Electronic device with spatial ranging calibration capability

Abstract

The invention relates to an electronic device with spatial ranging calibration capability. An electronic device may include a radar circuit. The control circuit may calibrate the radar circuit using a multi-tone calibration signal. A first mixer may up-convert the calibration signal for transmission by a transmit antenna. A de-chirp mixer may mix a calibration signal output by the first mixer with a calibration signal received by a receive antenna or loopback path to produce a baseband multi-tone calibration signal. The baseband signal will be offset from the DC by a frequency gap. This may prevent DC noise or other system effects from interfering with the calibration signal. A control circuit may scan the first mixer within a radio frequency at which the radar circuit operates to estimate a power drop and a phase shift of the radar circuit based on a baseband calibration signal. A distortion circuit may distort a transmit signal used in a spatial ranging operation to invert the estimated power drop and phase shift.

Description

[0001] Related application citations

[0002] This application is a divisional application of the invention patent application with Chinese national application number 202210039402.7, application date January 13, 2022, and invention name “Electronic device with space ranging calibration capability”.

[0003] This patent application claims priority to U.S. patent application No. 17 / 150,974, filed on January 15, 2021, which is hereby incorporated by reference in its entirety. Technical Field

[0004] The present disclosure relates generally to electronic devices and, more particularly, to electronic devices having wireless circuitry. Background Art

[0005] Electronic devices often have wireless capabilities. These devices have wireless circuitry, including one or more antennas. The wireless circuitry is sometimes used to perform spatial ranging operations, where radio frequency signals are used to estimate the distance between the electronic device and an external object.

[0006] Providing wireless circuitry that accurately estimates this distance can be challenging. For example, wireless circuitry often introduces undesirable power drops and / or phase shifts into the radio frequency signal. If care is not taken, these power drops and phase shifts can cause the wireless circuitry to inaccurately estimate the distance between the electronic device and the external object. Summary of the Invention

[0007] An electronic device may include a wireless circuit. The wireless circuit may include a spatial ranging circuit and an antenna. In one embodiment described herein as an example, the spatial ranging circuit includes a radar circuit, such as a frequency modulated continuous wave (FMCW) radar circuit. The antenna may include a transmitting antenna for a transmitting chain in the radar circuit and a receiving antenna for a receiving chain in the radar circuit. The transmitting chain may include a transmitting signal generator (e.g., a chirp generator), a digital-to-analog converter (DAC), a first mixer, and a signal splitter. The receiving chain may include a second mixer (e.g., a dechirp mixer) and a measurement circuit. A path (e.g., a dechirp path) may couple the signal splitter to the second mixer. The transmitting signal generator may generate a transmitting signal (e.g., a chirp signal) that is transmitted by the transmitting antenna and received by the receiving antenna. The Doppler shift in the received signal may be processed to estimate or detect the velocity of an external object. The time-correlated frequency difference between the transmitted signal and the received signal may be processed to estimate or detect the distance between the device and the external object. The angle of arrival of the received signal may also be estimated.

[0008] If care is not taken, components of the radar circuitry may impose undesirable power drops and phase shifts on the chirp signal, limiting the accuracy of the estimated position and / or velocity. The control circuitry can calibrate the radar circuitry to mitigate these issues. During calibration, the DAC can transmit a multi-tone calibration signal. This multi-tone calibration signal consists of two or more tones separated by a frequency gap. A first mixer can upconvert the multi-tone calibration signal, which is then transmitted via an antenna or loopback path before being received by a second mixer. If necessary, an additional mixer can upconvert the multi-tone calibration signal to a higher frequency before being transmitted via the antenna or loopback path, and an additional mixer can downconvert the multi-tone calibration signal received via the loopback path or antenna. A second mixer can mix the multi-tone calibration signal output by the first mixer with the multi-tone calibration signal received via the antenna or loopback path to produce a baseband multi-tone calibration signal. This baseband multi-tone calibration signal is frequency-gapped with the DC offset. This prevents DC noise, LO leakage, or other system / process noise from interfering with the baseband multi-tone calibration signal.

[0009] The control circuitry can sweep the first mixer (or additional mixers in embodiments where the radar circuitry includes additional mixers) across different operating frequencies of the radar circuitry while the second mixer continues to generate a baseband multi-tone calibration signal. The measurement circuitry can measure the amplitude and phase of the baseband multi-tone calibration signal. The control circuitry can estimate the power drop and phase shift of the radar circuitry based on the amplitude and phase measurements. Distortion circuitry in the transmit chain, such as predistortion circuitry, can then predistort the transmit signal to invert the power drop and phase shift effects of the radar circuitry, thereby ensuring that accurate range, position, and / or velocity estimates can be obtained over the lifetime of the device.

[0010] One aspect of the present disclosure provides a wireless communication circuit for performing a spatial ranging operation on an external object using a transmitted signal. The wireless circuit may include a digital-to-analog converter (DAC) configured to generate a multi-tone calibration signal having a first tone and a second tone separated from the first tone by a frequency gap. The wireless circuit may include a first mixer configured to up-convert the multi-tone calibration signal from a first frequency band to a second frequency band. The wireless circuit may include a second mixer having a first input configured to receive a multi-tone calibration signal in a second frequency band from an output of the first mixer via a signal path, and a second input configured to receive a multi-tone calibration signal in a second frequency band via an intermediate circuit communicatively coupled between the output of the first mixer and the second input. The second mixer may be configured to generate a baseband multi-tone calibration signal. The wireless circuit may include a measurement circuit configured to measure the amplitude of the baseband multi-tone calibration signal. The wireless circuitry may include a control circuit configured to estimate a power drop of the intermediate circuit based on the amplitude measured by the measurement circuit.The control circuitry may be configured to distort the transmit signal based on the estimated power drop.

[0011] One aspect of the present disclosure provides a method for calibrating a radar circuit. The method may include, in a transmit chain of the radar circuit, generating a multi-tone calibration signal having a first tone and a second tone spaced apart from the first tone by a frequency gap of less than 20 MHz using a digital-to-analog converter (DAC). The method may include, in the transmit chain, upconverting the multi-tone calibration signal from baseband to a first frequency band using a first mixer. The method may include, in the transmit chain, upconverting the multi-tone calibration signal from the first frequency band to a second frequency band using a second mixer. The method may include, in a receive chain of the radar circuit, downconverting the multi-tone calibration signal upconverted by the second mixer from the second frequency band to the first frequency band using a third mixer. The method may include, in the receive chain, generating a baseband multi-tone calibration signal by mixing the multi-tone calibration signal upconverted by the first mixer with the multi-tone calibration signal downconverted by the third mixer, wherein the baseband multi-tone calibration signal is spaced apart from a direct current (DC) frequency by a frequency gap. The method may include, using control circuitry, estimating a power drop and a phase shift of the radar circuitry based on a baseband multi-tone calibration signal generated by a dechirp mixer. The method may include, using predistortion circuitry in the transmit chain, predistorting a chirped signal transmitted by the transmit chain based on the power drop and phase shift estimated by the control circuitry.

[0012] One aspect of the present disclosure provides an electronic device. The electronic device may include a first antenna. The electronic device may include a second antenna. The electronic device may include radar circuitry configured to generate a transmit signal transmitted using the first antenna. The second antenna may be configured to receive a reflected version of the transmit signal transmitted using the first antenna. The electronic device may include control circuitry configured to perform a spatial ranging operation based on the reflected version of the transmit signal received using the second antenna. The electronic device may include a digital-to-analog converter (DAC) in the radar circuitry. The DAC may be configured to generate a multi-tone calibration signal transmitted using the first antenna. The multi-tone calibration signal may include a first tone and a second tone spaced apart from the first tone by a frequency gap of less than 20 MHz. The control circuitry may be configured to use the multi-tone calibration signal to estimate power drop of the radar circuitry. The control circuitry may be configured to distort the transmit signal based on the estimated power drop. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a functional block diagram of an illustrative electronic device with calibrated spatial ranging circuitry, according to some embodiments.

[0014] Figure 2 is a circuit diagram of an illustrative spatial ranging circuit calibrated using a multi-tone calibration signal, according to some implementations.

[0015] Figure 3 is a flow chart of illustrative operations involved in calibrating spatial ranging circuitry using a multi-tone calibration signal, according to some implementations.

[0016] Figure 4 is a frequency plot of an exemplary multi-tone calibration signal that may be used to estimate power drop and / or phase shift of a spatial ranging circuit, according to some implementations.

[0017] Figure 5 is a graph of exemplary power reduction that can be estimated using a multi-tone calibration signal, according to some embodiments.

[0018] Figure 6 is a diagram illustrating how an exemplary digital predistortion circuit may be used to compensate for an estimated power drop and / or phase shift of a spatial ranging circuit, according to some embodiments.

[0019] Figure 7 is a diagram of an illustrative spatial ranging circuit having at least a first mixer and a second mixer that can be calibrated using a multi-tone calibration signal, according to some embodiments. DETAILED DESCRIPTION

[0020] Figure 1The electronic device 10 may be: a computing device, such as a laptop computer, a desktop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular phone, a media player, or other handheld or portable electronic device; a smaller device, such as a wristwatch device, a pendant device, a headset or earpiece device, a device embedded in glasses; or other equipment worn on the user's head; or other wearable or miniature devices, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system (such as a system in which electronic equipment with a display is installed in an information kiosk or a car), a voice-controlled speaker connected to wireless Internet, a home entertainment device, a remote control device, a game controller, a peripheral user input device, a wireless base station or access point, equipment that implements the functions of two or more of these devices; or other electronic equipment.

