A distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization

Abstract

The application relates to a distributed radar coherent synthesis detection method based on non-cooperative signal sensitive synchronization, belongs to the technical field of radar signal processing, and particularly relates to a distributed millimeter wave radar coherent synthesis detection method based on weak and small target non-cooperative signal sensitive synchronization. For non-cooperative weak and small targets in a radar detection space, traditional methods are difficult to obtain coherent parameters to realize effective receiving coherent synthesis. The method uses special point targets in the space, adaptively compensates phase differences caused by relative positions of multiple targets and system errors, can effectively realize mixed receiving coherent synthesis of multiple targets in the space, and improves signal-to-noise ratios and detection performances of the multiple targets.

Description

Technical Field

[0001] This invention relates to a distributed radar coherent synthesis detection method based on non-cooperative signal sensitive synchronization, belonging to the field of radar signal processing technology, and particularly to a distributed millimeter-wave radar coherent synthesis detection method based on non-cooperative signal sensitive synchronization of weak targets. Background Technology

[0002] Signal-to-noise ratio (SNR) is a key factor affecting radar target detection performance. Weak targets emit weak echoes with low SNR, leading to decreased detection performance. Limited by signal power, a single radar cannot effectively improve SNR and thus enhance detection performance. However, by performing signal-level fusion processing on multiple radars, the SNR of weak targets can be improved. At the distributed radar receiver, coherent parameter estimation finely adjusts the time delay and phase of different radar echo signals, enabling simultaneous in-phase superposition of multiple radar target echoes, thereby improving the target echo SNR.

[0003] Target coherent parameter estimation is a prerequisite for distributed receiver coherent estimation. Traditional coherent parameter estimation methods use the coherent parameters of prominent points (strong scattering points) to replace the coherent parameters of weak targets to correct the time and phase differences of weak targets in each channel. However, when the weak targets are far from the prominent points, this method cannot guarantee that the weak targets will be in phase simultaneously in each channel after correction. As a result, the coherent accumulation will not achieve the intended effect, and may even result in reverse accumulation due to phase misalignment. Therefore, directly using the coherent parameters of prominent points to replace the coherent parameters of weak targets will result in a significant gain loss after coherent synthesis. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a distributed millimeter-wave radar coherent synthesis detection method based on sensitive synchronization of non-cooperative signals from weak targets. This method approximates the coherent parameters of weak targets (which cannot be directly detected) by adaptively correcting the coherent parameters of prominent points. Multiple sets of correction parameters are designed, and the one with the best approximation effect is selected. This parameter is used to correct the echo of the weak target, achieving coherent synthesis of weak target reception. The specific operation is as follows: First, the coherent parameters are estimated using prominent point targets in space, and the echo is coarsely compensated; then, the echo is adaptively finely compensated, including correcting the coupling term between system error and spatial position in the multi-channel phase term, deriving the phase term error tolerance based on the coherent gain loss boundary, and adaptively correcting the multi-channel phase parameters; finally, multi-target hybrid reception coherent synthesis is achieved in the millimeter-wave radar detection space. The purpose of this invention is to use the corrected prominent point coherent parameters to adaptively compensate for the time and phase difference of weak targets between multiple channels, achieving multi-target hybrid reception coherent synthesis and improving target detection performance.

[0005] The method of this invention is achieved through the following technical solution:

[0006] A distributed radar coherent synthesis detection method based on non-cooperative signal-sensitive synchronization, the method comprising the following steps:

[0007] Step 1: Establish the echo signal model;

[0008] Step 2: Estimate the coherent parameters of the prominent points in the echo signal model established in Step 1, and use the estimated coherent parameters of the prominent points to coarsely compensate for the time delay and phase of the weak target signal to obtain the coarsely compensated weak target signal.

[0009] Step 3: Remove the spatial location coupling terms of system errors from the weak target signal after coarse compensation in Step 2;

[0010] Step 4: Adaptive Correction. Step 3 eliminated the phase of the weak target signal after removing the spatial position coupling term of the system error, thus completing the detection based on distributed radar coherent synthesis with sensitive synchronization of non-cooperative signals.

