Interference Mitigation for Multi-Radar Coexistence

Abstract

Methods, systems, computer-readable media, and apparatus for transmitting and receiving radar signals from a radar source while minimizing interference with other radar sources are presented. A transmit signal comprising a first chirp sequence is generated according to a waveform parameter set, wherein at least one waveform parameter is changed for one or more chirps in the first chirp sequence. In addition, each chirp of the first chirp sequence can be phase modulated. A received signal comprising a second chirp sequence and corresponding to the transmit signal reflected from an object in the surrounding environment is then sampled to determine one or more properties of the object. In some embodiments, the properties include distance and velocity values ​​calculated using a discrete Fourier transform (DFT). Other properties that can be calculated from the received signal include azimuth and elevation.

Description

[0001] Priority declaration

[0002] This patent application claims priority to U.S. Non-Provisional Application No. 16 / 503,011, filed on July 3, 2019, entitled “INTERFERENCE SUPPRESSION FOR MULTI-RADAR COEXISTENCE,” which is assigned to the assignee of the present application and is expressly incorporated herein by reference. Background Art

[0003] Aspects of the present disclosure relate to the transmission and detection of signals from a radar source in the presence of interfering radar sources.

[0004] Radar signals are often used to detect the presence of objects in the surrounding environment. For example, motor vehicles are sometimes equipped with radar units that transmit radar signals to detect corresponding signals reflected from another object, such as a nearby vehicle. Detection may be difficult if there are other radar sources transmitting signals that interfere with the reflected signal. Summary of the invention

[0005] Various illustrative embodiments are described that enable a radar source to coexist with other radar sources. In particular, techniques for generating radar signals in a manner that minimizes interference between the radar source and any additional radar sources that may be present in the surrounding environment are described. Techniques for processing received radar signals in a manner in which interference from another radar source can be easily distinguished from reflected signals are also described. In certain embodiments, a radar system may include one or more hardware processors or circuits configured to generate a radar signal based on one or more waveform parameters selected to minimize interference. The radar signal may be a frequency modulated continuous wave (FMCW). However, the techniques described herein may be applied to other types of radar signals, such as a phase modulated continuous wave (PMCW) radar.

[0006] In certain embodiments, the transmitted radar signal comprises a sequence of chirps, wherein waveform parameters vary on a per-chirp basis based on a set of parameter patterns that have been configured for suppressing interference and / or for shaping interference in a manner that makes interfering signals easily distinguishable from reflected signals during receiver processing. The set of parameter patterns may be selected from a codebook that includes a plurality of sets of parameter patterns that have been configured for high autocorrelation and low cross-correlation (also referred to as cross-correlation).

[0007] In some embodiments, the transmitted radar signal is generated by performing phase modulation on each chirp based on an additional set of parameters corresponding to a phase code. The addition of phase modulation reduces the likelihood that the transmitted radar signal was generated using exactly the same parameters as an interference source.

[0008] In some embodiments, in response to determining that a previously transmitted portion of the radar signal (e.g., a previous chirp sequence) is interfered with, a waveform parameter of the radar signal is changed. Interference can be detected by attempting to perform object detection based on a first waveform parameter set that is different from a second waveform parameter set for the previously transmitted portion of the radar signal. If the attempt is successful, this indicates that the interference source using the first waveform parameter set may contribute to the received radar signal. Therefore, the first waveform parameter set can be excluded for use with a subsequently transmitted portion of the radar signal. For example, the first waveform parameter set can remain unused for a period of time.

[0009] In certain embodiments, a method, one or more non-transitory computer-readable media storing instructions, and a radar system configured to perform the method are provided, the instructions being executable by one or more processors so that the one or more processors perform the method. The method includes generating a transmit signal including a first chirp sequence. Each chirp in the first chirp sequence is generated according to a waveform parameter set. The method also includes: for one or more chirps in the first chirp sequence, changing at least one waveform parameter in the waveform parameter set; and receiving a receive signal including a second chirp sequence. The receive signal corresponds to a transmit signal that is reflected from an object in the surrounding environment and sampled. The method also includes using the sampled receive signal to determine one or more properties of the object. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Various aspects of the present disclosure are illustrated by way of examples. In the accompanying drawings, like reference numerals represent like elements.

[0011] Figure 1 Illustrated are example scenarios in which radar jamming may occur.

[0012] Figure 2 Exemplary transmit waveforms in accordance with certain embodiments are illustrated.

[0013] Figure 3 is a simplified illustration of a codebook according to certain embodiments.

[0014] Figure 4 is a simplified block diagram of an exemplary radar system in accordance with certain embodiments.

[0015] Figure 5 is a simplified flow chart of a method for generating and receiving radar signals according to certain embodiments.

[0016] Figure 6 is a graphical representation of a process for applying a two-dimensional discrete Fourier transform (DFT) to a received waveform in accordance with certain embodiments.

[0017] Figure 7is a graphical representation of a process for applying a two-dimensional DFT to a received waveform after performing equalization and resampling in accordance with certain embodiments.

[0018] Fig. 8A The result of applying a first DFT to a single chirp in a received radar signal is illustrated when the slope and frequency offset of the received chirp matches the slope and frequency offset of the transmitted chirp.

[0019] Figure 8B Illustrated is the result of applying a first DFT to a single chirp in a received radar signal when the slope of the received chirp matches the slope of the transmitted chirp, but the frequency offset does not match.

[0020] Figure 8C Illustrated is the result of applying a first DFT to a single chirp in a received radar signal when the slope of the received chirp does not match the slope of the transmitted chirp.

[0021] Fig. 9A The results of applying a second DFT to the output of the first DFT in a mismatched frequency offset and matched slope scenario are illustrated.

[0022] Fig. 9B The results of applying a second DFT to the output of the first DFT in a mismatched slope scenario are illustrated.

[0023] Fig. 10A An example of radar signals that are not aligned with respect to time is illustrated.

[0024] Fig. 10B An example of radar signals aligned with respect to time is illustrated.

[0025] Fig.11 is a simplified flow chart of a method for selecting a codeword according to certain embodiments.

[0026] Fig.12 An example computing system is illustrated in which one or more embodiments may be implemented. DETAILED DESCRIPTION

[0027] Several illustrative embodiments will now be described with reference to the drawings.While specific embodiments are described below in which one or more aspects of the disclosure may be implemented, other embodiments may be used and various modifications may be made without departing from the scope of the disclosure or the spirit of the appended claims.

[0028] Various illustrative embodiments are described that enable a radar source to coexist with other radar sources. In particular, techniques are described for generating radar signals in a manner that minimizes interference between the radar source and any additional radar sources that may be present in the surrounding environment. Techniques for processing received radar signals in a manner that interference from another radar source can be easily distinguished from reflected signals are also described. In certain embodiments, a radar system may include one or more hardware processors or circuits configured to generate a radar signal based on one or more waveform parameters selected to minimize interference. The radar signal may be a frequency modulated continuous wave (FMCW). However, the techniques described herein may be applied to other types of radar signals.

[0029] In certain embodiments, the transmitted radar signal comprises a sequence of chirps, wherein waveform parameters vary on a per-chirp basis based on a set of parameter patterns that have been configured for suppressing interference and / or for shaping interference in a manner that makes the interfering signal easily distinguishable from reflected signals during receiver processing. The set of parameter patterns may be selected from a codebook comprising a plurality of parameter pattern sets that have been configured for high autocorrelation and low cross-correlation.