[0021] like Figure 1 As shown in the functional block diagram in FIG, device 10 may include components located on or within an electronic device housing, such as housing 12. Housing 12 (sometimes referred to as a casing) may be formed from plastic, glass, ceramic, fiber composite materials, metal (e.g., stainless steel, aluminum, metal alloys, etc.), other suitable materials, or combinations of these materials. In some cases, part or all of housing 12 may be formed from a dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other cases, housing 12 or at least some of the structures comprising housing 12 may be formed from metal elements.

[0022] Device 10 may include control circuitry 14. Control circuitry 14 may include storage, such as storage circuitry 16. 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), etc. Storage circuitry 16 may include storage integrated within device 10 and / or removable storage media.

[0023] Control circuitry 14 may include processing circuitry, such as processing circuitry 18. Processing circuitry 18 may be used to control the operation of device 10. Processing circuitry 18 may include one or more microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application-specific integrated circuits, central processing units (CPUs), 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. Software code for performing operations in device 10 may be stored on storage circuitry 16 (e.g., storage circuitry 16 may include a non-transitory (tangible) computer-readable storage medium storing software code). This software code may sometimes be referred to as program instructions, software, data, instructions, or code. The software code stored on storage circuitry 16 may be executed by processing circuitry 18.

[0024] Control circuitry 14 may be used to run software on device 10, such as satellite navigation applications, internet browsing applications, voice over internet protocol (VOIP) phone call applications, email applications, media playback applications, operating system functions, and the like. To support interaction with external equipment, control circuitry 14 may be used to implement communication protocols. Communication protocols that may be implemented using control circuitry 14 include: Internet Protocol, wireless local area network (WLAN) protocols (e.g., IEEE 802.11 protocols—sometimes referred to as ), protocols for other short-range wireless communication links such as The present invention relates to a wireless personal area network (WPAN) protocol or other wireless personal area network (WPAN) protocol, an IEEE 802.11ad protocol (e.g., an ultra-wideband protocol), a cellular telephone protocol (e.g., a 3G protocol, a 4G (LTE) protocol, a 5G protocol, etc.), an antenna diversity protocol, a satellite navigation system protocol (e.g., a global positioning system (GPS) protocol, a global navigation satellite system (GLONASS) protocol, etc.), an antenna-based space ranging protocol (e.g., a radio detection and ranging (RADAR) protocol for signals transmitted at millimeter and centimeter wave frequencies or other desired distance detection protocols), or any other desired communication protocol. Each communication protocol may be associated with a corresponding radio access technology (RAT), which specifies the physical connection method used to implement the protocol.

[0025] Device 10 may include input-output circuitry 20. Input-output circuitry 20 may include input-output devices 22. Input-output devices 22 may be used to allow data to be supplied to device 10 and to allow data to be provided from device 10 to external devices. Input-output devices 22 may include user interface devices, data port devices, and other input-output components. For example, input-output devices 22 may include touch sensors, displays (e.g., touch-sensitive displays and / or force-sensitive displays), light-emitting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), scroll wheels, touchpads, 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 a display to detect pressure applied to the display), and the like. In some configurations, keyboards, headsets, displays, pointing devices such as trackpads, mice, and joysticks, and other input-output devices may be coupled to device 10 using wired or wireless connections (e.g., some of input-output devices 22 may be peripheral devices coupled to a main processing unit or other portion of device 10 via wired or wireless links).

[0026] Input-output circuitry 20 may include wireless circuitry 24 to support wireless communications. Wireless circuitry 24 (sometimes referred to herein as wireless communications circuitry 24) may include two or more antennas 40. Wireless circuitry 24 may also include baseband processor circuitry, transceiver circuitry, amplifier circuitry, filter circuitry, switching circuitry, radio frequency transmission lines, and / or any other circuitry for transmitting and / or receiving radio frequency signals using antennas 40.

[0027] Wireless circuitry 24 may transmit and / or receive radio frequency signals within a corresponding band of radio frequencies (sometimes referred to herein as a communication band or simply a “band”). The bands processed by wireless circuitry 24 may include wireless local area network (WLAN) bands (e.g., (IEEE 802.11) or other WLAN communication bands) such as the 2.4 GHz WLAN band (e.g., 2400 MHz to 2480 MHz), the 5 GHz WLAN band (e.g., 5180 MHz to 5825 MHz), 6E band (e.g., 5925 MHz to 7125 MHz) and / or other frequency bands (e.g., 1875 MHz to 5160 MHz); Wireless Personal Area Network (WPAN) bands such as 2.4 GHz frequency bands or other WPAN communication bands; cellular telephone frequency bands (e.g., frequency bands from about 600 MHz to about 5 GHz, 3G frequency bands, 4G LTE frequency bands, 5G new radio frequency range 1 (FR1) bands below 10 GHz, 5G new radio frequency range 2 (FR2) bands between 20 GHz and 60 GHz, etc.); other centimeter or millimeter wave frequency bands between 10 GHz and 300 GHz; near field communication frequency bands (e.g., 13.56 MHz); satellite navigation frequency bands (e.g., GPS frequency bands from 1565 MHz to 1610 MHz, Global Navigation Satellite System (GLONASS) frequency bands, BeiDou Satellite Navigation System (BDS) frequency bands, etc.); ultra-wideband (UWB) frequency bands operating under the IEEE 802.15.4 protocol and / or other ultra-wideband communication protocols; communication frequency bands under the 3GPP wireless communication standard family; communication frequency bands under the IEEE 802.XX standard family, and / or any other desired frequency bands of interest.

[0028] Any desired antenna structure may be used to form antenna 40. For example, antenna 40 may include an antenna having a resonant element formed from a loop antenna structure, a patch antenna structure, an inverted-F antenna structure, a slot antenna structure, a planar inverted-F antenna structure, a helical antenna structure, a monopole antenna, a dipole, a hybrid of these designs, etc. Filter circuits, switching circuits, impedance matching circuits, and / or other antenna tuning components may be adjusted to adjust the frequency response and wireless performance of antenna 40 over time.

[0029] The radio frequency signals processed by antenna 40 may be used to communicate wireless communication data between device 10 and an external wireless communication device (e.g., one or more other devices such as device 10). The wireless communication data may be transmitted bidirectionally or unidirectionally by wireless circuitry 24. 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, etc.

[0030] Wireless circuitry 24 may additionally or alternatively use antennas 40 to perform spatial ranging operations. In the event that wireless circuitry 24 both transmits wireless communication data and performs spatial ranging operations, one or more of the same antennas 40 may be used for both transmitting wireless communication data and performing spatial ranging operations. In another specific implementation, wireless circuitry 24 may include a set of antennas 40 that only transmit wireless communication data and a set of antennas 40 that only perform spatial ranging operations.

[0031] When performing spatial ranging operations, antenna 40 may transmit radio frequency signal 36. Wireless circuitry 24 may transmit radio frequency signal 36 in a corresponding radio frequency band (e.g., a band including frequencies greater than approximately 10 GHz, greater than approximately 20 GHz, less than 10 GHz, etc.). Radio frequency signal 36 may reflect off of an object external to device 10, such as external object 34. External object 34 may be, for example, the ground, a building, a wall, furniture, a ceiling, a person, a body part, an animal, a vehicle, a landscape or geographical feature, an obstacle, or any other object or entity external to device 10. Antenna 40 may receive reflected radio frequency signal 38. Reflected signal 38 may be a reflected version of transmitted radio frequency signal 36 that has reflected off external object 34 and returned to device 10.

[0032] The control circuit 14 can process the transmitted radio frequency signal 36 and the received reflected signal 38 to detect or estimate the distance R between the device 10 and the external object 34. If necessary, the control circuit 14 can also process the transmitted and received signals to identify the two-dimensional or three-dimensional spatial position (orientation) of the external object 34, the speed of the external object 34, and / or the angle of arrival of the reflected signal 38. In one embodiment described herein as an example, the wireless circuit 24 uses a frequency modulated continuous wave (FMCW) radar scheme to perform spatial ranging operations. This is merely exemplary, and other radar schemes or spatial ranging schemes (e.g., OFDM radar schemes, FSCW radar schemes, phase coded radar schemes, etc.) can generally be used.

[0033] To support spatial ranging operations, wireless circuitry 24 may include spatial ranging circuitry, such as radar circuitry 26. In one embodiment, sometimes described herein as an example, radar circuitry 26 includes FMCW radar circuitry that performs spatial ranging using an FMCW radar scheme. Therefore, radar circuitry 26 may sometimes be referred to herein as FMCW radar circuitry 26. Radar circuitry 26 may use one or more antennas 40 to transmit a radio frequency signal 36 (e.g., a continuous wave of radio frequency energy, as in the case of an FMCW radar scheme). One or more antennas 40 may also receive a reflected signal 38 (e.g., a continuous wave of radio frequency energy, as in the case of an FMCW radar scheme). Radar circuitry 26 may process radio frequency signal 36 and reflected signal 38 to identify / estimate range R, the position of external object 34, the velocity of external object 34, and / or the angle of arrival of reflected signal 38. In embodiments where radar circuitry 26 uses an FMCW radar scheme, the Doppler shift in the continuous wave signal may be detected and processed to identify the velocity of external object 34, and the time-correlated frequency difference between radio frequency signal 36 and reflected signal 38 may be detected and processed to identify range R and / or the position of external object 34. For example, using a continuous wave signal to estimate distance R may allow control circuit 10 to reliably distinguish external objects 34 from other background or slower moving objects.