[0011] The method for establishing the echo signal model in step one is as follows:

[0012] (1) Obtain the echo signal;

[0013] (2) The echo signal obtained in step (1) is deskewed to obtain the echo signal model;

[0014] In step (1), let there be M radars in the distributed radar system, m = 1, 2, 3, ..., M, n = 1, 2, 3, ..., M, and the radars are frequency-modulated continuous wave radars. Then, the echo signal obtained at time t, transmitted by the m-th radar and received by the n-th radar, is:

[0015]

[0016] Where f0 represents the signal carrier frequency, and k represents the frequency modulation slope. c is the speed of electromagnetic wave propagation, R mn ΔT represents the sum of the radial distances from the m-th radar to the target and the radial distances from the n-th radar to the target; mn =ΔT m -ΔT n , This represents the phase offset of the m-th radar relative to the transmitting radar in the reference channel. Let ΔT represent the phase shift of the nth radar relative to the receiving radar in the reference channel. Let the channel through which radar 1 transmits and receives be the reference channel. m Let ΔT represent the time delay offset of the m-th radar relative to the transmitting radar in the reference channel. n This represents the time delay offset of the nth radar relative to the receiving radar in the reference channel, i.e., the time synchronization error.

[0017] In step (2), at the receiving end, the echo signal is de-skewing processed using the local oscillator signal to obtain the echo signal model of the m-th radar transmitting and the n-th radar receiving at time t:

[0018]

[0019] In step two, the premise of distributed radar coherent accumulation is that target points in each channel are in phase simultaneously. However, due to the influence of time synchronization error and phase synchronization error, there are differences in the time delay and phase information of the prominent points in each channel. To compensate for the offset between channels, it is first necessary to estimate the time delay and phase difference, i.e., coherent parameter estimation.

[0020] The estimated coherent parameters of the salient point include the salient point time parameter and the salient point phase parameter. The estimation result of the salient point time parameter is as follows:

[0021]

[0022] The phase parameter estimation results for the prominent point are as follows:

[0023]

[0024] In step two, the coarsely compensated weak target signal transmitted by the m-th radar and received by the n-th radar at time t is as follows:

[0025]

[0026] Among them, R mn|B Let represent the sum of the radial distances from the m-th radar to the weak target B and the radial distances from the n-th radar to the weak target B, where point A is the prominent point and point B is the weak target point; j represents the imaginary part.

[0027] In step three, the phase of the weak target signal transmitted by the m-th radar and received by the n-th radar at time t, after removing the spatial position coupling term of the system error in the weak target signal after coarse compensation, is:

[0028]

[0029] To eliminate the phase term after the coupling term between time synchronization error and target distance, it can be seen that it is only related to the target's spatial position;

[0030] in,

[0031]

[0032] It consists of two parts. The first part is only related to the spatial location of the target, and the second part... This is a term that couples time synchronization error with target distance.

[0033] In step four, the method for adaptively correcting the phase of the weak target signal after removing the spatial location coupling term of the system error is as follows: the phase of the weak target signal is compensated with the phase tolerance as the interval to obtain the phase-compensated weak target signal. The channel with the highest signal-to-noise ratio is selected as the detection channel, and the detection is based on distributed radar coherent synthesis with non-cooperative signal sensitive synchronization.

[0034] The phase tolerance θ sc for:

[0035]

[0036]

[0037] P GL The signal power after coherent accumulation is the sum of the theoretical maximum signal attenuation, expressed in dB.

[0038]

[0039] i=1,2,3,…,M, j=1,2,3,…,M;

[0040] Where, φ 1i φ represents the phase difference between the transmit / receive channel 1 and the reference channel. 1j This represents the phase difference between the transmit and receive channels and the reference channel.

[0041] Only the phase compensation amount for M-1 channels needs to be determined, with each channel compensated... The interval θ between two consecutive compensations sc ,total A combination of compensation schemes.

[0042] The method of the present invention has the following advantages compared with existing technologies:

[0043] This invention relates to a distributed radar coherent synthesis detection method based on non-cooperative signal-sensitive synchronization, belonging to the field of radar signal processing technology, and particularly to a distributed millimeter-wave radar coherent synthesis detection method based on non-cooperative signal-sensitive synchronization of weak targets. For non-cooperative weak targets in radar detection space, traditional methods struggle to obtain their coherent parameters for effective reception coherent synthesis. This method utilizes prominent point targets in space and adaptively compensates for phase differences caused by the relative positions of multiple targets and system errors, effectively achieving mixed reception coherent synthesis of multiple targets in space, while simultaneously improving the signal-to-noise ratio and detection performance of multiple targets. Attached Figure Description

[0044] Figure 1 Flowchart of a multi-target hybrid receiver coherent synthesis method;

[0045] Figure 2 This is a schematic diagram illustrating the spatial location differences of the target.

