阅读说明：本技术 雷达系统 (Radar system ) 是由 K·苏布拉吉 S·拉奥 S·穆拉利 K·拉玛苏布拉马尼安 于 2020-03-25 设计创作，主要内容包括：本公开的各方面提供了一种雷达系统,该雷达系统包括雷达IC(300),该雷达IC(300)包括定时引擎(342)、本地振荡器(330)和调制器(350)。定时引擎被配置为生成一个或多个线性调频脉冲控制信号。本地振荡器被配置为接收一个或多个线性调频脉冲控制信号并根据一个或多个线性调频脉冲控制信号生成包括第一线性调频脉冲序列的帧。调制器被配置为调制第一线性调频脉冲序列以生成第二线性调频脉冲序列,使得帧包括第一线性调频脉冲序列和偏移第一频率值的第二线性调频脉冲序列。(Aspects of the present disclosure provide a radar system including a radar IC (300), the radar IC (300) including a timing engine (342), a local oscillator (330), and a modulator (350). The timing engine is configured to generate one or more chirp control signals. The local oscillator is configured to receive one or more chirp control signals and generate a frame including a first sequence of chirps according to the one or more chirp control signals. The modulator is configured to modulate the first chirp sequence to generate a second chirp sequence such that the frame includes the first chirp sequence and the second chirp sequence offset by a first frequency value.)

1. A radar system, comprising:

radar transceiver integrated circuit (radar transceiver IC) comprising:

a timing engine configurable to generate one or more chirp control signals;

a local oscillator coupled to the timing engine, the local oscillator configured to:

receiving the one or more chirp control signals; and

generating a frame comprising a first chirp sequence from the one or more chirp control signals; and

a modulator coupled to the local oscillator, the modulator configured to modulate the first chirp sequence to generate a second chirp sequence such that the frame includes the first chirp sequence and the second chirp sequence offset by a first frequency value.

2. The radar system of claim 1, wherein the radar transceiver IC further comprises a control module coupled to the timing engine and the modulator, and wherein the control module is configured to:

transmitting one or more parameter values to the timing engine to at least partially control generation of the chirp control signal; and

transmitting one or more signals to the modulator to at least partially control the modulation of the first chirp sequence.

3. The radar system of claim 1, wherein the radar transceiver IC is configured to:

receiving a reflected frame of chirps, the reflected chirps comprising the first and second sequences of chirps reflected by an object within a field of view of the radar system;

generating a digital intermediate frequency signal (IF) corresponding to the reflected chirp frame; and

demodulating the digital IF signal to obtain a first demodulated digital IF signal corresponding to the first chirp sequence and a second demodulated digital IF signal corresponding to the second chirp sequence, wherein the first chirp signal sequence is offset from the second chirp sequence by the first frequency value in the digital IF signal prior to demodulation.

4. The radar system of claim 3, further comprising a processing element configured to:

performing a range fast Fourier transform (range FFT) on the first demodulated digital IF signal and the second demodulated digital IF signal to generate a first range array of the first demodulated digital IF signal and a second range array of the second demodulated digital IF signal; and

performing a Doppler FFT on the first range array and the second range array to generate a first range-Doppler array corresponding to the first range array and a second range-Doppler array corresponding to the second range array.

5. The radar system of claim 4, wherein to determine the velocity of the object within the field of view of the radar system, the processing element is further configured to:

calculating a first velocity estimate of the object within the field of view of the radar system based on at least one of the first range-Doppler array or the second range-Doppler array;

calculating a second velocity estimate for the object within the field of view of the radar system based on a phase difference of peaks corresponding to the object within the field of view of the radar system in the first and second range-doppler arrays; and

calculating the velocity of the object based on the first velocity estimate and the second velocity estimate.

6. The radar system of claim 1, wherein the frame containing the first chirp sequence is associated with a first maximum measurable speed, and wherein the frame containing the first chirp sequence and the second chirp sequence is associated with a second maximum measurable speed that is greater than the first maximum measurable speed.

7. The radar system of claim 1, wherein the radar system is configured to operate in a calibration mode to determine a system phase offset between receive channels of the radar transceiver IC, and wherein the system phase offset is used to determine a velocity of an object within a field of view of the radar system.

8. The radar system of claim 1, wherein the first chirp sequence and the second chirp sequence are defined by 1+ e^j2πΔftDescribe, wherein Δ f is the first frequency value, and wherein t represents time.

9. The radar system of claim 1, wherein the first chirp sequence and the second chirp sequence are transmitted using a same antenna of the radar system.

10. A method for determining an approximate velocity in a radar system, the method comprising:

initiating transmission of a chirp frame via a transmission channel having a first chirp sequence and a second chirp sequence offset in frequency (Δ f) from the first chirp sequence;

receiving a reflected chirp frame via a receive channel, the reflected chirp comprising the first and second chirp sequences reflected by an object within a field of view of the radar system;

generating a digital intermediate frequency signal (digital IF signal) corresponding to the reflected chirp frame via the receive channel; demodulating, via a processor, the digital IF signal to form a first demodulated IF signal corresponding to the first chirp sequence and a second demodulated IF signal corresponding to the second chirp sequence; and

determining, via the processor, the approximate velocity based at least in part on the first demodulated IF signal and the second demodulated IF signal.

11. The method of claim 10, wherein determining the approximate velocity of an object within a field of view of the radar system based at least in part on the first and second demodulated IF signals comprises:

performing a range fast fourier transform (range FFT) on the first and second demodulated IF signals to generate a first range array corresponding to the first demodulated IF signal and a second range array corresponding to the second demodulated IF signal; and

performing a Doppler FFT on the first range array and the second range array to generate a first range-Doppler array and a second range-Doppler array.

12. The method of claim 11, further comprising determining the approximate velocity of the object within the field of view of the radar system using at least one of the first range-doppler array or the second range-doppler array by:

calculating a first velocity estimate of the object within the field of view of the radar system based on at least one of the first range-Doppler array or the second range-Doppler array;

calculating a second velocity estimate for the object within the field of view of the radar system based on a phase difference of peaks corresponding to the object within the field of view of the radar system in the first and second range-doppler arrays; and

calculating the approximate velocity of the object based on the first velocity estimate and the second velocity estimate.

13. The method of claim 12, further comprising operating in a calibration mode to determine a system phase offset between receive channels of a radar transceiver integrated circuit (radar transceiver IC), wherein the system phase offset is used to determine the approximate velocity of the object within the field of view of the radar system.

14. The method of claim 10, wherein initiating transmission of the chirp frame having the first chirp sequence and the second chirp sequence offset by Δ f from the first chirp sequence comprises:

generating one or more chirp control signals according to the chirp parameter value;

generating a frame comprising the first chirp sequence from the one or more chirp control signals, the frame comprising the first chirp sequence and being associated with a first maximum measurable speed; and

modulating the first chirp sequence to generate a second chirp sequence such that the frame contains the first chirp sequence and the second chirp sequence offset by the Δ f, the frame including the first chirp sequence and the second chirp sequence and being associated with a second maximum measurable speed greater than the first maximum measurable speed.

15. The method of claim 14, wherein the first chirp sequence and the second chirp sequence are defined by 1+ e^j2πΔftAnd wherein t represents time.

16. The method of claim 10, wherein the second chirp sequence is offset from the first chirp sequence by the Δ f in the digital IF signal prior to demodulation.

