A constant frequency auxiliary-based method and device for resolving speed ambiguity

Abstract

This invention relates to a method and apparatus for resolving velocity ambiguity based on constant frequency assistance. The method includes the following steps: a radar sequentially transmits a constant frequency band signal and a linear continuously modulated pulse train, and acquires the radar echo signal; both the constant frequency band echo signal and the sawtooth band echo signal are mixed to obtain a constant frequency band intermediate frequency signal and a sawtooth band intermediate frequency signal; the constant frequency band intermediate frequency signal is processed by a fast Fourier transform to obtain a target true velocity estimate; the sawtooth band intermediate frequency signal is sequentially processed by a two-dimensional fast Fourier transform, a two-dimensional constant false alarm rate (CFAR) processing, and a centroid condensation processing to obtain a target range velocity estimate; based on a velocity matching method using a Fourier rotation factor, the target true velocity estimate is matched with the target range velocity estimate to obtain the true velocity of all targets. This method not only resolves velocity ambiguity but also improves velocity accuracy, offering advantages such as high velocity measurement accuracy, high real-time performance, and simplicity.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing technology, specifically relating to a method and apparatus for resolving velocity ambiguity based on constant frequency assistance. Background Technology

[0002] Linear frequency modulated continuous wave (LFMCW) radar obtains radial velocity information of moving targets by estimating their Doppler frequency. When dealing with high-speed moving targets or when the radar's pulse repetition frequency (PRF) is low, the slow-time-dimensional sampling frequency (PRF) is lower than the target's Doppler frequency, leading to velocity ambiguity.

[0003] To address this issue, Reference 1 proposes a velocity de-ambiguity algorithm based on multiple pulse repetition frequencies. This algorithm transmits multiple sets of pulse repetition frequencies that are co-prime numbers, obtains the blurred velocity under each PRF using a target detection algorithm, and estimates the true target velocity using the remainder theorem. However, this requires transmitting multiple sets of PRF pulses, resulting in long scanning times and poor real-time performance. Building on this, Reference 2 proposes a new clustering algorithm to replace the Chinese remainder theorem for de-ambiguity velocity de-ambiguity, achieving better algorithm performance; it also addresses the different blurred velocities of targets under different carrier frequencies. Reference 3 proposes a velocity de-ambiguity algorithm based on signal multiplexing, building upon staggered repetition frequency (PRF) transmission. This algorithm de-ambiguates velocity by transmitting a single set of PRF transmission signals, dividing the signal into main and sub-signal segments. Compared to the staggered PRF method, this reduces scanning time, but does not improve ranging accuracy. Reference 4 obtains the true target velocity by performing multi-target correlation and velocity de-ambiguity de-images processed by MTD over three cycles. Reference 5 proposes a lookup-based velocity ambiguity resolution algorithm. By traversing an established ambiguity resolution table, it determines the number of times the target is blurred based on the minimum mean square error criterion and the detection criterion, thus obtaining the target's velocity. Reference 6 provides an effective velocity ambiguity resolution scheme using the concept of the least common multiple. It transmits two sets of PRF data, multiplies the slow-time dimension complex vector of the target's distance cell with a discrete Fourier transform rotation factor calculated based on the target distance and ambiguity velocity, and finds the true unambiguous velocity corresponding to the maximum value. Reference 7 proposes a wavelength difference method for velocity ambiguity resolution, the basic idea being to use the linear relationship between Doppler and wavelength to resolve velocity ambiguity. Meanwhile, since the target ambiguity velocities corresponding to signals with different carrier frequencies are different, Reference 8 proposes a multi-carrier frequency-based velocity ambiguity resolution algorithm based on this principle. Reference 9 transmits signal segments with multiple different repetition periods, performs two FFT processes on each repetition period, obtains different ambiguity Doppler frequencies for each repetition period, and calculates the true velocity of the target based on the relationship between the ambiguity Doppler frequencies and the actual Doppler frequency. Reference 10 proposes transmitting multiple frames with different PRFs and using multiple CPIs to solve the speed ambiguity problem.

[0004] However, existing algorithms mostly employ the transmission of multiple frequency or multiple carrier frequency signals, which results in problems such as long radar scanning time, large data volume, low real-time performance, and low velocity measurement accuracy, and are not feasible for engineering implementation. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a constant-frequency-assisted velocity ambiguity resolution method and apparatus.

