Doppler velocity measurement method based on phase difference

Abstract

The invention discloses a Doppler velocity measurement method based on a phase difference. The method comprises the following steps: step 1, carrying out distance dimension matched filtering on a two-dimensional echo data matrix acquired by a radar to obtain a data matrix after matched filtering; step 2, taking out phase data of velocity dimension data corresponding to a peak value in the matched and filtered data matrix; step 3, subtracting two adjacent phase data in all the phase data one by one to obtain a group of phase differences; 4, preprocessing the phase difference, namely, when the phase difference exceeds a set range, considering that the phase difference is unqualified, and removing the phase difference; 5, averaging all the phase differences after rejecting the unqualified phase differences to obtain an estimated phase difference; and 6, according to the estimated phase difference and the pulse repetition period, calculating to obtain the target speed. According to the method, the radar speed measurement precision is effectively improved, and meanwhile, compared with an existing method, the calculated amount is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of radar speed measurement and relates to a Doppler speed measurement method based on phase difference. Background Art

[0002] Radar technology has always been one of the important applications in the fields of military, aviation, astronomy, etc., and plays an irreplaceable role in modern society. Speed ​​measurement is one of the important functions of radar systems. Especially in the process of monitoring and tracking dynamic targets, accurate speed information is crucial to system performance. In traditional radar speed measurement, two-dimensional fast Fourier transform (FFT) is often used to realize moving target detection (MTD), match the Doppler frequency of the echo signal, and calculate the target speed. In fact, the FFT result of the speed dimension can only match a number of limited frequency points. The target Doppler frequency will not coincide with the limited frequency points, so there is a mismatch loss. In this process, the number of frequency points is determined by the number of pulses, which directly affects the accuracy of frequency estimation and thus the accuracy of speed measurement. Although the speed measurement accuracy can be improved by increasing the number of pulses and improving the signal-to-noise ratio, it will also increase the observation energy consumption and time, and even cause speed migration. In actual engineering, it is unrealistic to improve the speed measurement accuracy simply by increasing the number of pulses. Summary of the invention

[0003] The purpose of the present invention is to provide a Doppler velocity measurement method based on phase difference, which solves the problem of insufficient FFT velocity measurement accuracy in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A Doppler velocity measurement method based on phase difference specifically comprises the following steps:

[0006] Step 1: Perform distance dimension matched filtering on the two-dimensional echo data matrix collected by the radar to obtain a data matrix after matched filtering;

[0007] Step 2: extract the phase data of the velocity dimension data corresponding to the peak value in the data matrix after matched filtering;

[0008] Step 3: Subtract two adjacent phase data from all the phase data obtained in step 2 one by one to obtain a set of phase differences;

[0009] Step 4: pre-processing the phase difference obtained in step 3, wherein when the phase difference exceeds a set range, the phase difference is considered unqualified and is eliminated;

[0010] Step 5: averaging all phase differences obtained in step 4 after removing unqualified phase differences to obtain an estimated phase difference;

[0011] Step 6: Calculate the target speed based on the estimated phase difference and pulse repetition period.

[0012] Furthermore, the calculation formula in step 3 is as follows:

[0013]

[0014] Where:

[0015] θ m - phase data;

[0016] θ m-1 —Previous phase data;

[0017] —The phase difference between two adjacent phase data.

[0018] Furthermore, in step 4, the setting range is -π~π.

[0019] Furthermore, the calculation formula in step six is ​​as follows:

[0020]

[0021] Where:

[0022] v—target speed;

[0023] λ—speed of light;

[0024] Δθ—estimated phase difference;

[0025] T r —Pulse repetition period.

[0026] The beneficial effects of the present invention are:

[0027] (1) In the present invention, the phase difference at the peak is estimated by the average value method, which effectively improves the radar speed measurement accuracy;

[0028] (2) In the present invention, the calculation speed is increased after the phase difference is obtained by the average method, which reduces the amount of calculation compared to the FFT method.

