Plasma sheath-coated target coherent accumulation method, system, device and storage medium based on improved keystone

Abstract

The present invention discloses a plasma sheath-encapsulated target coherent accumulation method, system, device and storage medium based on improved keystone. The coherent accumulation method is specifically as follows: establishing a multi-period radar echo model of a plasma sheath-encapsulated target; extracting the intra-pulse Doppler frequency of the multi-period radar echo signal of the plasma sheath-encapsulated target; constructing an intra-pulse Doppler frequency compensation function and determining a scale transformation factor; performing cyclic compensation through the intra-pulse Doppler frequency compensation function, performing energy focusing on all compensation results, and obtaining a frequency domain representation of the compensated pulse compression result; transforming the frequency domain representation of the compensated pulse compression result to obtain a coherent accumulation result Y, and obtaining the initial distance and movement speed of the target through peak search. The present invention estimates the movement speed and initial distance through peak search, significantly improving the energy gain of the true target and realizing the detection of hypersonic aircraft.

Description

Technical Field

[0001] The invention belongs to the technical field of radar target detection, and relates to a plasma sheath-enclosed target coherent accumulation method, system, equipment and storage medium based on an improved keystone. Background Art

[0002] When a hypersonic vehicle flies in near space at a speed greater than 10 Ma, the air molecules in the stationary area are subjected to "aerodynamic thermal ionization" to form plasma, and the plasma and the vehicle move relative to each other to form a plasma sheath. Since the plasma sheath is an electromagnetic medium composed of a large number of charged particles, when detecting a target covered by the plasma sheath, the radar echo will experience amplitude attenuation, phase distortion, and an increase in Doppler frequency components, resulting in a mismatch in the traditional target detection algorithm and the appearance of "false targets" in the one-dimensional range image, which seriously affects the reliable detection of hypersonic vehicles.

[0003] Existing research mainly aims at suppressing traditional false targets caused by delay, asynchronous interference, surround and ghosting, but the false targets generated by plasma sheath are very different from traditional targets, and the "false targets" are stable in each cycle echo. At the same time, the high-speed motion characteristics of hypersonic targets make the cross-distance unit walk phenomenon appear, which further affects the coherent accumulation of hypersonic aircraft. Therefore, there is no effective suppression technology to effectively perform coherent accumulation of multi-cycle echo signals of plasma sheath-covered targets. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a plasma sheath-enclosed target coherent accumulation method based on improved keystone, which performs coherent accumulation of multi-cycle echo signals of a plasma sheath-enclosed target moving at a uniform speed, estimates the movement speed and initial distance through peak search, greatly improves the energy gain of the true target, realizes the detection of hypersonic aircraft, and solves the problems existing in the prior art.

[0005] The second object of the present invention is to provide an improved Keystone plasma sheath-encapsulated target coherent accumulation system.

[0006] A third object of the present invention is to provide an electronic device.

[0007] A fourth object of the present invention is to provide a computer storage medium.

[0008] The technical solution adopted by the present invention is a plasma sheath-coated target coherent accumulation method based on an improved keystone, comprising the following steps:

[0009] Step 1, establish a multi-cycle radar echo model of the plasma sheath covering the target;

[0010] Step 2: Extract the intra-pulse Doppler frequency f of the multi-period radar echo signal of the target covered by the plasma sheath di ;

[0011] Step 3: Construct the intrapulse Doppler frequency compensation function Based on the intrapulse Doppler frequency compensation function Improved scale transformation factor t of keystone algorithm u ;

[0012] Step 4: Pulse compression and Fourier transform are performed on the multi-period radar echo signal of the plasma sheath-enclosed target to obtain the range domain representation y(t q ,f), through the intrapulse Doppler frequency compensation function For y(t q ,f) Perform cyclic compensation, focus the energy of all compensation results, and obtain the frequency domain representation of the compensated pulse compression result y com (t q ,f),Effectively suppress false targets;

[0013] Step 5, based on the scale transformation factor t u , the frequency domain representation of the compensated pulse compression result y is obtained by sinc interpolation com (t q ,f) transform to obtain the coherent accumulation result Y, and obtain the initial distance and movement speed of the target through peak search.

[0014] Furthermore, in the Step 1, the plasma sheath covers the target radar echo model Echo (t q ,t) see the following formula:

[0015]

[0016] Among them, R m represents the complex reflection coefficient at each reference point of the target, m is the reference point number of the target surface m = 1, 2, 3....M, t represents the time series, τ0 represents the time delay of the initial distance of the target, τ q represents the target echo delay of each period, the number of echo signal periods q=1, 2, 3....Q, j represents an imaginary number, f dm represents the Doppler frequency component of the echo signal coupled at each reference point, f c Indicates the carrier frequency.

[0017] Furthermore, in Step 2, the intrapulse Doppler frequency f di How to obtain:

[0018] Based on the multi-period radar echo model of the plasma sheath covering the target, the echo signal is processed by using Wigner transform to obtain the time-frequency curve ξ(t,f) of the echo signal:

[0019]

[0020] Among them, R m represents the complex reflection coefficient at each reference point of the target, m is the reference point number on the target surface m = 1, 2, 3....M, f represents the frequency, f c Indicates the carrier frequency, f dm represents the Doppler frequency component of the echo signal coupled at each reference point, k represents the modulation frequency of the echo signal, t represents the time series, CT represents the sum of all cross terms, and δ() represents the impulse function;

[0021] The time-frequency curve ξ(t,f) is converted to polar coordinates through Hough transform to achieve effective accumulation of the energy of the time-frequency curve ξ(t,f). The peak value is searched for the accumulated result to obtain the peak coordinates (ρ i ,θ i ), calculate all measurable intrapulse Doppler frequencies f by peak coordinates di :

[0022]

[0023] Among them, l represents the image width after Hough transform, and Fs represents the sampling frequency.