[0046] Figure 3 For coherent accumulation of single-channel range images;

[0047] Figure 4 For adaptive correction of the previous range image;

[0048] Figure 5 This is the adaptively corrected range image. Detailed Implementation

[0049] The embodiments of the method of the present invention will be described in detail below with reference to the accompanying drawings.

[0050] like Figure 1 As shown, a distributed radar coherent synthesis detection method based on non-cooperative signal-sensitive synchronization includes the following steps:

[0051] Step 1: Estimate the coherent parameters of the prominent point and perform coarse compensation for weak targets. The specific steps are explained below: Taking a frequency-modulated continuous wave radar as an example, let the signal transmitted by the m-th radar and received by the n-th radar be:

[0052]

[0053] in:

[0054] ΔT mn =ΔT m -ΔT n

[0055]

[0056]

[0057] Where ΔT m This represents the transmission delay offset (also known as time synchronization error) of the m-th radar relative to the reference radar (the transmitting radar in the reference channel, where the channel through which radar 1 transmits and radar 1 receives is taken as the reference channel). R represents the phase offset of the m-th radar relative to the reference radar. mn This represents the sum of the radial distances from the m-th radar to the target and the radial distances from the n-th radar to the target. At the receiving end, the echo signal is de-skewing using the local oscillator signal, resulting in the following signal:

[0058]

[0059] Where f0 represents the signal carrier frequency and k represents the frequency modulation slope.

[0060] Distributed radar coherent accumulation relies on the simultaneous and synchronized phase of target points across all channels. However, due to time synchronization and phase synchronization errors, differences exist in the time delay and phase information of prominent points in each channel. To compensate for the offset between channels, it is first necessary to estimate the time delay and phase difference, i.e., coherent parameter estimation. Step 101: Estimation of prominent point time parameters.

[0061] The intermediate frequency signal in the reference channel can be represented as:

[0062]

[0063] The target position can be obtained by locating the peak point in the echo signal of each channel. By calculating the target position difference between channel mn and the reference channel, the estimated value of channel mn with respect to the time parameter can be obtained.

[0064]

[0065] Step 102: Estimation of phase parameters for prominent points.

[0066] Similarly, the target phase can be obtained by calculating the phase of the peak point in the echo signal of each channel. Therefore, the phase of the prominent point in the intermediate frequency signal of channel mn is:

[0067]

[0068] By calculating the phase difference between the prominent points of channel mn and the reference channel, the estimated phase parameters of channel mn can be obtained.

[0069]

[0070] Step 103: Use the coarse compensation parameters of the special point to compensate for the weak target.

[0071] Let point A be the prominent target and point B be the weak target. The two targets have different spatial positions, as shown in the diagram. Figure 2 As shown. To compensate for the echo signal of the weak target B using the estimated time and phase parameters of each channel's prominent point A, the signal can be expressed as:

[0072]

[0073] Where R mn|B This represents the sum of the radial distances from the m-th radar to the weak target B and the radial distances from the n-th radar to the weak target B.

[0074] Step 2: Correction of the spatial location coupling term of the system error and adaptive correction of the phase parameter. The specific steps are explained below:

[0075] Ideally, using the target's own coherent parameters to compensate for the echo can ensure that all channels of the target are in phase after compensation, thus achieving the maximum coherent signal-to-noise ratio. To measure the coherent accumulation effect of weak targets after coarse compensation, the time delay and phase information difference between the target's own compensated signal and the signal after coarse compensation at the prominent point are calculated.

[0076] Using the coherent parameters of the weak target B itself to analyze the echo signal S mn By compensating for (t), we can obtain:

[0077]

[0078] S″ mn (t) and S′ mn The difference between (t) indicates a discrepancy in time delay and phase information between compensating for weak targets using specific point coherent parameters and using weak target self-coherent parameters. The difference in the range dimension is negligible, not exceeding one range resolution unit; however, the difference in phase is not negligible. The phase error is observed to be composed of:

[0079]

[0080] It consists of two parts. The first part is only related to the spatial location of the target, and the second part... As the time synchronization error is coupled with the target distance, this step eliminates the coupling term by multiplying each distance unit of all channels by the corresponding conjugate factor of the coupling term.

[0081] Step 201: Decouple time synchronization error from target distance.

[0082] To ensure that the phase error of multiple targets in each channel after coarse compensation depends only on the spatial positional relationship of the multiple targets, the above-mentioned... The analysis of the composition can be performed by multiplying each distance unit of all channels by the corresponding conjugate factor of the coupling term to eliminate the coupling terms.

