High-efficiency target distance migration compensation method based on chirp-z transform

Abstract

The application discloses a high-efficiency target distance migration compensation method based on Chirp-Z transformation and belongs to the field of radar target detection signal processing.The application realizes the method as follows: FFT is conducted on a reference signal and an echo signal along a fast time dimension, the fast time time domain is transformed into a frequency domain, and the echo signal is pulse compressed by conjugate multiplication, so that target echo energy is more concentrated in the fast time dimension; a Doppler ambiguity compensation function is transformed from an integer form into a fractional form, so that a compensation Doppler frequency interval is changed from a fixed value into a value that can be changed as required; a CZT formula with the fractional Doppler ambiguity number compensation function is used to transform the pulse-compressed signal, target distance migration is compensated, and the efficiency of target distance migration compensation is improved; IFFT is conducted on the fast time dimension of the signal, so that the fast time frequency domain is changed back into a time domain; and two-dimensional data containing target distance information and Doppler information are detected, so that distance and speed information of the target is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-efficiency target range migration compensation method based on Chirp-Z transform, belonging to the field of radar target detection signal processing. BACKGROUND

[0002] Long-time coherent accumulation is an important means to improve the signal-to-noise ratio of radar received echo and improve the target detection capability. However, in a long accumulation time, the target motion distance will cross the distance unit, that is, the problem of range migration occurs. Range migration will cause the dispersion of target peak energy in the coherent accumulation result and the decrease of signal-to-noise ratio, and then affect the detection capability of the radar to the target, so a method needs to be found to solve it.

[0003] Keystone transform (KT) is an effective method to compensate for target range migration, and there are Sinc interpolation, DFT+IFFT, Chirp-Z transform (CZT) and other implementation methods, among which the CZT method has the smallest amount of calculation and is commonly used in engineering. The Doppler frequency range compensated by a CZT calculation is [0, f r ), where f r is the pulse repetition frequency. When the Doppler frequency of the target exceeds this range, that is, there is Doppler ambiguity, a Doppler ambiguity compensation function needs to be used to compensate for the Doppler ambiguity.

[0004] The Doppler ambiguity number q is defined as q = floor(f d / f r ), where floor(·) is the floor function, and f d is the Doppler frequency generated by the target. After ambiguity compensation, the Doppler frequency range compensated by the CZT method becomes [qf r , (q+1)f r ). When the radar detects targets within a certain speed range, the Doppler frequency range compensated by the CZT method will be adjusted according to the speed range of the target. If the compensated Doppler frequency range crosses multiple Doppler compensation intervals, multiple corresponding Doppler ambiguity numbers need to be set to perform multiple CZT calculations on the echo signal.

[0005] When the radar compensates for the received narrow speed range target signal for range migration, the narrow speed range refers to the difference between the maximum and minimum Doppler frequencies generated by the target being less than the pulse repetition frequency f rThe Doppler frequency range to be compensated is less than the width of a Doppler frequency interval, but when it crosses two Doppler compensation intervals, two adjacent Doppler ambiguity numbers need to be set, and two times of CZT calculation compensation are needed to complete the range migration compensation. Since the Doppler range of the target is actually small, the Doppler frequency range to be compensated is less than half of the total compensation interval of two times of operation, resulting in low operation efficiency, and therefore, a high-efficiency range migration compensation method needs to be designed for narrow speed range targets from the perspective of reducing the number of compensation calculations. SUMMARY

[0006] The purpose of the present application is to provide a high-efficiency target range migration compensation method based on Chirp-Z transform, which respectively performs FFT calculation on the reference signal and the echo signal along the fast time dimension, transforms the fast time time domain to the frequency domain, and performs conjugate multiplication to realize pulse compression processing of the echo signal, so that the target echo energy is more concentrated in the fast time dimension; the Doppler ambiguity compensation function is transformed from an integer form to a fractional form, so that the compensation Doppler frequency interval changes from a fixed value to a value that can be changed as needed; the CZT formula with the fractional Doppler ambiguity compensation function is used to transform the pulse-compressed signal, compensate the target range migration, and improve the efficiency of target range migration compensation; IFFT is performed on the fast time dimension of the signal to transform the fast time frequency domain back to the time domain; and the two-dimensional data containing the motion target distance information and Doppler information are detected to obtain the distance and speed information of the target.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] The high-efficiency target range migration compensation method based on Chirp-Z transform disclosed by the present application comprises the following steps:

[0009] Step 1: FFT calculation is performed on the reference signal and the echo signal along the fast time dimension to transform the fast time time domain to the fast time frequency domain.