17. A method for determining velocity in a radar system, the method comprising:

calculating, via a processing element, a first velocity estimate based on at least one range-doppler array obtained based on transmission of frames having a first chirp sequence and a second chirp sequence offset by a frequency (Δ f) from the first chirp sequence;

calculating, via the processing element, a second velocity estimate based on a phase difference of a first peak in the at least one range-doppler array and a second peak corresponding to the first peak in at least a second range-doppler array, wherein the at least second range-doppler array is obtained based on transmitting the chirp frame having the first chirp sequence and the second chirp sequence offset from the first chirp sequence by the Δ f; and

calculating, via the processing element, the speed based on the first speed estimate and the second speed estimate.

18. The method of claim 17, wherein the method is performed according to 1+ e by using an I/Q modulator^j2πΔftModulating the first chirp sequence to offset the second chirp sequence from the first chirp sequence, and wherein t represents time.

19. The method of claim 18, wherein the first chirp sequence is modulated such that it is in accordance with 1+ e^j2πΔftDescribing the first chirp sequence and the second chirp sequence increases the maximum measurable speed of the radar system by aboutWherein T is_CIs the period of the first chirp sequence and the second chirp sequence, whereinAnd wherein s is the slope of the first chirp sequence.

20. The method of claim 17, wherein calculating the speed based on the first and second speed estimates comprises:

determining a degree of ambiguity associated with the first and second velocity estimates; and

calculating the velocity of an object in a field of view of the radar system based on the first velocity estimate, the second velocity estimate, and the determined ambiguity.

Background

Various examples of Frequency Modulated Continuous Wave (FMCW) radar systems may be embedded in a variety of applications, such as industrial applications, automotive applications, and the like. For example, an embedded FMCW radar system may be included in a vehicle to provide data for adaptive cruise control, collision warning, blind spot assist/warning, lane change assist, parking assist, and the like. In other examples, an embedded FMCW radar system in an industrial application may provide data to help navigate autonomous devices in a plant, track motion, and the like.

Disclosure of Invention

Aspects of the present disclosure provide a radar system. In one example, a radar system includes a radar transceiver Integrated Circuit (IC). The radar transceiver IC includes a timing engine, a local oscillator coupled to the timing engine, and a modulator coupled to the local oscillator. The timing engine is configured to generate one or more chirp control signals. The local oscillator is configured to receive one or more chirp control signals and generate a frame including a first sequence of chirps according to the one or more chirp control signals. The modulator is configured to modulate the first chirp sequence to generate a second chirp sequence such that the frame includes the first chirp sequence and the second chirp sequence offset by a first frequency value.

Other aspects of the disclosure provide a method for determining an approximate velocity in a radar system. In one example, the method includes initiating transmission of a chirp frame having a first chirp sequence and a second chirp sequence offset in frequency (Δ f) from the first chirp sequence via a transmission channel. The method further includes receiving a reflected chirp frame via a receive channel, the reflected chirp comprising a first sequence of chirps and a second sequence of chirps reflected by an object within a field of view of the radar system. The method further includes generating a digital Intermediate Frequency (IF) signal corresponding to the reflected chirp frame via the receive channel. The method further includes demodulating, via the processor, the digital IF signal to form a first demodulated IF signal corresponding to the first chirp sequence and a second demodulated IF signal corresponding to the second chirp sequence, and determining, via the processor, an approximate velocity based at least in part on the first demodulated IF signal and the second demodulated IF signal.

Other aspects of the disclosure provide a method for determining velocity in a radar system. In one example, the method includes calculating, via a processing element, a first velocity estimate based on at least one range-doppler array obtained based on transmitting a chirp frame having a first chirp sequence and a second chirp sequence offset by Δ f from the first chirp sequence. The method further includes calculating, via the processing element, a second velocity estimate based on a phase difference of a first peak in at least one range-doppler array and at least a second range-doppler array, wherein the at least a second range-doppler array is obtained based on transmitting a chirp frame having a first chirp sequence and a second chirp sequence offset Δ f from the first chirp sequence. The method further includes calculating, via the processing element, a speed based on the first speed estimate and the second speed estimate.

Drawings

For a detailed description of various examples, reference will now be made to the accompanying drawings in which:

FIG. 1 is a waveform diagram illustrating chirp transmission;

FIG. 2 shows a block diagram of an illustrative Frequency Modulated Continuous Wave (FMCW) radar system;

FIG. 3 shows a block diagram of an illustrative radar transceiver Integrated Circuit (IC);

FIG. 4 shows a flow diagram of one illustrative method for an FMCW radar;

figure 5 shows a schematic diagram of an illustrative range-doppler array;

FIG. 6 shows a flow diagram of one illustrative method for initiating chirp frame transmission;

FIG. 7 shows a flow diagram of one illustrative method for determining the velocity of an object detected by an FMCW radar system;

FIG. 8 shows a flow chart of an illustrative method for calibrating an FMCW radar system; and

FIG. 9 shows a flow chart of one illustrative method for calibrating an FMCW radar system.

Detailed Description

At least some examples of Frequency Modulated Continuous Wave (FMCW) radar systems transmit a frame that contains a series of frequency ramps called chirps. These chirps may be reflected back to the FMCW radar system by the subject object. Upon receiving a signal containing the reflected chirp, the FMCW radar system may down-convert, digitize, and process the received signal to determine characteristics of the subject object. These characteristics may include range, velocity, angle of arrival, etc. of the subject object when the subject object is in view of the FMCW radar system. At least some examples of FMCW radar systems are capable of accurately estimating the velocity of a subject object up to a maximum unambiguous velocity. For subject objects having a velocity greater than the maximum unambiguous velocity, the velocity of the subject object measured by the FMCW radar system may be inaccurate in one or both of the velocity amplitude and/or sign.

In at least some FMCW radar systems, a plurality of chirp sequences (e.g., such as a sequence of consecutive equally spaced chirps) are transmitted and reflections of the chirps are received to generate a radar signal. After each chirp sequence, there may be some idle time (e.g., inter-frame idle time) to allow processing of the radar signal produced by the reflected chirp. The acquisition time of the chirp sequence and the subsequent inter-frame idle time together may form a radar frame. In at least one example, the reflected signals received by each antenna of the FMCW radar system are mixed with the transmit signals to generate filtered and digitized Intermediate Frequency (IF) signals. Signal processing may then be performed on the resulting digital IF signals (e.g., one for each receive antenna in an FMCW radar system) to extract any one or more of range, velocity, and/or angle of potential objects in the radar field of view.

In at least one example, for each receive channel (e.g., receive antenna and/or associated processing hardware in an FMCW radar system), a range Fast Fourier Transform (FFT) is performed on the digitized samples of each reflected chirp to convert the data from the time domain to the frequency domain. At least some of the peaks in the resulting frequency domain array correspond to ranges (distances) of potential objects. In some examples, the results of the distance FFT are saved in memory, e.g., for further processing. In some examples, an FMCW radar system may generate a set of range FFT results (e.g., one range array (or range matrix)) for each receive antenna in the FMCW radar system. In at least one example, if there are N time samples in the chirp, N range results, each corresponding to a particular range bin, are stored for the chirp. Similarly, if there are M chirps in the chirp sequence, an array of MxN distance values is generated by the distance FFT, where N columns are the signal values across the respective distance bins of the M chirps.

In at least one example, for each range array, a doppler FFT is performed on each of the corresponding range values of the chirps in the chirp sequence. For example, a doppler FFT is performed on each of the N columns of the MxN array. At least some of the peaks in the resulting MxN range-doppler plane (which may also be referred to as a range-doppler array or range-doppler slice) correspond to the range and relative velocities (e.g., velocities) of potential objects in the radar field of view. In at least one example, the FMCW radar system generates one range-doppler array for each receive antenna of the FMCW radar system.