[0029] In summary, without changing the radar system parameters or adding additional equipment, the method proposed in the present invention is used to directly calculate the target speed. Through simulation analysis, a high speed estimation accuracy can be obtained even at a low signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the result after distance dimension matched filtering in the simulation experiment;

[0031] Figure 2 It is a process schematic diagram of step one and step two in the simulation experiment;

[0032] Figure 3 is the phase data of target 1 in the simulation experiment;

[0033] Figure 4 is the phase data of target 2 in the simulation test;

[0034] Figure 5 is the phase difference of target 1 in the simulation experiment;

[0035] Figure 6 is the phase difference of target 2 in the simulation experiment;

[0036] Figure 7 It is the phase difference preprocessing information of target 1 in the simulation experiment;

[0037] Figure 8 It is the phase difference preprocessing information of target 2 in the simulation test;

[0038] Fig. 9 This is a comparison chart of two speed measurement methods in the simulation experiment. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] The Doppler velocity measurement method based on phase difference provided by the present invention specifically comprises the following steps:

[0041] Step 1: Perform distance-dimensional matched filtering on the two-dimensional echo data matrix collected by the radar to obtain a data matrix after matched filtering.

[0042] Step 2: Take out the phase data of the velocity dimension data corresponding to the peak value in the matched filtered data matrix obtained in step 1.

[0043] Step 3: Subtract two adjacent phase data from all the phase data obtained in step 2 one by one to obtain a set of phase differences.

[0044] Specifically, the calculation formula is as follows:

[0045]

[0046] Where:

[0047] θ m - phase data;

[0048] θ m-1 —Previous phase data;

[0049] —The phase difference between two adjacent phase data.

[0050] Step 4: Preprocess the phase difference obtained in step 3.

[0051] Specifically, due to the influence of noise, the phase difference will fluctuate greatly. When the phase difference exceeds the range of -π to π, a large error will be generated. Therefore, the phase differences that exceed the range are eliminated, as shown in the following formula:

[0052]

[0053] Where: Δθ n —Phase difference after removing unqualified data;

[0054] Step 5: Calculate the average value of all phase differences obtained in step 4 after removing the unqualified phase differences to obtain the estimated phase difference, as shown in the following formula:

[0055] Δθ=mean(Δθ n )

[0056] Where:

[0057] Δθ—estimated phase difference;

[0058] mean—average function;

[0059] Step 6: Calculate the target speed, the formula is as follows:

[0060]

[0061] Where:

[0062] v—target speed;

[0063] λ—speed of light;

[0064] Δθ—estimated phase difference;

[0065] T r —Pulse repetition period.

[0066] In order to prove the feasibility and effectiveness of the present invention, the following simulation test is carried out for verification.

[0067] There is a moving target 6km and 9km away from the radar: target 1 and target 2. The speeds of target 1 and target 2 are 1300m / s and 957m / s respectively. The radar 2D echo matrix data size is 64*4096. The signal-to-noise ratio is set to four scenarios: -10dB, -5dB, 0dB and 5dB. The speed of target 1 is measured from 1289m / s to 1336m / s. The speed measurement accuracy of FFT and phase difference method is compared. The specific parameters of the radar are shown in the table below.

[0068] Table 1 Parameter list

[0069] Carrier frequency Sampling frequency Number of pulses Number of samples per pulse Pulse Width bandwidth 10e9 100e6 64 4096 10e-6 10e6 Signal-to-Noise Ratio Target 1 distance Target 1 speed Target 2 distance Target 2 Speed / -10 / -5 / 0 / 5 6km 1300m / s 9km 957m / s /

[0070] Step 1: Perform distance dimension matched filtering on the two-dimensional echo data matrix collected by the radar to obtain the matched filtered data, in which 64 pulses all produce a peak in the distance dimension. Figure 1 It can be seen that there are two targets (target 1 and target 2), with corresponding distances of 6km and 9km, and the speed dimension data at the peak fluctuates, indicating that these two targets are moving targets.

