Fast inter-frame distance walk correction method and device based on cross-correlation IFFT

Abstract

The application relates to a fast inter-frame distance migration correction method and device based on cross-correlation IFFT, and relates to the field of radar target detection. A target speed rough value is estimated by using the relationship between adjacent two frames of echoes, then the target speed is finely searched to obtain an accurate estimation value of the target speed, so that a compensation function is constructed, and distance migration correction is completed. The experimental results show that the method can more accurately estimate the target speed value, realizes distance migration correction between multiple frames of echoes, and is beneficial to effective accumulation of multiple frame energies.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radar target detection, and in particular to a fast inter-frame range migration correction technology based on cross-correlation IFFT. BACKGROUND

[0002] In target detection, it is usually necessary to extend the accumulation time to improve the detection performance. However, for fan-scan and circular-scan radars, the received echo signals of targets are very limited and show strong discontinuity. Moreover, due to the motion of targets, the envelope of the echo signals of targets will produce a cross-range cell migration phenomenon between multiple fan-scan or circular-scan periods (inter-frame), which will seriously affect the long-time coherent accumulation effect of targets. Therefore, the inter-frame target range migration phenomenon must be corrected before radar detection.

[0003] The cross-range cell migration phenomenon caused by the uniform motion of targets is called linear range migration. The linear range migration is expressed as a linear coupling between fast-time frequency and slow-time in the fast-time frequency domain. Existing range migration correction technologies mainly include Keystone transformation, Radon Fourier transformation, and coordinate axis rotation algorithm. Keystone transformation completes the correction of the first-order range migration of targets by performing a scale transformation on the slow time in the range frequency domain, without the need to know the target speed information. However, Keystone transformation has a Doppler ambiguity problem, and the ambiguity factor needs to be searched. Radon Fourier transformation extracts the echo signals of targets by jointly searching the radial distance and radial speed in the range-slow time domain, and constructs a phase compensation function to compensate for the Doppler phase term, thereby realizing the correction of the echo range migration. However, this algorithm has a high computational load due to the two-dimensional joint search, and also has a blind speed sidelobe problem. The coordinate axis rotation algorithm realizes the range migration correction by searching the rotation angle, and uses the one-to-one correspondence between the range migration angle and the target speed to rotate the signal energy into the same range cell by the coordinate axis rotation method, and then the rotation angle is obtained, so that the target speed value can be obtained accordingly, and the range migration is corrected. However, this algorithm has a range offset and Doppler frequency offset phenomenon, which will cause the estimation of the motion parameters of targets to deviate. The above range correction methods are all proposed in the radar staring mode, that is, the target is always in the range of the radar beam. When the radar adopts fan-scan or circular-scan, due to the discontinuous characteristics of the echo signals, the existing range correction methods have great differences in mathematical representation and algorithm design, so that the range migration correction fails. SUMMARY

[0004] The technical problem to be solved by the present application is:

[0005] In view of the problem that the existing algorithm fails in interframe range walk correction of fan scan or circular scan radar, the application provides a fast interframe range walk correction method and device based on cross-correlation IFFT, which adopts cross-correlation IFFT method to process adjacent two frames of echo signals, roughly estimates a target speed value according to the relationship among multiple frames of echo signals, sets a reasonable search interval, further searches the speed value, and then realizes range walk correction of multiple frames of echo signals.

[0006] In order to solve the above technical problems, the technical scheme adopted by the application is:

[0007] A fast interframe range walk correction method based on cross-correlation IFFT, characterized in that it comprises:

[0008] Pulse compression is performed on radar multiple frames of target echo signals;

[0009] Cross-correlation IFFT processing is performed on adjacent two frames of echo signals after pulse compression, and the processed signals are arranged in sequence as a matrix, the energy values of the matrix are superimposed along the distance unit, and a speed estimation value is obtained according to the distance unit corresponding to the maximum energy value;

[0010] A target accurate speed search interval is determined according to the speed estimation value and a speed resolution, and a speed search sequence is obtained;

[0011] A first phase compensation function is constructed according to the speed search sequence, and IFFT is performed after the first phase compensation function is multiplied by multiple frames of target echo signals in the frequency domain; the speed corresponding to the maximum peak value is the final target speed estimation value;

[0012] A second phase compensation function is constructed according to the final target speed estimation value, multiple frames of target echo signals are multiplied by the second phase compensation function in the distance frequency domain, and distance walk correction is completed.