[0034] like Figure 1 As shown, radar circuitry 26 may include transmit (TX) signal generator circuitry, such as transmit signal generator 28. Transmit signal generator 28 may generate a transmit signal for transmission via antenna 40. In some embodiments described herein by way of example, transmit signal generator 28 includes a chirp generator that generates a chirp signal for transmission via antenna 40 (e.g., in embodiments where radar circuitry 26 utilizes an FMCW radar scheme). Therefore, transmit signal generator 28 may sometimes be referred to herein as chirp generator 28. Transmit signal generator 28 may, for example, generate a chirp signal as a continuous wave transmission of radio frequency signal 36. For example, the chirp signal may be formed by periodically increasing the frequency of the transmit signal in a linear manner over time. Radar circuitry 26 may also include digital-to-analog converter (DAC) circuitry, such as DAC 32. DAC 32 may convert the transmit signal (e.g., the chirp signal) from the digital domain to the analog domain before transmission by antenna 40 (e.g., in radio frequency signal 36). Radar circuitry 26 may also include analog-to-digital converter (ADC) circuitry such as ADC 42. ADC 42 may convert signals from the analog domain to the digital domain for subsequent processing by control circuitry 14. Although for clarity, the ADC 42 may be used to convert signals from the analog domain to the digital domain for subsequent processing by control circuitry 14. Figure 1 In the example shown, control circuitry 14 is shown as separate from wireless circuitry 24, but wireless circuitry 24 may include processing circuitry that forms part of processing circuitry 18 and / or memory circuitry that forms part of memory circuitry 16 of control circuitry 14 (e.g., portions of control circuitry 14 may be implemented on wireless circuitry 24).

[0035] In practice, components within wireless circuitry 24 may introduce frequency-dependent power drops and / or phase shifts into the RF signal transmitted by antenna 40. For example, power drops may be caused by circuit, filter, and / or cable frequency dependencies, as well as the directivity / gain limitations of antenna 40 with respect to frequency. When using an FMCW radar scheme, frequency-dependent power drops can increase the width of the main target lobe in the baseband (BB) spectrum, which can reduce the range resolution of radar circuitry 26. Furthermore, the signal-to-noise ratio (SNR) in the baseband signal may be degraded due to the discrete and fixed gain stages within wireless circuitry 24. Therefore, when performing spatial ranging operations, it may be desirable to avoid or compensate for any power drops or phase shifts introduced by wireless circuitry 24.

[0036] To compensate for the power drop and phase shift introduced by the radio circuitry 24 when performing spatial ranging operations, the radio circuitry 24 may estimate or track the power drop and phase shift introduced by the radio circuitry 24 during operation throughout the lifetime of the device 10. The DAC 32 may generate a multi-tone calibration signal that is used to estimate the power drop and phase shift. The multi-tone calibration signal includes two or more tones separated by a relatively small gap in frequency space (sometimes referred to herein as a frequency gap Δf). Once the power drop and / or phase shift have been estimated, the radar circuitry 26 may use the distortion circuitry 30 to distort the transmit signal (e.g., a chirp signal) generated by the transmit signal generator 28. The distortion circuitry 30 may include a pre-distortion circuit that pre-distorts the transmit signal before it is transmitted by the antenna 40, and / or may include a post-distortion circuit that distorts the receive signal. The distortion introduced by distortion circuit 30 can be used to invert the effects of power drops and phase shifts, thereby ensuring that radar circuit 26 can continue to produce accurate estimates of range R, position, velocity, and / or angle of arrival, even if the power drops or phase shifts change over time. Distortion circuit 30 can be implemented using hardware and / or software on control circuit 14, using one or more processors in radar circuit 26 and / or control circuit 14, using digital logic on radar circuit 26 (e.g., a separate digital pre-distortion circuit block), using analog circuitry in radar circuit 26 (e.g., a separate analog pre-distortion circuit block), etc. The distortion circuit can include, for example, a multiplier, a lookup table, a memory, and / or any other desired components for distorting an input signal to produce a distorted output signal (e.g., a pre-distorted output signal in embodiments in which distortion circuit 30 includes a pre-distortion circuit).

[0037] Figure 2 is a circuit diagram of radar circuit 26 (e.g., in an embodiment in which radar circuit 26 performs multiple frequency upconversions before being transmitted by antenna 40). If desired, the components of radar circuit 26 may be mounted to a common substrate (e.g., a shared rigid or flexible printed circuit board) or may be formed on a common integrated circuit (IC) or package. Figure 2 As shown, radar circuitry 26 may include a transmit chain 52 (sometimes referred to herein as a transmitter chain 52 , transmit line 52 , or transmit path 52 ) and a receive chain 54 (sometimes referred to herein as a receiver chain 54 , receive line 54 , or receive path 52 ).

[0038] Radar circuit 26 may have a first (transmit) port coupled to a first antenna 40, such as transmit antenna 40TX (e.g., transmit antenna 40TX may form part of transmit chain 52). Radar circuit 26 may have a second (receive) port coupled to a second antenna 40, such as receive antenna 40RX (e.g., receive antenna 40RX may form part of receive chain 54). A signal path, such as dechirp path 48, may couple transmit chain 52 to receive chain 54.

[0039] The transmit chain 52 may include a transmit signal generator 28 (e.g., a chirp generator), a DAC 32, a first mixer (such as mixer 56), amplifier circuits (such as amplifiers 58 and 66) (e.g., power amplifiers), a signal splitter (such as splitter 62), and a second RF mixer (such as mixer 64). The receive chain 54 may include an ADC 42, a phase and amplitude measurement circuit 88, a filter circuit (such as a low-pass filter (LPF) 76), a third mixer (such as a dechirp mixer 74), a fourth mixer (such as mixer 72), and an amplifier circuit (such as amplifier 70) (e.g., a low-noise amplifier (LNA)).

[0040] like Figure 2 As shown, the output of transmit signal generator 28 can be coupled to the input of DAC 32 (e.g., transmit signal generator 28 can be formed by digital logic in radar circuit 26 and can operate in the digital domain). The output of DAC 32 can be coupled to a first input of mixer 56 (e.g., via an I / Q signal path). Mixer 56 can have a second input that receives a local oscillator (LO) signal from Band 1 local oscillator (FB1LO) 50. The output of mixer 56 can be coupled to the input of amplifier 58. The output of amplifier 58 can be coupled to the input of splitter 62. Splitter 62 can have a first output terminal coupled to a first input of mixer 64. Mixer 64 can have a second input that receives an LO signal from Band 2 local oscillator (FB2LO) 46. The output of mixer 64 can be coupled to the input of amplifier 66. The output of amplifier 66 can be coupled to transmit antenna 40TX (e.g., via one or more RF transmission lines).

[0041] In receive chain 54, an input of amplifier 70 may be coupled to receive antenna 40RX. An output of amplifier 70 may be coupled to a first input of mixer 72. Mixer 72 may have a second input receiving an LO signal from FB2LO 46. An output of mixer 72 may be coupled to a first input of dechirp mixer 74. Dechirp mixer 74 may have a second input coupled to a second output terminal of splitter 62 via dechirp path 48. If desired, an amplifier such as amplifier 68 may be inserted in dechirp path 48. Although not shown for clarity, Figure 2 4. Although not shown in the example of FIG. 4, the dechirp path 48 may also include a signal splitter having a first output terminal and a second output terminal coupled to the dechirp mixer 74, with a 90 degree phase delay applied to the second output terminal (e.g., so that the dechirp mixer 74 can operate on I / Q signals). The output of the dechirp mixer 74 may be coupled to the input of the LPF 76 (e.g., via the I / Q signal path). The output of the LPF 76 may be coupled to the input of the phase and amplitude measurement circuit 88. The output of the phase and amplitude measurement circuit 88 may be coupled to the input of the ADC 42. The output of the ADC 42 may be coupled to the control circuit 14 (e.g., via the digital output path 78) via the digital output path 78. Figure 1 If desired, an optional loopback path 80 can couple the output of amplifier 66 in transmit chain 52 to the input of amplifier 70 in receive chain 54. If desired, a radio frequency coupler and / or switching circuit can be inserted in loopback path 80. Loopback path 80 can be used to calibrate radar circuitry 26 in the event that antennas 40TX and 40RX are not used for calibration.

[0042] The transmission lines in the wireless circuit 24 (e.g., the RF transmission line for coupling the mixer 64 to the transmit antenna 40TX, the RF transmission line for coupling the receive antenna 40RX to the mixer 72, etc.) may include coaxial cables, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, transmission lines formed by combinations of these types of transmission lines, etc. If desired, one or more of the transmission lines may be integrated into a rigid and / or flexible printed circuit board.

