillator (LO) signal;

a second laser configured to generate a second optical LO signal;

A first self-injection locking ring path coupled around the first laser and configured to self-injection lock the first laser;

a second self-injection locking ring path coupled around the second laser and configured to self-injection lock the second laser; and

an optical reference forming part of both the first self-injection locking loop path and the second self-injection locking loop path.

15. The clock circuit of claim 14, wherein the optical reference comprises an optical delay line.

16. The clock circuit of claim 14, wherein the optical reference comprises an optical resonator.

17. The clock circuit of claim 14, further comprising:

an additional optical reference that forms part of the first self-injection locking ring path but does not form part of the second self-injection locking ring path.

18. The clock circuit of claim 14, further comprising:

a photodiode configured to generate a radio frequency signal based on the first optical LO signal and the second optical LO signal;

A first mixer having a first input coupled to the first laser and a second input coupled to the photodiode, the first mixer configured to generate a first optical signal based on the radio frequency signal and the first optical LO signal;

a second mixer having a first input coupled to the photodiode, an output coupled to an input of the first laser, and a second input; and

an optical path coupling an output of the first optical mixer to the second input of the second mixer, wherein the second mixer is configured to generate a second optical signal based on the radio frequency signal and the first optical signal, the optical reference is disposed on the optical path, the first self-injection locking loop path includes the first mixer, the optical path, the optical reference, and the second mixer, and the second self-injection locking loop path includes the photodiode, the first mixer, the optical reference, and a portion of the optical path.

19. An electronic device, the electronic device comprising:

A first laser configured to emit a first optical Local Oscillator (LO) signal;

a second laser configured to emit a second optical LO signal;

an antenna configured to transmit a radio frequency signal based on the first and second optical LO signals;

a first ring path coupled between an output of the first laser and an input of the first laser;

a second ring path coupled between an output of the second laser and an input of the second laser, the photodiode disposed on the second ring path;

a first mixer disposed on the first loop path and the second loop path;

a second mixer disposed on the first ring path; and

an optical reference is disposed on the first ring path between the first mixer and the second mixer and on the second ring path between the first mixer and the second laser.

20. The electronic device of claim 19, wherein the first mixer has a first input coupled to an output of the first laser, a second input coupled to the photodiode, and an output coupled to an input of the optical reference, the second mixer has a third input coupled to an output of the optical reference, a fourth input coupled to the photodiode, and an output coupled to an input of the first laser, and the output of the optical reference is coupled to an input of the second laser.