Electronic device with spatial ranging calibration capability

Abstract

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

Description

[0001] 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

[0002] The present disclosure generally relates to electronic devices, and more particularly to electronic devices having wireless circuitry. Background Art

[0003] Electronic devices often have wireless capabilities. An electronic device having wireless capabilities has wireless circuitry that includes 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.

[0004] Providing wireless circuitry that accurately estimates this distance can be challenging. For example, the wireless circuitry typically introduces undesirable power drops and / or phase shifts to the radio frequency signals. If not carefully accounted for, 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

[0005] An electronic device may include wireless circuitry. The wireless circuitry may include spatial ranging circuitry and an antenna. In one embodiment described herein as an example, the spatial ranging circuitry includes radar circuitry, such as frequency modulated continuous wave (FMCW) radar circuitry. The antenna may include a transmit antenna for a transmit chain in the radar circuitry and a receive antenna for a receive chain in the radar circuitry. The transmit chain may include a transmit signal generator (e.g., a chirp generator), a digital-to-analog converter (DAC), a first mixer, and a signal splitter. The receive chain may include a second mixer (e.g., a de-chirp mixer) and measurement circuitry. A path (e.g., a de-chirp path) may couple the signal splitter to the second mixer. The transmit signal generator may generate a transmit signal (e.g., a chirp signal) that is transmitted by the transmit antenna and received by the receive antenna. Doppler shifts in the received signal may be processed to estimate or detect the velocity of an external object. The time-dependent frequency difference between the transmit 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.

[0006] If not careful, components of the radar circuit may impose an undesired power drop and phase shift on the chirp signal, which can limit the accuracy of the estimated position and / or velocity. The control circuit can calibrate the radar circuit to mitigate these issues. During calibration, the DAC can transmit a multi-tone calibration signal. The multi-tone calibration signal includes two or more tones spaced apart by a certain frequency gap. The first mixer can up-convert the multi-tone calibration signal, which is transmitted through an antenna or a loopback path before being received by the second mixer. If needed, an additional mixer can up-convert the multi-tone calibration signal to a higher frequency before it is transmitted through the antenna or loopback path, and the additional mixer can down-convert the multi-tone calibration signal received through the loopback path or antenna. The second mixer can mix the multi-tone calibration signal output by the first mixer with the multi-tone calibration signal received on the antenna or loopback path to generate a baseband multi-tone calibration signal. The baseband multi-tone calibration signal will have a frequency gap from the DC offset. This can prevent DC noise, LO leakage, or other system / process noise from interfering with the baseband multi-tone calibration signal.

[0007] The control circuit can scan the first mixer (or the additional mixer in an embodiment where the radar circuit includes an additional mixer) within different operating frequencies of the radar circuit while the second mixer continues to generate the baseband multi-tone calibration signal. The measurement circuit can measure the amplitude and phase of the baseband multi-tone calibration signal. The control circuit can estimate the power drop and phase shift of the radar circuit based on the amplitude and phase measurements. Then, a distortion circuit such as a pre-distortion circuit in the transmit chain can pre-distort the transmit signal to invert the power drop and phase shift effects of the radar circuit, thus ensuring accurate distance, position, and / or velocity estimates can be obtained over the lifespan of the device.

[0008] One aspect of the present disclosure provides a wireless communication circuit for performing spatial ranging operations 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 spaced apart 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 terminal configured to receive, via a signal path, the multi-tone calibration signal in the second frequency band from an output terminal of the 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 the output terminal of the first mixer and the second input terminal. 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 circuit 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 circuit may be configured to distort the transmitted signal based on the estimated power drop.

[0009] One aspect of the present disclosure provides a method for calibrating a radar circuit. The method may include generating, in a transmit chain of the radar circuit using a digital-to-analog converter (DAC), 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. The method may include up-converting, in the transmit chain using a first mixer, the multi-tone calibration signal from a baseband to a first frequency band. The method may include up-converting, in the transmit chain using a second mixer, the multi-tone calibration signal from the first frequency band to a second frequency band. The method may include down-converting, in a receive chain of the radar circuit using a third mixer, the multi-tone calibration signal up-converted by the second mixer from the second frequency band to the first frequency band. The method may include generating, in the receive chain using a de-chirp mixer, a baseband multi-tone calibration signal by mixing the multi-tone calibration signal up-converted by the first mixer with the multi-tone calibration signal down-converted by the third mixer, the baseband multi-tone calibration signal being spaced apart from a direct current (DC) frequency by a frequency gap. The method may include estimating, using a control circuit, a power drop and a phase shift of the radar circuit based on the baseband multi-tone calibration signal generated by the de-chirp mixer. The method may include pre-distorting, in the transmit chain using a pre-distortion circuit, a chirp signal transmitted through the transmit chain based on the power drop and the phase shift estimated by the control circuit.

[0010] 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 a radar circuit configured to generate a transmission signal transmitted using the first antenna. The second antenna may be configured to receive a reflected version of the transmission signal transmitted using the first antenna. The electronic device may include a control circuit configured to perform a spatial ranging operation based on the reflected version of the transmission signal received using the second antenna. The electronic device may include a digital-to-analog converter (DAC) in the radar circuit. The DAC may be configured to generate a multi-tone calibration signal transmitted using the first antenna. The multi-tone calibration signal may have a first tone and a second tone with a frequency gap spaced less than 20 MHz from the first tone. The control circuit may be configured to use the multi-tone calibration signal to estimate a power drop of the radar circuit. The control circuit may be configured to distort the transmission signal based on the estimated power drop. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a functional block diagram of an exemplary electronic device having a calibrated spatial ranging circuit according to some embodiments.

[0012] Figure 2 is a circuit diagram of an exemplary spatial ranging circuit calibrated using a multi-tone calibration signal according to some embodiments.

[0013] Figure 3 is a flowchart of an exemplary operation involved in calibrating a spatial ranging circuit using a multi-tone calibration signal according to some embodiments.

[0014] Figure 4 is a frequency diagram of an exemplary multi-tone calibration signal that can be used to estimate a power drop and / or phase shift of a spatial ranging circuit according to some embodiments.

[0015] Figure 5 is a graph of an exemplary power drop that can be estimated using a multi-tone calibration signal according to some embodiments.

[0016] Figure 6 is a diagram showing how an exemplary digital pre-distortion circuit can be used to compensate for an estimated power drop and / or phase shift of a spatial ranging circuit according to some embodiments.

[0017] Figure 7 is a diagram of an exemplary 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

[0018] Figure 1The electronic device 10 can be: a computing device, such as a laptop computer, a desktop computer, a computer monitor including an embedded computer, a tablet computer, a cellular phone, a media player, or other handheld or portable electronic devices; 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 micro devices, a television, a computer monitor without 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 a kiosk or a vehicle), a voice-controlled speaker connected to a 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.

[0019] As Figure 1 As shown in the functional block diagram, the device 10 may include components located on or within an electronic device housing, such as the housing 12. The housing 12 (which may sometimes be referred to as a case) may be formed of plastic, glass, ceramic, fiber composite material, metal (e.g., stainless steel, aluminum, metal alloy, etc.), other suitable materials, or a combination of these materials. In some cases, part or all of the housing 12 may be formed of a dielectric or other low electrical 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 of metal elements.

[0020] The device 10 may include control circuitry 14. The control circuitry 14 may include storage means, such as storage circuitry 16. The storage circuitry 16 may include hard drive storage means, non-volatile memory (e.g., flash memory configured to form a solid state drive or other electrically programmable read-only memory), volatile memory (e.g., static random access memory or dynamic random access memory), etc. The storage circuitry 16 may include storage means integrated within the device 10 and / or removable storage media.

[0021] 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 microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application specific integrated circuits, central processing units (CPUs), etc. The control circuit 14 may be configured to perform operations in the device 10 using hardware (e.g., dedicated hardware or circuitry), firmware, and / or software. Software code for performing operations in the device 10 may be stored in the storage circuit 16 (e.g., the storage circuit 16 may include 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. The software code stored in the storage circuit 16 may be executed by the processing circuitry 18.