[0043] Figure 2The examples are merely illustrative. In general, other circuit architectures may be used to form radar circuit 26. Mixers 56 and 74 may be I / Q mixers. Additional filters, amplifiers, switches, delay stages, splitters, and / or other circuit components may be formed at other locations in radar circuit 26. For example, a bandpass filter may be inserted between amplifier 58 and splitter 62. If desired, phase and amplitude measurement circuit 88 may be formed at other locations or multiple locations (e.g., measurement circuit 88 may be coupled to the output of ADC 42, the input of ADC 42, and / or the input of LPF 76). If desired, mixers 64 and 72 and FB2LO 46 may be omitted. If desired, dechirp mixer 74 may operate in the digital domain (e.g., the output of ADC 42 may be coupled to the input of dechirp mixer 74, ADC 42 may be inserted into receive chain 54 at any desired location between receive antenna 40RX and the input of dechirp mixer 74, etc.). From Figure 1 The digital predistortion circuit and / or analog predistortion circuit of the distortion circuit 30 can be inserted at any desired location on the transmit chain 52 and / or receive chain 54. In addition to being used to perform the spatial ranging operation of the radar circuit 26, if necessary, the transmit antenna 40TX and / or the receive antenna 40RX can also be used to transmit and / or receive wireless communication data (for example, using a signal source not shown in the figure for clarity). Figure 2 ). The radar circuitry 26 may, for example, form part of a transmitter such as a 5G NR transmitter.

[0044] When performing spatial ranging operations, the transmit signal generator 28 can generate a digital transmit signal (e.g., a digital chirp signal) for subsequent transmission by the transmit antenna 40TX (e.g., using a continuous wave of radio frequency energy). The DAC 32 can convert the digital transmit signal into a corresponding analog transmit signal (e.g., an analog chirp signal). The DAC 32 can provide the analog transmit signal (e.g., such as an I / Q signal) to the mixer 56. The mixer 56 can use the FB1LO 50 to up-convert the analog transmit signal from baseband to the first frequency band FB1.

[0045] The first frequency band FB1 may be at a higher frequency than the baseband and lower frequency than the radio frequency signal 36 transmitted by the transmit antenna 40TX (eg, at a frequency where multiple up-conversions are performed). Figure 2As an example, RF signal 36 may be transmitted in a second frequency band FB2, such as a radio frequency (RF) band. Frequency band FB2 may include frequencies greater than 10 GHz (e.g., RF bands approximately 25 GHz, greater than 20 GHz, greater than 30 GHz, greater than 50 GHz, etc.) and / or frequencies less than 10 GHz. Frequency band FB1 may include frequencies less than frequency band FB2 (e.g., frequencies less than 10 GHz, less than 5 GHz, etc.). Frequency band FB1 may sometimes be referred to as an intermediate frequency (IF) band. In embodiments where mixers 64 and 72 are omitted, frequency band FB1 may be any desired frequency band (e.g., an RF band) above baseband.

[0046] Amplifier 58 can amplify the FB1 transmit signal (e.g., the FB1 chirp signal) for transmission to splitter 62. Distributing the transmit signal in frequency band FB1 rather than in higher frequency band FB2 can be used to minimize signal attenuation because the signal is distributed to a location in device 10 relatively far from DAC 32, particularly when frequency band FB2 is at a relatively high frequency that would otherwise be subject to significant signal attenuation (e.g., frequencies greater than 10 GHz). Splitter 62 can transmit the FB1 transmit signal to mixer 64 and de-chirp path 48 (e.g., splitter 62 can split the FB1 transmit signal between mixer 64 and de-chirp path 48). Mixer 64 can up-convert the FB1 transmit signal from frequency band FB1 to frequency band FB2 for transmission by transmit antenna 40TX. Amplifier 66 can amplify the FB2 transmit signal (e.g., the FB2 chirp signal), and transmit antenna 40TX can transmit the FB2 transmit signal (e.g., as RF signal 36). In an embodiment in which mixers 64 and 72 are omitted, transmit antenna 40TX may transmit the FB1 transmit signal as RF signal 36 .

[0047] The receiving antenna 40RX can receive the reflected signal 38 (e.g., transmitted by the transmitting antenna 40TX but has passed through the Figure 134 reflects a reflected version of the FB2 transmit signal. In examples where the transmit signal includes a chirp signal, the reflected signal 38 may sometimes be referred to herein as a reflected chirp signal. Amplifier 70 may amplify the reflected signal. Mixer 72 may downconvert the reflected signal from frequency band FB2 to frequency band FB1 for distribution to dechirp mixer 74 (e.g., as an FB1 reflected signal). Dechirp path 48 may transmit the FB1 transmit signal from splitter 62 to dechirp mixer 74. Amplifier 68 may amplify the FB1 transmit signal on dechirp path 48 (e.g., to compensate for attenuation associated with splitter 62). Dechirp mixer 74 may mix the FB1 transmit signal received via dechirp path 48 with the FB1 reflected signal received from mixer 72 to produce a baseband signal (e.g., a baseband chirp signal). In an embodiment in which mixers 64 and 72 are omitted, dechirp mixer 74 may mix the FB1 transmit signal received via dechirp path 48 with the FB1 reflected signal received by receive antenna 40RX. Dechirp mixer 74 may provide a baseband signal to LPF 76. LPF 76 may low-pass filter the baseband signal to remove noise, harmonic effects, etc. The baseband signal may be transmitted to ADC 42 (e.g., via phase and amplitude measurement circuit 88). ADC 42 may convert the baseband signal into a digital signal (e.g., a digital chirp signal). Control circuit 14 may process the baseband signal to estimate distance R, the position of external object 34, and / or the velocity of external object 34 ( Figure 1 ).

[0048] In practice, transmit antenna 40TX, receive antenna 40RX, transmission lines, filter circuits (which typically cannot support the full FMCW bandwidth), and other components in transmit chain 52 and receive chain 54 may introduce undesirable power drops and / or phase shifts to radar circuitry 26. For example, components along dashed path 82 may introduce power drops and / or phase shifts to the signal provided to dechirp mixer 74, which may be characterized by composite weight values k1 and k3. Similarly, components along dashed path 84 (or dashed path 86 if loopback path 80 is used for calibration instead of antennas 40TX and 40RX) may introduce power drops and / or phase shifts to the signal provided to dechirp mixer 74, which may be characterized by composite weight values k2 and k4.

[0049] If care is not taken, power drops and phase shifts may cause control circuitry 14 to generate inaccurate estimates of range R, position, and / or velocity. Furthermore, the amount of power drops and phase shifts may vary over time. Control circuitry 14 and radar circuitry 26 may perform calibration operations to estimate power drops and phase shifts and compensate for the estimated power drops and phase shifts, even if the power drops and phase shifts vary over time, thereby ensuring that control circuitry 14 can accurately estimate range R and the position / velocity of external objects throughout the life of device 10.

[0050] However, in practice, the presence of dechirp path 48, the relatively low RF bandwidth of the system after dechirping (e.g., 1 MHz to 10 MHz) given the relatively high RF bandwidth of the system (e.g., 3 GHz to 5 GHz), and the presence of DC / flicker noise or other process noise (e.g., LO leakage) at the baseband can make it particularly difficult to estimate the power drop and / or phase shift of radar circuitry 26. To mitigate these issues and ensure that accurate estimates of the power drop and phase shift are collected, a multi-tone calibration signal can be used to calibrate radar circuitry 26. The multi-tone calibration signal can include two or more tones (e.g., two tones, three tones, four tones, five tones, six tones, more than six tones, etc.) separated by a relatively small frequency gap Δf in frequency space.

[0051] like Figure 2 As shown, during the calibration operation, DAC 32 can generate a multi-tone calibration signal mtone at a baseband frequency. Transmit signal generator 28 can avoid transmitting a signal (e.g., a chirp signal) during the calibration operation. Mixer 56 can up-convert the multi-tone calibration signal mtone to frequency band FB1 using FB1LO 50. Amplifier 58 can amplify and transmit the multi-tone calibration signal mtone. Splitter 62 can provide the multi-tone calibration signal mtone to mixer 64. Splitter 62 can also provide the multi-tone calibration signal mtone to de-chirp mixer 74 via de-chirp path 48. Mixer 64 can up-convert the multi-tone calibration signal mtone to frequency band FB2, amplifier 66 can amplify the multi-tone calibration signal mtone, and transmit antenna 40TX can transmit the multi-tone calibration signal mtone.

[0052] Receive antenna 40RX can receive the multi-tone calibration signal mtone transmitted by transmit antenna 40TX (e.g., directly wirelessly transmitted in a closed-loop path). In another specific implementation, loopback path 80 can be used to transmit the multi-tone calibration signal mtone from the output of amplifier 66 to the input of amplifier 70. In this example, transmit antenna 40TX is not used to transmit the multi-tone calibration signal. Amplifier 70 can amplify the multi-tone calibration signal mtone received using receive antenna 40RX or loopback path 80.