[0010] The two-dimensional data matrix of the reference signal is

[0011] u(l,m)=A u p(l,m) (1)

[0012] Wherein, A u is the reference signal amplitude, p(l,m) is the baseband signal transmitted by the radar, l represents the fast time sampling point serial number, the total number of fast time sampling points is L, and m represents the slow time sampling point serial number, the total number of slow time sampling points is M.

[0013] FFT calculation is performed on the sampled reference signal along the fast time dimension, which is represented by the following formula

[0014] U(f l ,m)=FFT[u(l,m)]=AU P(f l ,m) (2)

[0015] wherein U(f l ,m) represents the transformed reference signal two-dimensional data matrix, A U represents the transformed reference signal amplitude, P(f l ,m) represents the baseband signal spectrum, f l represents the sampling point sequence number of the fast time frequency domain.

[0016] Suppose that there is a uniformly moving target in the radar detection space, the initial distance between the target and the radar is R0, and the radial movement speed is v0, then the equation of the distance R between the target and the radar changing with the slow time is

[0017] R = R0-v0mT r (3)

[0018] wherein T r is the pulse repetition period.

[0019] The radar receives the echo signal of the target, and after down-conversion processing, the obtained baseband echo signal is

[0020]

[0021] wherein A r is the baseband echo signal amplitude, and f c is the carrier frequency. It is shown from equation (4) that the pulse envelope center position shifts with the slow time, and when the envelope shift exceeds the distance unit, the range migration problem occurs, resulting in the dispersion of target signal energy and the decrease of coherent accumulation gain.

[0022] The FFT calculation is performed on the echo signal along the fast time dimension, and is expressed by the following equation

[0023]

[0024] wherein S(f l ,m) represents the transformed two-dimensional data matrix of the echo signal, and A R represents the fast time frequency domain amplitude of the echo signal. The phenomenon of the envelope shifting with the slow time in equation (4) is expressed as the coupling between the fast time frequency f l and the slow time m in equation (5).

[0025] Step two: the echo signal matrix S R (f l ,m) obtained in step one and the reference signal matrix U(f l ,m) are conjugated and multiplied, so as to realize the pulse compression processing of the echo signal in the frequency domain, and make the target echo energy more concentrated in the fast time dimension.

[0026] Step two: Pulse compression in frequency domain

[0027] S PC (f l ,m)=S R (f l ,m)·U * (f l ,m) (6)

[0028] Where * represents the conjugate operation, S PC (f l ,m) represents the two-dimensional data matrix of the pulse compressed echo signal. After pulse compression, the target echo energy is more concentrated in the fast time dimension.

[0029] Step three: Transform the integer form of the Doppler ambiguity compensation function into a fractional form, so that the CZT compensation Doppler frequency interval changes from a fixed value to a value that can be changed on demand, so that the compensation Doppler frequency interval can cover the Doppler range generated by the narrow speed target, and improve the compensation calculation efficiency.

[0030] The Doppler frequency interval compensated by the CZT method is [0, f r ), where f r is the pulse repetition frequency. For target signals whose Doppler frequency is not in this interval, the integer form of the Doppler ambiguity compensation function is used in the traditional method to compensate for Doppler ambiguity. The integer form of the ambiguity compensation function is

[0031]

[0032] Where q is the ambiguity number, and the value range is an integer. After Doppler ambiguity compensation, the CZT method compensates the Doppler frequency interval to [qf r ,(q+1)f r ). Transform the integer form of the ambiguity compensation function into a fractional form, and define the fractional Doppler ambiguity compensation function as

[0033]

[0034] The compensation frequency interval adjusted using the fractional Doppler ambiguity compensation function is Where N is the CZT point number, and the fractional ambiguity number parameter k s is an integer that satisfies and

[0035] ​For the Doppler of the narrow speed range target crossing two compensation intervals, the adjusted interval using the fractional Doppler ambiguity compensation function can contain the Doppler frequency range generated by the narrow speed range target, the calculation number of CZT is reduced from two to one, and the calculation amount is reduced.

[0036] Step four: using the CZT formula with the fractional Doppler ambiguity compensation function obtained in step three to transform the pulse compression signal S PC (f l ,m) in the slow time dimension, and distance migration compensation is obtained. l ,k) is obtained.

