An adaptive velocity deambiguity method based on dual-frequency radar

Abstract

The application discloses an adaptive speed deambiguating method based on dual-frequency radar, which is based on radar dual-frequency echo information and point information, and realizes low-repetition-frequency and small-bandwidth radar target speed deambiguating to obtain real-time high-precision radial speed of the target. The processing method of the application comprises the following steps: performing spectrum transformation on radar echo, extracting Doppler spectrum line, adaptively calculating Doppler frequency shift folding times, and calculating high-precision speed of the target. The algorithm in the application is relatively simple, does not occupy too many system resources and time consumption, and has real-time performance. In the case that energy resources and time resources of the radar are limited, high-precision target speed is obtained, and the radar measurement performance and tracking accuracy are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar data processing and radar signal processing, in particular to an adaptive velocity deblurring method based on a dual-frequency radar. BACKGROUND

[0002] A measurement radar obtains the position, radial velocity and other information of a target by transmitting electromagnetic waves to the target and performing signal processing and data processing on the echo reflected by the target. However, when the radar resources or hardware conditions are limited, the radar cannot transmit a radar waveform with a large bandwidth, a high pulse repetition frequency and a long dwell time, and the velocity precision, distance precision and angle precision of the target cannot meet the required precision. When the radar is in a pulse working state and the Doppler frequency exceeds half of the pulse repetition frequency of the radar, the up-conversion component and the down-conversion component are arranged in front of and behind each other in the spectrum line, and the real velocity of the target cannot be distinguished, that is, velocity blurring occurs.

[0003] When the radar hardware and resources are limited and only a low pulse repetition frequency waveform can be transmitted, the maximum unblurred velocity of the target is very small, and the Doppler spectrum of the target is folded multiple times, so that the real radial velocity of the target cannot be obtained. To solve this problem, the radar usually transmits multiple groups of pulses with different repetition frequencies, and the real radial velocity of the target is calculated by using the different Doppler shifts obtained. However, this method requires a large amount of time resources and has poor real-time performance. SUMMARY

[0004] The present application aims to provide an adaptive velocity deblurring method based on a dual-frequency radar to solve the problems in the background.

[0005] To solve the above technical problems, the present application provides an adaptive velocity deblurring method based on a dual-frequency radar, which uses the dual-frequency echo information and the track information of the radar to complete the velocity deblurring of a low pulse repetition frequency and small bandwidth radar target and obtain the real-time high-precision radial velocity of the target.

[0006] The method comprises the following steps:

[0007] Step S1: taking the radar echo at the current time, performing fast Fourier transform processing to obtain the frequency domain signal of the radar echo;

[0008] Step S2: removing the zero-frequency component from the frequency domain signal of the radar echo, extracting the extreme value component in the spectrum, and selecting the maximum value in the extreme value as the Doppler spectrum frequency shift f' of the echo after folding di , i = 1, 2,..., n, wherein i represents the i th echo of the target;

[0009] Based on the current echo of the target and the radar echo spectrum signal at the previous time of the target, the pulse repetition frequencies are f r1 and f r2The frequency shifts of the folded dual-frequency Doppler spectrum are f' di and f' d(i-1) ;

[0010] Step S3: Take the radial distance of the latest M points accumulated by the target, and calculate the average displacement velocity v' of the latest M points;

[0011] Step S4: Based on f' obtained in step S2 di f' d(i-1) And calculate the number of folds {N'1, N'2} for multiple sets of target velocities v';

[0012] Step S5: Based on f' di f' d(i-1) {N'1,N'2}, adaptively calculate the optimal N1, N2 and the target high-precision radial velocity v.

[0013] In one implementation, the extreme point detection method in step S2 is: traversing the spectral signal points f of a single echo. k (k = 1, 2, ..., n), if f k-1 <f k <f k+1 f k The extreme point is selected as the maximum value of the echo spectrum and taken as the Doppler frequency shift f' after target folding. di , where i represents the index of this echo in the target track point.

[0014] In one implementation, in step S3, the radial distance of the current target point is set to r. i The radial distances of the latest M points are r respectively. i-1 ,r i-2 ,...,r i-M+1 The formula for calculating the average displacement velocity of the latest M points is as follows: v'=(r i-M+1 -r i ) / M.