[0030] In some embodiments, the transmitted radar signal is generated by performing phase modulation on each chirp based on an additional set of parameters corresponding to a phase code. The addition of phase modulation reduces the likelihood that the transmitted radar signal was generated using exactly the same parameters as an interference source.

[0031] In some embodiments, in response to determining that a previously transmitted portion of the radar signal (e.g., a previous chirp sequence) is interfered with, a waveform parameter of the radar signal is changed. Interference can be detected by attempting to perform object detection based on a first waveform parameter set that is different from a second waveform parameter set for the previously transmitted portion of the radar signal. If the attempt is successful, this indicates that the interference source using the first waveform parameter set may contribute to the received radar signal. Therefore, the first waveform parameter set can be excluded for use with a subsequently transmitted portion of the radar signal. For example, the first waveform parameter set can remain unused for a period of time.

[0032] As used herein, the term "codeword" or "parameter pattern" refers to data (e.g., a set of digital values) that indicates a specific combination of waveform parameters of a transmitted radar signal. A codeword can be used to form at least a portion of a transmitted radar signal. The term "codebook" refers to a plurality of predefined codewords that can be selected to generate a radar signal. As described below, a codeword can be selected to determine the characteristics of a given chirp in a transmitted waveform. By selecting different codewords, the transmitted waveform can be changed on a per-chirp basis. The terms "radar signal" and "radar waveform" are used interchangeably herein because a radar signal is transmitted as a wave (e.g., a frequency modulated radio wave).

[0033] Figure 1 Figure 2 shows an example scenario where radar interference may occur. Figure 1 As shown, the first vehicle 110 transmits radar signals reflected from the second vehicle 120 and the third vehicle 130. Both vehicles 120 and 130 are located within the transmission range of vehicle 110. Vehicle 130 is farther away from vehicle 110 than vehicle 120. Vehicle 120 may receive a copy 112 of the radar signal transmitted by vehicle 110 to reflect back a corresponding signal 112'. Similarly, vehicle 130 may receive a copy 114 of the radar signal transmitted by vehicle 110 to reflect back a corresponding signal 114'. In addition, vehicle 120 transmits its own radar signal 155, which acts as an interference signal.

[0034] Interference signal 155 is a direct signal that interferes with reflected signals 112' and 114'. Typically, direct signals are much stronger than reflected signals. For example, if the received power of signals 155, 112' and 114' is measured (e.g., in decibel milliwatts) as a function of distance, the measurement results may indicate that interference signal 155 presents two exponentially decaying powers, while reflected signals 112' and 114' present four exponentially decaying powers. Therefore, the signal-to-interference (SIR) ratio of reflected signals 112' and 114' decreases rapidly as the distance from the receiver (i.e., vehicle 110) increases. Since interference signal 155 is relatively high power compared to reflected signals 112' and 114', interference signal 155 has a greater contribution to the received signal (e.g., the combination of interference signal 155 and reflected signals 112' and 114'), thereby preventing reflected signals 112' and 114' from being detected at vehicle 110.

[0035] In addition, the jamming signal 155 may cause the radar receiver in the vehicle 110 to mistakenly identify the jamming signal 155 as an actual reflection. The distance to an object may be measured based on a round trip time, e.g., from the time the radar signal is transmitted to the time the corresponding reflected signal is received back at the radar source. Since the jamming signal 155 is transmitted directly, the jamming signal 155 may be mistakenly detected as corresponding to a target that appears at half the actual distance from the vehicle 120. Therefore, the jamming signal 155 may cause a "ghost" target to be detected.

[0036] Methods for minimizing interference to achieve multi-radar coexistence (e.g., Figure 1 The technology of coexistence of radar sources corresponding to vehicles 110 and 120).

[0037] Figure 2 An exemplary transmit waveform 200 is illustrated in accordance with certain embodiments. Waveform 200 is an FMCW waveform comprising a sequence of chirps, each chirp having a duration “T c” 206, and the total number of chirps in the sequence is “N c A chirp is a sound that is emitted at a specific time period (T in this example). c ) where the frequency of the signal increases or decreases during the time period. Figure 2 The waveform 200 is depicted as a function of frequency versus time. If the waveform 200 were depicted as a function of amplitude versus time, the waveform 200 would appear to be a sinusoidal signal oscillating at a varying speed. The first chirp 210 has a frequency offset "f0" 202 and a frequency bandwidth "B" 204. Figure 2 As depicted, the waveform varies on a per-chirp basis, with the first chirp 210 ramping linearly in frequency from f0 to B+f0. The next chirp 212 after chirp 210 ramps faster and has a slope approximately twice that of chirp 210. Thus, during time period T c During the chirp 212, the frequency is around the frequency range [f0, B+f0]. The slope of each chirp can be set according to the slope parameter. In addition, the chirp 212 has a frequency offset greater than f0. As explained later, the slope and / or frequency offset can be changed on a per-chirp basis. It should be noted that the change of the waveform on a per-chirp basis does not exclude the reuse of the same waveform parameters during the chirp sequence. For example, Figure 2 As shown, the last chirp 214 has the same slope as the first chirp 210, but with a different frequency offset. In some embodiments, a chirp sequence may include identical chirps, i.e., the same set of waveform parameters for a first chirp may be reused for a second chirp in the same chirp sequence, as long as at least one waveform parameter is varied for at least one chirp in the sequence.

[0038] Figure 3 3 is a simplified illustration of a codebook 300 according to some embodiments. The codebook 300 includes a set of codewords 310, i.e., parameter patterns. Each codeword 310 differs from any other codeword 310 in the codebook 300 by at least one parameter. Figure 3 As depicted, each codeword 310 may include transmit waveform parameters 320 and phase modulation parameters 330 used in conjunction with the transmit waveform parameters 320. The transmit waveform parameters 320 may include, for example, slope and frequency offset values ​​that form a "base" set of parameters for the transmit waveform. Phase codes are described later and may include slope and frequency offset values ​​for a phase signal used to modulate the transmit waveform.

[0039] exist Figure 3, each codeword 310 is depicted as including a transmit waveform parameter paired with a phase modulation parameter. In an alternative embodiment, the transmit waveform parameter 320 and the phase modulation parameter 330 may be independently selected. For example, a codeword may be formed by selecting a waveform parameter, selecting a phase modulation parameter, and combining the selected waveform parameter with the selected phase modulation parameter.

[0040] The transmit waveform parameters 320 can be configured for high autocorrelation and low cross-correlation. This means that the statistical correlation between a waveform generated using any particular set of transmit waveform parameters 320 and a delayed version of the same waveform (e.g., a waveform received back at a radar source after reflection from a target) will indicate a relatively high similarity between the two waveforms. In contrast, the correlation between a waveform generated using a first waveform parameter set from codebook 300 (e.g., transmit waveform parameters 310-A) and a waveform generated using a second waveform parameter set from codebook 300 (e.g., transmit waveform parameters 310-B) will indicate a relatively low similarity. As explained later, such correlation properties can be achieved by selecting waveform parameters that produce a Zadoff-Chu (ZC) sequence. However, parameters that do not produce an exact ZC sequence may also be used.