[0071] In this embodiment, a single pulse Doppler radar emitting a linear frequency modulation signal is taken as an example, and the two-dimensional echo data matrix A collected by the radar is subjected to distance dimension matching filtering to obtain a data matrix B after matching filtering, as shown in FIG. Figure 2 .

[0072] Step 2: If Figure 2 As shown, using the findpeaks function and angle function in MATLAB, Figure 1 The data matrix B after matched filtering in is processed to obtain the phase data C of the slow time (speed) dimension data corresponding to the peak value (i.e., the target position) after matched filtering. The peak data corresponding to target 1 and target 2 are 64 each. The phase data of the 64 speed dimension data corresponding to target 1 and target 2 are respectively as follows: Figure 3 and Figure 4 shown.

[0073] Step 3: According to the speed measurement principle, the change of speed will eventually be reflected in the change of phase. The difference between two adjacent phase values ​​is calculated one by one to obtain a set of phase difference data, such as Figure 5 , Figure 6 Theoretically, this group of phase difference data should be the same number, and the target speed can be calculated based on this data.

[0074] Step 4: Because there are errors in the actual process, the phase difference is not a fixed number, so the data needs to be preprocessed. The processing results are as follows: Figure 7 , Figure 8 As shown, through Figure 7 , Figure 8 It can be seen that all the data basically fluctuate around a theoretical value.

[0075] Step 5: Find the average value of the eliminated data to get the estimated phase difference. Figure 6 The 2.71806 and Figure 7 The marked 2.005 is the average value of the phase difference corresponding to each target.

[0076] Step 6: Measure the speed of target 1, and calculate the target speed by using FFT and the phase difference method of the present invention. Figure 8 As shown in the figure, during the process of target 1's speed changing from 1289m / s to 1336m / s, the speed measurement result using the FFT method is always 1312.5m / s. Figure 8 As shown by the dotted line in FIG. , when the phase difference method in the present invention is used for measurement, it can change with the speed change, such as Figure 8 As shown by the dotted line in .

[0077] Comparison of computational complexity: The computational complexity of the existing FFT method is O(nlog2(n)), and the computational complexity of the phase difference average method of the present invention is O(n). From the computational complexity expression, it can be seen that the computational complexity of the average value method in the present invention is much smaller than that of the FFT method.

Claims

1. A Doppler velocity measurement method based on phase difference, characterized in that: The specific steps include: Step 1: Perform distance dimension matched filtering on the two-dimensional echo data matrix collected by the radar to obtain a data matrix after matched filtering; Step 2: extract the phase data of the velocity dimension data corresponding to the peak value in the data matrix after matched filtering; Step 3: Subtract two adjacent phase data from all the phase data obtained in step 2 one by one to obtain a set of phase differences; Step 4: pre-processing the phase difference obtained in step 3, wherein when the phase difference exceeds a set range, the phase difference is considered unqualified and is eliminated; Step 5: averaging all phase differences obtained in step 4 after removing unqualified phase differences to obtain an estimated phase difference; Step 6: Calculate the target speed based on the estimated phase difference and pulse repetition period.

2. The Doppler velocity measurement method based on phase difference as claimed in claim 1, characterized in that: The calculation formula in step 3 is as follows: Where: θ m - phase data; θ m-1 —Previous phase data; —The phase difference between two adjacent phase data.

3. The Doppler velocity measurement method based on phase difference as claimed in claim 1, characterized in that: In step 4, the setting range is -π~π.

4. The Doppler velocity measurement method based on phase difference as claimed in claim 1, characterized in that: The calculation formula in step six is ​​as follows: Where: v—target speed; λ—speed of light; Δθ—estimated phase difference; T r —Pulse repetition period.

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