In at least some examples, the FMCW radar system then processes the range-doppler array to determine information for at least some potential objects in the radar field of view. When using multiple receivers, each connected to a receive antenna, each reflected signal may have a different delay, depending on the angle at which the object reflected the signal. In at least one example, potential objects in the radar field of view are detected by considering peaks in the range-doppler array. The information about the potential object may then be used to apply specific processing, such as object tracking, object movement rate, movement direction, and the like. In an automotive environment, object data may be used for any one or more of lane change assist, parking assist, blind spot detection, rear collision warning, emergency braking, and/or cruise control, for example.

In at least one example, an FMCW radar system estimates the velocity of a potential object in a radar field of view by measuring the phase difference between successively received chirps. In some examples, a large chirp period (T)_c) (e.g., the time elapsed from the start of one chirp in a sequence of chirps to the start of the next chirp) can cause a phase flip, causing an error in the estimated velocity. In at least one example, the maximum unambiguous velocity (v) achievable by an FMCW radar system_max) And T_cIn inverse proportion. In at least one example of this, the system,where λ is the wavelength corresponding to the starting frequency of the chirp. However, various factors may limit the minimum achievable T_cThereby limiting the achievable v_max. For example, such factors may include the bandwidth spanned by the chirp, the slope of the chirp, and in some FMCW radar systems, multiple transmitters transmit in sequence.

In some examples, the bandwidth of the chirp affects the range resolution (e.g., the larger the bandwidth of the chirp, the better the range resolution). However, increasing chirp bandwidth to improve range resolution also increases T_cAnd decrease v_max. Furthermore, the maximum slope of the chirp may be limited by the bandwidth of the chirp generation circuitry, the IF bandwidth of the receive channel, and the maximum range supported by the radar. For a given bandwidth spanned by the chirp, the chirp follows the chirpDecrease in the impact slope, T_cIncrease and decrease v_max. In an example of an FMCW radar system that provides a time division multiplexed multiple input multiple output (TDM-MIMO) mode of operation (e.g., angular resolution may be improved), multiple transmitters transmit in sequence, which may increase the effective T_cAnd decrease v_max. In the context of TDM-MIMO, T_cDefined as the time elapsed from the start of one chirp to the start of the next chirp sent from the same transmitter. Thus, T present in FMCW radar systems and achievable by a minimum_cWithin imposed limits, increase v_maxAnd difficulties arise.

At least some aspects of the present disclosure provide for increasing the v of a radar system, such as an FMCW radar system_max. In at least some examples, the FMCW radar system implements a radar transceiver Integrated Circuit (IC) configured to be coupled to one or more antennas (e.g., a transmit antenna and/or a receive antenna) to transmit chirps and receive reflected chirps. For example, the radar transceiver IC generates an equally spaced frame of chirps and provides the frame of chirps to at least one transmit antenna for transmission. In at least some examples, prior to providing the frame of chirps to the transmit antenna, the radar transceiver IC modulates the chirps in the frame to convert a single chirp sequence to two chirp sequences separated by a separation frequency Δ f. In at least some examples, Δ f in the field of view of the bandwidth of the radar transceiver IC is relatively small. For example, Δ f is about 0.01 gigahertz (Ghz) in some embodiments, such as in a system where a first chirp spans a frequency range of 79.1Ghz to 80.1Ghz and a second chirp, spaced Δ f from the first chirp, spans a frequency range of 79.11Ghz to 80.11 Ghz. In other examples, Δ f takes any suitable value. As shown in fig. 1, the first chirp in the first sequence may start at time t and frequency a, where the horizontal axis represents time and the vertical axis represents frequency. The first chirp in the second sequence may start at the same time t and frequency α + Δ f. Similarly, a second line in the first sequenceThe chirp may be at time T + T_cAnd at frequency alpha. The second chirp in the second sequence may be at the same time T + T_cAnd a frequency α + Δ f. In this way, in at least some examples, corresponding chirps (e.g., identical chirps of the first and second sequences) are separated in frequency by a frequency Δ f at any given time T and separated in time by a time Δ T at any given frequency f, whereAnd S is the slope of the chirp.

Although illustrated as a frame having two sequences including only two chirps at an offset Δ f, the FMCW radar system of the present disclosure may be adapted to frames having sequences including more than two chirp sequences and/or each sequence including more than two chirps, where each chirp sequence is offset by a certain frequency, and such examples are included within the scope of the present disclosure. In one example, to at least partially compensate for T achievable by the minimum_cThe imposed limitation, modulating the chirp in the frame to facilitate approximation of the disclosed FMCW radar systemV is_max. In at least one example, reducing the time interval of a chirp sequence and its corresponding modulated chirp sequence in a frame increases the v of an FMCW radar system_maxWhile utilizing a single radar transceiver IC. Much less than T at Δ T_cIn one example of FMCW radar system, v_maxIncrease byBy a factor given by the order of magnitude of (a). In one example, the magnitude value of Δ f may be selected such that the corresponding Δ T is greater than the maximum round trip delay from the FMCW radar system to the farthest object and back to the FMCW radar system. In one example, this provides a first chirp corresponding toThe reflections of the pulse sequence do not overlap in the frequency domain with the reflections corresponding to the second chirp sequence. In one example, such interleaved reflections further enable the reflections to be spaced and digital processing to be performed on the reflections. In an example where a third chirp sequence is also present, the time difference between any pair of chirp sequences is greater than the round trip delay described above. In one example, the furthest object refers to an object (if present) that is capable of producing a reflected signal of significant intensity received at the FMCW radar system that is capable of corrupting the FMCW radar system's detection of signals corresponding to other chirp sequences or that is capable of being corrupted by the presence of such other reflected signals from multiple chirp sequences. If the farthest object corresponds to T_farthestThe round trip delay of F_farthest＝S*T_farthestMay be the estimated maximum IF frequency of the FMCW radar system.

Referring now to fig. 2, fig. 2 shows a block diagram of an illustrative FMCW radar system 200. In at least one example, FMCW radar system 200 includes a radar transceiver IC 205 and a processing unit 210. In some examples, the FMCW radar system 200 further includes a transmit antenna 215 and a receive antenna 220, while in other examples, the FMCW radar system 200 does not include the transmit antenna 215 and the receive antenna 220 but is configured to be coupled to the transmit antenna 215 and the receive antenna 220. An illustrative architecture for radar transceiver IC 205 is illustrated in fig. 3 and described below.

In at least one example, radar transceiver IC 205 may be referred to as a front end of FMCW radar system 200 and processing unit 210 may be referred to as a back end of FMCW radar system 200. In at least one example, radar transceiver IC 205 and processing unit 210 are implemented separately and may be configured to be coupled together, while in other examples, radar transceiver IC 205 and processing unit 210 are implemented together, e.g., in a single chip package or system on a chip (SoC) (e.g., a single integrated circuit). In examples where radar transceiver IC 205 and processing unit 210 are implemented on a SoC, radar transceiver IC 205 may correspond to a sub-circuit of an IC forming the SoC. In at least one example, processing unit 210 is coupled to radar transceiver IC 205 via an interface 225, which interface 225 may facilitate any suitable communication method (e.g., a serial interface or a parallel interface) and is configured to receive data from radar transceiver IC 205 and/or transmit data to radar transceiver IC 205.