[0053] Mixer 72 can downconvert the received multi-tone calibration signal mtone to frequency band FB1 using FB2LO 46. Dechirp mixer 74 can mix the multi-tone calibration signal mtone in frequency band FB1 received via dechirp path 48 with the multi-tone calibration signal mtone in frequency band FB1 received from mixer 72 to generate a baseband multi-tone calibration signal mtone′. LPF 76 can filter the baseband multi-tone calibration signal mtone′ to remove high-frequency mixer products from the baseband multi-tone calibration signal. Phase and amplitude measurement circuit 88 can measure the amplitude and / or phase of the baseband multi-tone calibration signal mtone′ and provide the measured amplitude and / or phase values to ADC 42. ADC 42 can convert the amplitude and / or phase values into digital data dat. The digital data dat can be provided to control circuit 14 via digital output path 78. Control circuit 14 can store the digital data dat in storage circuit 16 for subsequent processing. This example is merely illustrative, and phase and amplitude measurement circuitry 88 may be located at other points or points within receive chain 54, if desired.

[0054] This process can be repeated while scanning within different frequency bands FB2 (e.g., while changing the radio frequency of the multi-tone calibration signal mtone generated by mixer 64). This can be used to generate a complete estimate of the power drop and / or phase shift of FMCW radar circuit 26 across the operating (radio) frequency of radar circuit 26. Once each of the desired radio frequencies has been characterized, distortion circuit 30 ( Figure 1 ) can distort a subsequently transmitted signal (e.g., a chirp signal) to reduce the estimated power (as estimated using the multi-tone calibration signal mtone) and / or invert the phase. The distorted chirp signal can then be used to produce an accurate and reliable estimate of range R, velocity, and / or position.

[0055] Figure 3 is a flow chart of illustrative operations that may be performed by radar circuit 26 and control circuit 14 in calibrating radar circuit 26 (eg, in embodiments in which radar circuit 26 performs multiple frequency upconversions prior to transmission by antenna 40). Figure 3 Operations may be performed during manufacture, assembly, or testing of radar circuit 26 or device 10 (e.g., in a manufacturing system or factory) and / or may be performed during routine operation of device 10 by an end user (e.g., during the useful life of device 10).

[0056] At operation 100, the DAC 32 may generate a multi-tone calibration signal mtone. The DAC 32 may generate the multi-tone calibration signal so that each tone is spaced apart (in frequency) from one or two adjacent tones by a selected frequency gap Δf. The frequency gap Δf may be large enough so that each tone is different in frequency, but small enough so that each tone experiences approximately the same power drop and the frequency gap Δf is within the relatively small bandwidth of the ADC 42. By way of example, the frequency gap Δf may be 20 MHz, 15 MHz, 10 MHz, 9 MHz, 8 MHz, 7 MHz, 6 MHz, 5 MHz, 4 MHz, 3 MHz, 2 MHz, less than 20 MHz, less than 15 MHz, less than 10 MHz, less than 7 MHz, less than 6 MHz, less than 5 MHz, less than 4 MHz, or other values.

[0057] At operation 102, mixer 56 may upconvert the multi-tone calibration signal mtone from baseband to frequency band FB1. Amplifier 58 may pass the multi-tone calibration signal mtone in frequency band FB1 to splitter 62. Splitter 62 may transmit the multi-tone calibration signal mtone to dechirp mixer 74 via dechirp path 48. Splitter 62 may also transmit the multi-tone calibration signal mtone to mixer 64.

[0058] At operation 104, control circuit 14 may select a first FB2 frequency (e.g., a first RF band) for transmitting multi-tone calibration signal mtone. This frequency may be the first frequency in a sweep within the operating radio frequency of radar circuit 26 performed when calibrating the radar circuit. As an example, this frequency may be greater than 10 GHz or 20 GHz, or less than 10 GHz.

[0059] At operation 106, mixer 64 may upconvert the multi-tone calibration signal mtone from frequency band FB1 to the selected FB2 frequency (e.g., using FB2LO 46). Amplifier 66 may amplify the RF multi-tone calibration signal mtone. Transmit antenna 40TX may transmit the RF multi-tone calibration signal mtone, and receive antenna 40RX may receive the transmitted RF multi-tone calibration signal mtone. The transmit antenna transmits each of the tones in the RF multi-tone calibration signal mtone simultaneously in time and, if desired, with the same polarization. In another specific implementation, the RF multi-tone calibration signal mtone may be transmitted to receive chain 54 via loopback path 80 rather than being transmitted by transmit antenna 40TX.

[0060] At operation 108, the dechirp mixer 74 may receive the multi-tone calibration signal mtone in frequency band FB2 via the dechirp path 48. The mixer 72 may down-convert the RF multi-tone calibration signal mtone received via the receive antenna 40TX or the loopback path 80 to frequency band FB1. The dechirp mixer 74 may mix the multi-tone calibration signal mtone in frequency band FB1 received via the dechirp path 48 with the multi-tone calibration signal mtone in frequency band FB1 generated by the mixer 72 to generate a baseband multi-tone calibration signal mtone′.

[0061] At operation 110, LPF 76 may filter the baseband multi-tone calibration signal mtone' to remove high-frequency mixer products from the baseband multi-tone calibration signal. Phase and amplitude measurement circuit 88 may measure the amplitude and / or phase of the baseband multi-tone calibration signal mtone'. When a single tone is used for calibration, the single tone, after downconversion by dechirp mixer 74, is at DC and subject to interference from DC noise and other LO leakage. However, when a multi-tone calibration signal mtone is used for calibration, each of the tones in the baseband multi-tone calibration signal mtone' is offset from DC by a frequency gap Δf. This prevents DC / flicker noise or other process noise (e.g., LO leakage) at the baseband from interfering with the baseband multi-tone calibration signal mtone', thereby enabling more accurate power drop and / or phase shift estimates than when only a single tone is used for calibration. ADC 42 may convert the amplitude and phase values into corresponding digital data dat. Control circuit 14 may store the digital data dat for subsequent processing.

[0062] If the frequency remains in the sweep of FB2 frequencies for estimating power drop and phase shift, processing can proceed to operation 114, as shown by path 112. At operation 114, the control circuit 14 can select a new FB2 frequency for the next transmission of the multi-tone calibration signal mtone. The process can then loop back to operation 106, as shown by path 116, to continue collecting amplitude and / or phase values from the baseband multi-tone calibration signal mtone for each of the FB2 frequencies in the sweep. This can allow the control circuit 14 to collect a complete estimate of the power drop and / or phase of the FMCW radar circuit 26 as a function of frequency (e.g., across the operating frequency range of the radar circuit 26) for use in distorting subsequently transmitted chirp signals.

[0063] If no frequency remains in the sweep of FB2 frequencies used to estimate power drops and phase shifts, processing may proceed to operation 120 via path 118. At operation 120, control circuitry 14 may process digital data dat (e.g., as stored at each iteration of operations 106 through 110) to estimate the magnitude and / or phase shift effects introduced by components of radar circuitry 26. The magnitude effects may indicate a power drop for the system.

[0064] At operation 122, radar circuit 26 may resume transmission of the transmit signal to determine a distance R ( Figure 1 ). The transmission signal generator 28 can transmit a signal (e.g., a chirp signal). The control circuit 14 can use the distortion circuit 30 to pre-distort and / or post-distort the signal. The distortion circuit 30 ( Figure 1 ) may distort the signal based on the estimated power drop and / or phase shift effects (e.g., as identified at operation 120). The distortion circuit 30 may include a digital predistortion circuit that predistorts the chirp signal in the digital domain before conversion by the DAC 32, an analog predistortion circuit that predistorts the chirp signal after conversion by the DAC 32, and / or a post-distortion circuit that distorts the received signal.

[0065] At operation 124, the transmit antenna 40TX may radiate the transmit signal. The receive antenna 40RX may receive a reflected version of the transmit signal that has reflected off the external object 34 (e.g., as Figure 1 38). The distortion performed at operation 124 may be an inverse transform of the estimated power drop and / or phase shift effects so that the distorted chirp signal, after passing through transmit chain 52, is transmitted by transmit antenna 40TX and received by receive antenna 40RX as if no power drop or phase shift had been introduced by radar circuitry 26. For example, distortion circuitry 30 may perform the distortion by complex multiplying the transmit signal with a complex value that inverts the estimated power drop and / or phase shift, as well as any I / Q imbalance in the system.

[0066] If desired, radar circuitry 26 and control circuitry 14 may periodically (e.g., after a predetermined period of time has elapsed) recalibrate radar circuitry 26 (e.g., by looping back to operation 100) upon receiving a user input or application instructing device 10 to calibrate radar circuitry 26, upon detecting a change in operating conditions of device 10, upon detecting a deterioration in wireless performance of device 10, or in response to any other desired triggering condition. This may allow radar circuitry 26 to continue to generate accurate estimates of range R, position, and velocity throughout the operational life of device 10. In another embodiment, radar circuitry 26 may be calibrated only once.

[0067] Figure 4 Included is a frequency diagram illustrating how an exemplary multi-tone calibration signal mtone may be used to generate a baseband multi-tone calibration signal mtone' for estimating power drops and / or phase shifts. Figure 4 The example shows the simplest case where the multi-tone calibration signal mtone is a two-tone calibration signal having two tones separated by a frequency gap Δf. This two-tone calibration signal may also sometimes be referred to as a two-tone pair or a pair of tones. This example is merely illustrative, and in general, the multi-tone calibration signal mtone may include any desired number of two or more tones, each tone separated from one or two other tones by a frequency gap Δf.