[0006] This invention provides a constant-frequency-assisted velocity ambiguity resolution method, comprising the following steps:

[0007] The radar sequentially transmits a constant frequency band signal and a linear continuous frequency modulated pulse train, and acquires radar echo signals, wherein the radar echo signals include constant frequency band echo signals and sawtooth band echo signals.

[0008] The constant frequency band echo signal and the sawtooth band echo signal are both mixed to obtain the constant frequency band intermediate frequency signal and the sawtooth band intermediate frequency signal.

[0009] The constant frequency band intermediate frequency signal is processed by fast Fourier transform to obtain the target's true speed estimate;

[0010] The sawtooth band intermediate frequency signal is sequentially subjected to two-dimensional fast Fourier transform, two-dimensional constant false alarm rate processing, and centroid condensation processing to obtain the target distance and velocity estimate.

[0011] The velocity matching method based on the Fourier rotation factor matches the target's true velocity estimate with the target's distance velocity estimate to obtain the true velocity of all targets.

[0012] In one embodiment of the present invention, the constant frequency band signal is a sine wave.

[0013] In one embodiment of the present invention, the linear continuous frequency modulated pulse train includes several segments of frequency modulated continuous waves with a transmission period equal to the pulse repetition time.

[0014] In one embodiment of the present invention, the sawtooth band intermediate frequency signal is sequentially subjected to two-dimensional fast Fourier transform, two-dimensional constant false alarm rate processing, and centroid condensation processing to obtain a target range velocity estimate, including:

[0015] The sawtooth band intermediate frequency signal is subjected to a fast time-dimensional fast Fourier transform to obtain a set of range cells containing the target.

[0016] A one-dimensional discrete Fourier transform is performed on the slow-time dimension data of each distance cell in the set of distance cells containing the target. The peak amplitude of the spectrum of the one-dimensional discrete Fourier transform is used as fuzzy velocity information. The set of distance cells containing the target and the fuzzy velocity information form the original target distance velocity estimate.

[0017] The original target distance and velocity estimate is subjected to two-dimensional constant false alarm rate processing and centroid condensation processing in sequence to obtain the target distance and velocity estimate.

[0018] In one embodiment of the present invention, a velocity matching method based on Fourier rotator factors matches the target true velocity estimate with the target distance velocity estimate of each distance unit to obtain the true velocity of all targets, including:

[0019] Calculate the DFT twitch factor for the slow time dimension corresponding to each velocity value in the target's true velocity estimate;

[0020] For each distance cell containing a target in the target distance-velocity estimation, the slow time dimension data and the DFT rotation factor are used to perform a vector inner product operation, and the operation results are sorted in descending order according to the peak amplitude of the spectrum to obtain a set of the true target velocities.

[0021] From the set of true target velocities, select the velocities corresponding to the number of targets in sequence as the true target velocities of each distance unit containing a target, thereby obtaining the true velocities of all targets.

[0022] In one embodiment of the present invention, the formula for calculating the DFT twitch factor is as follows:

[0023]

[0024] in, The speed is in the slow time dimension. DFT twitch factor, It is a constant frequency band target true velocity estimation Each velocity value in the set, PRT It is the transmission period of the sawtooth band, and CPN is the cumulative period number of the sawtooth band.

[0025] In one embodiment of the present invention, for each distance unit containing a target in the target distance-velocity estimation, the slow time dimension data and the DFT rotation factor are performed as a vector inner product, and the results are sorted in descending order according to the peak amplitude of the spectrum. The formula for calculating the sorted results is as follows:

[0026]

[0027] in, It is slow-time dimension data with distance units to the target. It is a distance unit where a target exists. The speed is in the slow time dimension. The DFT twiddle factor, I, is the slow-time dimension data under all estimated true target velocities. and DFT twiddle factor The set of vector dot product results; sort sorts the result set in descending order. It is the set of the actual velocity of the target corresponding to the distance unit where the target exists.

[0028] Another embodiment of the present invention provides a velocity ambiguity resolution device based on constant frequency assistance, comprising:

[0029] The radar echo signal acquisition module is used to enable the radar to sequentially transmit a constant frequency band signal and a linear continuous frequency modulated pulse train, and to acquire the radar echo signal, wherein the radar echo signal includes a constant frequency band echo signal and a sawtooth band echo signal.