[0037] Step four: using the CZT formula with the fractional Doppler ambiguity compensation function obtained in step three to transform the pulse compression signal S PC (f l ,m) in the slow time dimension, and distance migration compensation is obtained.

[0038]

[0039] Wherein, X(f l ,k) is the fast time frequency-Doppler frequency two-dimensional data matrix after distance migration compensation, k is the Doppler frequency point serial number, and distance migration compensation of the narrow speed range target is realized.

[0040] Step five: performing IFFT on the fast time dimension of the two-dimensional spectrum X(f l ,k) to change the fast time frequency back to the time domain, and the distance-Doppler two-dimensional matrix X(l,k) after distance migration compensation is obtained.

[0041] Step six: detecting the two-dimensional data containing the distance information and Doppler information of the moving target obtained in step five to obtain the distance and speed information of the target.

[0042] Advantages:

[0043] 1. The high-efficiency target distance migration compensation method based on Chirp-Z transformation disclosed in the application performs FFT on the reference signal and the echo signal along the fast time dimension, changes the fast time time domain to the frequency domain, performs conjugate multiplication, realizes pulse compression processing of the echo signal, makes the target echo energy more concentrated in the fast time dimension, changes the Doppler ambiguity compensation function from an integer form to a fractional form, changes the compensation Doppler frequency interval from a fixed value to a value that can be changed as needed, uses the CZT formula with the fractional Doppler ambiguity compensation function to transform the pulse compression signal, compensates the target distance migration, improves the target distance migration compensation efficiency, performs IFFT on the fast time dimension of the signal to change the fast time frequency domain back to the time domain, and detects the two-dimensional data containing the distance information and Doppler information of the moving target to obtain the distance and speed information of the target.

[0044] 2. The high-efficiency target range migration compensation method based on Chirp-Z transform, which transforms the Doppler ambiguity compensation function from an integer form to a fractional form, changes the CZT compensation Doppler frequency interval from a fixed value to a value that can be changed as needed, and enables the compensation Doppler frequency interval to cover the Doppler range generated by a narrow-speed target in the case of a Doppler frequency spanning two compensation intervals.

[0045] 3. The high-efficiency target range migration compensation method based on Chirp-Z transform, which uses the CZT formula with a fractional Doppler ambiguity compensation function to transform the slow-time dimension of the pulse-compressed signal S PC (f l ,m) to obtain a fast-time frequency-Doppler frequency two-dimensional data matrix X(f l ,k) after range migration compensation, reduces the number of CZT calculations from two to one, and greatly improves the CZT calculation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is an image drawn using part of the data in the target area in the range-Doppler result after range migration compensation, where (a) is a three-dimensional view and (b) is a two-dimensional view;

[0047] Figure 2 is an image drawn using part of the data in the target area in the range-Doppler result without range migration compensation, where (a) is a three-dimensional view and (b) is a two-dimensional view;

[0048] Figure 3 is an image drawn using part of the data in the target area in the pulse compression result without range migration compensation, where (a) is a three-dimensional view and (b) is a two-dimensional view;

[0049] Figure 4 is an image drawn using part of the data in the target area in the pulse compression result after range migration compensation, where (a) is a three-dimensional view and (b) is a two-dimensional view;

[0050] Figure 5 is an image drawn using part of the data in the target area in the range-Doppler result after migration compensation when the compensation ambiguity number is set to 0, where (a) is a three-dimensional view and (b) is a two-dimensional view;

[0051] Figure 6 is an image drawn using part of the data in the target area in the range-Doppler result after migration compensation when the compensation ambiguity number is set to -1, where (a) is a three-dimensional view and (b) is a two-dimensional view;

[0052] Figure 7 A flow chart of the high-efficiency target distance migration compensation method based on Chirp-Z transform is disclosed in the present application. DETAILED DESCRIPTION

[0053] For better illustrating the purposes and advantages of the present application, the following further illustrates the content of the present application in combination with the drawings and examples.

[0054] The present embodiment uses simulation experiment to illustrate the effectiveness of the disclosed method, and the simulation software used is MATLAB. The radar transmitting signal is set to be a linear frequency modulation signal, the signal baseband bandwidth is 20MHz, the time width is 4us, the pulse repetition frequency is 2000Hz, the carrier frequency is 1GHz, the baseband sampling rate is 160MHz, the sampling point number of the transmitting pulse signal is 640, the sampling point number of the echo pulse signal is 1706, the detection distance range is 0 to 1km, and the accumulated pulse number is 512. Two point targets are set in the detection space, the distance between target 1 and the radar at the initial moment is 0.5km, the radial velocity between target 1 and the radar is 120m / s, the velocity direction is positive in the direction towards the radar, the distance between target 2 and the radar at the initial moment is 0.6km, the radial velocity between target 2 and the radar is -120m / s, and the received target signal signal-to-noise ratio is -20dB.