In at least one example, the interface 225 may be a high-speed serial interface such as a Low Voltage Differential Signaling (LVDS) interface. In another example, interface 225 may be a low speed interface such as a Serial Peripheral Interface (SPI). In at least one example, radar transceiver IC 205 includes functionality to generate one or more digital IF signals (alternatively referred to as a dechirp signal, a beat signal, or a raw radar signal) from reflected chirps received via receive antenna 220. Further, in at least one example, radar transceiver IC 205 includes functionality to perform at least a portion of signal processing on radar signals (e.g., reflected chirps and/or digital IF signals) received in radar transceiver IC 205 and provide results of the signal processing to processing unit 210 via interface 225. In at least one example, radar transceiver IC 205 performs a range FFT on each received frame (e.g., each chirp sequence of a frame) of radar transceiver IC 205. In at least some examples, radar transceiver IC 205 also performs a doppler FFT on each received frame of radar transceiver IC 205 (e.g., after performing the range FFT and based on the results of the range FFT).

In at least one example, processing unit 210 includes functionality to process data received from radar transceiver IC 205 to, for example, determine any one or more of range, speed, and/or angle of any object detected by FMCW radar system 200. In some examples, the processing unit 210 may also or alternatively include functionality for performing post-processing of information about detected objects, such as tracking objects, determining the rate and direction of motion, and so forth. In at least one example, processing unit 210 provides an increase v of FMCW radar system 200, e.g., according to the present disclosure_maxThe velocity of the detected object is determined. In various examples, a processing unit210 includes any suitable processor or combination of processors necessary for processing data received from radar transceiver IC 205 and/or providing data to radar transceiver IC 205. For example, processing unit 210 may include one or more of a Digital Signal Processor (DSP), a microcontroller, a system on a chip (SOC) that combines DSP and microcontroller processing, a Field Programmable Gate Array (FPGA), or any combination of the above.

Referring now to fig. 3, fig. 3 shows a block diagram of an illustrative radar transceiver IC 300. In at least some examples, radar transceiver IC 300 is suitable for implementation as radar transceiver IC 205 of FMCW radar system 200 of fig. 2. In other examples, radar transceiver IC 300 is suitable for implementation in other radar systems. In at least one example, the radar transceiver IC includes one or more transmit channels 304 and one or more receive channels 302A-302N (where N is any positive integer). Each of transmit channel 304 and receive channels 302A-302N may be individually coupled to a transmit antenna or a receive antenna, such as transmit antenna 215 or receive antenna 220, respectively, as discussed above with respect to fig. 2, rather than as shown in fig. 3. Although illustrated as including two receive channels 302A and 302N and one transmit channel 304 for simplicity, in various examples, radar transceiver IC 300 may include any suitable number of receive channels 302N and/or any suitable number of transmit channels 304. Further, the number of receive channels 302N and the number of transmit channels 304 may be different numbers.

In at least one example, transmit channel 304 includes a Power Amplifier (PA)307, the Power Amplifier (PA)307 coupled between a transmit antenna (not shown) and I/Q modulator 350 to amplify the output of I/Q modulator 350 for transmission via the first transmit antenna. In at least some examples, each additional transmit channel 304 may be substantially similar and may be coupled to its own respective transmit antenna (not shown) or the same transmit antenna.

In at least one example, the first receive channel 302A includes a Low Noise Amplifier (LNA)303A, the Low Noise Amplifier (LNA)303A coupled between a receive antenna (not shown) and the mixer 306A to amplify a Radio Frequency (RF) signal (e.g., reflected chirp) received via the receive antenna before providing the amplified signal to the mixer 306A. In at least one example, mixer 306A is coupled to clock multiplier 340 and is configured to receive a clock signal from clock multiplier 340, e.g., to mix with a received RF signal to generate an IF signal. In at least one example, baseband bandpass filter 310A is coupled to mixer 306A and configured to filter the IF signal, Variable Gain Amplifier (VGA)314A is coupled to baseband bandpass filter 310A and configured to amplify the filtered IF signal, and analog-to-digital converter (ADC)318A is coupled to VGA 314A and configured to convert the analog IF signal to a digital IF signal. The baseband bandpass filter 310A, VGA 314A and ADC 318A of each receive channel 302A may be collectively referred to as an analog baseband, baseband chain, complex baseband, or baseband filter chain. Further, baseband bandpass filter 310A and VGA 314A may be collectively referred to as an IF amplifier (IFA). In at least some examples, each additional receive channel 302N may be substantially similar to the first receive channel 302A and may be coupled to its own respective receive antenna (not shown) or the same receive antenna. For example, each receive channel 302N may include LNA 303N, mixer 206N, baseband bandpass filter 310N, VGA 314N, and ADC 318N. In at least one example, ADC 318A is coupled to a Digital Front End (DFE)322, e.g., to provide a digital IF signal to DFE 322. DFE 322 (which may also be referred to as digital baseband) includes functionality to perform decimation filtering or other processing operations on the digital IF signal, for example, to reduce the data transfer rate of the digital IF signal, in at least one example. In various examples, DFE 322 may also perform other operations on the digital IF signals, such as Direct Current (DC) offset removal and/or compensation (e.g., digital compensation) of non-idealities (such as inter-receiver gain imbalance non-idealities, inter-receiver phase imbalance non-idealities, etc.) in receive channels 302A-302N. In at least one example, DFE 322 is coupled to signal processor 344 and is configured to provide the output of DFE 322 to signal processor 344.

In at least one example, signal processor 344 is configured to perform at least a portion of the signal processing on the digital IF signals resulting from the received radar frames and to transmit the results of the signal processing via terminal 352 and/or terminal 354. In at least one example, signal processor 344 transmits the results of the signal processing to a processing unit (not shown), such as processing unit 210 described above with respect to fig. 2. In various examples, the results are provided from signal processor 344 to terminal 352 and/or terminal 354 via high speed interface 324 and/or SPI 328, respectively. In at least one example, the signal processor 344 performs a range FFT on each chirp sequence in the received radar frame. In at least one example, the signal processor 344 additionally performs a doppler FFT on the results of the range FFT.

The signal processor 344 may include any suitable processor or combination of processors. For example, the signal processor 344 may be a DSP, a microcontroller, an FFT engine, a DSP plus microcontroller processor, an FPGA, or an Application Specific Integrated Circuit (ASIC). In at least one example, the signal processor 344 is coupled to the memory 348, for example, to store intermediate results of partial signal processing performed on the digital IF signals in the memory 348 and/or to read instructions from the memory 348 for execution by the signal processor 344.

In at least one example, the memory 348 provides on-chip storage (e.g., a non-transitory computer-readable storage medium) that may be used to transfer data between various components of the radar transceiver IC 300, for example, to store software programs executed by a processor on the radar transceiver IC 300 or the like. Memory 348 may include any suitable combination of read-only memory (ROM) and/or Random Access Memory (RAM), such as static RAM, for example. In at least one example, a Direct Memory Access (DMA) component 346 is coupled to memory 348 to perform data transfers from memory 348 to high speed interface 324 and/or SPI 328.

In at least one example, SPI 328 provides an interface for communicating between radar transceiver IC 300 and another device (e.g., a processing unit such as processing unit 210 of fig. 2) via terminal 354. For example, radar transceiver IC 300 may receive control information, such as the timing and frequency of the chirp, the output power level, triggering of a monitoring function, etc., via SPI 328. In at least one example, radar transceiver IC 300 may communicate the test data to, for example, processing unit 210 via SPI 328.

In at least one example, control module 326 includes functionality for controlling at least a portion of the operation of radar transceiver IC 300. Control module 326 may include, for example, a microcontroller executing firmware to control the operation of radar transceiver IC 300. For example, the control may be to provide data parameters to other components of radar transceiver IC 300 and/or to provide control signals to other components of radar transceiver IC 300.