[0030] The mixing module is used to perform mixing processing on both the constant frequency band echo signal and the sawtooth band echo signal to obtain a constant frequency band intermediate frequency signal and a sawtooth band intermediate frequency signal.

[0031] The target true velocity estimation module is used to perform a fast Fourier transform on the constant frequency band intermediate frequency signal to obtain the target true velocity estimate;

[0032] The target distance and velocity estimation module is used to sequentially perform two-dimensional fast Fourier transform, two-dimensional constant false alarm rate processing and centroid condensation processing on the sawtooth band intermediate frequency signal to obtain the target distance and velocity estimate.

[0033] The true velocity matching module is used to match the target true velocity estimate with the target distance velocity estimate using a velocity matching method based on the Fourier rotation factor, so as to obtain the true velocity of all targets.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The constant-frequency-assisted velocity ambiguity resolution method of this invention does not require the transmission of multiple sets of repetitive frequencies. It utilizes a combination of constant-frequency and sawtooth band waveforms to resolve velocity ambiguity, thereby improving the data refresh rate, reducing the amount of data, and correspondingly reducing the computational load, thus improving matching efficiency. Simultaneously, by processing the constant-frequency band signal to obtain a target's true velocity estimate, and processing the sawtooth band signal to obtain a target distance-velocity estimate to determine the number and position information of the target, velocity matching is performed using a velocity matching method based on the Fourier rotation factor. Constant-frequency band velocity measurement does not suffer from velocity ambiguity and has higher accuracy than sawtooth band measurement. Therefore, while resolving velocity ambiguity, it also improves velocity accuracy, offering advantages such as high velocity measurement accuracy, high real-time performance, and simple method. Attached Figure Description

[0036] Figure 1 A flowchart illustrating a constant-frequency-assisted velocity ambiguity resolution method provided in an embodiment of the present invention;

[0037] Figure 2 A flowchart illustrating a constant-frequency-assisted velocity ambiguity resolution method as described in this embodiment of the invention.

[0038] Figure 3 A flowchart illustrating another velocity ambiguity resolution method based on constant frequency assistance provided in an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of a constant-frequency assisted hybrid waveform transmission signal provided in an embodiment of the present invention;

[0040] Figures 5a-5b The range-Doppler amplitude spectrum of two frequencies provided in this embodiment of the invention;

[0041] Figures 6a-6b This is an echo spectrum diagram provided by a constant frequency assisted method in an embodiment of the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0043] Example 1

[0044] Given the problems with most existing algorithms that employ multiple frequency or multiple carrier frequency signals, this embodiment replaces the initial sawtooth band with a constant frequency band, thus completing the speed ambiguity resolution without changing the PRF and dechirp processing mechanisms.

[0045] Please see Figure 1 , Figure 2 and Figure 3 , Figure 1This is a flowchart illustrating a constant-frequency-assisted velocity ambiguity resolution method provided in an embodiment of the present invention. Figure 2 This is a flowchart illustrating a constant-frequency-assisted velocity ambiguity resolution method as described in an embodiment of the present invention. Figure 3 A flowchart illustrating another velocity ambiguity resolution method based on constant frequency assistance provided in this embodiment of the invention. The method includes the following steps:

[0046] S1. The radar sequentially transmits a constant frequency band signal and a linear continuous frequency modulated pulse train, and acquires radar echo signals, wherein the radar echo signals include constant frequency band echo signals and sawtooth band echo signals.

[0047] Please see Figure 3 and Figure 4 , Figure 4 This is a schematic diagram of a constant-frequency assisted hybrid waveform transmission signal provided in an embodiment of the present invention. Figure 3 and Figure 4 As shown, the transmitted waveform used in this embodiment consists of a constant-frequency signal plus a linear continuous-frequency modulated pulse train with a repetition frequency (PRF). The constant-frequency signal is a sine wave, and the linear continuous-frequency modulated pulse train includes several segments of frequency-modulated continuous waves with a transmission period equal to the pulse repetition time. These frequency-modulated continuous waves are sawtooth band pulses. Specifically, the transmitted waveform process is as follows: first, a segment with a duration of... , frequency is The first sine wave is denoted as data 1, followed by a frequency-modulated continuous wave with a transmission period of pulse repetition time (PRT) and an accumulation period of CPN, denoted as data 2.