[0055] The specific implementation steps are as follows:

[0056] Step one: FFT calculation is performed on the reference signal and the echo signal along the fast time dimension, and the fast time time domain is transformed to the fast time frequency domain.

[0057] FFT calculation of 2048 points is performed on the sampled reference signal along the fast time dimension, which is expressed by the following formula

[0058] U(f l ,m)=FFT[u(l,m)]=A U P(f l ,m) (10)

[0059] Wherein, U(f l ,m) represents the two-dimensional data matrix of the transformed reference signal, the fast time frequency dimension point number is 2048, and the slow time dimension point number is 512.

[0060] There are two uniform motion targets in the radar detection space, and the target echo signal received by the radar is the superposition of the echoes of the two targets. After the down-conversion processing of the echo, the obtained baseband echo signal is

[0061]

[0062] Wherein, A ri represents the baseband echo signal of target i, R idenotes the initial distance between target i and radar, v i denotes the velocity of target i, i = 1 denotes target 1, i = 2 denotes target 2. In order to make the data produced by simulation closer to the actual, Gaussian white noise is added in the echo signal, so that the signal-to-noise ratio of the echo signal is -20dB.

[0063] The 2048-point FFT calculation is performed on the echo signal along the fast time dimension, which is expressed by the following formula

[0064]

[0065] where S(f l ,m) denotes the two-dimensional data matrix of the echo signal after transformation, the number of points in the fast time frequency dimension is 2048 points, and the number of points in the slow time dimension is 512 points, A Ri denotes the fast time frequency domain amplitude of the echo signal of target i.

[0066] Step two: the echo signal matrix S R (f l ,m) obtained in step one and the reference signal matrix U(f l ,m) are conjugated and multiplied, the pulse compression processing of the echo signal is realized in the frequency domain, and the target echo energy is more concentrated in the fast time dimension.

[0067] The echo signal matrix obtained in step one and the transmit signal matrix are conjugated and multiplied, and the pulse compression in the frequency domain is realized according to formula (6)

[0068] S PC (f l ,m) = S R (f l ,m) · U * (f l ,m) (13)

[0069] where S PC (f l ,m) denotes the two-dimensional data matrix of the echo signal after pulse compression.

[0070] In order to intuitively display the pulse compression result and the range migration phenomenon, the IFFT is performed on S PC (f l ,m) in the fast time frequency dimension, the fast time frequency domain is transformed into the fast time time domain, S PC (l,m) is obtained, and the part of data where the target is located in the processed data result is plotted into image 1. As Figure 1 shown, after pulse compression, the target echo energy is more concentrated in the fast time dimension, but due to the target movement, the pulse shift phenomenon of the energy peaks of the two targets is obvious, and the range migration problem is serious.

[0071] In order to intuitively show the influence of the range migration on the coherent integration gain, the S PC (1, m) is made, and the uncompensated range-Doppler two-dimensional matrix C(l, k) is obtained, as shown in Figure 2 Figure 2 The data processing result in the table is influenced by the range migration, and the target energy is spread to the surrounding cells, resulting in a decrease in the accumulation gain.

[0072] Step three: transform the Doppler ambiguity compensation function from an integer form to a fractional form, change the Doppler frequency compensation interval of the CZT from a fixed value to a value that can be changed as needed, so that the compensation Doppler frequency interval can cover the Doppler range generated by the narrow speed target, and improve the compensation calculation efficiency.

[0073] In the traditional method, an integer form Doppler ambiguity compensation function is used for Doppler ambiguity compensation. After the Doppler ambiguity compensation, the Doppler frequency compensation interval of the CZT method is changed to [qf r , (q+1)f r ). In this embodiment, the Doppler frequency f d1 =800Hz generated by the target 1 is within the compensation Doppler frequency interval [0, 2000) Hz of q=0, and the Doppler frequency f d2 =-800Hz generated by the target 2 is within the compensation Doppler frequency interval [-2000, 0) Hz of q=-1, and the target echo spans two compensation intervals.

