Self-adaptive speed ambiguity resolution method based on dual-frequency radar

Abstract

The invention discloses a self-adaptive speed ambiguity resolution method based on a dual-frequency radar, which is used for completing low-repetition-frequency and small-bandwidth radar target speed ambiguity resolution based on radar dual-frequency echo information and trace point information to obtain a real-time high-precision radial speed of a target. The processing method comprises the steps of performing frequency spectrum transformation on radar echoes, performing Doppler spectral line extraction, performing adaptive calculation on Doppler frequency shift folding times, performing target high-precision speed calculation and the like. The method is simple in algorithm, does not occupy too many system resources and time overhead, has real-time performance, obtains high-precision target speed under the condition that radar energy resources and time resources are limited, and improves radar measurement performance and tracking accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of radar data processing and radar signal processing, and in particular to an adaptive speed deambiguation method based on dual-frequency radar. Background Art

[0002] The measuring radar transmits electromagnetic waves to the target and performs signal processing and data processing on the echo reflected by the target to obtain information such as the target's position and radial velocity. However, when the radar resources or hardware conditions are limited and it is impossible to transmit a radar waveform with a large bandwidth, high repetition rate, and long dwell time, the target's velocity accuracy, distance accuracy, and angle accuracy cannot meet the required accuracy. When the radar is in a pulse working state and the Doppler frequency exceeds half of the radar pulse repetition frequency, the up-conversion component and the down-conversion component intersect at the front and back positions of the spectral line arrangement, and it is impossible to distinguish the target's true speed, that is, flicker occurs, resulting in velocity ambiguity.

[0003] When radar hardware and resources are limited and only low repetition frequency waveforms can be emitted, the maximum unambiguous velocity of the target is very small, resulting in multiple folding of the target's Doppler spectrum and the inability to obtain the target's true radial velocity. To solve this problem, radars usually emit multiple groups of pulses with different repetition frequencies and deduce the target's true radial velocity by obtaining different Doppler frequency shifts. However, this requires a lot of time resources and has poor real-time performance. Summary of the invention

[0004] The object of the present invention is to provide an adaptive velocity deambiguation method based on dual-frequency radar to solve the problems in the background technology.

[0005] In order to solve the above technical problems, the present invention provides an adaptive velocity deambiguation method based on dual-frequency radar, which completes the velocity deambiguation of low-repetition-rate and small-bandwidth radar targets based on the dual-frequency echo information and point trace information of the radar, and obtains the real-time high-precision radial velocity of the target;

[0006] The method comprises the following steps:

[0007] 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;

[0008] Step S2: For the frequency domain signal of the radar echo, remove the zero-frequency component, extract the extreme value component in the spectrum, and select the maximum value among the extreme values ​​as the Doppler spectrum frequency shift f' after the echo is folded di , i=1,2,...,n, where i represents the i-th echo of the target;

[0009] Based on the target's current echo and the target's previous moment radar echo spectrum signal, the 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 speed v' of the latest M points;

[0011] Step S4: f' obtained in step S2 di 、f' d(i-1) and target displacement velocity v' to calculate the folding times of multiple sets of target velocities {N'1, N'2};

[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 embodiment, the extreme point detection method in step S2 is: traverse the spectrum signal point f of a single echo k (k=1,2,...,n), if f k-1 <f k <f k+1 , called f k is the extreme point; the maximum extreme point of the echo spectrum is selected as the Doppler frequency shift f' after the target folding di , i represents the index of this echo in the target track point.

[0014] In one embodiment, 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 i-1 ,r i-2 ,...,r i-M+1 The average displacement velocity of the latest M points is calculated as follows: v' = (r i-M+1 -r i ) / M.

[0015] In one embodiment, in step S4, the folding times N are calculated as follows:

[0016]

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

[0018] In one embodiment, in step S5, the optimal matching target speed folding times N1, N2 are calculated as follows:

[0019] Use multiple sets of folding times to match the solution speed, select the best matching target speed folding times N1, N2; assume that the radar dual frequency 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] Taking N'1, N'2 as the center, select multiple groups of N1, N2 to calculate the optimal number of target folding times; according to the following formula and multiple groups of N1, N2 combinations, calculate the speed {v1, v2} of the corresponding target, and select the N1, N2 corresponding to the group with the smallest difference of {v1, v2} as the target number of folding times:

[0021]

[0022] Where λ is the radar wavelength, and the radar repetition frequency f r1 and f r2 Substitute into the above formula f r In step S4, N1 and N2 are substituted into the above formula N to obtain the speeds v1 and v2.

[0023] In one implementation, the target speed solution is determined to be valid when the speeds v1 and v2 satisfy the following formula:

[0024] |v1-v2|<γ

[0025] When the speed difference calculated by two adjacent repetition frequencies is less than the threshold γ, the target speed defuzzification is determined to be effective, otherwise, it is determined to be invalid defuzzification.