[0068] like Figure 4 As shown in frequency graph 126 of FIG. 1 , DAC 32 can generate a multi-tone calibration signal mtone in a first frequency band B1 (e.g., baseband). DAC 32 can use a tone generator, synthesizer, or other digital circuitry / logic to generate the multi-tone calibration signal mtone. The tones of the multi-tone calibration signal mtone are spaced apart by a frequency gap Δf. Mixer 56 can up-convert the multi-tone calibration signal mtone to a second frequency band B2 (e.g., in frequency band FB1), as indicated by arrow 130. This signal can be provided to mixer 64 and dechirp path 48.

[0069] Mixer 64 can up-convert the multi-tone calibration signal mtone to a third frequency band B3 (e.g., in frequency band FB2), as indicated by arrow 132. The frequency gap Δf remains unchanged after each up-conversion. The multi-tone calibration signal mtone in frequency band B3 can be transmitted by transmit antenna 40TX or loopback path 80. Mixer 72 can down-convert the multi-tone calibration signal mtone from frequency band B3 back to frequency band B2. Dechirp mixer 74 can mix the multi-tone calibration signal mtone in frequency band B2 received via dechirp path 48 with the multi-tone calibration signal mtone in frequency band B2 down-converted by mixer 72 to recover the baseband multi-tone calibration signal mtone′, as indicated by arrow 136.

[0070] like Figure 4 As shown in the frequency diagram 128, the baseband multi-tone calibration signal mtone' has an amplitude A1, which is measured by the phase and amplitude measurement circuit 88 and converted to a digital value in the digital data dat by the ADC 42. The next radio frequency in the FB2 frequency sweep (e.g., Figure 3During subsequent iterations of operations 106 to 110 of . This can produce a multi-tone calibration signal mtone at another frequency in frequency band B3, such as the multi-tone calibration signal mtone represented by dashed arrow 135 in frequency plot 126. Due to a power drop in the system (e.g., as shown by power drop 134), the amplitude of this multi-tone calibration signal may be different from the amplitude of the previously transmitted multi-tone calibration signal. After mixing by dechirp mixer 74, the resulting baseband multi-tone calibration signal mtone′ may have an amplitude A2, as shown by dashed arrow 129 in frequency plot 128. Amplitude A2 may be measured by phase and amplitude measurement circuit 88 and converted to a digital value in digital data dat by ADC 42.

[0071] Amplitude A2 is less than amplitude A1 due to the frequency-dependent power drop imposed by the components of wireless circuitry 24. This may be repeated for each FB2 frequency in the sweep to recover a complete estimate of the power drop 134 across the operating frequencies as exhibited by wireless circuitry 24. In other words, radar circuitry 26 may shift the two-tone of the generated multi-tone calibration signal mtone along the frequency axis (e.g., by iteratively shifting the two-tone of the generated multi-tone calibration signal mtone). Figure 3 Operations 106 to 110 of FIG. 10 are repeated while maintaining a constant frequency gap Δf until the operating frequency range of radar circuit 26 is fully covered or sampled with two tones. Generally, the finer the offset of the radio frequency between each iteration, the more accurately the droop function (e.g., power droop 134) can be estimated. In embodiments where radar circuit 26 performs only a single upconversion, a sweep of the operating frequency can be performed within band B2 without further upconversion to band B3 (e.g., radar circuit 26 can transmit a multi-tone calibration signal across different FB1 frequencies where power droop 134 is observed within band FB1). Control circuit 14 can process the amplitude stored in digital data dat to estimate power droop 134. The phase of each baseband multi-tone calibration signal mtone' can also be estimated, as needed, to identify any phase shifts imposed by components of radar circuit 26.

[0072] In the case of using only a single-tone calibration signal, the resulting baseband tone will be restored at DC in the frequency diagram 128, where any measurement of amplitude / phase will be negatively affected by DC noise or LO leakage. However, by generating a multi-tone calibration signal mtone having two or more tones separated by a frequency gap Δf, the output of the mixing operation performed by the dechirp mixer 74 (the baseband multi-tone calibration signal mtone') will be offset in frequency from the DC offset frequency gap Δf. Therefore, the frequency gap Δf can be selected so that the baseband multi-tone calibration signal mtone' does not overlap with any DC noise, LO leakage or other baseband system noise. Compared to the case of using a single-tone calibration signal, this can allow for more accurate measurement of amplitude (e.g., amplitude A1, A2, etc.) and thus the collection of power drops, thereby allowing accurate estimates of distance R, position and velocity to be obtained over time.

[0073] Figure 5 Graphs illustrating three examples of potential power reductions that may be used by radar circuitry 26 and control circuitry 14 for predistorting a chirp signal based on the amplitude estimate of the baseband multi-tone calibration signal mtone′. Figure 5 As shown, curve CA illustrates a linear power drop that can be estimated by radar circuitry 26 and control circuitry 14. Curve CC illustrates a parabolic power drop that can be estimated by radar circuitry 26 and control circuitry 14. Curve CB illustrates a combination of linear and parabolic power drops that can be estimated by radar circuitry 26 and control circuitry 14. Each point on curves CA, CB, and CC can correspond to a corresponding radio frequency in the radio frequency sweep used in transmitting the multi-tone calibration signal mtone. A linear power drop, such as that associated with curve CA, is typically associated with the drop-off effect of a cable. A parabolic power drop, such as that associated with curve CC, is typically associated with the drop-off effect of antennas 40TX and 40RX. A combination of linear and parabolic power drops, such as that associated with curve CB, can represent, for example, a combination of the drop-off effect of a cable and antennas 40TX and 40RX. These examples are merely illustrative, and in practice, the estimated power drop can have other shapes.

[0074] The multi-tone calibration signal mtone is a dual-tone calibration signal (e.g., Figure 4 In the simplest case (as shown), the two-tone pair can be expressed as a complex tone using, for example, Equation 1.

[0075]

[0076] In Equation 1, ω is the angular frequency, Δ is the frequency gap Δf in units of angular frequency, "*" is the complex conjugate operator, "●" is the dot product operator, t is time, and j is the square root of -1. By executing Figure 3By operating the control circuit 14, the power drop and / or phase shift effects introduced by the radar circuit 26 can be estimated, and thus the complex weight values k1 and k2 can be estimated. The complex weight values k1 and k2 can then be used to form values for predistorting the chirp signal (e.g., the chirp signal can be multiplied by a value such as to pre-distort the chirp signal, thereby inverting the subsequent power drop and phase shift effects applied by components of the radar circuit 26).

[0077] In baseband of transmit chain 52, the two-tone calibration signal may be represented by one complex tone or two real tones consisting of four symmetrical complex tones, as given by Equation 2.

[0078] cos(ωt)+cos((1+Δ)ωt)=0.5((e -jωt +e jωt )+(e -j(1+Δ)ωt +e j(1+Δ)ωt )) (2)

[0080] In the FB2 (eg, RF) domain, the complex tone pair is frequency dependently attenuated, where the mixer path is represented by Expression 3 and the antenna path is represented by Expression 4.

[0081] ((k1e -jωt +k3e jωt )+(k1e -j(1+Δ)ωt +k3e j(1+Δ)ωt )) * (3)

[0082] (k2e -jωt +k4e jωt )+(k2e -j(1+Δ)ωt +k4e j(1+Δ)ωt ) (4)

[0083] In the baseband of the receive chain 54, after mixing by the dechirp mixer 74 (a process sometimes referred to herein as dechirping), several mixing products are generated. The ±n·ω mixing products at ≈1 GHz are attenuated by the LPF 76. The ±Δ·ω mixing products at less than 20 MHz (e.g., ≈1 MHz) can be evaluated to estimate the power drop. More generally, one complex tone can be modeled using expression 5, two complex tones can be modeled using expression 6, and four complex tones (e.g., two real tones) can be modeled using expression 7.

[0084]

[0085]

[0086] In expressions 6 and 7, "T" is the transposition operator and n is an integer exponent. Expression 6 represents five equations, two of which are linearly dependent on the other three. Simultaneously estimating two parameters of interest (low frequency) and (high frequency). IQ-imbalance correction can be performed before the down-estimation. Using two real tones can allow the radar circuit 26 to be produced at a lower manufacturing cost than using two complex tones. However, when using two complex tones, the two paths can be calibrated separately, while when using two real tones, the two paths cannot be calibrated separately. To support the generation of two complex tones, the size of the sin / cos table used to generate the multi-tone calibration signal mtone can be doubled or can be run at half rate, where, for example, the signal is interpolated in I / Q and complex mixing is used to reach the appropriate frequency band.

[0087] The distortion performed by distortion circuit 30 may be performed in the digital domain or in the analog domain. Figure 6 is a diagram showing one example of how the distortion circuit 30 may include a pre-distortion circuit in the digital domain. Figure 6 As shown, the input of DAC 32 can be coupled to digital circuit 140. Digital circuit 140 can include transmit signal generator 28 and predistortion circuit 146 (for example, distortion circuit 30 can include a digital predistortion (DPD) circuit such as predistortion circuit 146). The input of predistortion circuit 146 can be coupled to the output of transmit signal generator 28. The output of predistortion circuit 146 can be coupled to the input of DAC 32. DAC 32 can have an output 142 ( Figure 2 The predistortion circuit 146 may have a control path 144 that receives a control signal ctrl from the control circuit 14 .