[0083] The specific steps are as follows:

[0084]

[0085] in To eliminate the phase term after the coupling term between time synchronization error and target distance, it can be seen that it is only related to the target's spatial position.

[0086] Step 202: Adaptive Correction of Phase Parameters at Key Points

[0087] Due to the spatial differences between strong and weak targets, after compensating for the weak target using the phase parameter of the prominent point, the phases of the different channels of the weak target are not aligned. The phases of each channel after eliminating the coupling term are observed.

[0088]

[0089]

[0090]

[0091] Where R m|B This represents the radial distance between radar m and the weak target B. The following conclusions can be drawn:

[0092] Δφ″ mn =Δφ″ 1m +Δφ″ 1n

[0093] Δφ″ nn =2·Δφ″ 1n

[0094] Given the quantitative relationship between the phase compensation quantities of each channel at the distinctive point obtained above, for a distributed system composed of N radars, let the signal functional power after coherent synthesis be...

[0095]

[0096] When implementing adaptive compensation, it is assumed that the signal power after coherent accumulation is lower than the theoretical maximum signal attenuation P. GL dB, then the requirement is:

[0097]

[0098] achievable

[0099]

[0100] make

[0101]

[0102] It can be deduced that:

[0103] (M 2 -M)cos(φ 1i -φ 1j )≥αM 2 -N

[0104]

[0105] Only the phase compensation amount for M-1 channels needs to be determined, with each channel compensated... Next, where θ sc for The interval θ between two adjacent compensation values sc ,total A combination of compensation schemes.

[0106] To verify the correctness of the above theory, the following experiment was conducted using measured data. The radar and target parameter settings are shown in Table 1.

[0107] Table 1 Experimental verification parameter settings

[0108] Parameter name Parameter value Parameter name Parameter value Number of unit radars 2 Number of single radar transmitting antennas 1 Radar bandwidth 500MHz radar operating frequency 77GHz Longitudinal distance of prominent points 36m Longitudinal distance of weak target 49m Lateral distance of the highlight point 0m lateral distance of weak target 0.5m

[0109] Figure 3 The echo range profile of a single channel (reference channel) before coherent accumulation is shown, and the signal-to-noise ratio of the two targets in the reference channel can be obtained. The statistical results of the signal-to-noise ratio of other channels are shown in Table 2.

[0110] Table 2 Target echo signal-to-noise ratio for each channel

[0111]

[0112] The theoretical signal-to-noise ratio (SNR) after synthesis is then calculated using the SNR of the multiple channels before coherent synthesis, which can be achieved through the following formula.

[0113]

[0114] Where γ mn The ratio of the noise power of channel mn to the noise power of the reference channel is used to obtain the theoretical signal-to-noise ratio of the prominent point and weak target after multi-channel coherent synthesis. The results are shown in Table 3.

[0115] Table 3 Experimental Results

[0116] Accumulated (before correction) SNR Accumulated (corrected) SNR Accumulated theoretical SNR Special features 32.13dB —— 32.24dB Weak Target 21.63dB 29.31dB 30.35dB

[0117] Theoretically, the signal-to-noise ratio after coherent reception at the definite point is 32.24 dB. However, the range image before adaptive correction after coherent accumulation is as follows: Figure 4 As shown, the signal-to-noise ratio (SNR) is 32.13 dB, and the coherent gain loss is 0.09 dB, indicating that the target is effectively accumulated. The theoretical SNR of the weak target after coherent synthesis is 30.35 dB, while the actual SNR after synthesis is 21.63 dB, an improvement of -8.72 dB, indicating that the target is not effectively accumulated.

[0118] Adaptive correction is performed on the echo signal. Since multiple correction schemes were designed, each scheme has a different effect on the power correction of the two target signals. Here, the scheme with the best effect on the power correction of the weak target signal is selected, such as... Figure 5 As shown, the signal-to-noise ratio of weak targets reaches 29.31dB, and the coherent gain loss is 1.04dB, which can be effectively accumulated; however, this correction scheme reduces the signal power of the prominent point.

[0119] Analysis of the above results shows that, for the problem of low signal-to-noise ratio and difficulty in detecting weak, non-cooperative targets, this method can effectively improve the signal-to-noise ratio of weak targets, thus verifying the effectiveness of this method.