[0015] In one implementation, the number of folds N in step S4 is calculated as follows:

[0016]

[0017] In the formula, f vd The foldless Doppler frequency shift calculated for the target displacement. v is the target displacement velocity v' obtained in step S3; f r For radar repetition frequency; set radar repetition frequency f r1 and f r2 Substitute each into the above equation f rIn the process, N'1 and N'2 are obtained. Based on N'1 and N'2, and combined with the dual-frequency parameters of the radar, multiple sets of {N'1, N'2} combinations are set.

[0018] In one implementation, the calculation method for the optimal matching target velocity folding times N1 and N2 in step S5 is as follows:

[0019] The velocity is calculated by matching multiple sets of folding times, and the optimal matching target velocity folding times N1 and N2 are selected; assuming the radar has dual frequencies f r1 >f r2 And f r1 f r2 The difference is small, and N'1 and N'2 are calculated according to the following formula;

[0020] Centered on N'1 and N'2, select multiple sets of N1 and N2 to calculate the optimal number of folds for the target; based on the following formula and multiple combinations of N1 and N2, calculate the corresponding target velocity {v1, v2}, and select the N1 and N2 corresponding to the set with the smallest difference between {v1 and v2} as the target fold number:

[0021]

[0022] In the formula, λ is the radar wavelength, and the radar repetition frequency f is... r1 and f r2 Substitute each into the above equation f r In the above equation, the velocities v1 and v2 are obtained by substituting N1 and N2 obtained in step S4 into N.

[0023] In one implementation, the target velocity calculation is deemed valid when the velocities v1 and v2 satisfy the following formula:

[0024] |v1-v2|<γ

[0025] When the velocity difference calculated from two adjacent repetition frequencies is less than the threshold γ, the target velocity is determined to be valid for defuzzification; otherwise, it is determined to be invalid for defuzzification.

[0026] This invention provides an adaptive velocity deambiguation method based on dual-frequency radar. The algorithm is relatively simple, does not consume too many system resources and time overhead, and has real-time performance. Under the condition of limited radar energy resources (low repetition rate, small bandwidth) and time resources, it can obtain high-precision target velocity, thereby improving radar measurement performance and tracking accuracy. Attached Figure Description

[0027] Figure 1 This is a design block diagram of the adaptive velocity deambiguation method based on dual-frequency radar according to the present invention.

[0028] Figure 2is the schematic diagram of the extracted Doppler spectrum line after folding of the target of the present application.

[0029] Figure 3 is a comparison diagram of the calculated radial velocity of the target and the 10-time average displacement velocity.

[0030] Figure 4 is a comparison diagram of the calculated radial velocity of the target and the 2-time average displacement velocity. DETAILED DESCRIPTION

[0031] The present application provides an adaptive velocity deambiguity method based on dual-frequency radar, and the principle block diagram is shown in

[0032] The present application provides an adaptive velocity deambiguity method based on dual-frequency radar, and the principle block diagram is shown in Figure 1 The method includes target Doppler spectrum line extraction from the echo signal, and combining the target track multiple radial distance information to calculate multiple sets of target Doppler spectrum folding times, and adaptively selecting the optimal folding time combination to calculate the radial velocity of the target.

[0033] The method includes target Doppler spectrum line extraction from the echo signal, and combining the target track multiple radial distance information to calculate multiple sets of target Doppler spectrum folding times, and adaptively selecting the optimal folding time combination to calculate the radial velocity of the target.

[0034] Step S1: taking the radar echo at the current time, after FFT (Fast Fourier Transform) processing, the frequency domain signal of the radar echo is obtained, and the FFT point number is 64;

[0035] Step S2: for the frequency domain signal of the radar echo, first remove the zero frequency component, then extract the extreme value component in the spectrum, and finally select the maximum value in the extreme value as the Doppler spectrum frequency shift f' of the echo after folding di (i = 1, 2,..., n), wherein i represents the i-th echo of the target. The current echo of the target and the radar echo at the previous time of the target (the pulse repetition frequencies are f r1 and f r2 , here f r1 = 208 and f r2 = 223) are taken to obtain the dual-frequency Doppler spectrum frequency shift f' of the current time after folding and the dual-frequency Doppler spectrum frequency shift f' of the previous time. di d(i-1)