[0022] The control circuit 14 may be used to run software on the device 10, such as satellite navigation applications, Internet browsing applications, Internet voice protocol (VOIP) phone call applications, email applications, media playback applications, operating system functions, etc. To support interaction with external equipment, the control circuit 14 may be used to implement communication protocols. Communication protocols that may be implemented using the control circuit 14 include: Internet protocol, wireless local area network (WLAN) protocol (e.g., IEEE 802.11 protocol - sometimes referred to as ), protocols for other short-range wireless communication links such as protocol or other wireless personal area network (WPAN) protocols, IEEE 802.11ad protocol (e.g., ultra-wideband protocol), cellular phone protocol (e.g., 3G protocol, 4G (LTE) protocol, 5G protocol, etc.), antenna diversity protocol, satellite navigation system protocol (e.g., Global Positioning System (GPS) protocol, Global Navigation Satellite System (GLONASS) protocol, etc.), antenna-based spatial ranging protocol (e.g., 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 for implementing the protocol.

[0023] Device 10 may include input-output circuitry 20. The input-output circuitry 20 may include input-output devices 22. The 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 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 displays and / or force-sensitive displays), light-emitting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), rollers, 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 a display to detect pressure applied to the display), etc. In some configurations, a keyboard, headphones, a display, pointing devices such as touch pads, mice, and joysticks, and other input-output devices may be coupled to device 10 using a wired or wireless connection (e.g., some of the input-output devices 22 may be peripheral devices coupled to the main processing unit or other parts of device 10 via a wired or wireless link).

[0024] The input-output circuitry 20 may include wireless circuitry 24 to support wireless communication. The wireless circuitry 24 (sometimes referred to herein as wireless communication circuitry 24) may include two or more antennas 40. The 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 the antennas 40.

[0025] The wireless circuitry 24 may transmit and / or receive radio frequency signals within a corresponding frequency band of the radio frequency (sometimes referred to herein as the communication band or simply "band"). The bands processed by the 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), the 6E band (e.g., 5925 MHz to 7125 MHz), and / or other bands (e.g., 1875 MHz to 5160 MHz); wireless personal area network (WPAN) bands such as 2.4 GHz a frequency band or other WPAN communication frequency band; a cellular phone frequency band (e.g., a frequency band from about 600 MHz to about 5 GHz, a 3G frequency band, a 4G LTE frequency band, a 5G New Radio Frequency Range 1 (FR1) frequency band below 10 GHz, a 5G New Radio Frequency Range 2 (FR2) frequency band between 20 GHz and 60 GHz, etc.); other centimeter or millimeter wave frequency bands between 10 GHz and 300 GHz; a Near Field Communication frequency band (e.g., 13.56 MHz); a satellite navigation frequency band (e.g., a GPS frequency band from 1565 MHz to 1610 MHz, a Global Navigation Satellite System (GLONASS) frequency band, a BeiDou Navigation Satellite System (BDS) frequency band, etc.); an Ultra-Wideband (UWB) frequency band operating under the IEEE 802.15.4 protocol and / or other ultra-wideband communication protocols; a communication frequency band under the 3GPP wireless communication standard family; a communication frequency band under the IEEE 802.XX standard family, and / or any other desired frequency band of interest.

[0026] Any desired antenna structure can be used to form antenna 40. For example, antenna 40 can include an antenna having a resonant element, which is formed by a loop antenna structure, a patch antenna structure, an inverted-F antenna structure, a slot antenna structure, a planar inverted-F antenna structure, a spiral antenna structure, a monopole antenna, a dipole, a hybrid of these designs, etc. Adjustable filter circuits, switching circuits, impedance matching circuits, and / or other antenna tuning components are used to adjust the frequency response and wireless performance of antenna 40 over time.

[0027] The radio frequency signals processed by antenna 40 can be used to transmit 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 can be transmitted bidirectionally or unidirectionally by wireless circuit 24. The wireless communication data can, for example, include data encoded into corresponding data packets, such as wireless data associated with a phone call, streaming media content, Internet browsing, wireless data associated with a software application running on device 10, an email message, etc.

[0028] Wireless circuit 24 can additionally or alternatively use antenna 40 to perform spatial ranging operations. In the case where wireless circuit 24 both transmits wireless communication data and performs spatial ranging operations, one or more of the same antennas 40 can be used to both transmit wireless communication data and perform spatial ranging operations. In another specific implementation, wireless circuit 24 can include a set of antennas 40 that only transmit wireless communication data and a set of antennas 40 that are only used to perform spatial ranging operations.

[0029] When performing spatial ranging operations, antenna 40 can transmit radio frequency signal 36. Radio circuitry 24 can transmit radio frequency signal 36 in a corresponding radio frequency band (e.g., a band including frequencies greater than about 10 GHz, greater than about 20 GHz, less than 10 GHz, etc.). Radio frequency signal 36 can reflect off an object external to device 10, such as external object 34. External object 34 can 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 can receive the reflected radio frequency signal 38. Reflected signal 38 can be a reflected version of transmitted radio frequency signal 36 that has reflected off external object 34 and returned to device 10.

[0030] Control circuitry 14 can process transmitted radio frequency signal 36 and received reflected signal 38 to detect or estimate the distance R between device 10 and external object 34. If desired, control circuitry 14 can also process the transmitted and received signals to identify the two-dimensional or three-dimensional spatial location (azimuth) of external object 34, the velocity of external object 34, and / or the angle of arrival of reflected signal 38. In one embodiment described herein by way of example, radio circuitry 24 performs spatial ranging operations using a frequency-modulated continuous wave (FMCW) radar scheme. This is merely illustrative, and other radar schemes or spatial ranging schemes can generally be used (e.g., an OFDM radar scheme, an FSCW radar scheme, a phase-coded radar scheme, etc.).

[0031] To support spatial ranging operations, radio circuitry 24 can include spatial ranging circuitry, such as radar circuitry 26. In one embodiment sometimes described herein by way of example, radar circuitry 26 includes an FMCW radar circuit that performs spatial ranging using an FMCW radar scheme. Thus, radar circuitry 26 can sometimes be referred to herein as FMCW radar circuitry 26. Radar circuitry 26 can use one or more antennas 40 to transmit radio frequency signal 36 (e.g., a continuous wave of radio frequency energy as in an FMCW radar scheme). One or more antennas 40 can also receive reflected signal 38 (e.g., a continuous wave of radio frequency energy as in an FMCW radar scheme). Radar circuitry 26 can process radio frequency signal 36 and reflected signal 38 to identify / estimate distance R, the location of external object 34, the velocity of external object 34, and / or the angle of arrival of reflected signal 38. In an embodiment in which radar circuitry 26 uses an FMCW radar scheme, the Doppler shift in the continuous wave signal can be detected and processed to identify the velocity of external object 34, and the time-dependent frequency difference between radio frequency signal 36 and reflected signal 38 can be detected and processed to identify distance R and / or the location of external object 34. For example, using a continuous wave signal to estimate distance R can allow control circuitry 10 to reliably distinguish external object 34 from other background or slower-moving objects.

[0032] As Figure 1 shown, the radar circuit 26 can include a transmit (TX) signal generator circuit, such as transmit signal generator 28. The transmit signal generator 28 can generate a transmit signal for transmission via antenna 40. In some embodiments described herein by way of example, the transmit signal generator 28 includes a chirp generator that generates a chirp signal for transmission via antenna 40 (e.g., in embodiments where the radar circuit 26 uses an FMCW radar scheme). Thus, the transmit signal generator 28 can sometimes be referred to herein as chirp generator 28. The transmit signal generator 28 can, for example, generate a chirp signal that is a continuous wave transmission as radio frequency signal 36. For example, a chirp signal can be formed by periodically increasing the frequency of the transmit signal linearly over time. The radar circuit 26 can also include a digital-to-analog converter (DAC) circuit such as DAC 32. The DAC 32 can convert the transmit signal (e.g., chirp signal) from the digital domain to the analog domain before transmission via antenna 40 (e.g., in radio frequency signal 36). The radar circuit 26 can also include an analog-to-digital converter (ADC) circuit such as ADC 42. The ADC 42 can convert the signal from the analog domain to the digital domain for subsequent processing by control circuit 14. Although, for clarity, in the Figure 1 example shown, the control circuit 14 is shown separate from the wireless circuit 24, the wireless circuit 24 can include processing circuitry and / or storage circuitry that forms part of the processing circuitry 18 and the storage circuitry that forms part of the storage circuitry 16 of the control circuit 14 (e.g., portions of the control circuit 14 can be implemented on the wireless circuit 24).