[0120] This invention proposes a multi-target hybrid reception coherent synthesis method for millimeter-wave radar. After coarsely compensating the echo using characteristic point coherent parameters, the echo phase parameters are adaptively corrected to improve the signal-to-noise ratio (SNR) of weak targets. The proposed method can effectively improve the SNR of weak targets and enhance the detection performance of multiple targets. Therefore, this invention is an effective radar signal processing method.

[0121] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization, characterized in that The steps of the method include: Step one, establishing an echo signal model; Step two, estimating the characteristic point coherent parameters in the echo signal model established in step one, and using the estimated characteristic point coherent parameters to perform coarse compensation on the time delay and phase of the weak target signal to obtain a weak target signal after coarse compensation; Step three, eliminating the system error spatial position coupling term in the weak target signal after coarse compensation in step two; Step four, adaptively correcting the phase of the weak target signal after the system error spatial position coupling term is eliminated in step three, and completing the detection of the distributed radar coherent integration based on non-cooperative signal sensitive synchronization.

2. The distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization according to claim 1, wherein: In step one, the method for establishing an echo signal model is: (1) obtaining an echo signal; (2) performing desquaring processing on the echo signal obtained in step (1) to obtain an echo signal model.

3. The distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization according to claim 2, wherein: In step (1), the number of radars in the distributed radar system is M, m = 1, 2, 3, …, M, n = 1, 2, 3, …, M, and the radar is a frequency-modulated continuous wave radar, so the echo signal received by the nth radar after the mth radar transmits at time t is: where f0 represents the signal carrier frequency, k represents the frequency modulation slope, c is the electromagnetic wave propagation speed, R mn represents the sum of the radial distances of the mth radar to the target and the nth radar to the target; ΔT mn = ΔT m - ΔT n , represents the phase offset of the mth radar relative to the transmitting radar in the reference channel, represents the phase offset of the nth radar relative to the receiving radar in the reference channel, assuming that the channel in which radar 1 transmits and radar 1 receives is the reference channel, ΔT m represents the time delay offset of the mth radar relative to the transmitting radar in the reference channel, ΔT n represents the time delay offset of the nth radar relative to the receiving radar in the reference channel, i.e. the time synchronization error.

4. The distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization according to claim 2 or 3, wherein: In step (2), at the receiving end, the echo signal is desquared using the local oscillator signal, and the echo signal model received by the nth radar after the mth radar transmits at time t is:

5. The distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization according to claim 1, wherein: In step two, the estimation of the characteristic point coherent parameters includes the characteristic point time parameter and the characteristic point phase parameter, wherein the estimation result of the characteristic point time parameter is: The estimation result of the characteristic point phase parameter is:

6. The distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization according to claim 1 or 5, wherein: In step two, the weak target signal after coarse compensation received by the nth radar after the mth radar transmits at time t is: wherein R mn|B represents the sum of the radial distance of the mth mine to the weak target B and the radial distance of the nth mine to the weak target B, A is the salient point, and B is the weak target point; j represents the imaginary part.

7. The distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization according to claim 6, wherein: In step three, the phase of the weak target signal after the elimination of the system error spatial position coupling term in the weak target signal after coarse compensation received by the nth radar after the mth radar transmits at time t is: wherein, 8. The distributed radar coherent integration detection method based on non-cooperative signal sensitive synchronization according to claim 7, wherein: The phase compensation method of the weak target signal after the adaptive correction eliminates the system error space position coupling term in step four is: taking the phase tolerance as an interval, the phase of the weak target signal is compensated to obtain the weak target signal after phase compensation, taking the channel with the highest signal-to-noise ratio as a detection channel, and based on the non-cooperative signal sensitive synchronization, the distributed radar phase correlation synthesis detection is carried out.

9. The non-cooperative signal sensitive synchronization based distributed radar phase correlation synthesis detection method according to claim 8, characterized in that: The phase tolerance θ sc is: P GL The in-phase accumulation after signal power compared to the theoretical signal maximum attenuation value, in dB, is then i = 1, 2, 3, …, M, j = 1, 2, 3, …, M; where φ 1i represents the phase difference of the ithtransmit-jthreceive channel with respect to the reference channel, and φ 1i represents the phase difference of the ithtransmit-jthreceive channel with respect to the reference channel.

10. The non-cooperative signal sensitive synchronization based distributed radar phase correlation synthesis detection method according to claim 9, characterized in that: The phase compensation amount for M-1 channels needs to be determined, and each channel is compensated The phase compensation amount for M-1 channels needs to be determined, and each channel is compensated sc , a total of A combined compensation scheme

Images