In at least one example, the programmable timing engine 342 includes functionality to receive a chirp parameter value for a sequence of chirps in a radar frame from the control module 326 and generate transmit and receive chirp control signals for the chirps in the control frame based on the parameter value. In some examples, the chirp parameters are defined by the radar system architecture and may include, for example, a transmitter enable parameter to indicate which transmit channels are enabled, a chirp frequency start value, a chirp frequency slope, an ADC sampling time, a ramp end time, a transmitter start time, and so forth.

In at least one example, the Radio Frequency Synthesizer (RFSYNTH)330 includes functionality to generate a signal (e.g., a chirp and/or a sequence of chirps) for transmission based on a chirp control signal received from the programmable timing engine 342. In some examples, RFSYNTH 330 includes a Phase Locked Loop (PLL) with a Voltage Controlled Oscillator (VCO). In at least one example, RFSYNTH 330 may be referred to as a Local Oscillator (LO).

In at least one example, the multiplexer 332 is coupled to the RFSYNTH 330 and the input buffer 336 and can be configured to select between a signal received from an external component (not shown) from the input buffer 336 and a signal generated by the RFSYNTH 330. In at least one example, output buffer 338 is coupled to multiplexer 332 and may, for example, provide signals selected by multiplexer 332 to an input buffer of another radar transceiver IC (not shown). In at least one example, the multiplexer is controlled by the control module 326 via a select signal.

In at least one example, clock multiplier 340 increases the frequency of the output of multiplexer 332 (e.g., an output such as RFSYNTH 330) to the operating frequency of mixer 306A. In at least one example, the clean-up PLL 334 is configured to increase the frequency of a signal of an external low frequency reference clock (not shown) received by the radar transceiver IC 300 to the frequency of the RFSYNTH 330 and filter out reference clock phase noise in the reference clock signal.

In at least one example, the I/Q modulator 350 receives the output of the clock multiplier 340 (e.g., a chirp and/or a sequence of chirps) and modulates the output of the clock multiplier 340 based on data received from the control module 326 to generate a frequency shifted copy of the output of the clock multiplier 340. In at least one example, the I/Q modulator is further coupled to a digital-to-analog converter (DAC)356 and a DAC 358, each of which may be coupled to the control module 326. In at least one example, DAC 356 receives 1+ e from control module 326^j2πΔftAnd DAC 358 receives 1+ e from control module 326^j2πΔftWhere t represents a continuous (e.g., real) time in the analog signal and a continuous (e.g., real) time of a given digital sample in the digital signal. Each of DAC 356 and DAC 358 convert their respective received signals to analog values and provide the analog values to I/Q modulator 350. For example, DAC 356 may provide its analog value output to the real component input of I/Q modulator 350, and DAC 358 may provide its analog value output to the in-phase component input of I/Q modulator 350.

In at least one example, I/Q modulator 350 generates the in-phase (I) and quadrature (Q) components of the clock signal received from clock multiplier 340 and multiplies the I and Q clock components by the analog values received from DACs 356 and 358, respectively, and sums the resulting product values prior to providing the signal to PA 307. In at least some examples, the multiplication modulates the output of the clock multiplier 340 to generate a resultant signal that includes a frequency shifted copy of the output of the clock multiplier 340, e.g., as shown and discussed above with reference to fig. 1, where the solid line represents the output of the clock multiplier 340 and the dashed line represents the frequency shifted (e.g., modulated) copy of the output of the clock multiplier 340. As described above, the I/Q modulator 350 may generate a complex-valued modulated signal comprising a first chirp sequence and a second chirp sequence, the second chirp sequence being frequency shifted by Δ f relative to the first chirp sequence. The complex-valued modulated signal may comprise an in-phase component corresponding to the real part of the complex-valued signal and a quadrature-phase component corresponding to the imaginary part of the complex-valued signal.

The receive channel 302A is illustrated in fig. 3 as the actual receive channel. In at least one example, the actual receive channel has a bandwidth of 0 to 2 Δ f (e.g., the bandwidth of baseband bandpass filter 310A, VGA 314A and ADC 318A may be at least 0 to 2 Δ f). In other examples not shown, receive channel 302A may be implemented as a composite receive channel. In at least one example, the composite receive channel includes a replica (not shown) of at least some of LNA 303A, mixer 306A, baseband bandpass filter 310A, VGA 314A, and/or ADC 318A. In at least one example, the composite receive channel has a bandwidth of- Δ f to Δ f. When receive channel 302A is implemented as a composite receive channel, mixer 306A may receive the I component of the clock signal generated by clock multiplier 340 and the replica of mixer 306A may receive the Q component of the clock signal generated by clock multiplier 340 such that mixer 306A and the replica of mixer 306A operate at a 90 degree phase difference. In various examples, the I and Q components of the clock signal may be generated by an I/Q splitter (not shown) that receives the clock signal generated by clock multiplier 340. For example, the signals generated by the I/Q splitter have a 90 degree phase difference between them. In some examples, the I/Q splitter is implemented as a discrete component of radar transceiver IC 300, while in other examples it is implemented as part of I/Q modulator 350.

Referring now to FIG. 4, FIG. 4 shows that v can be increased_maxIs shown in the flow chart of an illustrative FMCW radar method 400. In at least some examples, method 400 is implemented by an FMCW radar system (such as FMCW radar system 200 of fig. 2), e.g., at least partially by a radar transceiver IC (such as radar transceiver IC 205 of fig. 2 and/or radar transceiver IC 300 of fig. 3).

At operation 405, the FMCW radar system initiates transmission of a chirp frame having a first chirp sequence and a second chirp sequence offset by Δ f from the first chirp sequence. The process of initiating transmission of a chirp frame is further described below in conjunction with fig. 6.

At operation 410, the FMCW radar system receives the reflected frames of chirps and generates a digital IF signal for each receive antenna of the FMCW radar system. In at least one example, the FMCW radar system generates a digital IF signal by combining (e.g., mixing or multiplying) a received frame of chirps with the chirps output by the clock multiplier 340, filters the combined signal, amplifies the filtered signal, e.g., using a mixer, and converts the filtered signal from an analog format to a digital format to form the digital IF signal. In some examples, the radar system may include an I/Q demodulator that demodulates a received frame of chirps with chirps output by clock multiplier 340 to generate in-phase components of the digital IF signal, and further demodulates the received frame of chirps with 90 degree phase shifted versions of the chirps output by clock multiplier 340 to generate quadrature components of the digital IF signal. The in-phase and quadrature-phase components of the digital IF signal may together form a complex-valued digital IF signal.

At operation 415, the FMCW radar system demodulates the digital IF signal. For example, when a chirp frame transmitted by the FMCW radar system (e.g., at operation 405) and subsequently received as a reflected chirp frame (e.g., at operation 410) includes two sequences of chirps offset by Δ f, the digital IF signal may similarly contain reflected chirp data corresponding to the two sequences and separated in the digital IF signal by Δ f. To access data from both chirp sequences, in at least one example, the FMCW radar system demodulates the digital IF signal and/or performs a first FFT on the digital IF signal to obtain data from the chirp originally belonging to the first chirp sequence. In at least some examples, the FMCW radar system may further demodulate the digital IF signal by Δ f (or perform an equivalent FFT process) to compensate for the frequency offset of Δ f to obtain data from the chirp originally belonging to the second chirp sequence offset by Δ f from the first chirp sequence. In at least one example, FFT and/or demodulation is performed in a signal processor of a radar transceiver IC of an FMCW radar system. In another example, the digital IF signal is passed to a processing unit of the FMCW radar system that performs FFT and/or demodulation. In one example, demodulation and FFT are implemented as separate subsets of operation 415, while in other examples demodulation includes execution of one or more FFTs and/or processing of one or more FFT bins.