[0033] In practice, components in the wireless circuit 24 can introduce frequency-dependent power drops and / or phase shifts to the radio frequency signal transmitted by antenna 40. For example, the power drop can be caused by circuit, filter, and / or cable frequency dependencies and the antenna 40's directivity / gain limitations with respect to frequency. When using an FMCW radar scheme, the frequency-dependent power drop increases the width of the main target lobe in the baseband (BB) spectrum, which reduces the range resolution of the radar circuit 26. Additionally, the signal-to-noise ratio (SNR) in the baseband signal can be reduced due to discrete and fixed gain stages in the wireless circuit 24. Thus, when performing spatial ranging operations, it may be desirable to be able to avoid or compensate for any power drops or phase shifts introduced by the wireless circuit 24.

[0034] To compensate for the power drop and phase shift introduced by radio circuit 24 during the performance of spatial ranging operations, radio circuit 24 can estimate or track the power drop and phase shift introduced during the operation of radio circuit 24 over the entire lifespan of device 10. DAC 32 can 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 that are spaced relatively closely apart in the frequency space (sometimes referred to herein as the frequency gap Δf). Once the power drop and / or phase shift have been estimated, radar circuit 26 can use distortion circuit 30 to distort the transmit signal (e.g., chirp signal) generated by transmit signal generator 28. Distortion circuit 30 can include a pre-distortion circuit that pre-distorts the transmit signal before it is transmitted by antenna 40, and / or can include a post-distortion circuit that distorts the received signal. The distortion introduced by distortion circuit 30 can be used to invert the effects of the power drop and phase shift, 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 drop or phase shift changes 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 standalone digital pre-distortion circuit block), using analog circuitry in radar circuit 26 (e.g., a standalone analog pre-distortion circuit block), etc. The distortion circuit can include, for example, multipliers, look-up tables, memories, 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 an embodiment where distortion circuit 30 includes a pre-distortion circuit).

[0035] Figure 2 is a circuit diagram of radar circuit 26 (e.g., in an embodiment where radar circuit 26 performs multiple up-conversions before being transmitted by antenna 40). If desired, the components of radar circuit 26 can be mounted to a common substrate (e.g., a shared rigid or flexible printed circuit board) or can be formed on a common integrated circuit (IC) or package. As Figure 2 shown, radar circuit 26 can include a transmit chain 52 (sometimes referred to herein as transmitter chain 52, transmit line 52, or transmit path 52) and a receive chain 54 (sometimes referred to herein as receiver chain 54, receive line 54, or receive path 52).

[0036] The radar circuit 26 may have a first (transmit) port coupled to a first antenna 40 such as a transmit antenna 40TX (e.g., the transmit antenna 40TX may form part of a transmit chain 52). The radar circuit 26 may have a second (receive) port coupled to a second antenna 40 such as a receive antenna 40RX (e.g., the receive antenna 40RX may form part of a receive chain 54). A signal path (such as a de-chirping path 48) may couple the transmit chain 52 to the receive chain 54.

[0037] 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 de-chirping mixer 74), a fourth mixer (such as mixer 72), and an amplifier circuit (such as amplifier 70) (e.g., a low-noise amplifier (LNA)).

[0038] As Figure 2 shown, the output of the transmit signal generator 28 may be coupled to the input of the DAC 32 (e.g., the transmit signal generator 28 may be formed by digital logic in the radar circuit 26 and may operate in the digital domain). The output of the DAC 32 may be coupled to the first input of the mixer 56 (e.g., via an I / Q signal path). The mixer 56 may have a second input for receiving a local oscillator (LO) signal from a frequency band 1 local oscillator (FB1LO) 50. The output of the mixer 56 may be coupled to the input of the amplifier 58. The output of the amplifier 58 may be coupled to the input of the splitter 62. The splitter 62 may have a first output terminal coupled to the first input of the mixer 64. The mixer 64 may have a second input for receiving an LO signal from a frequency band 2 local oscillator (FB2LO) 46. The output of the mixer 64 may be coupled to the input of the amplifier 66. The output of the amplifier 66 may be coupled to the transmit antenna 40TX (e.g., via one or more RF transmission lines).

[0039] In receive chain 54, the input of amplifier 70 may be coupled to receive antenna 40RX. The output of amplifier 70 may be coupled to a first input of mixer 72. Mixer 72 may have a second input that receives an LO signal from FB2LO 46. The output of mixer 72 may be coupled to a first input of dechirping mixer 74. Dechirping mixer 74 may have a second input coupled to the second output terminal of splitter 62 via dechirping path 48. If desired, an amplifier such as amplifier 68 may be interposed on dechirping path 48. Although not shown in the example of Figure 2 for clarity, dechirping path 48 may also include a signal splitter having a first output terminal and a second output terminal coupled to the first output terminal of dechirping mixer 74, with a 90-degree phase delay applied to the second output terminal (e.g., so that dechirping mixer 74 may operate on I / Q signals). The output of dechirping mixer 74 may be coupled to the input of LPF 76 (e.g., via an I / Q signal path). The output of LPF 76 may be coupled to the input of phase and amplitude measurement circuit 88. The output of phase and amplitude measurement circuit 88 may be coupled to the input of ADC 42. The output of ADC 42 may be coupled to control circuit 14 via digital output path 78( Figure 1 ). If desired, an optional loopback path 80 may 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 switch circuit may be interposed on loopback path 80. When antennas 40TX and 40RX are not used for calibration, loopback path 80 may be used to calibrate radar circuit 26.

[0040] The transmission lines in radio circuit 24 (e.g., the radio frequency transmission line for coupling mixer 64 to transmit antenna 40TX, the radio frequency transmission line for coupling receive antenna 40RX to 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.

[0041] Figure 2The examples are illustrative only. Generally, other circuit architectures can also be used to form the radar circuit 26. The mixers 56 and 74 can be I / Q mixers. Additional filters, amplifiers, switches, delay stages, splitters, and / or other circuit components can be formed at other locations in the radar circuit 26. For example, a bandpass filter can be interposed between the amplifier 58 and the splitter 62. If desired, the phase and amplitude measurement circuit 88 can be formed at other locations or multiple locations (e.g., the measurement circuit 88 can be coupled to the output of the ADC 42, the input of the ADC 42, and / or the input of the LPF 76). If desired, the mixers 64 and 72 and the FB2LO 46 can be omitted. If desired, the de-chirp mixer 74 can operate in the digital domain (e.g., the output of the ADC 42 can be coupled to the input of the de-chirp mixer 74, and the ADC 42 can be interposed at any desired location between the receive antenna 40RX and the input of the de-chirp mixer 74 in the receive chain 54, etc.). The digital pre-distortion circuit and / or the analog pre-distortion circuit from Figure 1 the distortion circuit 30 can be interposed at any desired location in the transmit chain 52 and / or the receive chain 54. In addition to performing the spatial ranging operation of the radar circuit 26, if desired, the transmit antenna 40TX and / or the receive antenna 40RX can also be used to transmit and / or receive wireless communication data (e.g., using other transceiver circuits and frequency-domain / time-domain multiplexing circuits not shown for clarity in Figure 2 ). The radar circuit 26 can form part of a transmitter (such as a 5G NR transmitter), for example.

[0042] When performing the spatial ranging operation, 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., as an I / Q signal) to the mixer 56. The mixer 56 can up-convert the analog transmit signal from the baseband to the first frequency band FB1 using the FB1LO 50.

[0043] The first frequency band FB1 can be at a higher frequency than the baseband and at a lower frequency than the radio frequency signal 36 transmitted by the transmit antenna 40TX (e.g., in a situation where multiple up-conversions are performed Figure 2in the arrangement). As an example, the radio frequency signal 36 can be transmitted in a second frequency band FB2, such as a radio frequency (RF) band. The frequency band FB2 can include frequencies greater than 10 GHz (e.g., an RF band of about 25 GHz, greater than 20 GHz, greater than 30 GHz, greater than 50 GHz, etc.) and / or frequencies less than 10 GHz. The frequency band FB1 can include frequencies less than those of the frequency band FB2 (e.g., frequencies less than 10 GHz, less than 5 GHz, etc.). The frequency band FB1 can sometimes be referred to as an intermediate frequency (IF) band. In an embodiment where the mixers 64 and 72 are omitted, the frequency band FB1 can be any desired frequency band above the baseband (e.g., an RF band).