[0088] The transmit signal generator 28 may generate a transmit signal (e.g., a chirp signal). The predistortion circuit 146 may multiply the transmit signal by a value used to predistort the transmit signal so that the predistortion in the transmit signal will offset the estimated power drop, phase shift, and / or any I / Q imbalance imposed by the components of the radar circuit 26. The control signal ctrl may include a value used by the predistortion circuit 146 to predistort the chirp signal. As the estimated power drop and / or phase shift changes over time, the control signal ctrl may change the value used by the predistortion circuit 146 to predistort the transmit signal. The DAC 32 may convert the predistorted transmit signal from the digital domain to the analog domain. Figure 6The examples are merely illustrative. Other pre-distortion schemes or architectures may be used. Pre-distortion circuit 146 may alternatively be implemented in the analog domain. Distortion circuit 30 may additionally or alternatively include post-distortion circuitry that operates on the received signal to compensate for power drops and phase shifts.

[0089] In this manner, device 10 can perform power droop estimation for the full RF bandwidth of radar circuitry 26, even if receive chain 54 does not support the full RF bandwidth. At the same time, direct access to the RF signal is not required to perform the power droop estimation. This can be used to reduce the receive chain bandwidth, thereby reducing current consumption in the system. Calibrating radar circuitry 26 using the multi-tone calibration signal mtone can allow device 10 to select a baseband offset frequency (e.g., via selection of a frequency gap Δf) to an ideal, system-dependent tone position so that the baseband multi-tone calibration signal mtone' is unaffected by system impairments, LO noise, etc. Power droop estimation and compensation can be performed during final production testing of device 10 and / or during the lifetime of device 10 to adapt droop compensation to any potential aging effects in device 10. Furthermore, droop tracking and compensation throughout the lifecycle of device 10 can be used to detect changes in the operation of device 10, such as when a housing or cover is attached to device 10, allowing device 10 to adjust system configuration (e.g., gain settings, background cancellation, etc.) accordingly.

[0090] wherein the radar circuit 26 performs multiple up-conversions Figures 2 to 4 The example of is merely one illustrative implementation showing how the multi-tone calibration signal mtone may be used to calibrate radar circuit 26. In general, radar circuit 26 may perform any desired number of one or more upconversions and may include any desired number of two or more mixers. Figure 7 is a circuit diagram of the radar circuit 26 in an example in which the radar circuit 26 performs at least one up-conversion and includes at least two mixers.

[0091] like Figure 7 As shown, radar circuitry 26 may include a first mixer, such as mixer 150 coupled to an output of DAC 32 (e.g., via an I / Q path), a signal splitter, such as splitter 154 having an input coupled to the output of mixer 150, a second mixer, such as mixer 152 (e.g., a dechirp mixer) having a first input coupled to a first output of splitter 154 via a signal (e.g., dechirp) path 158, and circuitry 156 (e.g., one or more line drops) coupled between a second output of splitter 154 and a second input of mixer 152. Other circuit components, such as amplifiers, filters, ADCs (e.g., Figure 2ADC 42) or other components can be inserted at any desired location within radar circuit 26. Circuit 156 may include other parts of radar circuit 26 (e.g., antenna, loopback path, transmission line, amplifier, filter, etc.) that introduce power drops and phase shifts to radar circuit 26. For example, when radar circuit 26 performs the following steps: Figure 2 In the illustrated embodiment of multiple upconversion, circuit 156 may include mixers 64 and 72, amplifiers 66 and 70, and antennas 40TX and 40RX. Circuit 156 may sometimes be referred to herein as an intermediate circuit.

[0092] During the space ranging operation, the DAC 32 may use the transmit signal generator 28 ( Figure 2 ) is passed to the mixer 150. The mixer 150 may use the LO 160 to up-convert the transmit signal to a higher frequency, such as Figure 2 1 or 2) in frequency band FB1 or frequency band FB2 (e.g., LO 160 may include Figure 2 FB1LO 50 or FB2LO 46). Splitter 154 can pass the up-converted transmit signal to mixer 152 through signal path 158 and to circuit 156. Circuit 156 can transmit the up-converted transmit signal (e.g., as Figure 1 RF signal 36) and can receive a corresponding reflected signal (e.g., Figure 1 The circuit 156 may pass the received reflected signal to the mixer 152. The mixer 152 may mix the received signal with the transmitted signal received via the signal path 158 to produce a corresponding baseband signal at the output path 162. Figure 1 ) can process the baseband signal and the transmitted signal to identify the distance R, position and / or speed of the external object 34.

[0093] During calibration, DAC 32 may transmit a multi-tone calibration signal mtone. Mixer 150 may upconvert the multi-tone calibration signal. Splitter 154 may transmit the upconverted multi-tone calibration signal to mixer 152 via signal path 158 and to circuit 156. Circuit 156 may transmit the upconverted multi-tone calibration signal (e.g., over the air in a closed loop or via a loopback path) and then receive it at mixer 152. Mixer 152 may mix the upconverted multi-tone calibration signal received via signal path 158 with the upconverted multi-tone calibration signal received from circuit 156 to generate a baseband multi-tone calibration signal mtone′. Control circuit 14 may repeat this process while sweeping mixer 150 across different frequencies (e.g., the operating frequency of radar circuit 26). Control circuit 14 may use the baseband multi-tone calibration signal generated by mixer 152 to estimate the power drop and / or phase shift of circuit 156. The control circuit 14 may then use the distortion circuit 30 ( Figure 1 ) distorts the subsequently transmitted signal to mitigate the power drop and phase shift of circuit 156. In other words, Figure 7 The radar circuit 26 can be based on Figure 3 The operation of the radar circuit 26 is calibrated using a multi-tone calibration signal mtone (e.g., in embodiments where radar circuit 26 performs only a single upconversion, the signal mtone may be calibrated in the embodiment of FIG. Figure 3 The FB1 frequency may be selected instead of the FB2 frequency at operation 104 , the upconversion at operation 106 may be omitted, the FB1 frequency may be processed in determining whether to proceed along path 112 or 118 , and a new FB1 frequency may be selected at operation 114 ).

[0094] Combination of the above Figures 1 to 7 The described methods and operations may be performed by the 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 device 10 (e.g., a computer-readable storage medium). Figure 1 The software code may sometimes be referred to as software, data, instructions, program instructions, or code. Non-transitory computer-readable storage media may include a drive, non-volatile memory such as non-volatile random access memory (NVRAM), a removable flash drive or other removable media, other types of random access memory, etc. The software stored on the non-transitory computer-readable storage media may be executed by processing circuitry on one or more of the components of device 10 (e.g., Figure 1 The processing circuit may include a microprocessor, a central processing unit (CPU), an application-specific integrated circuit with a processing circuit, or other processing circuits. Figure 2 、 Figure 6 and Figure 7 The components may be implemented using hardware (eg, circuit components, digital logic gates, etc.) and / or using software.

[0095] According to one embodiment, a wireless communication circuit for performing a spatial ranging operation on an external object using a transmitted signal is provided, the wireless communication circuit comprising: a digital-to-analog converter (DAC) configured to generate a multi-tone calibration signal having a first tone and a second tone spaced apart from the first tone by a frequency gap; a first mixer configured to up-convert the multi-tone calibration signal from a first frequency band to a second frequency band; and a second mixer having a first input terminal configured to receive an output from the first mixer via a signal path. The transmitter comprises a first mixer and a second input terminal configured to receive the multi-tone calibration signal in the second frequency band via an intermediate circuit communicatively coupled between an output terminal of the first mixer and the second input terminal, the second mixer being configured to generate a baseband multi-tone calibration signal; a measurement circuit configured to measure an amplitude of the baseband multi-tone calibration signal; and a control circuit configured to estimate a power drop of the intermediate circuit based on the amplitude measured by the measurement circuit and to distort the transmit signal based on the estimated power drop.

[0096] According to another embodiment, the transmit signal includes a chirped signal, and the signal path includes a de-chirp path, the wireless circuit includes a chirp generator configured to generate the chirped signal for transmission by the transmit antenna, the first mixer is configured to up-convert the chirped signal to a second frequency band, the first input of the second mixer is configured to receive the chirped signal in the second frequency band via the de-chirp path, and the second input is configured to receive a reflected version of the chirped signal via the receive antenna.

[0097] According to another embodiment, wireless communication circuitry includes a signal splitter having an input coupled to an output of a first mixer, a first output coupled to an intermediate circuit, and a second output coupled to a first input of a second mixer via a signal path.

[0098] According to another embodiment, the intermediate circuit includes a third mixer, which is communicatively coupled to the first output end of the signal splitter and is configured to up-convert the multi-tone calibration signal from the second frequency band to the third frequency band; and a fourth mixer, which is communicatively coupled to the second input end and is configured to down-convert the multi-tone calibration signal from the third frequency band to the second frequency band.

[0099] According to another embodiment, the first frequency band includes baseband frequencies, the second frequency band includes frequencies greater than the baseband frequencies and less than 10 GHz, and the third frequency band includes frequencies greater than the second frequency band.