[0013] The further technical scheme of the application is that the determination of the target accurate speed search interval to obtain the speed search sequence is specifically:

[0014] Supposing that the speed estimation value obtained by the cross-correlation IFFT method is , the target accurate speed search interval is , , the speed resolution is set as , and the speed search sequence is determined as , wherein is the total number of search speeds.

[0015] The further technical scheme of the application is that the construction of the first phase compensation function according to the speed search sequence is:

[0016]

[0017] wherein, denotes the distance frequency variable corresponding to the fast time, is the speed of light, denotes the slow time.

[0018] A further technical solution of the present application is that the second phase compensation function constructed according to the final target speed estimation value is:

[0019]

[0020] wherein, is the accurate target speed estimation value.

[0021] The fast inter-frame distance migration correction method and device based on cross-correlation IFFT are characterized by comprising:

[0022] a pulse compression module; pulse compression is performed on the radar multi-frame target echo signal;

[0023] a cross-correlation IFFT processing module; cross-correlation IFFT is performed on the adjacent two frames of echo signals after pulse compression, and a target speed estimation value is obtained;

[0024] a search module; a target accurate speed search interval is determined according to the speed estimation value and the speed resolution, and a speed search sequence is obtained;

[0025] a speed estimation module; a first phase compensation function is constructed according to the speed search sequence, and IFFT is performed after multiplication in the frequency domain with the multi-frame target echo signal; the speed corresponding to the maximum peak value is the final target speed estimation value;

[0026] a correction module; a second phase compensation function is constructed according to the final target speed estimation value, and distance migration correction is completed.

[0027] An application of the fast inter-frame distance migration correction method based on cross-correlation IFFT is characterized by the following: for fan-scan and circular-scan radars, the echo signal envelope of a target produces a cross-range cell migration phenomenon during multiple fan-scan or circular-scan periods, which will seriously affect the long-time coherent accumulation effect of the target. The above method is used to correct the inter-frame target distance migration phenomenon.

[0028] A computer system comprises one or more processors, a computer readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the above method.

[0029] A computer readable storage medium stores computer executable instructions, and the instructions, when executed, are used to implement the above method.

[0030] The present application has the advantages of:

[0031] The present application provides a fast inter-frame distance migration correction method and device based on cross-correlation IFFT, which estimates the target speed rough value by using the relationship between adjacent two frames of echoes, then searches the target speed again to obtain the accurate estimation value of the target speed, thereby constructing a compensation function to complete the distance migration correction.

[0032] The present application solves the distance migration phenomenon of the moving target between multiple frames of echo data in the fan scanning or circle scanning radar detection mode, thereby avoiding the leakage of target energy in multiple range cells, realizing the effective accumulation of target energy, and improving the detection ability of the radar to the target. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and serve to explain the principles of the present application.

[0034] Figure 1 The present application introduces the overall architecture flow chart of the inter-frame distance migration correction method based on cross-correlation IFFT.

[0035] Figure 2 The envelope trajectory graph after the original 3 frames of echo pulse compression.

[0036] Figure 3 Analysis of the inter-frame migration number caused by speed.

[0037] Figure 4 The approximate estimation value of the target speed.

[0038] Figure 5 The target envelope trajectory after the distance migration correction is completed.

[0039] Figure 6 The energy focusing range cell situation after correction. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as there is no conflict.

[0041] The application provides a fast inter-frame distance walk correction method based on cross-correlation IFFT.

[0042] As shown in Figure 1 , the application comprises the following steps:

[0043] Step 1: pulse compression of radar multi-frame target echo

[0044] For a radar system, it is assumed that the radar transmitted signal is an LFM signal, which is represented as:

[0045]

[0046] In the formula, represents a rectangular window function, represents a pulse duration, is a frequency modulation rate of the transmitted signal, B is a modulation bandwidth.

[0047] Supposing that the working carrier frequency of the radar is , the pulse repetition period is , the antenna scanning period is , and , is the total number of pulses transmitted by the radar antenna in one scanning period. Therefore, the first pulse transmitted by the radar in the first antenna scanning period can be represented as:

[0048]

[0049] In the formula, represents fast time, represents slow time.