[0041] Figure 4 4 is a simplified block diagram of an exemplary radar system 400 according to certain embodiments. Radar system 400 includes a transmitter unit 410 and a receiver unit 430, both of which share access to antenna 425. In alternative embodiments, transmitter unit 410 and receiver unit 430 may include separate antennas, one for transmitting radar signals and one for receiving radar signals. The depicted block elements of transmitter unit 410 and receiver unit 430 may be implemented in hardware, software, or a combination thereof. Transmitter unit 410 and receiver unit 430 may share components other than antenna 425. For example, although not depicted at the block level, hardware components such as one or more processors and one or more memory or storage device elements may be shared by transmitter unit 410 and receiver unit 430. In some embodiments, the functionality described with respect to transmitter unit 410 and receiver unit 430 may be implemented using a single processing unit (e.g., a microprocessor including one or more separate processing cores).

[0042] Transmitter unit 410 may include transmit (Tx) waveform selection logic 412, codebook 414, carrier signal generator 416, and Tx waveform generator 418. Transmitter unit 410 may be communicatively coupled to receiver unit 430, for example, via one or more communication buses (not shown).

[0043] Tx waveform selection logic 412 is configured to select a codeword from codebook 414 to generate a radar signal for transmission via antenna 425. The selected codeword may be transmitted to receiver unit 430 to enable processing of radar signals received via antenna 425, for example, a received radar signal including one or more reflected versions of the transmitted radar signal and one or more interference signals. In some embodiments, a different codeword may be selected for each chirp. In other embodiments, a codeword may be reused for a certain number of consecutive chirps and then switched out for a different codeword.

[0044] The codebook 414 may correspond to Figure 3 The codebook 300 in FIG. 1 includes a plurality of codewords for generating a transmit waveform. Figure 3 As discussed, a codeword may include parameters that determine the characteristics of a given chirp and optionally phase modulation parameters.

[0045] The carrier signal generator 416 is configured to generate a carrier signal by which the transmit waveform is modulated. For example, if the transmit waveform is an FMCW waveform, the carrier signal may be generated to have a carrier frequency “f c " is a periodic signal.

[0046] The transmit waveform generator 418 is configured to generate a radar signal for transmission based on the codeword selected by the Tx waveform selection logic 412. The transmit waveform generator 418 may include a digital-to-analog converter, a transmit buffer, a frequency modulation circuit, and / or other circuits typically used to generate radar signals. Before transmission, the radar signal may be digitally represented as a function of variables "m" and "n", where m is the sequence number of the current chirp and n is the nth sample of the chirp. Therefore, the transmit waveform x[m,n] may be represented in the digital domain as a function of m and n. The transmit waveform is transmitted as an analog signal x(t) that varies with time.

[0047] The receiver unit 430 may include a receive (Rx) signal processing unit 434 , a fast-time discrete Fourier transform (DFT) module 436 , an equalization and resampling module 438 , a slow-time DFT module 440 , and a peak detection module 442 .

[0048] The Rx signal processing unit 434 is configured to receive a radar signal from the antenna 425 and apply signal processing to condition the received radar signal for subsequent processing, e.g., in preparation for object detection by the peak detection module 442. The Rx signal processing unit 434 may receive the radar signal as an analog signal y(t) in the time domain and convert the received radar signal into a corresponding signal y[m,n] in the digital domain. The Rx signal processing unit 434 is also configured to select waveform parameters for processing the received radar signal. In particular, the Rx signal processing unit 434 may identify a codeword used to generate a transmitted radar signal. The codeword may be communicated from the Tx waveform selection logic 412 to the Rx signal processing unit 434, e.g., directly or by storing a previously used codeword in a shared memory location.

[0049] Fast time DFT module 436 is configured to apply fast time DFT to the digital form of the received radar signal. Fast time DFT can be implemented using a fast Fourier transform (FFT) algorithm, and can be applied to generate a separate Fourier transform value set for each individual chirp of the received radar signal. For any particular chirp, the output of the fast time DFT may include one or more amplitude values ​​as a function of frequency. The frequency domain can be divided into a set of boxes representing delays. These boxes can be graphically represented as a one-dimensional array in the delay domain, where each box is located at a different delay index. Amplitudes above a certain threshold can be considered as peaks. As described below, the box position of the peak can be used to determine the speed and distance of the target, and to distinguish between reflected signals and interference signals.

[0050] The equalization and resampling module 438 is configured to adjust the output of the fast time DFT module 436 to compensate for the effects of the changing waveform parameters. The equalization and resampling enable the peaks to be coherently combined with each other during processing by the slow time DFT module 440. Figure 7 Describes equalization and resampling.

[0051] The slow time DFT module 440 is configured to apply a second DFT on the output of the fast time DFT module 436 after the fast time DFT output has been equalized and resampled. The slow time DFT is more time consuming and processing intensive than the fast time DFT. Although the second DFT does not strictly have to be a slow time DFT, the use of the slow time DFT generally provides more detailed information about the frequency characteristics of the input data. The first DFT and the second DFT together can be considered as a two-dimensional DFT because the second DFT adds another dimension to the result of the first DFT. The output of the second DFT can be graphically represented as a two-dimensional array of boxes, where the first dimension is the delay dimension of the fast time DFT and the second dimension represents the Doppler shift. The delay corresponds to the distance of the target. The Doppler shift corresponds to the speed of the target. Therefore, the speed and distance of the target can be calculated based on the position of the corresponding peak in the two-dimensional array.

[0052] The peak detection module 442 is configured to identify peaks in the output of the slow time DFT module 440 and determine the speed and distance of the object based on the bin positions of the identified peaks. In some embodiments, the peak detection module 242 can perform a constant false alarm rate (CFAR) algorithm to exclude false peaks.

[0053] Figure 5 is a simplified flow chart of a method 500 for generating and receiving radar signals in accordance with certain embodiments. Figure 5 The depicted processing may be performed by a radar system, e.g. Figure 4 Radar system 400. At step 510, parameters are selected for the transmit waveform, for example based on a codeword from a codebook. In some embodiments, the parameters may include parameters that determine the shape of the FMCW waveform and additional parameters that determine the shape of the phase signal of the modulated waveform. Without considering the addition of phase modulation, and assuming that all chirps are formed using the same set of parameters (e.g., the same slope and offset), the transmit waveform can be represented in the time domain as:

[0054] x(t)=exp(-j2πf c t)exp(-jπ(βt+f o )t) (1)

[0055] where f c is the carrier frequency, f0 is the frequency offset, t is the time, and β is the slope. In Equation 1, the transmitted waveform x(t) is represented by two exponential terms. The first exponent is the carrier frequency f c The second index is a function of the frequency offset f0 and the slope β, and corresponds to the transmission waveform before modulation.

[0056] If the parameters include slope and frequency offset values ​​selected individually for each chirp, the parameters of the mth chirp can be expressed as follows:

[0057]

[0058] The right side of Equation 2 corresponds to the slope and offset parameters of the parameters u and q converted to a Zadoff-Chu sequence, where u varies from 0 to the length of the ZC sequence (in this example, the length is equal to BT c ), and q can be any integer value. As shown in Equation 2, u depends on the slope, and q depends on the offset. Therefore, u and q represent the slope and offset, respectively.

[0059] Therefore, the transmitted waveform (in the digital domain) can be expressed as:

[0060]

[0061] where the exponential term of Equation 3 is a complex value similar to the nth sample of the ZC sequence.

[0062] In addition, if the transmitted waveform is a phase-modulated FMCW waveform, the transmitted waveform becomes:

[0063]

[0064] where x FMCW is the FMCW waveform, for example, x[m,n] in Equation 3, and is a parameter for the ZC sequence representation of the phase signal, and N is the largest prime value less than or equal to the total number of chirps Nc. Thus, a codeword may include the parameter set: The transmit waveform may be considered as a two-dimensional ZC sequence formed by modulating a first ZC sequence corresponding to the FMCW waveform with a second ZC sequence corresponding to the phase signal.