[0048] Afterwards, the radar receives the echo signals, which include constant frequency band echo signals and sawtooth band echo signals.

[0049] S2. Mix the constant frequency band echo signal and the sawtooth band echo signal to obtain the constant frequency band intermediate frequency signal and the sawtooth band intermediate frequency signal.

[0050] Specifically, suppose there is a range radar for... Speed ​​is Target, radar carrier Constant frequency band signal transmission duration The frequency of the emitted sine wave is The linear continuous frequency modulated pulse train is a sawtooth wave with a transmission period of PRT, a bandwidth of B, and a number of pulses of CPN.

[0051] The signal expression for constant frequency band transmission is as follows:

[0052] (1)

[0053] in, The frequency of the emitted sine wave.

[0054] Received echo expression:

[0055] (2)

[0056] The constant-frequency intermediate frequency signal after mixing is:

[0057] (3)

[0058] The method of mixing the echo signal of the sawtooth band to obtain the intermediate frequency signal of the sawtooth band is existing technology, and will not be described in detail in this embodiment.

[0059] S3. Perform a Fast Fourier Transform on the constant frequency band intermediate frequency signal to obtain the target's true velocity estimate.

[0060] Specifically, as can be seen from equation (3), the intermediate frequency signal in the constant frequency band is a sinusoidal signal with a frequency of... Since the velocity is related to the target's velocity, the true velocity of the target can be estimated by using the peak position of a one-dimensional (velocity dimension) Fast Fourier Transform (FFT), thus completing the detection and estimation of the target's true velocity. Furthermore, the set of true target velocities obtained through the FFT transform is... Where N represents the number of actual speeds.

[0061] S4. The sawtooth band intermediate frequency signal is sequentially subjected to two-dimensional fast Fourier transform (2D-FFT), two-dimensional constant false alarm rate processing (2D-CFAR), and centroid condensation processing to obtain the target distance and velocity estimate.

[0062] Specifically, for sawtooth band intermediate frequency signals, after 2D-FFT, 2D-CFAR, and centroid condensation, it is known that at the distance cell... A target was detected, and its distance and velocity were estimated. The estimated target distance and velocity are: , where M is the number of targets.

[0063] Step S4 specifically includes:

[0064] S41. Perform a fast Fourier transform on the sawtooth band intermediate frequency signal in a fast time dimension to obtain a set of range cells containing the target.

[0065] Please see Figure 3 , Figure 3In the data from the intermediate frequency (IF) signal in the sawtooth band, the distance dimension represents the fast time dimension, and the velocity dimension represents the slow time dimension. Specifically, performing a fast time dimension FFT on the IF signal yields several peaks. One peak represents a distance cell indicating the presence of a target, and multiple peaks represent multiple distance cells indicating the presence of targets. Therefore, based on the peaks of the FFT, all distance cells indicating the presence of targets can be obtained, thus forming a set of distance cells indicating the presence of targets. .

[0066] S42. Perform a one-dimensional discrete Fourier transform on the slow-time dimension data of each distance cell in the set of distance cells containing the target to obtain fuzzy velocity information. The set of distance cells containing the target and the fuzzy velocity information form the original target distance velocity estimate.

[0067] Specifically, for each distance unit where a target exists... The slow-time data is processed by one-dimensional discrete Fourier transform (DFT). Through DFT processing, several spectral peak amplitude results can be obtained. Multiple peaks are regarded as multiple velocities corresponding to multiple targets in a range cell, thereby obtaining fuzzy velocity information for each range cell.

[0068] Furthermore, step S41 yields the set of distance cells containing the target. The fuzzy velocity information obtained in step S42 is used to form the original target distance-velocity estimate.

[0069] S43. The original target distance and velocity estimate is subjected to two-dimensional constant false alarm rate processing and centroid condensation processing in sequence to obtain the target distance and velocity estimate.

[0070] Specifically, the original target range-velocity estimate is subjected to two-dimensional constant false alarm rate (CFAR) processing and centroid condensation processing in sequence to filter out noise in the estimation results and obtain a more accurate set of range cells. By combining fuzzy velocity information, the final target distance and velocity estimate can be obtained.