[0026] The invention provides an adaptive speed deambiguation method based on dual-frequency radar, which has a relatively simple algorithm, does not occupy too much system resources and time overhead, and has real-time performance. When radar energy resources (low repetition rate, small bandwidth) and time resources are limited, high-precision target speed is obtained, and radar measurement performance and tracking accuracy are improved. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2It is a schematic diagram of Doppler spectrum line extraction after the target folding of the present invention.

[0029] Figure 3 It is a comparison diagram of the target radial velocity calculated by the present invention and 10 average displacement velocities.

[0030] Figure 4 It is a comparison diagram of the target radial velocity calculated by the present invention and the 2nd average displacement velocity. DETAILED DESCRIPTION

[0031] The following is a further detailed description of an adaptive speed deambiguation method based on a dual-frequency radar proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0032] The present invention provides an adaptive speed deambiguation method based on dual-frequency radar, the principle block diagram is as follows: Figure 1 As shown, by extracting the target Doppler spectrum line of the echo signal and combining the multiple radial distance information of the target point trace, the folding times of multiple groups of target Doppler spectrum are calculated, and the optimal folding times combination is adaptively selected to calculate the radial velocity of the target.

[0033] The method includes spectrum transformation of radar echo, Doppler spectrum line extraction, Doppler frequency shift folding times calculation, target true speed calculation, etc. The specific steps are as follows:

[0034] Step S1: Take the radar echo at the current moment, perform FFT (Fast Fourier Transform) processing, and obtain the frequency domain signal of the radar echo. The number of FFT points 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 among the extreme values ​​as the Doppler spectrum frequency shift f' after echo folding di (i=1,2,...,n), where i represents the i-th echo of the target. Take the current echo of the target and the radar echo of the target at the previous moment (with repetition frequencies of f r1 and f r2 , where f r1 =208 and f r2 =223) After the spectrum signal is folded, the dual-frequency Doppler spectrum shift at the current moment is f' di , the frequency shift of the dual-frequency Doppler spectrum at the previous moment is f' d(i-1) ;

[0036] Step S3: Take the radial distance of the latest M points accumulated by the target, and calculate the average displacement speed v' (low precision) of the latest M points, where M is 10;

[0037] Step S4: f' obtained in step S2 di 、f' d(i-1) and the target displacement velocity v' to calculate the target velocity folding times N'1, N'2;

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

[0039] like Figure 2 As shown, firstly, the extreme point of the target frequency domain signal obtained in step S1 is extracted, that is, at the target echo spectrum signal point f k (k=1,2,...,n)(n=64 in the present invention), if f k-1 <f k <f k+1 , then f k is an extreme point, such as Figure 2 As shown in the small and medium black squares. Figure 2 The maximum value point in the middle amplitude is taken as the target. The number of Doppler frequency shift points after folding is 28, then f' di =(28÷64)×223, i represents the index of this echo in the batch of target track points.

[0040] As shown in Table 1, these are the radial distance measurement values ​​of the latest ten points of a target, so the displacement speed 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 ten points near the target

[0043] The present invention uses measured data to verify the algorithm. The dual frequencies of the radar are f r1 =223 and f r2 =208, radar carrier frequency f = 15.7GHz, the target's nearly ten radial distance units are shown in Table 1, then the target's displacement speed is -11m / s. According to the formula Available f vd Substitute into the following formula f vd In the r1 、f r2 Substitute f into the following formulas respectively r In this case, we can obtain N'1=5, N'2=6.

[0044]

[0045] As shown in Table 2, in order to reduce the error caused by low-precision displacement, 5 groups of velocity folding matching times are selected with N'1 = 5 and N'2 = 6 as the center. Among them, each column is the N of the corresponding set of solution velocities.

[0046] <![CDATA[f r1 Corresponding N1]]> 4 6 5 5 6 <![CDATA[f r2 Corresponding N2]]> 5 6 6 5 7

[0047] Table 2 Multiple groups of speed matching folding times N

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

[0049]

[0050] In addition, when v1 and v2 satisfy the following formula, the target speed solution is determined to be effective, that is, when the speed difference calculated by two adjacent repetition frequencies is less than the threshold γ, the target speed defuzzification is determined to be effective, otherwise, it is determined to be invalid defuzzification. In the present invention, γ=0.1 is taken, and the γ value can also be modified according to the actual speed accuracy requirements.