[0100] According to another embodiment, the second frequency band includes frequencies greater than 20 GHz.

[0101] According to another embodiment, the intermediate circuit includes a transmitting antenna, which is communicatively coupled to the output of the third mixer and is configured to transmit the multi-tone calibration signal in the third frequency band; and a receiving antenna, which is communicatively coupled to the input of the fourth mixer and is configured to receive the multi-tone calibration signal transmitted by the transmitting antenna in the third frequency band.

[0102] According to another embodiment, the intermediate circuit includes a loopback path communicatively coupled between an output of the third mixer and an input of the fourth mixer, the loopback path configured to transmit the multi-tone calibration signal in the third frequency band.

[0103] According to another embodiment, the distortion circuit includes a digital predistortion circuit communicatively coupled to an input of a DAC.

[0104] According to another embodiment, the measurement circuit is configured to measure the phase of the baseband multi-tone calibration signal, the control circuit is configured to estimate the phase shift of the intermediate circuit based on the phase measured by the measurement circuit, and the control circuit is configured to distort the transmit signal based on the phase shift estimated by the measurement circuit.

[0105] According to another embodiment, the control circuit is configured to control the first mixer to scan within a plurality of radio frequencies, the second mixer is configured to generate a baseband multi-tone calibration signal for each of the plurality of radio frequencies, the measurement circuit is configured to measure the amplitude of the baseband multi-tone calibration signal for each of the plurality of radio frequencies, and the control circuit is configured to estimate a power drop across an intermediate circuit for each of the plurality of radio frequencies.

[0106] According to another embodiment, the baseband multi-tone calibration signal is spaced apart from a direct current (DC) frequency by a frequency gap, and the frequency gap is less than or equal to 20 MHz.

[0107] According to one embodiment, a method for calibrating a radar circuit is provided, the method comprising: generating, using a digital-to-analog converter (DAC) in a transmit chain of the radar circuit, a multi-tone calibration signal having a first tone and a second tone spaced apart from the first tone by a frequency gap of less than 20 MHz; up-converting, using a first mixer in the transmit chain, the multi-tone calibration signal from baseband to a first frequency band; up-converting, using a second mixer in the transmit chain, the multi-tone calibration signal from the first frequency band to a second frequency band; and up-converting, using a third mixer in a receive chain of the radar circuit, the multi-tone calibration signal up-converted by the second mixer. downconverting from the second frequency band to the first frequency band; generating, using a dechirp mixer in a receive chain, a baseband multi-tone calibration signal by mixing the multi-tone calibration signal upconverted by the first mixer with the multi-tone calibration signal downconverted by the third mixer, the baseband multi-tone calibration signal being spaced apart from a direct current (DC) frequency by a frequency gap; estimating, using a control circuit, a power drop and a phase shift of a radar circuit based on the baseband multi-tone calibration signal generated by the dechirp mixer; and predistorting, using a predistortion circuit in a transmit chain, a chirp signal transmitted through the transmit chain based on the power drop and phase shift estimated by the control circuit.

[0108] According to another embodiment, the method includes: scanning a second frequency band within a plurality of radio frequencies with a second mixer; downconverting a multi-tone calibration signal with a third mixer for each of the plurality of radio frequencies; generating a baseband multi-tone calibration signal with a dechirp mixer for each of the plurality of radio frequencies; and estimating, with a control circuit, a power drop of the radar circuit based on the baseband multi-tone calibration signal generated by the dechirp mixer for each of the plurality of radio frequencies.

[0109] According to another embodiment, the method includes utilizing a low-pass filter to low-pass filter a baseband multi-tone calibration signal for each of the plurality of radio frequencies; utilizing a measurement circuit to measure an amplitude and a phase of the baseband multi-tone calibration signal for each of the plurality of radio frequencies; utilizing an analog-to-digital converter (ADC) to convert the amplitude and the phase measured by the measurement circuit into digital data; utilizing a control circuit to store the digital data; and utilizing the control circuit to estimate a power drop based on the stored digital data.

[0110] According to another embodiment, predistorting the chirped signal includes multiplying the chirped signal by a factor selected to invert a power drop estimated by the control circuit when transmitting the chirped signal through the transmit chain.

[0111] According to another embodiment, the method includes transmitting, with the transmit chain, a multi-tone calibration signal in a second frequency band using a transmit antenna, and receiving, with a third mixer, the multi-tone calibration signal in the second frequency band using a receive antenna.

[0112] According to one embodiment, an electronic device is provided, comprising: a first antenna; a second antenna; a radar circuit configured to generate a transmit signal transmitted using the first antenna, the second antenna configured to receive a reflected version of the transmit signal transmitted using the first antenna; a control circuit configured to perform a spatial ranging operation based on the reflected version of the transmit signal received using the second antenna, and a digital-to-analog converter (DAC) in the radar circuit, the DAC configured to generate a multi-tone calibration signal transmitted using the first antenna, the multi-tone calibration signal having at least a first tone and a second tone spaced apart from the first tone by a frequency gap of less than 20 MHz, the control circuit configured to estimate a power drop of the radar circuit using the multi-tone calibration signal, and the control circuit configured to distort the transmit signal based on the estimated power drop.

[0113] According to another embodiment, the DAC is configured to convert the transmit signal from the digital domain to the analog domain.

[0114] According to another embodiment, the multi-tone calibration signal has a third tone spaced apart in frequency from the second tone by a gap and a fourth tone spaced apart in frequency from the third tone by a gap.

[0115] The foregoing is merely exemplary and various modifications may be made to the embodiments described. The foregoing embodiments may be implemented independently or in any combination.

Claims

1. A wireless circuit, comprising: one or more antennas; a transmitter configured to transmit a radio frequency signal using the one or more antennas, the radio frequency signal having a first tone and a second tone separated from the first tone by a frequency gap; as well as a mixer configured to receive the radio frequency signal transmitted by the transmitter using the one or more antennas, the mixer configured to generate a baseband signal based on the radio frequency signal transmitted by the transmitter and the radio frequency signal received using the one or more antennas. 2 . The wireless circuit of claim 1 , wherein the mixer is configured to generate the baseband signal by mixing the radio frequency signal transmitted by the transmitter with the radio frequency signal received using the one or more antennas.

3. The wireless circuit according to claim 2, further comprising: A signal path couples the transmitter to the mixer, the mixer being configured to receive the radio frequency signal transmitted by the transmitter through the signal path. 4 . The wireless circuit of claim 1 , wherein the transmitter is configured to transmit a radar signal based on the baseband signal using the one or more antennas. 5 . The wireless circuit of claim 4 , wherein the transmitter is configured to distort the radar signal based on the baseband signal.

6. The wireless circuit according to claim 5, further comprising: The measurement circuit is configured to generate phase and amplitude information based on the baseband signal, and the transmitter is configured to distort the radar signal based on the phase and amplitude information.

7. The wireless circuit of claim 1, wherein the mixers comprise in-phase and quadrature-phase I / Q mixers. The wireless circuit according to claim 1 , wherein the frequency gap is less than or equal to 20 MHz.

9. The wireless circuit of claim 1, wherein the baseband signal is separated from a direct current (DC) frequency by the frequency gap.

10. The wireless circuit of claim 1 , wherein the transmitter comprises: a signal generator configured to generate the first tone and the second tone; a digital-to-analog converter configured to convert the first tone and the second tone into an analog domain; as well as An additional mixer is configured to upconvert the first tone and the second tone to a radio frequency.

11. A method of operating a radar circuit, the method comprising: transmitting, using a transmit chain, a radio frequency signal comprising a first tone and a second tone separated from the first tone by a frequency gap; receiving, using a receive chain and one or more antennas, the radio frequency signal transmitted using the transmit chain; receiving the radio frequency signal at a mixer in the receive chain via a signal path between the transmit chain and the receive chain; as well as A baseband signal is generated using the mixer based on the radio frequency signal received using the one or more antennas and the radio frequency signal received through the signal path.

12. The method of claim 11, wherein generating the baseband signal comprises mixing the radio frequency signal received using the one or more antennas with the radio frequency signal received via the signal path.

13. The method of claim 11, wherein the baseband signal is offset from a DC frequency by the frequency offset. The method of claim 13 , wherein the frequency offset is less than or equal to 20 MHz.

15. The method according to claim 11, further comprising: A radar waveform based on the baseband signal is transmitted using the transmit chain.

16. The method of claim 15, wherein transmitting the radar waveform comprises distorting the radar waveform based on the baseband signal.

17. The method of claim 15, wherein the signal path comprises a dechirp path, the mixer comprises a dechirp mixer, and the radar waveform comprises a frequency ramp.

18. An electronic device comprising: one or more antennas; radar circuitry configured to generate a first signal to be transmitted and received using the one or more antennas and a second signal to be transmitted and received using the one or more antennas, the first signal comprising a first tone and a second tone separated from the first tone by a frequency gap; as well as One or more processors configured to detect an external object based on the second signal.

19. The electronic device of claim 18, the radar circuit configured to distort the second signal based on the first signal.

20. The electronic device of claim 19, the one or more processors configured to estimate a power drop of the radar circuit based on the first signal, and the radar circuit configured to distort the second signal based on the estimated power drop.

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