[0065] The parameters selected in step 510 vary with the chirp. In particular, the transmit waveform may be generated according to equation 4 above, wherein at least one parameter varies with the chirp. For example, the transmit waveform may be generated according to the equation 4 above, wherein at least one parameter varies with the chirp. Figure 3 The code words in the codebook 300 are used to set u, q, The value of u, q, or At least one of the parameters is different between any two consecutive chirps. In some embodiments, the parameters are selected for multiple chirps (possibly the entire chirp sequence) at the same time, so that the parameters are determined before the chirps are generated. In other embodiments, the parameters can be selected "on-the-fly" for each chirp. As an alternative to using a codebook, the parameters can be varied randomly. For example, a new slope or a new frequency offset can be randomly selected for each subsequent chirp. However, the advantage of using a codebook is that the parameters can be specifically selected to ensure low mutual interference between codewords.

[0066] In step 512 , a transmit waveform is generated according to the parameter selection in step 510 .

[0067] At step 514, the waveform is received by the radar system and sampled (e.g., by an analog-to-digital converter of the receiver unit 430) to generate an input to a first DFT algorithm (e.g., a fast time DFT). The sampling rate may correspond to the rate of change of one of the chirps (e.g., a sampling rate of 1 / β (1) , where β (1) The sampling is performed using a sampling rate (where t is the slope of the first chirp in the chirp sequence). In some embodiments, the same sampling rate is applied to each chirp in the chirp sequence.

[0068] The first DFT is applied to each chirp of the chirp sequence individually to generate a corresponding representation of the chirp in the delay domain for each chirp. When the transmit waveform x(t) is reflected back to the receiver, the corresponding received signal can be represented in the time domain as:

[0069]

[0070] where v is the relative velocity of the reflecting object, and λ is the wavelength of the carrier signal. The exponential term corresponds to the Doppler frequency shift, and the βt0 exponential term corresponds to the time delay (representing the distance). In equation 5, the time value t in the digital domain can be expressed as:

[0071]

[0072] In the digital domain, the received waveform y(t) can be expressed as:

[0073]

[0074] Where K φ is the phase factor corresponding to the first exponential term from Equation 5. The approximation in Equation 7 is based on the assumption that any phase shift due to the Doppler effect within a given chirp is negligible.

[0075] In certain embodiments, upon receiving a receive waveform, the receiver unit multiplies the receive waveform by the conjugate of the previous (eg, last used) transmit waveform:

[0076]

[0077] Since the receiver unit is part of the radar system, the receiver unit can access information about previously transmitted waveforms. For example, as previously discussed, the receiver unit 430 can access the codeword previously selected by the Tx waveform selection logic 412. The multiplication can be performed in the analog domain or in the digital domain as shown in Equation 8, and has the effect of canceling the x(t) or x[m,n] terms so that only the exponential terms from Equation 5 or Equation 7 remain. Although not strictly required, this additional step operates to simplify the receiver processing. For example, the multiplication is performed before sampling the received waveform in order to achieve a lower sampling rate.

[0078] Figure 6 is a graphical representation of a process for applying a two-dimensional DFT to a received waveform in accordance with certain embodiments. Figure 6 As depicted, a first DFT (e.g., the DFT in step 514) is applied to N c Each chirp in the chirp sequence is counted to produce amplitude values ​​that are grouped into bins in the delay domain. As mentioned before, amplitudes above a certain threshold can be considered peaks. Figure 6 , the peaks (610, 612, and 614) are represented as black boxes. The results of the first DFT are then combined by applying a second DFT (e.g., the DFT in step 518 discussed below), which produces a two-dimensional array of bins in the Doppler delay domain. Peaks (e.g., peaks 610, 612, and 614) in the same bin position (i.e., the same delay index) in the output of the first DFT will be coherently added to produce a peak (e.g., peak 650) in the output of the second DFT.

[0079] As long as the waveform parameters of each chirp are the same, Figure 6 The process depicted works well. However, when the waveform parameters vary, the peaks in the output of the first DFT can shift to different locations so that the peaks cannot be coherently added after applying the second DFT. This is because β is changed to adjust the slope, and the phase factor K Φ is a function of β and the frequency offset f0.

[0080] Therefore, it can be Figure 5 Step 516 applies equalization and resampling to correct for the effects of the changing parameters, such as Figure 7 Depicted.

[0081] Figure 7is a graphical representation of a process for applying a two-dimensional DFT to a received waveform after performing equalization and resampling, according to certain embodiments. Figure 7 As shown, the position of peak 710 is Figure 6 The peak 610 in FIG. 7 is the same as the peak 610 in FIG. 7 because the peak 710 is produced by applying the DFT to the first chirp output before changing any parameters. Once the waveform parameters begin to change (e.g., for N c The peak positions (e.g., peaks 712 and 714) are shifted to different positions and are different from those of the second chirp and each subsequent chirp in the sequence of chirps. Figure 6 The equalization and resampling correct for the shift in phase and position, respectively.

[0082] Equalization and resampling can be performed simultaneously at the output of the first DFT. In some embodiments, equalization is applied first, and then resampling. The output of the first DFT can be expressed as:

[0083]

[0084] where l is the delay index to a particular bin, t0 is the unknown time delay, where the t0 value of one of the chirps corresponds to the actual time delay of the target, and δ is a well-known delta function. Equalization takes into account phase variations and can be achieved by This is performed by multiplying by the following equalization function, which has the effect of canceling out K in Equation 9. φ (m) The effect of term (first index):

[0085]

[0086] Equilibrium function W (m) [l] Equalization is performed for each t0, which can be resolved to a corresponding delay index (e.g., l=0, 1, 2, etc.). Therefore, each bin is affected regardless of whether the bin includes a peak. However, this does not affect the ability to detect peaks because non-peak locations essentially consist of noise that is rotated by the equalization function without changing the noise statistics.

[0087] Resampling corrects for the change in the delta term in Equation 9. Without resampling, the position of each peak in the output of the first DFT would depend on the slope of that particular chirp. Resampling takes into account the slope change. For example, if the slope of the first chirp is β (1) , and the slope of the second chirp is twice that of the first chirp, i.e. β (2) =2β (1), then the DFT output can be resampled by discarding every other sample (e.g., every even sample or every odd sample). As another example, if the slope of the second chirp is negative, such as β (2) =-β (1) , the samples can be rotated by switching the value of the first sample with the value of the last sample, the value of the second sample with the value of the second to last sample, etc. In this way, the slope β of the first chirp can be (1) The sampling is performed so that the delay index becomes aligned for each chirp. Although the example just discussed uses the slope of the first chirp, any slope can be used as a reference or common slope to perform the resampling. For example, the common slope can be the minimum slope of the transmitted waveform.

[0088] return Figure 5 At step 518, after equalization and resampling are performed at step 516, a second DFT (e.g., a slow-time DFT) is applied to the output of the first DFT. Figure 6 As mentioned, the second DFT produces a two-dimensional array of bins in the Doppler delay domain. The peak positions in this two-dimensional array can be used to calculate the speed and distance of the target. The received waveform can be represented in the Doppler delay domain as follows:

[0089]

[0090] where k and l are the Doppler and delay indices, respectively, for the bin positions in the two-dimensional array, and β is the common slope to which the output of the first DFT is resampled in step 516 .