[0071] S5. A velocity matching method based on Fourier rotation factor is used to match the target's true velocity estimate with the target's distance velocity estimate to obtain the true velocity of all targets.

[0072] In this embodiment, after obtaining the target's true velocity estimate in the constant frequency band and the target's range velocity estimate in the sawtooth band, it is necessary to perform target velocity matching using the target's true velocity estimate and the target's range velocity estimate. The constant frequency band data is used as the actual target's true velocity to match the estimated target in the sawtooth band, thus completing the velocity ambiguity resolution process. Therefore, how to correctly match all estimated target true velocities with their corresponding targets becomes a crucial step. Based on this, this embodiment proposes a method for resolving velocity ambiguity based on the Fourier rotation factor.

[0073] Step S5 specifically includes the following steps:

[0074] S51. Calculate the DFT rotation factor of the slow time dimension corresponding to each velocity value in the target true velocity estimate.

[0075] Specifically, for the set of true velocities of targets in the constant frequency band Each velocity value in The DFT twiddle factor corresponding to the slow time dimension is calculated using equation (4):

[0076]

[0077] in, The speed is in the slow time dimension. DFT twitch factor, It is a constant frequency band target true velocity estimation Each velocity value in the set, PRT It is the transmission period of the sawtooth band, and CPN is the cumulative period number of the sawtooth band.

[0078] S52. For each distance unit containing a target in the target distance-velocity estimation, perform a vector inner product operation between the slow time dimension data and the DFT rotation factor, and sort the operation results in descending order according to the peak amplitude of the spectrum to obtain a set of true target velocities.

[0079] Specifically, the first step is to estimate the target distance and velocity. Find the distance cell information where the target exists. Then the distance unit containing the target The slow-time dimension data is subjected to a vector dot product operation with the DFT rotation factor calculated in step S51. Then, the operation results are sorted from largest to smallest according to the spectral peak amplitude of the fuzzy velocity information in step S43. The mathematical process is described as follows:

[0080]

[0081] in, It is slow-time dimension data representing the distance unit to the target, and is presented as a column vector. It is a distance unit where a target exists. The speed is in the slow time dimension. The DFT rotation factor is a row vector, and I is the slow-time dimension data under all estimated true target velocities. and DFT twiddle factor The set of vector dot product results; sort sorts the result set in descending order. It is the set of the actual velocity of the target corresponding to the distance unit where the target exists.

[0082] S53. Select the speed corresponding to the number of targets from the set of target true speeds in sequence as the target true speed of each distance unit with a target, thereby obtaining the true speed of all targets.

[0083] Specifically, assuming distance unit Given k targets, the speeds corresponding to the first k sorted values ​​from the set of true speeds of the targets are taken as the defuzzification speeds of the distance unit, thereby obtaining the true speeds of the targets in the distance unit.

[0084] Furthermore, traverse the set Repeat steps S52 and S53 for all elements in the target velocity deblurring process until all targets have completed the velocity deblurring process and the true velocity of all targets is obtained.

[0085] This embodiment of the constant-frequency-assisted velocity ambiguity resolution method does not require the transmission of multiple sets of repetitive frequencies. It utilizes a combination of constant-frequency and sawtooth band waveforms to resolve velocity ambiguity, improving the data refresh rate, reducing the amount of data, and consequently reducing the computational load, thus improving matching efficiency. Simultaneously, by processing the constant-frequency band signal, a target true velocity estimate is obtained, while processing the sawtooth band signal yields a target distance-velocity estimate to determine the number and location information of targets. Then, a velocity matching method based on the Fourier rotation factor is used for velocity matching. Constant-frequency band velocity measurement does not suffer from velocity ambiguity and has higher accuracy than sawtooth band measurement. Therefore, while resolving velocity ambiguity, it also improves velocity accuracy, offering advantages such as high precision, high real-time performance, and simple method.

[0086] Furthermore, to verify the correctness of the method in this embodiment, it was simulated and verified using MATLAB, and compared with the staggered double-frequency velocity defuzzification algorithm.

[0087] First, the experimental procedure for the staggered double-frequency velocity ambiguity resolution experiment is as follows:

[0088] The simulation parameters for unambiguous velocity defuzzification of staggered double-frequency frequencies are shown in Table 1.