In one example, the digital IF signal contains a sum of signals corresponding to reflections from the object, the signals corresponding to both the first chirp sequence and the second chirp sequence. In the digital IF signal, the signal offset frequency corresponding to the first chirp sequence and the second chirp sequence is Δ f. Alternatively, the data may be digitally processed (e.g., time domain digital data multiplied by e)^-j2πΔft(sometimes referred to as frequency shifting)) produces a new version of the digital IF signal corresponding to the second chirp sequence. In the new version of the digital IF signal, the signal corresponding to the second chirp sequence occupies the same frequency range as the signal corresponding to the first chirp sequence in the original version of the digital IF signal. To enable further digital processing (e.g., such as performing a range dimension FFT), the new version of the digital IF signal may be passed through a digital filter to suppress excess frequencies of interest (e.g., 0 to F)_farthest) The frequency component of (a). The new version of the digital IF signal produced at the output of the digital filter may be referred to as the demodulated digital IF signal corresponding to the second chirp sequence. The original digital IF signal itself may (e.g., without any frequency shift) be passed through a similar digital filter to reject frequency components beyond the actual frequency of interest and be referred to as a demodulated version of the first chirp sequence (or as a demodulated digital IF signal corresponding to the first chirp sequence). Any third chirp sequence, if present,may undergo processing similar to the second chirp sequence except that af is replaced by the corresponding frequency difference between the first chirp sequence and the third chirp sequence. In some examples, the demodulated digital IF signal of the second (and/or subsequent) chirp sequence is sampled with a delay of Δ T (or an integer multiple of Δ T) compared to the samples of the demodulated digital IF signal corresponding to the first chirp sequence. In some examples, such sampling delays cause the demodulated digital IF signals of the first, second, and any subsequent chirp sequences to correspond to substantially the same starting RF frequency. The demodulated digital RF signal discussed herein is sampled according to the delay.

At operation 420, the FMCW radar system performs a range FFT on each demodulated digital IF signal to generate a range array for each demodulated digital IF signal. For example, the radar system may perform a first range FFT on a first demodulated digital IF signal and a second range FFT on a second demodulated digital IF signal, wherein the second demodulated digital signal is a frequency-shifted version of the first digital demodulated signal. Each range FFT operation may generate an MxN range array (or range matrix), where M is the number of chirps in the chirp sequence and N is the number of time samples to receive a chirp. N may also correspond to the number of distance intervals in the distance array. In some examples, a range FFT operation may be performed on each chirp sequence received by each receive antenna of the FMCW radar system. In at least one example, a corresponding range FFT is performed in a signal processor of a radar transceiver IC of an FMCW radar system, and the resulting range array is transmitted to a processing unit of the FMCW radar system. In another example, the demodulated digital IF signal is passed to a processing unit of an FMCW radar system that performs a range FFT.

In another example, the digital IF signal may be used to directly perform the range FFT without performing demodulation as described above. In such an example, the length of the FFT may be doubled (e.g., to preserve information corresponding to both the first chirp sequence and the second chirp sequence). In this case, corresponding to, for example, from 0 to F_farthestThe range FFT bin of frequencies of (a) will contain the range FFT value corresponding to the first chirp sequence. In the same case, corresponding for example to from Δ F to Δ F + F_farthestThe range FFT bin of frequencies of (a) will contain the range FFT value corresponding to the second chirp sequence. Any third sequence will similarly correspond to 2 Δ F + F_farthest(e.g., the resulting range FFT must be three times longer to hold information corresponding to the first, second, and third chirp sequences).

At operation 425, the FMCW radar system performs a doppler FFT on each range array generated at operation 420 to generate a corresponding range-doppler array (or range-doppler matrix). For example, a doppler FFT is performed on each of the N columns of each range array generated at operation 420. In some examples, operation 425 may generate a first range-doppler array corresponding to the first chirp sequence and a second range-doppler array corresponding to the second chirp sequence.

At operation 430, the FMCW radar system determines a velocity of a potential object in a field of view of the FMCW radar system from each range-doppler array. In at least one example, peaks in the range-doppler array indicate potential objects, and the velocity of these potential objects is determined by the location of each peak in the range-doppler array. An example of a range-doppler array is shown in figure 5. In this example, MxN array 500 represents a range-doppler array corresponding to a first chirp sequence from a received radar frame, and MxN array 502 represents a range-doppler array corresponding to a second chirp sequence from a received radar frame. In at least some examples, the shaded boxes of array 500 and array 502 indicate peaks in the respective arrays that correspond to potential objects in the field of view of the FMCW radar system. In at least one example, the number of rows and columns of peaks in the range-doppler array correspond to the velocity and range, respectively, of a potential target in the field of view of the FMCW radar system. In at least one example, the velocity of the potential object is further refined by finding the difference between the phases of the peaks in the range-doppler array, for example, as described below with reference to fig. 7. In executionIn an example where a long FFT (e.g., a 2N-point FFT) is performed instead of performing demodulation, array 500 may be generated by extracting an interval corresponding to the first half of the longer FFT (e.g., 0 to N-1), and array 502 may be generated by extracting an interval corresponding to the second half of the longer FFT (e.g., N to 2N-1). In one example, to delay the demodulated digital IF signal corresponding to the second chirp sequence (and subsequent chirp sequences) by a sample Δ T (or an integer multiple of Δ T), the phase of the values in each range bin of array 502 is modified by adding 2 × pi IF Δ T, where IF is the sum of the values obtained by the first chirp sequence and the second chirp sequenceGiven the frequency values corresponding to the range interval, Fs is the sampling rate, N is the number of samples per chirp, and N is the range interval index from 0 to N-1.

In one example, the maximum unambiguous velocity of a potential object in the field of view of the FMCW radar system, when determined solely from the number of rows of one or more range-Doppler arrays, may be V1, and the FMCW radar system will estimateAndthe velocity in between. If there is an object with a velocity p x V1+ V in the field of view of the FMCW radar system, where p is an integer (positive or negative) and V is fromToThe FMCW radar system may determine the velocity of the object as V without error based on the number of rows of the one or more range-doppler arrays when p is non-zero. The FMCW radar system then determines an approximation of the actual velocity of the object (e.g., via equation 3 discussed below). The FMCW radar system is used for detecting the difference between peak phases in a range-Doppler array by comparing the peak phases of objectsThe velocity is determined as the p-value of the approximation closest to the actual velocity of the object, further refining the calculation of the velocity of the object.

Referring now to fig. 6, fig. 6 shows a flow diagram of an illustrative method 600 for initiating transmission of a chirp frame. In at least some examples, method 600 is implemented by an FMCW radar system (such as FMCW radar system 200 of fig. 2), for example, at least in part by a radar transceiver IC (such as radar transceiver IC 205 of fig. 2 and/or radar transceiver IC 300 of fig. 3).

At operation 605, a control module of the FMCW radar system (or alternatively, the radar transceiver IC and/or a component external to the FMCW radar system) transmits parameter values for generating chirps transmitted by the FMCW radar system to the timing engine. In some examples, the timing engine generates a chirp control signal that controls the transmission and/or reception of a chirp by the FMCW radar system in the frame based on the parameter values. In some examples, the chirp parameters are defined by the radar system architecture and may include, for example, a transmitter enable parameter to indicate which transmit channels are enabled, a chirp frequency start value, a chirp frequency slope, an ADC sampling time, a ramp end time, a transmitter start time, and so forth.