[0044] The amplifier 58 can amplify the FB1 transmission signal (e.g., the FB1 chirp signal) for transmission to the splitter 62. Allocating the transmission signal in the frequency band FB1 rather than in the higher frequency band FB2 can be used to minimize signal attenuation because the signal is allocated to a location in the device 10 that is relatively far from the DAC 32, especially when the frequency band FB2 is at a relatively high frequency and would otherwise be subject to significant signal attenuation (e.g., frequencies greater than 10 GHz). The splitter 62 can transmit the FB1 transmission signal to the mixer 64 and the de-chirping path 48 (e.g., the splitter 62 can split the FB1 transmission signal between the mixer 64 and the de-chirping path 48). The mixer 64 can up-convert the FB1 transmission signal from the frequency band FB1 to the frequency band FB2 for transmission by the transmit antenna 40TX. The amplifier 66 can amplify the FB2 transmission signal (e.g., the FB2 chirp signal) and the transmit antenna 40TX can transmit the FB2 transmission signal (e.g., as the radio frequency signal 36). In an embodiment where the mixers 64 and 72 are omitted, the transmit antenna 40TX can transmit the FB1 transmission signal as the radio frequency signal 36.

[0045] The receive antenna 40RX can receive the reflected signal 38 (e.g., transmitted by the transmit antenna 40TX but having been reflected from) Figure 1(the reflected version of the FB2 transmit signal reflected from the external object 34). In an example where the transmit signal includes a chirp signal, the reflected signal 38 may sometimes be referred to herein as a reflected chirp signal. The amplifier 70 may amplify the reflected signal. The mixer 72 may down-convert the reflected signal from the frequency band FB2 to the frequency band FB1 for distribution to the de-chirp mixer 74 (e.g., as the FB1 reflected signal). The de-chirp path 48 may convey the FB1 transmit signal from the splitter 62 to the de-chirp mixer 74. The amplifier 68 may amplify the FB1 transmit signal on the de-chirp path 48 (e.g., to compensate for the attenuation associated with the splitter 62). The de-chirp mixer 74 may mix the FB1 transmit signal received via the de-chirp path 48 with the FB1 reflected signal received from the mixer 72 to generate a baseband signal (e.g., a baseband chirp signal). In an embodiment where the mixers 64 and 72 are omitted, the de-chirp mixer 74 may mix the FB1 transmit signal received via the de-chirp path 48 with the FB1 reflected signal received by the receive antenna 40RX. The de-chirp mixer 74 may provide the baseband signal to the LPF 76. The LPF 76 may perform low-pass filtering on the baseband signal to remove noise, harmonic effects, etc. The baseband signal may be conveyed to the ADC 42 (e.g., via the phase and amplitude measurement circuit 88). The ADC 42 may convert the baseband signal to a digital signal (e.g., a digital chirp signal). The control circuit 14 may process the baseband signal to estimate the distance R, the position of the external object 34, and / or the velocity of the external object 34( Figure 1 ).

[0046] In practice, the transmit antenna 40TX, the receive antenna 40RX, the transmission lines, the filter circuits (which typically cannot support the full FMCW bandwidth), and other components in the transmit chain 52 and the receive chain 54 may introduce undesirable power drops and / or phase shifts to the radar circuit 26. For example, the components along the dashed path 82 may introduce a power drop and / or a phase shift to the signal provided to the de-chirp mixer 74, which may be characterized by the composite weight values k 1 and k 3 . Similarly, the components along the dashed path 84 (or the dashed path 86 in the case where the loopback path 80 rather than the antennas 40TX and 40RX is used for calibration) may introduce a power drop and / or a phase shift to the signal provided to the de-chirp mixer 74, which may be characterized by the composite weight values k 2 and k 4 .

[0047] If not careful, power drops and phase shifts can cause control circuit 14 to generate inaccurate estimates of distance R, position, and / or velocity. Additionally, the amount of power drop and phase shift can vary over time. Control circuit 14 and radar circuit 26 can perform calibration operations to estimate the power drop and phase shift and compensate for the estimated power drop and phase shift, even if the power drop and phase shift vary over time, thus ensuring that control circuit 14 can accurately estimate the distance R and the position / velocity of an external object throughout the useful life of device 10.

[0048] However, in practice, the presence of the dechirp path 48, the relatively high RF bandwidth of a given system (e.g., 3 GHz to 5 GHz) and the relatively low RF bandwidth of the system after dechirping (e.g., 1 MHz to 10 MHz), as well as the presence of DC / flicker noise or other process noise (e.g., LO leakage) at baseband make it particularly difficult to estimate the power drop and / or phase shift of radar circuit 26. To mitigate these problems and ensure an accurate estimate of the power drop and phase shift is collected, a multi-tone calibration signal can be used to calibrate radar circuit 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.) spaced apart by a relatively small frequency gap Δf in the frequency space.

[0049] As Figure 2 shown, during the calibration operation, DAC 32 can generate a multi-tone calibration signal mtone at baseband frequency. The transmit signal generator 28 can avoid transmitting a transmit signal (e.g., a chirp signal) during the calibration operation. Mixer 56 can up-convert the multi-tone calibration signal mtone to 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 dechirp mixer 74 through dechirp path 48. Mixer 64 can up-convert the multi-tone calibration signal mtone to band FB2, amplifier 66 can amplify the multi-tone calibration signal mtone, and transmit antenna 40TX can transmit the multi-tone calibration signal mtone.

[0050] 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, a loopback path 80 can be used to convey 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.

[0051] The mixer 72 can down-convert the received multi-tone calibration signal mtone to the frequency band FB1 using FB2LO 46. The de-chirp mixer 74 can mix the multi-tone calibration signal mtone in the frequency band FB1 received through the de-chirp path 48 with the multi-tone calibration signal mtone in the frequency band FB1 received from the mixer 72 to generate a baseband multi-tone calibration signal mtone'. The LPF 76 can filter the baseband multi-tone calibration signal mtone' to remove high-frequency mixer products from the baseband multi-tone calibration signal. The phase and amplitude measurement circuit 88 can measure the amplitude and / or phase of the baseband multi-tone calibration signal mtone', and can provide the measured amplitude and / or phase values to the ADC 42. The ADC 42 can convert the amplitude and / or phase values into digital data dat. The digital data dat can be provided to the control circuit 14 through the digital output path 78. The control circuit 14 can store the digital data dat in the storage circuit 16 for subsequent processing. This example is merely illustrative, and if desired, the phase and amplitude measurement circuit 88 can be located at other points or multiple points within the receive chain 54.

[0052] This process can be repeated while scanning within different frequency bands FB2 (e.g., when changing the radio frequency of the multi-tone calibration signal mtone generated by the mixer 64). This can be used to generate a complete estimate of the power drop and / or phase shift across the operating (radio) frequencies of the FMCW radar circuit 26. Once each radio frequency in the desired radio frequencies has been characterized, the distortion circuit 30 ( Figure 1 ) can distort the subsequently transmitted transmit signal (e.g., chirp signal) to invert the estimated (as estimated using the multi-tone calibration signal mtone) power drop and / or phase shift. Then, the distorted chirp signal can be used to generate an accurate and reliable estimate of the range R, velocity, and / or position.

[0053] Figure 3 is a flowchart of an illustrative operation that can be performed by the radar circuit 26 and the control circuit 14 in calibrating the radar circuit 26 (e.g., in an embodiment where the radar circuit 26 performs multiple up-conversions before being transmitted by the antenna 40). Figure 3 The operation can be performed during the manufacture, assembly, or testing of the radar circuit 26 or the device 10 (e.g., in a manufacturing system or factory), and / or can be performed during the normal operation of the device 10 by an end user (e.g., during the useful life of the device 10).

[0054] At operation 100, the DAC 32 may generate a multi-tone calibration signal mtone. The DAC 32 may generate the multi-tone calibration signal such that each tone is spaced apart from one or two adjacent tones (in frequency) by a selected frequency gap Δf. The frequency gap Δf may be large enough such that each tone is different in frequency, but small enough such that each tone experiences a substantially equal power drop and such that the frequency gap Δf lies within a relatively small bandwidth of the ADC 42. As an 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.

[0055] At operation 102, the mixer 56 may up-convert the multi-tone calibration signal mtone from baseband to the frequency band FB1. The amplifier 58 may pass the multi-tone calibration signal mtone in the frequency band FB1 to the splitter 62. The splitter 62 may transmit the multi-tone calibration signal mtone to the de-chirp mixer 74 via the de-chirp path 48. The splitter 62 may also transmit the multi-tone calibration signal mtone to the mixer 64.

[0056] At operation 104, the control circuit 14 may select a first FB2 frequency (e.g., a first RF band) for transmitting the multi-tone calibration signal mtone. This frequency may be the first frequency in a scan within the operating radio frequency of the 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.