[0089] Table 1 Simulation Parameters of Staggered Frequency Repetition Rate Radar System

[0090]

[0091] The distance and speed settings for the moving target are shown in Table 2.

[0092] Table 2. Radar target velocity and range settings using the staggered repetition rate method.

[0093]

[0094] The echo data of repetition frequency 1 and repetition frequency 2 are processed by 2D-FFT respectively, and then processed by 2D-CFAR and centroid aggregation algorithm in sequence. The fuzzy velocity of repetition frequency 1 and 2 is calculated together to estimate the true distance velocity.

[0095] Please see Figures 5a-5b , Figures 5a-5b The two-frequency range-Doppler amplitude spectrum provided in this embodiment of the invention, wherein, Figure 5a This is the RD graph of the data after 2D-FFT processing, assuming a repetition rate of 1. Figure 5b The RD graph of the data after 2D-FFT processing is given for a repetition frequency of 2.

[0096] set up This is the set of target distance and velocity estimated from waveform 1. The set of target range velocities estimated from waveform 1, where The target number.

[0097] First, initial target matching is performed using the distance dimension. If only one target exists within the same distance cell, target matching within that cell can be completed directly. If multiple targets exist within the same distance cell, the first target in one distance cell from one waveform data is fixed. The velocities of targets in the same distance cell from another waveform data are then matched using the Chinese Remainder Theorem to find targets with matching velocities. This method is used for target matching in the case of multiple targets within the same distance cell. The following section details the velocity ambiguity resolution process using the case of a single target within the same distance cell.

[0098] Assuming that at a certain distance unit, waveform 1 indicates that a target can be detected. Waveform 2 detects the target Then we have:

[0099] (6)

[0100] Among them, the maximum unambiguous speed of waveform 1 The maximum unambiguous velocity of the waveform is 15.6250 m / s. It is 18.75 m / s. and This represents the possible ambiguity number within the system's speed measurement range. Because... and Both have estimation errors (the errors are related to factors such as noise power, sampling frequency, and calculation accuracy), so there is no absolute equality that can make formula (6) hold. Instead, a certain error range is allowed. Inside, satisfying the following expression:

[0101] (7)

[0102] Traversing the radar speed measurement range and Find the one that satisfies (7) and This is the correctly solved fuzzy number. The velocity of the matching target in this distance cell is... or Only one of them needs to be selected. Table 3 shows the simulation results of the velocity fuzzy algorithm using the staggered repetition frequency method.

[0103] Table 3 Simulation results of target range and velocity using the staggered repetition rate method

[0104]

[0105] The staggered repetition frequency (RFF) method for resolving speed ambiguity has the following problems: 1. Low system real-time performance: The staggered RF method requires transmitting at least two sets of waveforms with different repetition frequencies. Each set of waveforms receives a similar amount of data, resulting in long waveform scanning time, large data accumulation, and low system real-time performance. 2. High data computation load: Both RFF1 and RFF2 undergo the same target detection algorithm process (2D-FFT, 2D-CFAR, centroid aggregation). 2D-FFT and 2D-CFAR have high computational complexity and long processing time, requiring significant hardware resources for engineering implementation. 3. Poor stability: For staggered RFF to correctly resolve the ambiguity speed, the target needs to be detected in both constant false alarm rate (CFAR) detections (CFAR 1 and RFF2). However, under low signal-to-noise ratio (SNR) conditions, target detection cannot be guaranteed every time.

[0106] Secondly, the specific experimental procedure for the constant frequency-assisted velocity ambiguity resolution experiment is as follows:

[0107] The radar system simulation parameters and target velocity and distance settings are shown in Tables 4 and 5, respectively.

[0108] Table 4 Parameter Settings for Constant Frequency Assisted Radar System

[0109]

[0110] Table 5 Target velocity and distance settings for constant frequency assisted method

[0111]

[0112] The constant-frequency difference-frequency signal is processed using range-dimensional FFT, followed by one-dimensional CFAR to detect multiple targets from the echo and estimate their true velocities. Simultaneously, the echo matrix data accumulated from the sawtooth wave is processed using 2D-FFT, 2D-CFAR, and centroid aggregation to detect the range cells containing targets and the number of targets within those range cells. Finally, a DFT rotation factor matching algorithm is used to achieve target velocity matching, completing velocity deambiguity resolution. Please refer to [link to relevant documentation]. Figures 6a-6b , Figures 6a-6b This invention provides a constant-frequency assisted echo spectrum diagram. Figure 6a The velocity amplitude spectrum of the constant frequency band echo signal. Figure 6b The amplitude spectrum of the sawtooth wave is shown in Table 6, which contains the simulated distance and velocity estimates.