[0091] At step 520, one or more attributes may optionally be calculated from the received signal (the waveform received at step 514). These attributes may be in addition to the range and Doppler values ​​calculated in step 524 below. For example, in some embodiments, the position of a target relative to the receiver / radar source may be detected in two or three dimensional space by measuring the azimuth of the target and / or the elevation of the target, as viewed from the perspective of the receiver. The azimuth and elevation together represent the direction of arrival (also referred to as the angle of arrival) of the target.

[0092] Azimuth and elevation can be calculated using DFT-based processing. The ability to calculate azimuth and elevation will depend on the antenna configuration of the receiver (e.g., whether the antennas are configured in a one-dimensional array or a two-dimensional array). For example, if the receiver has an antenna array arranged in a horizontal direction, a DFT can be performed across the receiving antennas in the horizontal direction to calculate the azimuth. Similarly, a DFT can be performed across the receiving antennas in the vertical direction to calculate the elevation. Therefore, the properties of the target determined using the received signal can include range, speed, azimuth, elevation, or any combination thereof.

[0093] Although step 520 is depicted as occurring after step 518, the additional properties may be calculated at a different point in time because the calculation of these additional properties may be performed independently of the DFT in steps 514 and 518. Thus, in another embodiment, step 520 may be performed before the first DFT in step 514.

[0094] In step 522, peaks are identified in the output of the second DFT. In some embodiments, a CFAR algorithm may be used to identify peaks. The threshold used to determine the peaks may vary depending on the detection algorithm used. In the CFAR algorithm, the threshold is set based on the target false alarm probability. Ideally, the output of the second DFT includes a separate peak for each real target, with no peaks corresponding to artifact targets. If there are multiple real targets, there may be multiple peaks in the output of the second DFT.

[0095] At step 524, the range and Doppler values ​​are calculated based on the location of the peak identified in step 522. If the peak is identified as being located at index [l, k], then the values ​​of l and k can be applied to equation 11 to calculate the following pair of values:

[0096]

[0097] The first value corresponds to the distance of the target from the radar source and can be calculated based on l, β, T c The second value corresponds to the speed of the target relative to the radar source and can be calculated based on k, N c and T c The radar system may then use the calculated relative speed of the target and the absolute speed of the radar source (eg, as measured by a speedometer or other sensor of a vehicle on which radar system 400 is installed) to calculate the absolute speed of the target.

[0098] In addition, although the description is made with reference to the FMCW waveform, Figure 5 The processing in can be applied to other types of waveforms (e.g., PMCW). For example, a PMCW waveform can be represented as a ZC sequence, which is generated by changing one or more waveform parameters (e.g., slope or frequency offset) and further phase modulated with a phase signal generated according to a phase code.

[0099] Fig. 8A The result of applying the first DFT to a single chirp in the received radar signal is shown when the slope β and frequency offset f0 of the received chirp match the slope β and frequency offset f0 of the transmitted chirp. The result is plotted in the amplitude delay domain rather than as discrete bins (e.g., as Figure 6 and7 as depicted in ). Fig. 8A As shown, the output of the first DFT includes pulses corresponding to peaks 810 located at particular delay indices.

[0100] Figure 8B The result of applying the first DFT to a single chirp in the received radar signal is shown when the slope of the received chirp matches the slope of the transmitted chirp, but the frequency offset does not match. Fig. 8A Compared to , the peak 820 is shifted. Figure 8B As depicted in FIG. 8 , peak 820 may be shifted outside of range of interest 815. Range of interest 815 is a range of delay indices to which actual targets may plausibly correspond. The slope, frequency offset, and / or other parameters of each codeword in the codebook may be selected so that when the radar source and the jammer use codewords with different frequency offsets, any peaks attributed to the jammer are shifted outside of the range of interest.

[0101] Figure 8C The result of applying the first DFT to a single chirp in the received radar signal is illustrated when the slope of the received chirp does not match the slope of the transmitted chirp. The mismatched slopes result in a spread 830 of energy across the delay domain.

[0102] Fig. 9A The figure shows the mismatch frequency offset and matching slope scenarios (e.g. Figure 8B The output of the first DFT includes amplitude values ​​in the delay domain of multiple chirps of the received waveform, and is transformed by the second DFT into amplitude values ​​in the Doppler delay domain (for example, by Figure 6 Since the individual peaks in the output of the first DFT (e.g., from Figure 8B The output of the second DFT is distributed across the Doppler domain (peak 820 of the first DFT being shifted). This distribution produces an energy spread 920 located at the same offset in the delay domain. That is, the energy spread 920 is located at the same delay index as the delay index of the shifted peak 820. If additional peaks in the output of the first DFT are also shifted due to mismatched frequency offsets, those additional peaks will be spread across the Doppler domain in a similar manner.

[0103] Fig. 9B The figure shows the mismatch slope scenario (for example, Figure 8C The result of applying the second DFT to the output of the first DFT in the scenario (e.g., Figure 8C As a result of the energy spread 830), the output of the second DFT is distributed in the Doppler delay domain as an energy spread 930.

[0104] based on Fig. 9A and 9B It is clear that as a result of applying the above techniques, when there is a slope mismatch, the interference is suppressed because the energy of the interferer is spread across the Doppler delay domain so that no detectable peak is formed for the interferer in the output of the second DFT. In addition, when there is a frequency offset mismatch, the interference is shaped because even if the energy of the interferer is not spread across the delay domain, any detected peak will be located in the range of actual interest (e.g., Figure 8B Therefore, if the peak is located at an untrusted delay index or the distance calculated based on the delay index is untrusted, the peak can be identified as corresponding to an interference source rather than a real target.

[0105] Fig. 9A and 9B The depicted results can be achieved by selecting slope and frequency offset parameters so that the transmitted waveform is represented as a ZC sequence. In particular, the ZC sequence exhibits correlation characteristics that produce a constant cross-correlation for any delay in a mismatch slope scenario (ZC parameter u), and that produce a peak at a delay index shifted according to the mismatch in parameter q in a mismatch offset scenario (ZC parameter q). Therefore, according to the techniques described herein, the ZC sequence has useful correlation characteristics for interference suppression and shaping. However, it should be noted that the transmitted waveform does not need to have a perfect ZC form. Instead, an approximate ZC sequence may be sufficient to achieve the above-described desired correlation characteristics.

[0106] The examples discussed above focus on transmitter and receiver processing when the parameters of the transmit waveform vary on a per-chirp basis. The following discussion expands on the previous examples and explains the additional processing that may occur if optional phase modulation is applied to the transmit waveform. Phase modulation is useful because the set of possible values ​​of the slope and offset parameters (e.g., u and q) of the transmit waveform that minimize interference while meeting performance requirements may be limited. For example, a radar system may be designed to meet performance requirements regarding a minimum distance between two targets that enables the targets to be identified as separate objects (referred to as range resolution) and a minimum Doppler separation between the two targets that enables the two targets to be identified as separate objects (referred to as Doppler resolution). This limited set of values ​​may be acceptable when only a small number of radar sources need to coexist (e.g., four radar sources, all within the transmission range of each other), rather than when a large number of radar sources are expected to coexist. For the coexistence of a small set of radar sources, the size of the codebook (e.g., the number of codewords) can be kept small, and the codewords can be designed so that the fraction of chirps that produce unacceptable levels of mutual interference between any given pair of codewords is also relatively small. The coexistence of a large number of users requires a larger codebook, and due to the limited number of available parameter values, the fraction of chirps that produce unacceptable levels of mutual interference between any given pair of codewords is much larger. In particular, when the slope used by the interference source is the same as the slope used by the radar source and the frequency offset used by the interference source is also the same as the frequency offset used by the radar source, a peak attributed to the interference source can be observed in the output of the first DFT.