[0036] ​​Step S3: taking the radial distance of the latest M point trails of the target accumulation, calculating the average displacement velocity v'(low precision) of the latest M point trails, where M is 10;

[0037] Step S4: calculating the target velocity folding times N'1, N'2 according to f' di , f' d(i-1) and the target displacement velocity v';

[0038] Step S5: adaptively calculating the optimal N1, N2 and the target high-precision radial velocity v(high precision) according to f' di , f' d(i-1) , N'1, N'2.

[0039] As shown in Figure 2 , first, the extreme points of the target frequency domain signal obtained in step S1 are extracted, that is, in the target echo frequency spectrum signal point f k (k=1, 2,..., n) (n=64 in the present application), if f k-1 <f k <f k+1 , f k is called an extreme point, as shown in the small black square in Figure 2 . The extreme point with the largest amplitude in Figure 2 is selected as the target folded Doppler frequency shift point number 28, that is, f' di =(28÷64)×223, i represents the index of the current echo in the batch of target track points.

[0040] As shown in Table 1, the radial distance measurement values of the latest ten point trails of a target are shown, and the displacement velocity of the target is (260-150) / 10=11 m / s.

[0041] Points 1 2 3 4 5 6 7 8 9 10 Distance 150 160 170 190 200 210 220 240 250 260

[0042] Table 1: radial distance measurement of the latest ten point trails of a target

[0043] The present application uses measured data to verify the algorithm, the radar double frequencies are f r1 =223 and f r2 =208, the radar carrier frequency f=15.7 GHz, and the target radial distance units of the latest ten times are shown in Table 1, and the displacement velocity of the target is -11 m / s. According to the formula , f Substitute f vd into the formula f vd , and substitute f r1 , f r2 into the formula f r , and N'1=5 and N'2=6 can be obtained.

[0044]

[0045] As shown in Table 2, to reduce the error caused by low-precision displacement, five sets of velocity folding matching times were selected, centered at N'1=5 and N'2=6. Each column represents the N value of a corresponding set of solution velocities.

[0046] f r1 corresponding N1 4 6 5 5 6 f r2 corresponding N2 5 6 6 5 7

[0047] Table 2. Number of folds (N) for multiple speed matching sets

[0048] Will Substitute all the N1 and N2 combinations from Table 2 into the following formula, where, when substituting N1, f r =f r1 =223, f d =f' di = (18 ÷ 64) × 223 = 62.64; Substituting into N2, f r =f r2 =208, f d =f' di-1 = (58 ÷ 64) × 208 = 188.5;

[0049]

[0050] Furthermore, the target velocity solution is considered valid when v1 and v2 satisfy the following formula: when the velocity difference calculated from two adjacent repetition frequencies is less than the threshold γ, the target velocity defuzzification is considered valid; otherwise, it is considered invalid defuzzification. In this invention, γ = 0.1 is taken, but the value of γ can be modified according to the actual velocity accuracy requirements.

[0051] |v1-v2|<γ

[0052] The five target radial velocity combinations shown in Table 3 are obtained, and f is selected. r1 f r2 The average velocity value corresponding to the smallest velocity difference is taken as the radial unambiguous velocity of the target. The true velocity solutions at the two repetition frequencies are v1 = -11.1189 and v2 = -11.1162, which satisfy |v1-v2|<0.1, indicating that the velocity solution is valid. Therefore, the unambiguous velocity of the target is -11.1175.

[0053] f r1 corresponding speed -8.9883 -13.2495 -11.1189 -11.1189 -13.2495 f r2 corresponding speed -9.1289 -11.1162 -11.1162 -9.1289 -13.1035

[0054] Table 3 Multiple sets of radial velocity unfuzzy combinations

[0055] As shown in Table 4, for the comparison of the deblurring speed of the application with the 2-time displacement average speed and the 10-time displacement average speed, it can be seen that the target radial speed accuracy and stability obtained by the deblurring of the application are higher than the average displacement speed.