[0050] After the carrier frequency processing, considering a general model, the target baseband echo signal model received by the radar is represented as:

[0051]

[0052] In the formula, represents signal amplitude, c is the speed of light, denotes the transmitted signal wavelength, is the instantaneous slant range of the moving target.

[0053] The baseband signal is pulse compressed, and the pulse-compressed signal is expressed in the range-Doppler-slow-time domain (RDST) as:

[0054]

[0055] where, denotes the Doppler frequency variable corresponding to the fast time.

[0056] Step 2: Estimate the approximate range of target speed by the cross-correlation IFFT method

[0057] According to the definition of the cross-correlation function, the cross-correlation of two signals and can be described as:

[0058]

[0059] where, denotes the convolution operation, is the conjugate.

[0060] According to the convolution theorem of Fourier transform and the conjugate symmetry, the above formula can be further written as:

[0061]

[0062] In the formula, and correspond to the frequency domain expressions of and respectively.

[0063] For multiple frames of signal echoes, taking the first and second frame echoes as an example, the frequency domain expressions of the adjacent two frames of signal echoes are respectively:

[0064]

[0065]

[0066] where, is the amplitude of the first frame signal, is the amplitude of the first frame signal;

[0067] The cross-correlation function of the adjacent two frames of echoes is:

[0068]

[0069] Continue to perform the IFFT operation on to obtain:​

[0070]

[0071] From the above formula, it can be seen that after processing the echo signals of two adjacent frames by using the cross-correlation IFFT method, the echo energy is concentrated in This distance unit, according to which the target speed can be estimated, and the speed resolution is Since the value of the speed resolution is often large, the accuracy of the speed estimation is low, which is difficult to meet the requirements of linear phase velocity compensation error. Therefore, in order to achieve accurate compensation, it is still necessary to further search for the speed value.

[0072] Step 3: Search for the target accurate speed according to the speed range

[0073] Suppose the speed estimation value obtained by using the cross-correlation IFFT method is , the target accurate speed search interval is , and the speed search interval is , so the speed search sequence can be determined as , wherein is the total number of search speeds.

[0074] According to the speed search sequence, the corresponding phase compensation function is constructed:

[0075]

[0076] Multiply the target multi-frame echo and the phase compensation function in the range frequency domain to obtain:

[0077]

[0078] In the range frequency domain, the inverse Fourier transform (IFFT) is performed on the above formula, and the expression of the echo signal in the fast time-slow time is:

[0079]

[0080] From the above formula, it can be seen that only when the search target speed is consistent with the target speed , there is an accumulation peak. Thus, the accurate estimation value of the target speed can be obtained:

[0081]

[0082] Step 4: Construct a compensation function according to the target estimated speed value to realize distance walk correction

[0083] The accurate estimation value of the target speed obtained from step 3 is , and the phase compensation function is constructed:

[0084]

[0085] After multiplying the target multiframe echoes and phase compensation function in the range-frequency domain and transforming them back to the fast-time-slow-time two-dimensional space, the expression is:

[0086]

[0087] Based on the properties of the sinc function, it can be seen that the processed echo energy is concentrated within the initial radial distance cell, and the distance migration phenomenon between multiple echo frames has been corrected.

[0088] Example:

[0089] radar system signal transmission time width ,bandwidth carrier frequency Sampling rate Pulse repetition frequency Initial radial distance of the target radial velocity Assume the number of pulses residing in each radar beam. The number of pulses emitted within one antenna scan cycle .

[0090] Step 1: Perform pulse compression on multi-frame target echoes from the radar.

[0091] The distance travel of three consecutive frames of target echo data after pulse compression is shown in the attached figure. Figure 2 As shown, there is a clear distance movement between frames.

[0092] Step 2: Estimate the approximate range of the target velocity using the cross-correlation IFFT method.

[0093] Perform an IFFT operation on the cross-correlation of two adjacent frames of echo data after pulse compression, and arrange the processed signals sequentially into a matrix. This matrix describes the inter-frame travel number caused by velocity, as shown in the appendix. Figure 3 As shown.