At operation 610, the timing engine transmits a chirp control signal to the RFSYNTH to generate one or more chirps. In at least some examples, RFSYNTH may be a local oscillator of an FMCW radar system. At operation 615, the one or more chirps are multiplied to increase the frequency of the one or more chirps to generate an amplified chirp (or multiplied chirp or modified chirp), for example to match the operating frequency of the receive component of the FMCW radar system.

At operation 620, the amplified chirp is modulated. In at least one example, modulating the amplified chirp generates a frequency shifted copy of the amplified chirp shifted by a frequency Δ f. In at least one example, the modulation is performed by an I/Q modulator. In at least one embodiment, Ithe/Q modulator receives the signal 1+ e^j2πΔftReal component of and signal 1+ e^j2πΔftFor modulating the amplified chirp. At operation 625, the modulated chirp is amplified and transmitted via one or more antennas.

Referring now to fig. 7, fig. 7 shows a flow diagram of an illustrative method 700 for determining a velocity of an object detected by an FMCW radar system. In at least some examples, method 700 is implemented by an FMCW radar system (such as FMCW radar system 200 of fig. 2), for example, at least in part by a radar transceiver IC (such as radar transceiver IC 205 of fig. 2 and/or radar transceiver IC 300 of fig. 3).

At operation 705, the FMCW radar system calculates a first velocity estimate (v) of a potential object in a field of view of the FMCW radar system based on the range-doppler array (v)_est1). In one example, the range-doppler array is one of a first range-doppler array corresponding to a first chirp sequence of the received radar frame or a second range-doppler array corresponding to a second chirp sequence of the received radar frame. In another example, the range-doppler array is an average or other relationship between or a combination of a first range-doppler array corresponding to a first chirp sequence of the received radar frame and a second range-doppler array corresponding to a second chirp sequence of the received radar frame. For example, an FMCW radar system calculates v according to method 400_est1This may be determined based on the location of the peak in the range-doppler array corresponding to the potential object, as described above. As described above, the number of rows of peaks in the range-doppler array corresponds to the velocity of the potential object. In at least one example, v_est1May be aliased (e.g., there may be phase reversal so that v is_est1Is the maximum measurable velocity (v)_max) Integer multiples of).

In at least one example, relative motion of an object with respect to an FMCW radar system introduces a phase change φ across subsequent chirps in a received reflected chirp frame_dWherein the phase change is defined as:

where v is the velocity of the object, T_cIs the chirp period and λ is the wavelength corresponding to the start frequency of the chirp. Because there is a linear progression of the phase between chirps in a frame, the phase change φ can be estimated using an FFT_d. In one example, once the phase change φ is estimated_dThe velocity estimate v can be estimated by inverting equation 1_est1To obtain v given below_est1：

In another example, v is estimated by performing a doppler FFT as described above and finding the location of a peak corresponding to the object of interest in the resulting range-doppler array_est1. When in useAnd if the velocity of the object exceeds +/-0.5 x v_maxorigThen v is_est1May have a value of about v_maxorigAn error of an integer multiple of. v. of_maxorigWhen only the first chirp sequence (or only the second chirp sequence) is used without using v_est2As discussed in more detail below.

At operation 710, the FMCW radar system calculates a second velocity estimate (v) of the object based on phase differences in corresponding range-doppler arrays (e.g., a range-doppler array corresponding to a first chirp sequence and a range-doppler array corresponding to a second chirp sequence offset by Δ f from the first chirp sequence)_est2). As described above, in at least one example, a range-doppler array is generated at least in part according to method 400. Once the phase difference is determined (e.g., by phase from the peak of the second range-Doppler arrayThe phase of the peak of a range-doppler array subtracted from the bit), the velocity estimate v can be estimated according to the following equation_est2：

Where delta phi is the phase difference (or average of multiple phase differences) of the peaks in a range-doppler array (e.g., to illustrate an FMCW radar system having multiple transmit and/or receive antennas), and λ is the transmit wavelength of the FMCW radar system at the time transmission is initiated (e.g., at operation 405 of method 400, discussed above with reference to fig. 4).

At operation 715, the FMCW radar system is based at least in part on v_est1And v_est2(v) calculating the object detected by FMCW radar system_true) Actual or true speed. For example, an FMCW radar system may determine v according to the following equation_true：

v_true＝v_est1+2nv_maxorig， (4)

Where n is the ambiguity in the estimated velocity calculation and is defined as n ═ v (v)_est2-v_est1)/2v_maxorigIs an integer of (1). In at least some examples, the calculated value of n may be rounded to the nearest integer before being used in equation 4 to determine the actual velocity of the object. In another example, v may be_maxorigIs added to v as an integer multiple of various negative and positive (including 0) s_est1To form various sums numerically closest to v_est2Is selected as v_true。

Referring now to fig. 8, fig. 8 shows a flow chart of an illustrative method 800 for calibrating an FMCW radar system. In at least some examples, method 800 is implemented by an FMCW radar system during a calibration mode of operation of the FMCW radar system. In at least one example, the FMCW radar system may be FMCW radar system 200 of fig. 2, e.g., implemented at least in part by a radar transceiver IC (such as radar transceiver IC 205 of fig. 2 and/or radar transceiver IC 300 of fig. 3).

At operation 805, the FMCW radar system begins a calibration process by initiating transmission of a chirp frame having a first chirp sequence and a second chirp sequence offset by Δ f from the first chirp sequence. The FMCW radar system may perform initiating transmission of the chirp frame in a substantially similar manner to operation 405 of method 400 discussed above, the details of which are not repeated herein.

At operation 810, the FMCW radar system receives the reflected frames of chirps and generates a digital IF signal for each receive antenna of the FMCW radar system. The FMCW radar system may perform the reception of the reflected frames of chirps and the generation of the digital IF signal in a substantially similar manner as operation 410 of method 400 discussed above, the details of which are not repeated herein.

At operation 815, the FMCW radar system demodulates the digital IF signal. The FMCW radar system may perform demodulation of the digital IF signal in a substantially similar manner as operation 415 of method 400 discussed above, the details of which are not repeated herein.

At operation 820, the FMCW radar system performs a range FFT on each result of operation 815 to generate a range array for each result of operation 815. The FMCW radar system may perform the generation of the range array in a substantially similar manner as operation 420 of method 400 discussed above, the details of which are not repeated herein.

At operation 825, the FMCW radar system performs a doppler FFT on each range array to generate a range-doppler array. The FMCW radar system may perform the generation of the range-doppler array in a substantially similar manner as operation 425 of method 400 discussed above, the details of which are not repeated herein.

At operation 830, the FMCW radar system calculates phase differences for the peaks of objects in the range-doppler array. The FMCW radar system calculates the phase difference, for example, by subtracting the phase of the object peak in one range-doppler array (e.g., the range-doppler array corresponding to the chirp of the first chirp sequence) from the phase of the object peak in another range-doppler array (e.g., the second chirp sequence corresponding to the shift of Δ f from the first chirp sequence). In at least one example, a search can be performed in each range-doppler array to locate an object peak. Because the stationary object is known, the approximate location of one or more peaks corresponding to the object may be known. Thus, a search can be performed in the approximate region of each range-doppler array to locate the peak. Furthermore, if an object is large, the peaks corresponding to that object may be numerous. If there are multiple peaks, any one peak may be used.