[0113] Table 6 Simulation results of target velocity and distance using the constant frequency assisted method

[0114]

[0115] As can be seen from Figure 6(b), the three targets all exhibited velocity ambiguity under sawtooth wave modulation. The method proposed in this embodiment solves the velocity ambiguity problem and also provides high-precision velocity measurement performance. Tables 5 and 6 show that the velocity measurement error of the staggered frequency repetition method is approximately 0.1 m / s, while the velocity measurement error of the method presented in this paper is approximately 0.01 m / s, making its accuracy about 10 times that of the staggered frequency repetition method.

[0116] In summary, this embodiment addresses the velocity ambiguity phenomenon in linear frequency modulated continuous wave radar (LFCR) under high-speed moving target conditions, where the slow-time dimension sampling frequency is lower than the Doppler frequency due to the limitation of the system's pulse frequency (PRF). A constant-frequency assisted velocity deambiguity method is proposed. First, the velocity deambiguity process is presented. Then, computer simulations of the proposed method are performed, and its performance is compared and analyzed with the staggered double-frequency method. Theoretical analysis and experiments show that the proposed velocity deambiguity method does not require transmitting multiple sets of repetition frequencies. It utilizes a combination of constant-frequency and sawtooth band waveforms to deambiguate velocity, improving the data refresh rate. The constant-frequency band is used to obtain the target's true velocity, achieving high-precision velocity measurement, while the sawtooth band is used for target detection. Based on the hybrid waveform, a corresponding DFT rotation factor velocity matching algorithm is designed to complete velocity matching, improving robustness.

[0117] Example 2

[0118] Based on Embodiment 1, this embodiment provides a velocity ambiguity resolution device based on constant frequency assistance. The device includes: a radar echo signal acquisition module, a mixing processing module, a target true velocity estimation module, a target range velocity estimation module, and a true velocity matching module.

[0119] Specifically, the radar echo signal acquisition module is used to cause the radar to sequentially transmit a constant-frequency band signal and a linear continuous frequency modulated pulse train, and acquire the radar echo signal, wherein the radar echo signal includes a constant-frequency band echo signal and a sawtooth band echo signal. The mixing processing module is used to mix both the constant-frequency band echo signal and the sawtooth band echo signal to obtain a constant-frequency band intermediate frequency signal and a sawtooth band intermediate frequency signal. The target true velocity estimation module is used to perform a fast Fourier transform on the constant-frequency band intermediate frequency signal to obtain a target true velocity estimate. The target range velocity estimation module is used to sequentially perform a two-dimensional fast Fourier transform, two-dimensional constant false alarm rate processing, and centroid condensation processing on the sawtooth band intermediate frequency signal to obtain a target range velocity estimate. The true velocity matching module is used to match the target true velocity estimate with the target range velocity estimate based on a velocity matching method using a Fourier rotation factor to obtain the true velocity of all targets.

[0120] Please refer to Example 1 for the specific implementation steps and beneficial effects of this device, which will not be repeated here.

[0121] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A constant frequency aided based method for resolving velocity ambiguity, characterized in that, The method comprises the steps of: causing a radar to emit a constant frequency signal and a linear continuous frequency pulse train in sequence, and acquiring a radar echo signal, wherein the radar echo signal comprises a constant frequency echo signal and a sawtooth wave band echo signal; performing mixing processing on the constant frequency echo signal and the sawtooth wave band echo signal to obtain a constant frequency intermediate frequency signal and a sawtooth wave band intermediate frequency signal; performing fast Fourier transform processing on the constant frequency intermediate frequency signal to obtain a target real speed estimate; performing two-dimensional fast Fourier transform, two-dimensional constant false alarm processing and centroid condensation processing on the sawtooth wave band intermediate frequency signal in sequence to obtain a target range speed estimate; matching the target real speed estimate and the target range speed estimate based on a speed matching method of a Fourier rotation factor to obtain real speeds of all targets.