[0107] Phase modulation can be applied to mitigate unwanted interference issues due to a limited set of available parameter values. As described above in conjunction with Equations 3 and 4, the parameters can be selected so that the transmit waveform and the phase modulated transmit waveform can be represented as a ZC sequence. Therefore, the waveform produced by applying phase modulation to the transmit waveform can be considered a two-dimensional ZC sequence. Changing the phase of the transmit waveform reduces the likelihood that peaks attributed to interference sources will add coherently when the second DFT is performed.

[0108] In some embodiments, the same phase modulation parameters may be applied to each chirp in a given chirp sequence. Alternatively, as with the base parameters of the transmit waveform, the parameters of the phase modulation may also be varied (e.g., randomly or according to a phase code). In some embodiments, the parameters are varied by varying at least one of the following with each chirp: the slope of the transmit waveform, the frequency offset of the transmit waveform, or the chirp phase. In addition, as previously described in connection with Figure 7As explained, equalization can be performed to correct for the effects of changing slope and frequency offset. In particular, the equalization function in Equation 10 can be applied to correct for phase changes caused by changing slope and frequency offset. Similarly, phase changes caused by applying phase modulation can be corrected by applying the equalization function. Equalization of phase modulation can be similar to Figure 7 The depicted equalization is performed simultaneously (e.g., in Figure 5 during step 516).

[0109] In some embodiments, the initial chirp in the chirp sequence is determined by randomly selecting slope and offset parameters for phase modulation (e.g., parameters and ) and randomly selected slope and offset parameters (e.g., parameters u and q) for the transmitted waveform. For example, the initial chirp can be formed by randomly selecting any codeword in the codebook. For the next chirp in the chirp sequence and each chirp thereafter, the slope and offset parameters of the phase modulation can remain random, while the slope and offset parameters of the transmitted waveform (e.g., parameters u and q) can be selected to maximize the "distance" metric between the codeword of the next chirp and the codeword of the previous chirp. In one example, the distance metric is defined so that as long as the slopes of the codewords are different, the distance is set to a certain maximum distance value, but when the slopes are different, the distance is set to be proportional to the difference in slope (e.g., the difference between the q values ​​of the codewords). Similarly, the distance metric can be defined as a function of the frequency offset difference or based on a combination of the frequency offset difference and the slope difference.

[0110] Fig. 10A An example of radar signals that are not aligned with respect to time is shown. Fig. 10A In FIG. 1 , a first source “i” generates a radar signal 1010 including a chirp sequence 1015, and a second source “j” generates a radar signal 1020 including a chirp sequence 1025. Each of the chirp sequences 1015 and 1025 includes a total of N c The radar signals 1010, 1020 are continuous signals, where the next sequence is sent immediately after the current sequence ends. Each chirp is labeled "PM" to indicate that the chirp has been phase modulated according to the embodiments discussed above and has a corresponding phase φ. The chirp sequences 1015 and 1025 are generated independently of each other so that they start and end at different times.

[0111] Fig. 10B An example of radar signals aligned with respect to time is shown. Fig. 10B, chirp sequences 1015' and 1025' are aligned so that they start and end at the same time. Alignment is useful because some phase encoding and decoding patterns in a codebook may not exhibit good correlation characteristics with delayed versions of other phase encoding and decoding patterns in the same codebook. For example, a codebook may be designed to have a first codeword including a phase modulation component and a second codeword including a phase modulation component, wherein the first codeword and the second codeword have a low cross-correlation when the corresponding transmitted waveforms are time-aligned, and the first codeword and the second codeword have a high cross-correlation when the transmitted waveforms are misaligned in a particular manner (e.g., whenever the first transmitted waveform is delayed by three seconds relative to the second transmitted waveform).

[0112] In certain embodiments, radar signals from different radar sources may be aligned based on a shared time reference, such as Coordinated Universal Time (UTC). For example, each radar source may receive the UTC time from a global navigation satellite system (GNSS) in order to determine when to send the next chirp. In this way, a synchronization "frame boundary" may be derived for each chirp sequence in order to align the chirp sequences of different radar sources.

[0113] Fig.11 is a simplified flow chart of a method 1100 for selecting a codeword according to some embodiments. Fig.11 The depicted processing may be performed by a radar system, e.g. Figure 4 The radar system 400 of claim 11. At step 1110, a transmit waveform is generated based on a plurality of codewords. For example, a different codeword may be selected for each chirp in a chirp sequence, each codeword including slope and offset parameters for a particular chirp in the chirp sequence, and slope and offset parameters for a phase modulation applied to the particular chirp. The transmit waveform is then transmitted into the surrounding environment to be reflected by any object that happens to be within the transmit range of the radar system.

[0114] At step 1112, a received waveform is captured after the transmit waveform generated in step 1110 is transmitted. The received waveform may be captured by a receiver unit of the radar system and may be captured as an analog continuous time signal. For example, an analog-to-digital converter may be used to convert the received waveform from the time domain to the digital domain to generate a digital representation of the received waveform as a function of the chirp number m and the sample number n.

[0115] At step 1114, object detection is performed on the received waveform based on a specific codeword not used to generate the transmitted waveform (e.g., any codeword other than the codeword used to generate the chirp sequence of the transmitted waveform). Object detection may include the above-mentioned combination of Figure 5Specifically, object detection may include applying a first DFT to each chirp of a chirp sequence in a received waveform and then applying a second DFT to the output of the first DFT to generate a two-dimensional representation of the received waveform in the Doppler delay domain.

[0116] At step 1116, it is determined whether the object detection in step 1114 was successful. In some embodiments, this determination may be based on whether a peak is clearly observed in the Doppler delay domain. For example, the receiver unit of the radar system may be configured to determine whether there are any bins whose amplitudes substantially exceed a threshold to define as peaks. If such peaks are identified, the object detection is deemed successful and the method proceeds to step 1118. Otherwise, the method proceeds to step 1120.

[0117] In step 1118, in response to determining in step 1116 that the object detection was successful, it is determined that a particular codeword should not be used for a certain time period (e.g., the next ten seconds). Successful object detection indicates that there may be a nearby radar source that uses a particular codeword to transmit its own radar signal. Therefore, the radar system can use other codewords, at least until the time period has expired, in order to avoid potential interference between the signal transmitted by the nearby radar source and the reflected signal obtained from the radar system's own transmission. This also benefits the nearby radar source because the subsequent transmission of the radar system will not interfere with the reception of the reflected signal by the nearby radar source.

[0118] In step 1120, in response to determining that object detection was unsuccessful in step 1116, it is determined that the particular codeword is eligible for use during a subsequent chirp sequence (e.g., the next chirp sequence). The subsequent chirp sequence can be formed by selecting a different codeword from the pool of eligible codewords for each chirp in the subsequent chirp sequence.

[0119] In some embodiments, steps 1114 to 1120 may be repeated for multiple codewords in the codebook to form a pool of eligible codewords for generating subsequent chirp sequences. For example, the pool may be formed one codeword at a time by adding eligible codewords based on a negative determination in step 1116. As another example, the pool may initially include the entire set of codewords from the codebook, with the pool gradually becoming smaller as codewords are eliminated from consideration based on a positive determination in step 1116.