At operation 835, the calculated phase difference may be stored by the FMCW radar system. In at least one example, the calculated phase difference may be referred to as a system phase offset for a particular receive channel through which the reflected chirp frame was received at operation 810. In at least one example, the FMCW radar system may use the system phase offset determined during calibration of method 800 in performing velocity calculations during normal operation of the FMCW radar system (e.g., such as when the FMCW radar system implements method 700).

For example, as part of the velocity calculation of the object, the system phase offset may be used for v as described with reference to the method of FIG. 7_est2In the calculation of (2). In at least one example, when the FMCW radar system includes a plurality of receive channels, the system phase offset of the receive channels is subtracted from the phase difference calculated for the receive channels before calculating an average of the phase differences. The system phase offset may also be used as part of the velocity calculation of the object, as described with reference to the method of fig. 4. For example, the systematic phase offset may be applied to the corresponding range array generated prior to interleaving the range array.

Referring now to fig. 9, fig. 9 shows a flow diagram of an illustrative method 900 for calibrating an FMCW radar system. In at least some examples, method 900 is implemented by an FMCW radar system during a normal operating mode of the FMCW radar system. In various examples, method 900 may be performed periodically, on command, and/or when the radar system is initialized. In at least one example, the FMCW radar system may be FMCW radar system 200 of fig. 2, e.g., implemented at least in part by a radar transceiver IC (such as radar transceiver IC 205 of fig. 2 and/or radar transceiver IC 300 of fig. 3).

In at least one example, the calibration process begins by transmitting a chirp frame by the radar transceiver IC at operation 905. The chirp frame may include a first chirp sequence and an offset Δ f from the first chirp sequence₁Of the second chirp sequence. Δ f₁Any suitable value may be used. At operation 910, a digital IF signal is generated for each receive channel of the FMCW radar system as the reflected chirp is received.

At operation 915, the digital IF signal is demodulated and, at operation 920, a range-doppler array is calculated for each receive channel. When a range-doppler array is available, at operation 925, the phase difference of the object peaks in the range-doppler array is calculated. For example, for each corresponding pair of receive channels, a difference between the phase of an object peak in the range-doppler array produced by a first chirp sequence in the chirp frame and the phase of an object peak in the range-doppler array produced by a second chirp sequence in the chirp frame is calculated (e.g., one phase value is subtracted from another phase value).

At operation 930, transmission of another chirp frame is initiated by the radar transceiver IC. The chirp frame may include a first chirp sequence and an offset Δ f from the first chirp sequence₂Of the second chirp sequence. Δ f₂Any suitable value may be used. At operation 935, a digital IF signal is generated for each receive channel of the FMCW radar system as the reflected chirp is received.

At operation 940, the digital IF signal is demodulated and, at operation 945, a range-doppler array is calculated for each receive channel. When a range-doppler array is available, at operation 950, phase differences of object peaks in the range-doppler array are calculated. For example, for each corresponding pair of receive channels, a difference between the phase of an object peak in the range-doppler array produced by a first chirp sequence in the chirp frame and the phase of an object peak in the range-doppler array produced by a second chirp sequence in the chirp frame is calculated (e.g., one phase value is subtracted from another phase value).

At operation 955, it is then determined whether a stationary object is present in the scene based on the two object peak phase differences. For example, for object peaks appearing in two range-doppler arrays, frequency offset Δ f is used₁Each of the phase differences determined for the peaks is compared with the use of a frequency offset Δ f₂The difference between the respective phase differences of the phase differences determined for the peaks is compared with a threshold determined by the signal-to-noise ratio. If each difference is less than the threshold, the peak corresponds to a stationary object. The object peaks may be searched until a peak corresponding to a stationary object is found or all object peaks have been considered. If there are no stationary objects, at operation 960, the method 900 terminates.

If a peak corresponding to a stationary object is found, at operation 965, based on using the frequency offset Δ f₁Determining phase differences for peaks and using frequency offsets Δ f₂A system phase offset is calculated for the phase difference determined for the peak. For example, the corresponding phase differences are averaged to determine the system phase offset, one for each corresponding pair of receive channels. For example, as described above, the system phase offset is stored for use in speed calculations performed during normal operation of the FMCW radar system.

In some examples, if multiple object peaks correspond to stationary objects, then system phase offsets are also determined for these peaks. In such an embodiment, the final system phase offset is determined by averaging the corresponding system phase offsets of all peaks.

In the case of a practical receiver, the first chirp sequence and the second chirp sequence may have a frequency offset of Δ F such that the digital IF signal is between 0 and F_farthestHas first sequence information andand is in the range of Δ F to Δ F + F_farthestHas a second sequence. In the case of a composite receiver, the same method may be followed, or the first sequence may be made to correspond to 0 to F_farthestAnd the second sequence corresponds to- Δ F + F_farthest. In some examples, the latter approach saves the composite receiver's bandwidth (e.g., reduces implementation area and power consumption) by relying on the fact that the composite receiver provides natural image rejection (e.g., + X hertz (Hz) components do not affect-X Hz frequency components or affect after significant image rejection provided by the composite receiver).

While operations of the various methods of the present disclosure have been discussed and labeled with reference numerals, each of the various methods may include additional operations not enumerated herein, any one or more of the operations enumerated herein may include one or more sub-operations, any one or more of the operations enumerated herein may be omitted, and/or any one or more of the operations enumerated herein may be performed in an order different than that presented herein (e.g., in reverse order, substantially simultaneous, overlapping, etc.), all of which are intended to fall within the scope of the present disclosure.

In the preceding discussion, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to …". Furthermore, the term "coupled" is intended to mean either an indirect or direct wired or wireless connection. Thus, if a first device, element or component couples to a second device, element or component, that coupling may be through a direct coupling or through an indirect coupling via other devices, elements or components and connections. Similarly, the coupling of a device, element or component between a first component or location and a second component or location may be through a direct connection or through an indirect connection via other devices, elements or components and/or couplings. A device "configured to" perform a task or function may be configured (e.g., programmed and/or hardwired) at the time of manufacture by the manufacturer to perform that function and/or may be configured (or reconfigured) after manufacture by the user to perform that function and/or other additional or alternative functions. Configuration may be through firmware and/or software programming of the devices, through configuration and/or layout of hardware components and interconnection of the devices, or a combination thereof. Further, a circuit or device that is said to include certain components may instead be configured to be coupled to those components to form the described circuit or device. For example, structures described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors and/or inductors) and/or one or more sources (such as voltage and/or current sources) may instead include only semiconductor elements (e.g., semiconductor dies and/or IC packages) within a single physical device, and may be configured to couple to at least some passive elements and/or sources to form the described structures at manufacture or post-manufacture, e.g., by an end user and/or a third party.

Although certain components are described herein as having a particular processing technology (e.g., MOSFET, NMOS, PMOS, etc.), these components may be replaced with components of other processing technologies (e.g., replacement of MOSFET with Bipolar Junction Transistor (BJT), replacement of NMOS with PMOS, etc., and vice versa), and the circuit including the replaced components reconfigured to provide a desired function at least partially similar to the function available prior to the component replacement. Additionally, in the discussion above, use of the phrase "ground voltage potential" is intended to include rack ground, earth ground, floating ground, virtual ground, digital ground, common ground, and/or any other form of ground connection suitable for or appropriate for the teachings of the present disclosure. Unless otherwise specified, "about," "approximately," or "substantially" preceding a value refers to +/-10% of the stated value.

The above discussion is meant to be illustrative of the principles and various examples of the present disclosure. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the present disclosure be construed as covering all such variations and modifications.