2. The constant frequency auxiliary based velocity ambiguity resolution method of claim 1, wherein, The constant frequency signal is a sine wave.

3. The constant frequency auxiliary based method of resolving velocity ambiguity as claimed in claim 1, wherein, The linear continuous frequency pulse train comprises a plurality of frequency modulation continuous wave segments with a transmission period of pulse repetition time.

4. The constant frequency auxiliary based method of resolving velocity ambiguity as claimed in claim 1, wherein, Performing two-dimensional fast Fourier transform, two-dimensional constant false alarm processing and centroid condensation processing on the sawtooth wave band intermediate frequency signal in sequence to obtain a target range speed estimate comprises: performing fast Fourier transform on the slow time dimension of the sawtooth wave band intermediate frequency signal to obtain a distance unit set in which a target exists; performing one-dimensional discrete Fourier transform on slow time dimension data of each distance unit in which a target exists in the distance unit set in which a target exists, taking a spectrum peak amplitude of the one-dimensional discrete Fourier transform as ambiguous speed information, and taking the distance unit set in which a target exists and the ambiguous speed information as an original target range speed estimate; performing two-dimensional constant false alarm processing and centroid condensation processing on the original target range speed estimate in sequence to obtain the target range speed estimate.

5. The constant frequency auxiliary based method of resolving velocity ambiguity as claimed in claim 1, wherein, Matching the target real speed estimate and the target range speed estimate based on a speed matching method of a Fourier rotation factor to obtain real speeds of all targets comprises: calculating a DFT rotation factor of a slow time dimension corresponding to each speed value in the target real speed estimate; performing vector inner product operation on the slow time dimension data and the DFT rotation factor for each distance unit in which a target exists in the target range speed estimate, and arranging operation results in descending order according to a spectrum peak amplitude to obtain a set of target real speeds; selecting speeds corresponding to a target number in sequence from the set of target real speeds as target real speeds of each distance unit in which a target exists, thereby obtaining real speeds of all targets.

6. The constant frequency auxiliary based method of resolving velocity ambiguity as claimed in claim 5, wherein, A calculation formula of the DFT rotation factor is: in, The speed is in the slow time dimension. DFT twitch factor, It is a constant frequency band target true velocity estimation Each velocity value in the set, PRT It is the transmission period of the sawtooth band, and CPN is the cumulative period number of the sawtooth band.

7. The constant frequency auxiliary based method of resolving velocity ambiguity as claimed in claim 6, wherein, A calculation formula of the sorting result of performing vector inner product operation on the slow time dimension data and the DFT rotation factor for each distance unit in which a target exists in the target range speed estimate and arranging operation results in descending order according to the spectrum peak amplitude is: wherein, is the distance cell slow time dimension data where a target exists, is the distance cell where a target exists, is the slow time dimension velocity where a target exists is the DFT rotation factor, I is the slow time dimension data at all estimated true target velocities and DFT rotation factor is the set of vector inner product results, sort is the descending order sorting of the result set, is the set of target true velocities corresponding to the distance cell where a target exists.

8. A constant frequency aided velocity deambiguating apparatus characterized by, The method comprises the steps of: a radar echo signal acquisition module configured to cause a radar to emit a constant frequency signal and a linear continuous frequency pulse train in sequence, and acquire a radar echo signal, wherein the radar echo signal comprises a constant frequency echo signal and a sawtooth wave band echo signal; The mixing processing module is configured to perform mixing processing on the constant frequency band echo signal and the sawtooth wave band echo signal to obtain a constant frequency band intermediate frequency signal and a sawtooth wave band intermediate frequency signal. The target real speed estimation module is configured to perform fast Fourier transform processing on the constant frequency band intermediate frequency signal to obtain a target real speed estimation. The target range speed estimation module is configured to sequentially perform two-dimensional fast Fourier transform, two-dimensional constant false alarm processing and centroid condensation processing on the sawtooth wave band intermediate frequency signal to obtain a target range speed estimation. The real speed matching module is configured to match the target real speed estimation and the target range speed estimation based on a speed matching method of a Fourier rotation factor to obtain real speeds of all targets.

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