[0074] The Doppler ambiguity compensation is performed on the frequency domain pulse compression result S(f l , m) using the ambiguity numbers 0 and -1 respectively, and then the CZT calculation is performed, and the fast time IFFT is performed, and the obtained results are shown in Figure 5 and Figure 6 . Figure 5 It is shown that when the compensation ambiguity number is 0, the compensated Doppler frequency range is [0, f r )=[0, 2000) Hz, so only the target 1 can be effectively compensated for range migration, and the target 2 cannot be compensated for migration, and even causes further spreading of the target 2 energy. Similarly, Figure 6 It is shown that when the compensation ambiguity number is -1, only the target 2 can be effectively compensated. The traditional method needs two compensation operations in total to complete the range migration compensation of the target in the detection speed range.

[0075] Transform the Doppler ambiguity compensation function from an integer form to a fractional form, set the transform point number N of the CZT to 512, and set the fractional ambiguity number parameter k s to N / 2, and the fractional Doppler ambiguity compensation function is

[0076] ​

[0077] The compensation frequency range adjusted using the fractional Doppler blur compensation function becomes: The compensated Doppler range can cover the target Doppler range.

[0078] In this embodiment, when the Doppler frequency of a target with a narrow velocity range spans two compensation intervals, the interval adjusted by the fractional Doppler fuzzy compensation function can include the Doppler frequency range generated by the target with a narrow velocity range, reducing the number of CZT calculations from two to one, thus reducing the computational load.

[0079] Step 4: Use the CZT formula with the fractional Doppler ambiguity compensation function obtained in Step 3 to process the pulse-compression signal S. PC (f l Transforming the slow time dimension of f(m) yields the distance migration compensated fast time frequency-Doppler frequency two-dimensional data matrix X(f). l ,k).

[0080] The CZT formula, with the fractional Doppler ambiguity compensation function obtained in step three, is used to analyze the post-pulse compression signal S. PC (f l The slow time dimension of m is compensated using the following formula:

[0081]

[0082] Where X(f) l ,k) is a two-dimensional data matrix of fast time frequency and Doppler frequency after range migration compensation. The fast time frequency dimension has 2048 points and the Doppler dimension has 512 points. k is the Doppler frequency point number, which realizes range migration compensation for targets with narrow velocity range.

[0083] Step 5: Analyze the two-dimensional spectrum X(f) l Perform an IFFT on the fast time dimension of (l,k) to transform the fast time frequency back to the time domain, and obtain the distance-Doppler two-dimensional matrix X(l,k) after distance migration compensation.

[0084] like Figure 1 As shown, after one CZT calculation, the range migration compensation for both targets was effectively achieved. The compensated targets have more concentrated energy, higher peak amplitude, and a higher cumulative gain compared to the previous method. Figure 2 The result before compensation was improved by 10.2 dB.

[0085] To further illustrate the effect of the above steps on range migration compensation, a 512-point Doppler IFFT was performed on X(l,k) to obtain the time-domain pulse compression result after range migration compensation. The results near the target signal peak are shown below. Figure 4 As shown, withFigure 3 The comparison shows that the target signal envelope position no longer changes with the slow time, and the distance migration is effectively compensated.

[0086] Step six: detecting the two-dimensional data containing the distance information and Doppler information of the moving target obtained in step five, obtaining the distance 0.5 km and the speed 120 m / s of target 1, and obtaining the distance 0.6 km and the speed -120 m / s of target 2.

[0087] The above detailed description further describes the purpose, technical scheme and beneficial effects of the application. It should be understood that the above description is only a specific embodiment of the application and is not used to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A high-efficiency target range migration compensation method based on Chirp-Z transform, characterized in that: The method comprises the following steps: Step one: FFT calculation is performed on the reference signal and echo signal along the fast time dimension, and the fast time time domain is transformed into the fast time frequency domain; Step 2: Convert the echo signal matrix S obtained in Step 1 into... R (f l (m) and reference signal matrix U(f) l The conjugate multiplication of m) enables pulse compression processing of the echo signal in the frequency domain, making the target echo energy more concentrated in the fast time dimension; Step three: the Doppler ambiguity compensation function is transformed from an integer form into a fractional form, the Doppler frequency interval compensated by the CZT is changed from a fixed value into a value that can be changed as required, and the Doppler frequency interval compensated can cover the Doppler range generated by a narrow speed target; Step four: using the CZT formula with the fractional Doppler ambiguity compensation function obtained in step three to process the signal S PC (f l , m) in the slow time dimension to obtain the range migration compensated fast time frequency-Doppler frequency two-dimensional data matrix X(f l , k); Step five: IFFT is performed on the fast time dimension of the two-dimensional spectrum X(f l , k) to convert the fast time frequency back to the time domain, obtaining the range-migrated compensated range-Doppler two-dimensional matrix X(l, k). Step six: the two-dimensional data containing the distance information and Doppler information of the moving target obtained in step five are detected to obtain the distance and speed information of the target.