[0094] Therefore, by accumulating matrix energy along the line, the number of inter-frame distance moves caused by velocity can be obtained, and a rough value of the target velocity can be estimated based on the number of inter-frame distance moves caused by velocity. As attached Figure 4 As shown.

[0095] Step 3: Obtain the target's precise speed by searching within the speed range.

[0096] Calculation Therefore, the approximate range of the target speed can be obtained as follows: The target speed range is evenly divided into The velocity search sequence is obtained, and then the corresponding phase compensation function is constructed to obtain the velocity value corresponding to the maximum peak value. .

[0097] Step 4: Construct a compensation function based on the velocity value obtained from the target estimation to achieve distance travel correction.

[0098] by A phase compensation function is constructed to correct the target's range movement in the range frequency domain. The corrected target envelope trajectory is shown in the attached figure. Figure 5 As shown, attached Figure 6 This indicates that the target energy is better concentrated within a range cell after correction, and the range spread phenomenon is compensated.

[0099] This example uses an inter-frame distance travel correction method based on cross-correlation IFFT, which can accurately estimate the target velocity and thus effectively achieve distance travel correction between multiple echo frames.

[0100] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A fast inter-frame distance movement correction method based on cross-correlation IFFT, characterized in that, include: Pulse compression is performed on multi-frame target echo signals from the radar. The cross-correlation IFFT processing is performed on the echo signals of two adjacent frames after pulse compression, and the processed signals are arranged into a matrix in order. The energy values ​​of the matrix are superimposed along the range cells, and the velocity estimate is obtained based on the range cell corresponding to the maximum energy value. Based on the velocity estimate and velocity resolution, the precise velocity search interval of the target is determined, resulting in a velocity search sequence; specifically: The velocity estimate obtained using the cross-correlation IFFT method is Then the target's precise speed search interval is taken as ,in Set the speed search interval to speed resolution. Determine the velocity search sequence ,in Total search speed; Based on the velocity search sequence, construct the corresponding phase compensation function: in, This represents the distance frequency variable corresponding to fast time. At the speed of light, Indicates slow time; Multiplying the target's multi-frame echoes with the phase compensation function in the range-frequency domain yields: in, B For modulation bandwidth, For the radar's operating carrier frequency, Radial velocity, The initial radial distance to the target. Indicates signal amplitude; In the distance frequency domain, performing an inverse Fourier transform on the above equation yields the expression for the echo signal in fast time versus slow time: in, Represents radar cross section, Indicates a fast time; A precise estimate of the target velocity is obtained: The first phase compensation function is constructed based on the velocity search sequence, and then multiplied with the frequency domain of the target echo signal from multiple frames and subjected to IFFT; the velocity corresponding to the maximum peak is the final target velocity estimate. A second phase compensation function is constructed based on the final target velocity estimate. The target echo signals from multiple frames are multiplied with the second phase compensation function in the range frequency domain to complete the range travel correction.

2. The fast inter-frame distance movement correction method based on cross-correlation IFFT according to claim 1, characterized in that, The second phase compensation function constructed based on the final target velocity estimate is as follows: in, This is a precise estimate of the target speed.

3. An apparatus for implementing the fast inter-frame distance movement correction method based on cross-correlation IFFT according to any one of claims 1-2, characterized in that... include: Pulse compression module; Pulse compression is performed on multi-frame target echo signals from the radar. Cross-correlation IFFT processing module; The target velocity estimate is obtained by performing cross-correlation IFFT on the echo signals of two adjacent frames after pulse compression. Search module; Based on the velocity estimate and velocity resolution, the precise velocity search interval of the target is determined, and the velocity search sequence is obtained. Velocity estimation module: Constructs a first phase compensation function based on the velocity search sequence, and performs IFFT after multiplying it with the frequency domain of the target echo signal from multiple frames; the velocity corresponding to the maximum peak is the final target velocity estimate; The correction module constructs a second phase compensation function based on the final target velocity estimate to complete the distance travel correction.

4. A computer system, characterized in that... include: One or more processors, a computer-readable storage medium, for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to perform the method of any one of claims 1-2.

5. A computer-readable storage medium, characterized in that... The device stores computer-executable instructions, which, when executed, are used to implement the method described in any one of claims 1-2.

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