[0056] Deblurring speed 2nd displacement average speed 10th displacement average speed 11.534684 15 13 11.534684 12.5 11 11.534684 6 11 11.534684 18 12 11.519158 14 12 11.519378 12 11 11.534684 11 11 11.532354 10 11 11.533554 10 10 11.519158 15 11 11.519738 12.5 12 11.534684 11 10 11.551329 15.5 11 11.535803 7.5 10 11.519158 13.5 11 11.534684 11.5 12 11.518038 10.5 11 11.517844 10 11 11.566854 15 11

[0057] Table 4 Comparison of deblurring speed with 2-time displacement and 10-time displacement average speed

[0058] As Figure 3 , Figure 4 shown, the target radial speed accuracy and stability obtained by the deblurring of the application are higher than the average displacement speed.

[0059] The above description is only a description of the preferred embodiments of the application, and does not limit the scope of the application in any way. Any modification or modification made by a person skilled in the art according to the above disclosure is within the protection scope of the claims.

Claims

1. An adaptive velocity deambiguation method based on dual-frequency radar, characterized in that, Based on radar dual-frequency echo information and spot information, the velocity deambiguation of low-repetition-rate and small-bandwidth radar targets is completed, and the real-time high-precision radial velocity of the target is obtained. The method includes the following steps: Step S1: Take the radar echo at the current moment, perform fast Fourier transform processing, and obtain the frequency domain signal of the radar echo. Step S2: For the frequency domain signal of the radar echo, remove the zero-frequency component, extract the extreme value components in the spectrum, and select the maximum value among the extreme values ​​as the Doppler spectrum frequency shift after echo folding. , where i represents the i-th echo of the target; Based on the target's current echo and the radar echo spectrum signal from the previous moment, the repetition frequencies are respectively... and The frequency shifts of the folded dual-frequency Doppler spectrum are respectively and ; Step S3: Take the radial distance of the latest M points accumulated by the target, and calculate the average displacement velocity of the latest M points. ; Step S4: Based on the results obtained in step S2 and target displacement velocity Calculate the number of folds for multiple target velocities { }; Step S5: Based on , , { }, adaptively calculate the optimal and the target's high-precision radial velocity v; In step S5, the optimal matching target velocity folding number of times The calculation method is as follows: The speed is calculated by matching multiple sets of fold counts, and the optimal number of fold counts for matching the target speed is selected. ; Assume radar dual frequency ,and The difference is small, and the calculation yields... ; by Centered on, select multiple groups Calculate the target optimal number of folds; based on the following formula and multiple sets of... Combine, calculate the velocity of the corresponding target, and select The group with the smallest difference The target number of folds: （1） In the formula, For the radar wavelength, the radar repetition frequency is... and Substitute each into the above equation In the middle, the result obtained in step S4 Substituting into N in the above equation, we get the velocity. , .

2. The adaptive velocity deambiguation method based on dual-frequency radar as described in claim 1, characterized in that, The extreme point detection method in step S2 is as follows: traverse the spectral signal points of a single echo, if... ,say The extreme point is selected as the point with the largest echo spectrum in this study, which is taken as the Doppler frequency shift after target folding. , where i represents the index of this echo in the target track point.

3. The adaptive velocity deambiguation method based on dual-frequency radar as described in claim 2, characterized in that, In step S3, let the radial distance of the current target point be... The radial distances of the latest M points are respectively The formula for calculating the average displacement velocity of the latest M points is as follows: .

4. The adaptive velocity deambiguation method based on dual-frequency radar as described in claim 3, characterized in that, In step S4, the number of folds N is calculated as follows: In the formula, The foldless Doppler frequency shift calculated for the target displacement. v is the target displacement velocity obtained in step S3. ; For radar repetition frequency; to convert radar repetition frequency and Substitute each into the above equation In the middle, we obtained ,by Based on the baseline, and combined with the dual-frequency parameters of the radar, multiple sets of { }combination.

5. The adaptive velocity deambiguation method based on dual-frequency radar as described in claim 4, characterized in that, The speed , The target velocity calculation is considered valid if the following formula is satisfied: When the velocity difference calculated from two adjacent repetition frequencies is less than the threshold If the target velocity is determined to be valid, then the defuzzification is considered valid; otherwise, it is considered invalid.

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