[0120] In some embodiments, a codeword may be selected for use in generating a subsequent chirp based on a positive determination in step 1116. Such a codeword may be selected based on a determination that a "distance" between the selected codeword from step 1114 and a particular codeword is greater than a distance between the particular codeword and other codewords in the codebook, where the distance is calculated based on the distance metric discussed previously. Thus, once an interfering codeword is identified, a codeword that is least likely to cause mutual interference with the interfering codeword may be selected.

[0121] The condition of a single clearly observed peak in step 1116 is merely exemplary. Other conditions may be used to determine whether object detection is successful. For example, instead of a single clearly observed peak, the condition may be that there are at least three peaks above a certain amplitude threshold, all within a certain distance of each other (e.g., three peaks in a 4×4 bin neighborhood).

[0122] Fig.12 An example computer system 1200 is illustrated in which one or more embodiments may be implemented. The computer system 1200 may be used with a radar system (e.g., Figure 4 In some embodiments, the computer system 1200 is deployed in a vehicle (e.g., Figure 1 In the vehicle 110). Fig.12 Provided are methods that can be performed as described herein (e.g., in conjunction with Figure 5 and 11 Schematic diagram of an embodiment of a computer system for implementing the method described herein. It should be noted that Fig.12 It is intended only to provide a generalized illustration of the various components, any or all of which may be used as appropriate. Fig.12 Broadly illustrated are how various system elements may be implemented in a relatively discrete or relatively more integrated manner.

[0123] like Fig.12 As depicted, computer system 1200 may include hardware elements that may be communicatively coupled via bus 1205 (or other appropriate wired and / or wireless communication infrastructure). The hardware elements may include one or more processing units 1210, which may include, but are not limited to, one or more general-purpose processors, one or more special-purpose processors, such as digital signal processors (DSPs), graphics acceleration processors, application-specific integrated circuits (ASICs), etc. Fig.12 As shown, some embodiments may have a separate DSP 1220. Processing unit 1210 and / or DSP 1220 may perform radar processing including, for example, sending and receiving radar signals, applying DFT, detecting interference from another radar source, and calculating the range and velocity of an object based on the received radar signals.

[0124] The computer system 1200 may include one or more input devices 1215, which may include but are not limited to a touch screen, a keyboard, a touchpad, a camera, a microphone, etc.; and one or more output devices 1250, which may include but are not limited to a display device, a speaker, etc.

[0125] The computer system 1200 may also include a wireless communication interface 1230, which may include but is not limited to a network card, an infrared communication device, a wireless communication device and / or a chipset (such as device, IEEE 802.11 device or cellular communication facility), etc., which can enable the computer system 1200 to communicate with external computer systems or electronic devices. Communication can be performed via one or more wireless communication antennas 1232 that send and / or receive wireless signals 1234.

[0126] Computer system 1200 may also include sensor 1240. Such sensors may include, but are not limited to, one or more of the following examples: radar sensor (e.g., Figure 4 ), inertial sensors (e.g., accelerometers and / or gyroscopes), cameras, magnetometers, altimeters, microphones, ultrasonic sensors, light sensors, etc., some of which may be used to supplement and / or facilitate the radar-related processing described herein.

[0127] The computer system 1200 may also include a GNSS receiver 1280 operable to receive a signal 1284 from one or more GNSS satellites using an antenna 1282. The signal 1284 may be used to supplement and / or incorporate the techniques described herein (e.g., deriving a shared time reference for aligning chirp sequences). In some embodiments, the signal 1284 may be used to determine the geographic location of the computer system 1200, such as for vehicle navigation.

[0128] The computer system 1200 may also include and / or be in communication with a memory 1260. The memory 1260 may include, but is not limited to, local and / or network accessible storage, disk drives, drive arrays, optical storage devices, solid state storage devices, such as random access memory ("RAM") and / or read only memory ("ROM"), which may be programmable, flash memory updateable, etc. Such storage devices may be configured to implement any suitable data storage, including but not limited to various file systems, database structures, etc. In some embodiments, the memory 1260 may store a codebook including parameters of the transmit waveform.

[0129] Memory 1260 may include a non-transitory computer-readable medium storing instructions executable by one or more processors (e.g., processing unit 1210) of computer system 1200. Such instructions may be stored as program code, such as an operating system, device driver, executable library, or other application. The instructions stored in memory 1260 may be configured to cause the processor to perform the radar-related processing described herein. By way of example only, the above discussion regarding Figure 5 One or more of the processes described in method 500 may be implemented as code and / or instructions executable by processing unit 1210 and / or DSP 1220. Then, in one aspect, such code and / or instructions may be used to configure and / or adapt a general purpose computer (or other computing device) to perform one or more operations according to the techniques described herein.

[0130] It will be apparent to those skilled in the art that substantial variations may be made depending on specific requirements. For example, customized hardware may also be used, and / or specific elements may be implemented in hardware, software (including portable software, such as applets, etc.), or both. In addition, connections to other computing devices such as network input / output devices may be employed.

[0131] With reference to the accompanying drawings, a component that may include a memory may include a non-transitory machine-readable medium. The terms "machine-readable medium" and "computer-readable medium" used herein refer to any storage medium that participates in providing data that causes a machine to operate in a particular manner. In the embodiments provided above, various machine-readable media may involve providing instructions / codes to a processing unit and / or other devices for execution. Additionally or alternatively, a machine-readable medium may be used to store and / or carry such instructions / codes. In some implementations, a computer-readable medium is a physical and / or tangible storage medium. Such a medium may take a variety of forms, including but not limited to non-volatile media, volatile media, and transmission media. Common forms of computer-readable media include, for example, magnetic and / or optical media, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or box, or any other medium from which a computer can read instructions and / or codes.

[0132] The methods, systems and devices discussed herein are examples. Various embodiments may appropriately omit, replace or add various processes or components. Features described with respect to certain embodiments may be combined in various other embodiments. Different aspects and elements of the embodiments may be combined in a similar manner. The various components of the accompanying drawings provided herein may be implemented with hardware and / or software. In addition, technology is constantly evolving, and therefore, many elements are examples that do not limit the scope of the present disclosure to these specific examples.

[0133] The foregoing description is provided to enable those skilled in the art to make or use the disclosed embodiments. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the techniques described herein may be applied to other embodiments without departing from the scope of the present disclosure. Therefore, the present disclosure is in accordance with the widest possible scope consistent with the principles and novel features defined by the appended claims.

Claims

1. A method comprising: generating, by a radar system, a frequency modulated signal comprising a first chirp sequence, wherein each chirp in the first chirp sequence is generated according to a set of waveform parameters; changing, by the radar system, at least one waveform parameter in the waveform parameter set for one or more chirps in the first chirp sequence; generating a phase signal according to a phase modulation parameter set, wherein the phase modulation parameter set includes a first parameter representing a slope of the phase signal and a second parameter representing a frequency offset of the phase signal; generating, by the radar system, a transmission signal by phase modulating the frequency modulated signal using the phase signal, such that each chirp in the first chirp sequence has a corresponding phase determined according to the phase signal; changing the phase signal by changing at least one phase modulation parameter in the phase modulation parameter set for at least one chirp in the first chirp sequence; receiving, by the radar system, a received signal comprising a second chirp sequence, the received signal corresponding to the transmitted signal reflected from an object in a surrounding environment, wherein the receiving comprises sampling the received signal; and The sampled received signals are used by the radar system to determine one or more properties of the object.