[0057] At operation 106, the mixer 64 may up-convert the multi-tone calibration signal mtone from the frequency band FB1 to the selected FB2 frequency (e.g., using FB2LO 46). The amplifier 66 may amplify the radio frequency multi-tone calibration signal mtone. The transmit antenna 40TX may transmit the radio frequency multi-tone calibration signal mtone, and the receive antenna 40RX may receive the transmitted radio frequency multi-tone calibration signal mtone. In time, the transmit antenna simultaneously transmits each of the tones in the radio frequency multi-tone calibration signal mtone, and if desired, in the same polarization. In another specific implementation, the radio frequency multi-tone calibration signal mtone may be conveyed to the receive chain 54 via the loopback path 80 instead of being transmitted by the transmit antenna 40TX.

[0058] At operation 108, the de-chirping mixer 74 may receive the multi-tone calibration signal mtone in the frequency band FB2 through the de-chirping path 48. The mixer 72 may down-convert the radio frequency multi-tone calibration signal mtone received through the receive antenna 40TX or the loopback path 80 to the frequency band FB1. The de-chirping mixer 74 may mix the multi-tone calibration signal mtone in the frequency band FB1 received through the de-chirping path 48 with the multi-tone calibration signal mtone in the frequency band FB1 generated by the mixer 72 to generate a baseband multi-tone calibration signal mtone'.

[0059] At operation 110, the LPF 76 may filter the baseband multi-tone calibration signal mtone' to remove high-frequency mixer products from the baseband multi-tone calibration signal. The phase and amplitude measurement circuit 88 may measure the amplitude and / or phase of the baseband multi-tone calibration signal mtone'. In the case of calibrating using a single tone, the single tone after being down-converted by the de-chirping mixer 74 is at DC and is interfered with by DC noise and other LO leaks. However, in the case of calibrating using the multi-tone calibration signal mtone, each tone in the baseband multi-tone calibration signal mtone' is frequency-offset by the frequency gap Δf from DC. This can be used to prevent DC / flicker noise or other process noise (e.g., LO leak) at the baseband from interfering with the baseband multi-tone calibration signal mtone', thereby allowing for a more accurate power drop and / or phase shift estimate than in the case of calibrating using only a single tone. The ADC 42 may convert the amplitude and phase values into corresponding digital data dat. The control circuit 14 may store the digital data dat for subsequent processing.

[0060] If the frequency remains within the scan of the FB2 frequencies for estimating the power drop and phase shift, the process may proceed to operation 114, as shown by path 112. At operation 114, the control circuit 14 may select a new FB2 frequency for the next transmission of the multi-tone calibration signal mtone. Then the process may loop back to operation 106, as shown by path 116, to continue collecting the amplitude and / or phase values from the baseband multi-tone calibration signal mtone for each of the FB2 frequencies in the scan. This may allow the control circuit 14 to collect a complete estimate of the power drop and / or phase varying with frequency (e.g., across the operating frequency range of the radar circuit 26) of the FMCW radar circuit 26 for distorting the subsequently transmitted chirp signals.

[0061] If there is no scan at the FB2 frequency that is maintained for estimating power drop and phase shift, the process can proceed via path 118 to operation 120. At operation 120, control circuit 14 can process digital data dat (e.g., as stored at each iteration of operations 106 to 110) to estimate the amplitude and / or phase shift effects introduced by components of radar circuit 26. The amplitude effect can indicate the power drop of the system.

[0062] At operation 122, radar circuit 26 can resume transmission of the transmit signal to determine the distance R between device 10 and external object 34 ( Figure 1 ). The transmit signal generator 28 can transmit a signal (e.g., a chirp signal). Control circuit 14 can use distortion circuit 30 to pre-distort and / or post-distort the signal. Distortion circuit 30 ( Figure 1 ) can distort the signal based on the estimated power drop and / or phase shift effects (e.g., as identified at operation 120). Distortion circuit 30 can include a digital pre-distortion circuit that pre-distorts the chirp signal in the digital domain before conversion by DAC 32, an analog pre-distortion circuit that pre-distorts the chirp signal after conversion by DAC 32, and / or a post-distortion circuit that distorts the received signal.

[0063] At operation 124, transmit antenna 40TX can radiate the transmit signal. Receive antenna 40RX can receive a reflected version of the transmit signal that has reflected off external object 34 (e.g., as Figure 1 reflected signal 38). The distortion performed at operation 124 can be an inverse transformation of the estimated power drop and / or phase shift effects such that the chirp signal distorted after passing through transmit chain 52 is transmitted by transmit antenna 40TX and received by receive antenna 40RX as if radar circuit 26 did not introduce a power drop or phase shift. For example, distortion circuit 30 can perform the distortion by complex multiplying the transmit signal with a complex value for inverting the estimated power drop and / or phase shift and any I / Q imbalance in the system.

[0064] If desired, radar circuit 26 and control circuit 14 can periodically (e.g., after a predetermined period of time) re-calibrate radar circuit 26 (e.g., by looping back to operation 100) upon receipt of a user input or an application indication to callibrate radar circuit 26, upon detection of a change in the operating conditions of device 10, upon detection of a deterioration in the wireless performance of device 10, or in response to any other desired trigger condition. This can allow radar circuit 26 to continue to generate accurate estimates of distance R, position, and velocity throughout the operating life of device 10. In another specific implementation, radar circuit 26 can be calibrated only once.

[0065] Figure 4 A frequency diagram is included that shows how an exemplary multi-tone calibration signal mtone can be used to generate a baseband multi-tone calibration signal mtone' for estimating power drop and / or phase shift. Figure 4 An example of Figure 4 shows the simplest case where the multi-tone calibration signal mtone is a two-tone calibration signal with two tones having a frequency gap Δf therebetween. This two-tone calibration signal may sometimes also be referred to as a two-tone pair or a pair of tones. This example is merely illustrative, and generally the multi-tone calibration signal mtone may include any desired number of two or more tones, each tone being spaced from one or two other tones by a frequency gap Δf.

[0066] As Figure 4 shown in the frequency diagram 126 of Figure 4 , the DAC 32 may generate a multi-tone calibration signal mtone in a first frequency band B1 (e.g., baseband). The DAC 32 may use a tone generator, synthesizer, or other digital circuit / logic to generate the multi-tone calibration signal mtone. These tones of the multi-tone calibration signal mtone are spaced by a frequency gap Δf. The mixer 56 may up-convert the multi-tone calibration signal mtone to a second frequency band B2 (e.g., in the frequency band FB1), as shown by the arrow 130. This signal may be provided to the mixer 64 and the de-chirp path 48.

[0067] The mixer 64 may up-convert the multi-tone calibration signal mtone to a third frequency band B3 (e.g., in the frequency band FB2), as shown by the arrow 132. The frequency gap Δf remains unchanged after each up-conversion. The multi-tone calibration signal mtone in the frequency band B3 may be transmitted by the transmit antenna 40TX or the loopback path 80. The mixer 72 may down-convert the multi-tone calibration signal mtone from the frequency band B3 back to the frequency band B2. The de-chirp mixer 74 may mix the multi-tone calibration signal mtone in the frequency band B2 received through the de-chirp path 48 with the multi-tone calibration signal mtone in the frequency band B2 down-converted by the mixer 72 to recover the baseband multi-tone calibration signal mtone', as shown by the arrow 136.

[0068] As Figure 4 shown in the frequency diagram 128 of Figure 4 , 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. Then the next radio frequency in the FB2 frequency scan may be used (e.g., in Figure 3During subsequent iterations of operations 106 to 110). This can generate a multi-tone calibration signal mtone at another frequency in band B3, such as the multi-tone calibration signal mtone represented by the dashed arrow 135 in the frequency diagram 126. Due to the power drop of the system (e.g., as shown by the 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 the de-chirp mixer 74, the resulting baseband multi-tone calibration signal mtone' may have an amplitude A2, as shown by the dashed arrow 129 in the frequency diagram 128. The amplitude A2 can be measured by the phase and amplitude measurement circuit 88 and converted to a digital value in the digital data dat by the ADC 42.