2. The high-efficiency range migration compensation method based on Chirp-Z transform of claim 1, wherein: The implementation method of step one is that, The reference signal two-dimensional data matrix is u(l,m) = A u p(l,m) (1) wherein A u is the reference signal amplitude, p(l,m) is the baseband signal transmitted by the radar, l represents the fast time sample point number, the total number of fast time samples is L, m represents the slow time sample point number, and the total number of slow time samples is M; FFT calculation is performed on the sampled reference signal along the fast time dimension, and the calculation is represented by the following formula U(f l ,m) = FFT[u(l,m)] = A U P(f l ,m) (2) wherein U(f l ,m) represents the transformed reference signal two-dimensional data matrix, A U represents the transformed reference signal amplitude, P(f l ,m) represents the baseband signal spectrum, f l represents the fast time-frequency domain sampling point sequence number; Suppose that there is a uniform speed moving target in the radar detection space, the initial distance between the target and the radar is R0, the radial motion speed is v0, and the distance R between the target and the radar changes with the slow time according to the following equation R = R0- v0mT r (3) where T r is the pulse repetition period; The radar receives the echo signal of the target, performs down-conversion processing, and obtains the baseband echo signal where A r is the baseband echo signal amplitude, f c is the carrier frequency; the center position of the pulse envelope shifts with the slow time, as indicated by equation (4), and when the envelope shift exceeds the distance unit, the range migration problem occurs, resulting in the dispersion of target signal energy and the decrease of coherent accumulation gain; FFT calculation is performed on the echo signal along the fast time dimension, and the calculation is represented by the following formula where S(f l , m) represents the two-dimensional data matrix of the transformed echo signal, A R represents the fast time frequency domain amplitude of the echo signal; the phenomenon of the envelope of the time domain in equation (5) shifting with the slow time m is shown in the frequency domain as the coupling of the fast time frequency f l and the slow time m.

3. The high-efficiency range migration compensation method based on Chirp-Z transform of claim 2, wherein: The implementation method of step two is that, The echo signal matrix and the transmitted signal matrix obtained in step one are multiplied, and pulse compression in the frequency domain is realized according to formula (6) S PC (f l ,m)=S R (f l ,m)·U * (f l ,m) (6) Wherein, * represents the conjugate operation, S PC (f l , m) represents the two-dimensional data matrix of the echo signal after pulse compression. After pulse compression, the echo energy of the target is more concentrated in the fast time dimension.

4. The high-efficiency range migration compensation method based on Chirp-Z transform of claim 3, wherein: The implementation method of step three is that, The Doppler frequency range compensated by the CZT method is [0, f r , where f r is the pulse repetition frequency; the Doppler ambiguity compensation function in integer form is Wherein, q is a fuzzy number, the value range is an integer; after Doppler fuzzy compensation, the Doppler frequency interval compensated by the CZT method becomes [qf r ,(q+1)f r ); the integer form of the fuzzy compensation function is transformed into a fractional form, and the fractional Doppler fuzzy compensation function is defined as The compensated frequency interval adjusted using the fractional Doppler ambiguity compensation function becomes where N is the number of CZT points, and k is the fractional ambiguity number parameter s to satisfy and is an integer; For the case that the Doppler of the narrow speed range target crosses two compensation intervals, the interval adjusted by using the fractional Doppler ambiguity compensation function can contain the Doppler frequency range generated by the narrow speed range target, and the CZT calculation times are reduced from two times to one time.

5. The high-efficiency range migration compensation method based on Chirp-Z transform of claim 4, wherein: The implementation method of step four is that, The CZT formula with the fractional Doppler blurring compensation function from step three is used on the pulse-echo signal S PC (f l , m) is compensated in the slow time dimension as follows wherein X(f l is the distance migration compensated fast time frequency-Doppler frequency two-dimensional data matrix, k is the Doppler frequency sequence number, and distance migration compensation for a narrow speed range target is achieved.

Images