2. The method according to claim 1, wherein: The changing of the at least one waveform parameter includes changing a slope of the one or more chirps, a frequency offset of the one or more chirps, or both.

3. The method according to claim 1, wherein: Determining the one or more properties of the object comprises: performing a first discrete Fourier transform (DFT) using the sampled received signal, wherein the first DFT is applied separately to each chirp in the second chirp sequence to generate a separate result for each chirp in the second chirp sequence; performing a second DFT using the result of the first DFT; and The radar system detects the distance and speed of the object based on the result of the second DFT.

4. The method according to claim 3, further comprising: performing equalization on the result of the first DFT before performing the second DFT, wherein the changing of the at least one waveform parameter comprises changing a frequency offset of the one or more chirps, and wherein performing the equalization comprises determining an equalization function based on the frequency offset of the one or more chirps, the equalization function being configured to correct a phase shift caused by changing the frequency offset of the one or more chirps.

5. The method according to claim 3, further comprising: Resampling is performed on the result of the first DFT before performing the second DFT, wherein the change in the at least one waveform parameter includes changing the slope of the one or more chirps, and wherein performing the resampling includes determining a resampling rate based on the slope of the one or more chirps, and the resampling rate is configured to correct a shift in a peak position in the result of the first DFT caused by changing the slope of the one or more chirps.

6. The method according to claim 1, wherein: The at least one waveform parameter varies with each consecutive chirp in the first chirp sequence.

7. The method according to claim 1, wherein: The waveform parameter set is determined based on a first codeword among a plurality of codewords in a codebook, and wherein the changing the at least one waveform parameter comprises switching to a second codeword among the plurality of codewords.

8. The method according to claim 7, further comprising: performing object detection based on a third codeword not used to generate the first chirp sequence; Determining the presence of an interference source in the surrounding environment based on successful object detection; as well as Responsive to the determination that an interferer is present, the third codeword is prevented from being used in a subsequently transmitted sequence of chips.

9. The method according to claim 1, wherein: The waveform parameter set enables the transmit signal to be generated as a Zadoff-Chu sequence.

10. A radar system comprising: one or more processors; as well as A memory storing instructions that, when executed by the one or more processors, cause the one or more processors to perform a process comprising: generating a frequency modulated signal comprising a first chirp sequence, wherein each chirp in the first chirp sequence is generated according to a set of waveform parameters; changing at least one waveform parameter in the waveform parameter set for one or more chirps in the first chirp sequence; generating a phase signal according to a phase modulation parameter set, wherein the phase modulation parameter set includes a first parameter representing a slope of the phase signal and a second parameter representing a frequency offset of the phase signal; generating a transmission signal by phase modulating the frequency modulated signal using the phase signal so that each chirp in the first chirp sequence has a corresponding phase determined according to the phase signal; changing the phase signal by changing at least one phase modulation parameter in the phase modulation parameter set for at least one chirp in the first chirp sequence; receiving a received signal including a second chirp sequence, the received signal corresponding to the transmitted signal reflected from an object in a surrounding environment, wherein the receiving includes sampling the received signal; and One or more properties of the object are determined using the sampled received signals.

11. The radar system according to claim 10, wherein: The changing of the at least one waveform parameter includes changing a slope of the one or more chirps, a frequency offset of the one or more chirps, or both.

12. The radar system according to claim 10, wherein: Determining the one or more properties of the object comprises: performing a first discrete Fourier transform (DFT) using the sampled received signal, wherein the first DFT is applied separately to each chirp in the second chirp sequence to generate a separate result for each chirp in the second chirp sequence; performing a second DFT using the result of the first DFT; and The radar system detects the distance and speed of the object based on the result of the second DFT.

13. The radar system according to claim 10, wherein: The set of waveform parameters is determined based on a first codeword of a plurality of codewords in a codebook, and wherein the changing of the at least one waveform parameter comprises switching to a second codeword of the plurality of codewords.

14. The radar system of claim 13, wherein: The instructions further cause the one or more processors to perform a process comprising: performing object detection based on a third codeword not used to generate the first chirp sequence; Determining the presence of an interference source in the surrounding environment based on successful object detection; as well as Responsive to the determination that an interferer is present, the third codeword is prevented from being used in a subsequently transmitted sequence of chips.

15. The radar system of claim 10, wherein: The instructions further cause the one or more processors to perform a process comprising: performing a first discrete Fourier transform (DFT) using the sampled received signal, wherein the first DFT is applied separately to each chirp in the second chirp sequence to generate a separate result for each chirp in the second chirp sequence; performing a second DFT using the result of the first DFT; and performing equalization on a result of the first DFT before performing the second DFT, wherein the changing of the at least one waveform parameter comprises changing a frequency offset of the one or more chirps, and wherein performing the equalization comprises determining an equalization function based on the frequency offset of the one or more chirps, the equalization function being configured to correct for a phase shift caused by changing the frequency offset of the one or more chirps; and The distance and speed of the object are detected based on the result of the second DFT.

16. The radar system of claim 10, wherein: The instructions further cause the one or more processors to perform a process comprising: performing a first discrete Fourier transform (DFT) using the sampled received signal, wherein the first DFT is applied separately to each chirp in the second chirp sequence to generate a separate result for each chirp in the second chirp sequence; performing a second DFT using the result of the first DFT; and performing resampling on the result of the first DFT before performing the second DFT, wherein the changing of the at least one waveform parameter comprises changing a slope of the one or more chirps, and wherein performing the resampling comprises determining a resampling rate based on the slope of the one or more chirps, the resampling rate being configured to correct a shift in a peak position in the result of the first DFT caused by changing the slope of the one or more chirps; and The distance and speed of the object are detected based on the result of the second DFT.

17. The radar system of claim 10, wherein: The instructions further cause the one or more processors to perform a process comprising: determining the set of waveform parameters based on a first codeword among a plurality of codewords in a codebook, wherein the changing the at least one waveform parameter comprises switching to a second codeword among the plurality of codewords; performing object detection based on a third codeword not used to generate the first chirp sequence; Determining the presence of an interference source in the surrounding environment based on the successful object detection; and Responsive to the determination that an interferer is present, the third codeword is prevented from being used in a subsequently transmitted sequence of chips.

18. One or more non-transitory computer-readable media storing instructions that, when executed by one or more processors of a computer system, cause the one or more processors to: generating a frequency modulated signal comprising a first chirp sequence, wherein: Each chirp in the first chirp sequence is generated according to a waveform parameter set; changing at least one waveform parameter in the waveform parameter set for one or more chirps in the first chirp sequence; generating a phase signal according to a phase modulation parameter set, wherein the phase modulation parameter set includes a first parameter representing a slope of the phase signal and a second parameter representing a frequency offset of the phase signal; generating a transmission signal by phase modulating the frequency modulated signal using the phase signal so that each chirp in the first chirp sequence has a corresponding phase determined according to the phase signal; changing the phase signal by changing at least one phase modulation parameter in the phase modulation parameter set for at least one chirp in the first chirp sequence; receiving a received signal including a second chirp sequence, the received signal corresponding to the transmitted signal reflected from an object in an ambient environment, wherein the receiving includes sampling the received signal; as well as One or more properties of the object are determined using the sampled received signals.

19. The non-transitory computer readable medium of claim 18, wherein: The changing of the at least one waveform parameter includes changing a slope of the one or more chirps, a frequency offset of the one or more chirps, or both.

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