[0069] Due to the frequency-dependent power drop imposed by the components of the radio circuit 24, the amplitude A2 is less than the amplitude A1. This can be repeated for each FB2 frequency in the scan to recover a complete estimate of the power drop 134 across the operating frequencies as exhibited by the radio circuit 24. In other words, the radar circuit 26 can shift the two-tone of the generated multi-tone calibration signal mtone along the frequency axis (e.g., by iterating Figure 3 operations 106 to 110), while maintaining a constant frequency gap Δf until the operating frequency range of the radar circuit 26 is sufficiently covered or sampled in two tones. Generally, the finer the offset of the radio frequency between each iteration, the more precisely the drop function (e.g., the power drop 134) can be estimated. In an embodiment where the radar circuit 26 only performs a single up-conversion, the scan of the operating frequencies can be performed within the band B2 without further up-conversion to the band B3 (e.g., the radar circuit 26 can transmit multi-tone calibration signals across different FB1 frequencies, where the power drop 134 is observed within the band FB1). The control circuit 14 can process the amplitudes stored in the digital data dat to estimate the power drop 134. The phase of each baseband multi-tone calibration signal mtone' can also be estimated as needed to identify any phase shifts imposed by the components of the radar circuit 26.

[0070] In the case of using only a single-tone calibration signal, the resulting baseband tone will be restored at DC in the frequency plot 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 with two or more tones having a frequency gap Δf spaced apart, the output of the mixing operation performed by the de-chirp mixer 74 (baseband multi-tone calibration signal mtone') will be frequency-offset from the DC by the frequency gap Δf. Thus, the frequency gap Δf can be selected such 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 a more accurate measurement of amplitude (e.g., amplitudes A1, A2, etc.) and thus collection of power drops, enabling an accurate estimation of distance R, position, and velocity over time.

[0071] Figure 5 is a graph showing three examples of potential power drops that can be estimated by the radar circuit 26 and the control circuit 14 based on the amplitudes of the baseband multi-tone calibration signal mtone' for pre-distorting the chirp signal. As Figure 5 shown, curve CA shows the linear power drop that can be estimated by the radar circuit 26 and the control circuit 14. Curve CC shows the parabolic power drop that can be estimated by the radar circuit 26 and the control circuit 14. Curve CB shows a combination of the linear and parabolic power drops that can be estimated by the radar circuit 26 and the control circuit 14. Each point on curves CA, CB, and CC can correspond to a respective 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 effect of a cable. A parabolic power drop such as that associated with curve CC is typically associated with the drop effect of the antennas 40TX and 40RX. A combination of the linear and parabolic power drops such as that associated with curve CB can represent, for example, a combination of the drop effects of the cable and the antennas 40TX and 40RX. These examples are merely illustrative, and in practice, the estimated power drops can have other shapes.

[0072] In the simplest case where the multi-tone calibration signal mtone is a two-tone calibration signal (e.g., as Figure 4 shown), the two-tone pair can be represented as complex tones using, for example, Equation 1.

[0073]

[0074] 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 performing Figure 3For the operation, the control circuit 14 can estimate the power drop and / or phase shift effects introduced by the radar circuit 26, and thus can estimate the complex weight values k 1 and k 2 . Then the complex weight values k 1 and k 2 can be used to form values for pre-distorting the chirp signal (e.g., the chirp signal can be multiplied by values such as to pre-distort the chirp signal so as to invert the subsequent power drop and phase shift effects imposed by the components of the radar circuit 26).

[0075] In the baseband of the transmit chain 52, the two-tone calibration signal can be represented by one complex tone or two real tones consisting of four symmetric complex tones, as given by Equation 2.

[0076] cos(ωt)+cos((1 + Δ)ωt) = 0.5((e -jωt + e jωt )+(e -j(1+Δ)ωt + e j(1+Δ)ωt ))(2)

[0077] In the FB2 (e.g., RF) domain, the complex tone pairs are frequency-dependent attenuated, where the mixer path is represented by Expression 3 and the antenna path is represented by Expression 4.

[0078] ((k 1 e -jωt + k 3 e jωt )+(k 1 e -j(1+Δ)ωt + k 3 e j(1+Δ)ωt )) * (3)

[0079] (k 2 e -jωt + k 4 e jωt )+(k 2 e -j(1+Δ)ωt + k 4 e j(1+Δ)ωt ) (4)

[0080] In the baseband of the receive chain 54, after mixing by the de-chirp mixer 74 (a process sometimes referred to herein as de-chirping), several mixing products are generated. The ±n·ω mixing products at ≈1 GHz are attenuated by the LPF 76. The ±n·ω mixing products less than 20 MHz (e.g., ≈1 MHz) can be evaluated to estimate the power drop. More generally, Expression 5 can be used to model a single complex tone, Expression 6 can be used to model two complex tones, and Expression 7 can be used to model four complex tones (e.g., two real tones).

[0081]

[0082]

[0083]

[0084] In Expressions 6 and 7, "T" is the transpose operator and n is an integer exponent. Expression 6 represents five equations, two of which are linearly related to the other three. Two parameters of interest (low frequency) and (high frequency) are estimated simultaneously. IQ-imbalance correction can be performed prior to the drop 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 for generating the multi-tone calibration signal mtone can be doubled or it can 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.

[0085] The distortion performed by the distortion circuit 30 can be carried out in the digital domain or the analog domain. Figure 6 is a diagram showing an example of how the distortion circuit 30 can include a pre-distortion circuit in the digital domain. As Figure 6 shown, the input of the DAC 32 can be coupled to the digital circuit 140. The digital circuit 140 can include a transmit signal generator 28 and a pre-distortion circuit 146 (e.g., the distortion circuit 30 can include a digital pre-distortion (DPD) circuit such as the pre-distortion circuit 146). The input of the pre-distortion circuit 146 can be coupled to the output of the transmit signal generator 28. The output of the pre-distortion circuit 146 can be coupled to the input of the DAC 32. The DAC 32 can have an output 142 coupled to the mixer 56 ( Figure 2 ). The pre-distortion circuit 146 can have a control path 144 that receives a control signal ctrl from the control circuit 14.

[0086] The transmit signal generator 28 can generate a transmit signal (e.g., a chirp signal). The predistortion circuit 146 can multiply the transmit signal by a value for predistorting the transmit signal so that the predistortion in the transmit signal will cancel the estimated power drop, phase shift, and / or any I / Q imbalance imposed by components of the radar circuit 26. The control signal ctrl can include the value used by the predistortion circuit 146 to predistort the chirp signal. As the estimated power drop and / or phase shift change over time, the control signal ctrl can change the value used by the predistortion circuit 146 to predistort the transmit signal. The DAC 32 can convert the predistorted transmit signal from the digital domain to the analog domain. Figure 6 The examples are illustrative only. Other predistortion schemes or architectures can be used. The predistortion circuit 146 can alternatively be implemented in the analog domain. The distortion circuit 30 can additionally or alternatively include a post-distortion circuit that operates on the received signal to compensate for power drop and phase shift.

[0087] In this way, even if the receive chain 54 does not support the full RF bandwidth, the device 10 can perform power drop estimation for the full RF bandwidth of the radar circuit 26. At the same time, direct access to the RF signal is not required to perform the power drop estimation. This can be used to reduce the receive chain bandwidth, thereby reducing the current consumption in the system. Calibrating the radar circuit 26 using the multi-tone calibration signal mtone can allow the device 10 to select the baseband offset frequency (e.g., via the selected frequency gap Δf) to an ideal tone position relevant to the system so that the baseband multi-tone calibration signal mtone' is not affected by system impairments, LO noise, etc. Power drop estimation and compensation can be performed during the final production test of the device 10 and / or during the service life of the device 10 so that the drop compensation adapts to any potential aging effects in the device 10. In addition, drop tracking and compensation throughout the life cycle of the device 10 can be used to check for changes in the operation of the device 10, such as the case where a housing or lid is attached to the device 10, thereby allowing the device 10 to adjust the system configuration (e.g., gain settings, background cancellation, etc.) accordingly.

[0088] where the radar circuit 26 performs multiple up-conversions Figures 2 to 4 The examples are merely illustrative embodiments showing how the multi-tone calibration signal mtone can be used to calibrate the radar circuit 26. Generally, the radar circuit 26 can perform any desired number of one or more up-conversions and can include any desired number of two or more mixers. Figure 7 is a circuit diagram in an example where the radar circuit 26 performs at least one up-conversion and includes at least two mixers.

[0089] As Figure 7As shown, the radar circuit 26 may include a first mixer, such as mixer 150 (e.g., via an I / Q path) coupled to the output of the DAC 32, 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 de-chirping mixer) having a first input coupled to the first output of splitter 154 via a signal (e.g., de-chirping) path 158, and a circuit 156 (e.g., one or more line drops) coupled between the second output of splitter 154 and the second input of mixer 152. Other circuit components (such as amplifiers, filters, ADCs (e.g., Figure 2 ADC 42)) or other components may be interposed at any desired location within the radar circuit 26. The circuit 156 may include other portions of the radar circuit 26 that introduce power drops and phase shifts to the radar circuit 26 (e.g., antennas, loopback paths, transmission lines, amplifiers, filters, etc.). For example, in an embodiment where the radar circuit 26 performs multiple up-conversions as Figure 2 shown, the circuit 156 may include mixers 64 and 72, amplifiers 66 and 70, and antennas 40TX and 40RX. The circuit 156 may sometimes be referred to herein as an intermediate circuit.