[0051] |v1-v2|<γ

[0052] We get five target radial velocity combinations as shown in Table 3, and select f r1 、f r2 The speed mean corresponding to the smallest speed difference is used as the target radial defuzzification speed, and the real speed solution v1 = -11.1189, v2 = -11.1162 under two repetition frequencies is obtained, satisfying |v1-v2|<0.1, and the speed solution is valid. Therefore, the target defuzzification speed is -11.1175.

[0053] <![CDATA[f r1 Corresponding speed]]> -8.9883 -13.2495 -11.1189 -11.1189 -13.2495 <![CDATA[f r2 Corresponding speed]]> -9.1289 -11.1162 -11.1162 -9.1289 -13.1035

[0054] Table 3 Multiple radial velocity defuzzification combinations

[0055] As shown in Table 4, the defuzzification speed of the present invention is compared with the average speed of 2 displacements and the average speed of 10 displacements. It can be seen that the accuracy and stability of the target radial speed obtained by the defuzzification of the present invention are higher than the average displacement speed.

[0056] Defuzzification speed Average speed of 2 displacements Average speed of 10 displacements 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 the fuzzy velocity with the average velocity of 2 displacements and 10 displacements

[0058] like Figure 3 , Figure 4 As shown, the accuracy and stability of the target radial velocity obtained by defuzzification of the present invention are higher than the average displacement velocity.

[0059] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. An adaptive velocity deambiguation method based on dual-frequency radar, characterized in that: Based on the radar dual-frequency echo information and point trace information, the low-repetition-rate and small-bandwidth radar target velocity deambiguation is completed to obtain the real-time high-precision radial velocity of the target; The method comprises 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 component in the spectrum, and select the maximum value among the extreme values ​​as the Doppler spectrum frequency shift f' after the echo is folded di , i=1,2,...,n, where i represents the i-th echo of the target; Based on the target's current echo and the target's previous moment radar echo spectrum signal, the repetition frequencies are f r1 and f r2 The frequency shifts of the folded dual-frequency Doppler spectrum are f' di and f' d(i-1) ; Step S3: Take the radial distance of the latest M points accumulated by the target and calculate the average displacement speed v' of the latest M points; Step S4: f' obtained in step S2 di 、f' d(i-1) and target displacement velocity v' to calculate the folding times of multiple sets of target velocities {N'1, N'2}; 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.

2. The adaptive speed deambiguation method based on dual-frequency radar as claimed in claim 1, characterized in that: The extreme point detection method in step S2 is: traverse the spectrum signal point f of a single echo k (k=1,2,...,n), if f k-1 <f k <f k+1 , called f k is the extreme point; the maximum extreme point of the echo spectrum is selected as the Doppler frequency shift f' after the target folding di , i represents the index of this echo in the target track point.

3. The adaptive speed deambiguation method based on dual-frequency radar as claimed in claim 2, characterized in that: 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 i-1 ,r i-2 ,...,r i-M+1 The average displacement velocity of the latest M points is calculated as follows: v' = (r i-M+1 -r i ) / M.

4. The adaptive velocity deambiguation method based on dual-frequency radar as claimed in claim 3, characterized in that: In step S4, the folding times N are calculated as follows: In the formula, f vd is the folded Doppler shift calculated from the target displacement, v is the target displacement velocity v' obtained in step S3; f r is the radar repetition frequency; the radar repetition frequency f r1 and f r2 Substitute into the above formula f r In the above equation, N'1, N'2 are obtained. Based on N'1, N'2 and combined with the dual-frequency parameters of the radar, multiple groups of {N'1, N'2} combinations are set.

5. The method for adaptive velocity deambiguation based on dual-frequency radar as claimed in claim 4, characterized in that: In step S5, the optimal matching target speed folding times N1 and N2 are calculated as follows: Use multiple sets of folding times to match the solution speed, and select the best matching target speed folding times N1, N2; Assume that the radar dual frequency f r1 >f r2 , and f r1 、f r2 The difference is small, and N′1, N′2 are calculated according to the following formula; Taking N'1, N'2 as the center, select multiple groups of N1, N2 to calculate the optimal number of target folding times; according to the following formula and multiple groups of N1, N2 combinations, calculate the speed {v1, v2} of the corresponding target, and select the N1, N2 corresponding to the group with the smallest difference of {v1, v2} as the target number of folding times: Where λ is the radar wavelength, and the radar repetition frequency f r1 and f r2 Substitute into the above formula f r In step S4, N1 and N2 are substituted into the above formula N to obtain the speeds v1 and v2.

6. The method for adaptive velocity deambiguation based on dual-frequency radar as claimed in claim 5, characterized in that: When the speeds v1 and v2 satisfy the following formula, the target speed solution is determined to be valid: |v1-v2|<γ When the speed difference calculated by two adjacent repetition frequencies is less than the threshold γ, the target speed defuzzification is determined to be effective, otherwise, it is determined to be invalid defuzzification.

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