[0090] During spatial ranging operations, the DAC 32 may transfer a transmit signal (e.g., a chirp signal) generated using the transmit signal generator 28 ( Figure 2 ) to the mixer 150. The mixer 150 may up-convert the transmit signal to a higher frequency using the LO 160, such as Figure 2 a frequency in the frequency band FB1 or frequency band FB2 (e.g., the LO 160 may include Figure 2 FB1LO 50 or FB2LO 46 of Figure 1 ). The splitter 154 may transfer the up-converted transmit signal via the signal path 158 to the mixer 152 and to the circuit 156. The circuit 156 may transmit the up-converted transmit signal (e.g., the radio frequency signal 36 as Figure 1 ) and may receive a corresponding reflected signal (e.g., Figure 1 the reflected signal 38). The circuit 156 may transfer the received reflected signal to the mixer 152. The mixer 152 may mix the received signal with the transmit signal received via the signal path 158 to generate a corresponding baseband signal at the output path 162. The control circuit 14 (

[0091] During calibration, the DAC 32 can transmit a multi-tone calibration signal mtone. The mixer 150 can up-convert the multi-tone calibration signal. The splitter 154 can transmit the up-converted multi-tone calibration signal through the signal path 158 to the mixer 152 and to the circuit 156. The circuit 156 can transmit the up-converted multi-tone calibration signal (e.g., in a closed loop in the air or through a loopback path), and then receive this signal at the mixer 152. The mixer 152 can mix the up-converted multi-tone calibration signal received through the signal path 158 with the up-converted multi-tone calibration signal received from the circuit 156 to generate a baseband multi-tone calibration signal mtone'. The control circuit 14 can repeat this process while scanning the mixer 150 at different frequencies (e.g., the operating frequency of the radar circuit 26). The control circuit 14 can use the baseband multi-tone calibration signal generated by the mixer 152 to estimate the power drop and / or phase shift of the circuit 156. The control circuit 14 can then use the distortion circuit 30( Figure 1 ) to distort the subsequently transmitted signal to mitigate the power drop and phase shift of the circuit 156. In other words, Figure 7 the radar circuit 26 can use the multi-tone calibration signal mtone to calibrate according to Figure 3 the operation of (e.g., in an embodiment where the radar circuit 26 only performs a single up-conversion, the FB1 frequency can be selected at the operation 104 of Figure 3 instead of the FB2 frequency, the up-conversion at the operation 106 can be omitted, the FB1 frequency can be processed when determining whether to proceed along the path 112 or 118, and a new FB1 frequency can be selected at the operation 114).

[0092] The methods and operations described above in connection with Figures 1 to 7 can be performed by the components of the device 10 using software, firmware, and / or hardware (e.g., dedicated circuits or hardware). The software code for performing these operations can be stored on a non-transitory computer-readable storage medium (e.g., a tangible computer-readable storage medium), which is stored on one or more of the components of the device 10 (e.g., Figure 1 the storage circuit 16). This software code is sometimes referred to as software, data, instructions, program instructions, or code. The non-transitory computer-readable storage medium can include drives, non-volatile memories such as non-volatile random access memories (NVRAMs), removable flash drives or other removable media, other types of random access memories, etc. The software stored on the non-transitory computer-readable storage medium can be executed by a processing circuit on one or more of the components of the device 10 (e.g., Figure 1 the processing circuit 18, etc.). The processing circuit can 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 of can be implemented using hardware (e.g., circuit components, digital logic gates, etc.) and / or using software.

[0093] 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 includes: 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; a second mixer having a first input terminal configured to receive the multi-tone calibration signal in the second frequency band from the output terminal of the first mixer via a signal path, and having a second input terminal configured to receive the multi-tone calibration signal in the second frequency band via an intermediate circuit communicatively coupled between the 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 the 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 distort the transmitted signal based on the estimated power drop.

[0094] According to another embodiment, the transmitted signal includes a chirp signal, and the signal path includes a de-chirp path. The wireless circuit includes a chirp generator configured to generate a chirp signal for transmission by a transmission antenna, the first mixer being configured to up-convert the chirp signal to a second frequency band, the first input terminal of the second mixer being configured to receive the chirp signal in the second frequency band via the de-chirp path, and the second input terminal being configured to receive a reflected version of the chirp signal via a reception antenna.

[0095] According to another embodiment, the wireless communication circuit includes a signal splitter having an input terminal coupled to the output terminal of the first mixer, a first output terminal coupled to the intermediate circuit, and a second output terminal coupled to the first input terminal of the second mixer via a signal path.

[0096] According to another embodiment, the intermediate circuit includes a third mixer communicatively coupled to the first output terminal of the signal splitter and configured to up-convert the multi-tone calibration signal from the second frequency band to a third frequency band; and a fourth mixer communicatively coupled to the second input terminal and configured to down-convert the multi-tone calibration signal from the third frequency band to the second frequency band.

[0097] 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.

[0098] According to another embodiment, the second frequency band includes frequencies greater than 20 GHz.

[0099] According to another embodiment, the intermediate circuit includes a transmit antenna communicatively coupled to the output of the third mixer and configured to transmit a multi-tone calibration signal in the third frequency band; and a receive antenna communicatively coupled to the input of the fourth mixer and configured to receive the multi-tone calibration signal transmitted by the transmit antenna in the third frequency band.

[0100] According to another embodiment, the intermediate circuit includes a loopback path communicatively coupled between the output of the third mixer and the input of the fourth mixer, the loopback path being configured to convey a multi-tone calibration signal in the third frequency band.

[0101] According to another embodiment, the distortion circuit includes a digital pre-distortion circuit communicatively coupled to the input of the DAC.

[0102] 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.

[0103] 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 radio frequencies within 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 radio frequencies within the plurality of radio frequencies, and the control circuit is configured to estimate the power drop of the intermediate circuit across each of the radio frequencies within the plurality of radio frequencies.

[0104] According to another embodiment, the baseband multi-tone calibration signal is frequency-offset from a direct current (DC) frequency by a frequency gap, and the frequency gap is less than or equal to 20 MHz.

[0105] According to one embodiment, a method for calibrating a radar circuit is provided, the method comprising; generating a multi-tone calibration signal having a first tone and a second tone with a frequency gap less than 20 MHz spaced apart from the first tone using a digital-to-analog converter (DAC) in a transmit chain of the radar circuit; up-converting the multi-tone calibration signal from baseband to a first frequency band using a first mixer in the transmit chain; up-converting the multi-tone calibration signal from the first frequency band to a second frequency band using a second mixer in the transmit chain; down-converting the multi-tone calibration signal up-converted by the second mixer from the second frequency band to the first frequency band using a third mixer in a receive chain of the radar circuit; generating a baseband multi-tone calibration signal by mixing the multi-tone calibration signal up-converted by the first mixer with the multi-tone calibration signal down-converted by the third mixer using a de-chirp mixer in the receive chain, the baseband multi-tone calibration signal being spaced apart from a direct current (DC) frequency by the frequency gap; using a control circuit to estimate a power drop and a phase shift of the radar circuit based on the baseband multi-tone calibration signal generated by the de-chirp mixer, and pre-distorting a chirp signal transmitted through the transmit chain using a pre-distortion circuit in the transmit chain based on the power drop and the phase shift estimated by the control circuit.

[0106] According to another embodiment, the method comprises: scanning the second frequency band within a plurality of radio frequencies using the second mixer; down-converting the multi-tone calibration signal for each of the radio frequencies in the plurality of radio frequencies using the third mixer; generating a baseband multi-tone calibration signal for each of the radio frequencies in the plurality of radio frequencies using the de-chirp mixer, and using a control circuit to estimate a power drop of the radar circuit based on the baseband multi-tone calibration signal generated by the de-chirp mixer for each of the radio frequencies in the plurality of radio frequencies.

[0107] According to another embodiment, the method comprises low-pass filtering the baseband multi-tone calibration signal for each of the radio frequencies in the plurality of radio frequencies using a low-pass filter; measuring an amplitude and a phase of the baseband multi-tone calibration signal for each of the radio frequencies in the plurality of radio frequencies using a measurement circuit; converting the amplitude and the phase measured by the measurement circuit into digital data using an analog-to-digital converter (ADC); storing the digital data using the control circuit, and estimating a power drop using the control circuit based on the stored digital data.

[0108] According to another embodiment, pre-distorting the chirp signal comprises multiplying the chirp signal by a factor selected to invert the power drop estimated by the control circuit when transmitting the chirp signal through the transmit chain.

[0109] According to another embodiment, the method includes: transmitting a multi-tone calibration signal in a second frequency band using a transmit antenna with a transmit chain, and receiving the multi-tone calibration signal in the second frequency band using a receive antenna with a third mixer.

[0110] According to one embodiment, an electronic device is provided, the electronic device includes: a first antenna; a second antenna; a radar circuit configured to generate a transmit signal transmitted using the first antenna, the second antenna being 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 being 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 with a frequency gap less than 20 MHz spaced from the first tone, the control circuit being configured to use the multi-tone calibration signal to estimate a power drop of the radar circuit, and the control circuit being configured to distort the transmit signal based on the estimated power drop.

[0111] According to another embodiment, the DAC is configured to convert the transmit signal from the digital domain to the analog domain.

[0112] According to another embodiment, the multi-tone calibration signal has a third tone spaced from the second tone by a frequency gap and a fourth tone spaced from the third tone by a frequency gap.

[0113] The foregoing is merely exemplary and various modifications may be made to the described embodiments. The foregoing embodiments may be implemented independently or in any combination.

Claims

1. A wireless communication circuit for performing spatial ranging operations on an external object using a transmitted signal, 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; a second mixer having a first input terminal configured to receive the multi-tone calibration signal in the second frequency band from an output terminal of the first mixer via a signal path, and having a second input terminal configured to receive the multi-tone calibration signal in the second frequency band via an intermediate circuit communicatively coupled between the output terminal of the first mixer and the second input terminal, wherein the second mixer is 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 distort the transmitted signal based on the estimated power drop.

2. The wireless communication circuit according to claim 1, wherein the transmitted signal includes a chirp signal, and the signal path includes a de-chirp path, and the wireless circuit further comprises: a chirp generator configured to generate the chirp signal for transmission by a transmission antenna, wherein the first mixer is configured to up-convert the chirp signal to the second frequency band, the first input terminal of the second mixer is configured to receive the chirp signal in the second frequency band via the de-chirp path, and the second input terminal is configured to receive a reflected version of the chirp signal via a reception antenna.

3. The wireless communication circuit according to claim 1, further comprises: a signal splitter having an input terminal coupled to the output terminal of the first mixer, a first output terminal coupled to the intermediate circuit, and a second output terminal coupled to the first input terminal of the second mixer via the signal path.

4. The wireless communication circuit according to claim 3, wherein the intermediate circuit comprises: a third mixer communicatively coupled to the first output terminal of the signal splitter and configured to up-convert the multi-tone calibration signal from the second frequency band to a third frequency band; and a fourth mixer communicatively coupled to the second input terminal and configured to down-convert the multi-tone calibration signal from the third frequency band to the second frequency band.

5. The wireless communication circuit according to claim 4, wherein the first frequency band includes a baseband frequency, the second frequency band includes a frequency greater than the baseband frequency and less than 10 GHz, and the third frequency band includes a frequency greater than the second frequency band.

6. The wireless communication circuit according to claim 5, wherein the second frequency band includes frequencies greater than 20 GHz.

7. The wireless communication circuit according to claim 4, wherein the intermediate circuit comprises: a transmitting antenna communicatively coupled to an output of the third mixer and configured to transmit the multi-tone calibration signal in the third frequency band; and a receiving antenna communicatively coupled to an input of the fourth mixer and configured to receive the multi-tone calibration signal transmitted by the transmitting antenna in the third frequency band.

8. The wireless communication circuit according to claim 4, wherein the intermediate circuit includes a loopback path communicatively coupled between the output of the third mixer and the input of the fourth mixer, the loopback path being configured to convey the multi-tone calibration signal in the third frequency band.

9. The wireless communication circuit according to claim 1, wherein the distortion circuit includes a digital pre-distortion circuit communicatively coupled to an input of the DAC.

10. The wireless communication circuit according to claim 1, wherein the measurement circuit is configured to measure a phase of the baseband multi-tone calibration signal, the control circuit is configured to estimate a phase shift of the intermediate circuit based on the phase measured by the measurement circuit, and the control circuit is configured to distort the transmitted signal based on the phase shift estimated by the measurement circuit.

11. The wireless communication circuit according to claim 1, wherein 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 the baseband multi-tone calibration signal for each of the radio frequencies among 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 radio frequencies among the plurality of radio frequencies, and the control circuit is configured to estimate a power drop of the intermediate circuit across each of the radio frequencies among the plurality of radio frequencies.

12. The wireless communication circuit according to claim 1, wherein the baseband multi-tone calibration signal is spaced apart from a direct current (DC) frequency by the frequency gap, and the frequency gap is less than or equal to 20 MHz.

13. A method for calibrating a radar circuit, the method comprises: generating, by 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 less than 20 MHz; up-converting, by using a first mixer in the transmit chain, the multi-tone calibration signal from baseband to a first frequency band; up-converting, by using a second mixer in the transmit chain, the multi-tone calibration signal from the first frequency band to a second frequency band; down-converting, by using a third mixer in a receive chain of the radar circuit, the multi-tone calibration signal up-converted by the second mixer from the second frequency band to the first frequency band; In the receiving chain, a de-chirping mixer is utilized to generate a baseband multi-tone calibration signal by mixing the multi-tone calibration signal up-converted by the first mixer with the multi-tone calibration signal down-converted by the third mixer, and the baseband multi-tone calibration signal is spaced from the direct current (DC) frequency by the frequency gap; A control circuit is utilized to estimate the power drop and phase shift of the radar circuit based on the baseband multi-tone calibration signal generated by the de-chirping mixer; And In the transmitting chain, a pre-distortion circuit is utilized to pre-distort the chirp signal transmitted through the transmitting chain based on the power drop and phase shift estimated by the control circuit.

14. The method according to claim 13, further comprising: Utilizing the second mixer to scan the second frequency band within a plurality of radio frequencies; Utilizing the third mixer to down-convert the multi-tone calibration signal for each of the radio frequencies among the plurality of radio frequencies; Utilizing the de-chirping mixer to generate the baseband multi-tone calibration signal for each of the radio frequencies among the plurality of radio frequencies; And Utilizing the control circuit to estimate the power drop of the radar circuit based on the baseband multi-tone calibration signal generated by the de-chirping mixer for each of the radio frequencies among the plurality of radio frequencies.

15. The method according to claim 14, further comprising: Utilizing a low-pass filter to perform low-pass filtering on the baseband multi-tone calibration signal for each of the radio frequencies among the plurality of radio frequencies; Utilizing a measurement circuit to measure the amplitude and phase of the baseband multi-tone calibration signal for each of the radio frequencies among 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 the control circuit to store the digital data; And Utilizing the control circuit to estimate the power drop based on the stored digital data.

16. The method according to claim 13, wherein pre-distorting the chirp signal includes multiplying the chirp signal by a factor selected to invert the power drop estimated by the control circuit when transmitting the chirp signal through the transmitting chain.

17. The method according to claim 13, further comprising: Utilizing the transmitting chain to transmit the multi-tone calibration signal in the second frequency band using a transmitting antenna; And Utilizing the third mixer to receive the multi-tone calibration signal in the second frequency band using a receiving antenna.

18. An electronic device, the electronic device comprising: A first antenna; A second antenna; A radar circuit configured to generate a transmission signal transmitted using the first antenna, and the second antenna is configured to receive a reflected version of the transmission signal transmitted using the first antenna; A control circuit configured to perform a spatial ranging operation based on the reflected version of the transmission signal received using the second antenna; And The digital-to-analog converter (DAC) in the radar circuit, wherein the DAC is 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 with a frequency gap less than 20 MHz spaced apart from the first tone, the control circuit being configured to use the multi-tone calibration signal to estimate a power drop in the radar circuit, and the control circuit being configured to distort the transmitted signal based on the estimated power drop.

19. The electronic device according to claim 18, wherein the DAC is configured to convert the transmitted signal from the digital domain to the analog domain.

20. The electronic device according to claim 18, wherein the multi-tone calibration signal has a third tone spaced apart from the second tone by the frequency gap and a fourth tone spaced apart from the third tone by the frequency gap.

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