[0024] Furthermore, in Step 3, the intrapulse Doppler frequency compensation function Determined according to the following formula:

[0025]

[0026] Wherein, i is the i-th extracted Doppler frequency i=1, 2, 3...I;

[0027] The scaling factor t u Determined according to the following formula:

[0028]

[0029] Among them, t q represents a slow time series; the scale transformation factor t u Traditional scale factor mismatches are eliminated.

[0030] Furthermore, the Step 4 is specifically as follows:

[0031] Based on the carrier frequency f c , pulse width T p, the actual speed of the target V, the initial distance of the target R0, set the matched filter h(t), and the matched filter h(t), the radar echo signal Echo(t q ,t) is convolved and output to obtain the pulse compression result y(t q ,t):

[0032]

[0033] Among them, f dv represents the Doppler frequency component corresponding to the actual target velocity V, B represents the bandwidth, τ q represents the target echo delay in each period, τ0 represents the time delay of the target initial distance;

[0034] The pulse compression result y(t q ,t) is transformed into the frequency domain representation of the pulse compression result y(t q ,f), through the intrapulse Doppler frequency compensation function For y(t q f) Perform cyclic compensation, each compensation eliminates the influence of Doppler frequency in the pulse; perform energy focusing on all compensation results to obtain the frequency domain representation of the pulse compression result after compensation y com (t q ,f).

[0035] Furthermore, the Step 5 is specifically as follows:

[0036] According to the scaling factor t u Frequency domain characterization of pulse compression results com (t q ,f), through the sinc interpolation process, the correction of the movement of the cross-distance unit is realized, and the virtual time axis transformation result y is obtained com (t u ,f):

[0037]

[0038] Among them, η(t u ) is the velocity blur elimination term, f c represents the carrier frequency, f represents the frequency, t q Represents a slow time series, the number of echo signal cycles q = 1, 2, 3....Q;

[0039] For com (t u ,f) Perform inverse Fourier transform to obtain the pulse compression result y related to virtual time com (t u ,t), for y com (tu ,t) perform multi-cycle coherent accumulation to obtain the coherent accumulation result Y of the multi-cycle echo;

[0040] Perform peak search on the coherent accumulation result Y and obtain the estimated initial distance R through the peak coordinates esti and estimated motion speed V esti .

[0041] Furthermore, the velocity blur elimination term η(t u ) is determined according to the following formula:

[0042]

[0043] Where W represents the speed measurement fuzzy number; for the repetition period T r Find the reciprocal and get the repetition frequency f r , take all measurable intrapulse Doppler frequencies f di The peak value of the pulse is searched for the maximum intrapulse Doppler frequency, combined with the repetition frequency f r , and obtain the velocity fuzzy number W of the radar target.

[0044] A plasma sheath-encapsulated target coherent accumulation system based on an improved keystone, comprising:

[0045] A radar echo model building module is used to build a multi-period radar echo model of a target covered by a plasma sheath;

[0046] The intra-pulse Doppler frequency extraction module is used to extract the intra-pulse Doppler frequency f of the multi-period radar echo signal of the plasma sheath-covered target. di ;

[0047] Compensation function building module, used to build intrapulse Doppler frequency compensation function Based on the intrapulse Doppler frequency compensation function Construct the scaling factor t u ;

[0048] The compensation module is used to perform pulse compression processing and Fourier transform on the multi-period radar echo signal of the plasma sheath-enclosed target to obtain the distance domain representation y(t q ,f), through the intrapulse Doppler frequency compensation function For y(t q ,f) Perform multi-channel parallel compensation, focus the energy of the compensation results, and obtain the frequency domain representation of the compensated pulse compression results y com (t q ,f);

[0049] Coherent accumulation module for scaling factor t u, the frequency domain representation of the compensated pulse compression result y is obtained by sinc interpolation com (t q ,f) transform and obtain the coherent accumulation result Y based on the improved keystone algorithm, and obtain the initial distance and movement speed of the target through peak search.

[0050] An electronic device adopts the above method to realize the coherent accumulation of plasma sheath covering the target.

[0051] A computer storage medium stores at least one program instruction, which is loaded and executed by a processor to implement the plasma sheath covering target coherent accumulation method.

[0052] The beneficial effects of the present invention are:

[0053] (1) The present invention aims at a plasma sheath-enclosed target moving at a uniform speed. By using a multi-channel parallel compensation method of intra-pulse Doppler frequency, the energy gain of the true target and the energy ratio of the true / false target are effectively improved, and the one-dimensional range image "false target" of the radar echo can be effectively suppressed.

[0054] (2) The present invention improves the scale transformation factor based on the intrapulse Doppler frequency component, solves the mismatch problem of the traditional Keystone algorithm, realizes the effective coherent accumulation of multi-cycle echo signals, and combines the intrapulse Doppler frequency cycle compensation to significantly improve the energy gain of the true target.

[0055] (3) Since the plasma sheath has fluid properties, the method proposed in the present invention is suitable for the coherent accumulation of multi-period radar echoes of a composite target of a fluid-encapsulated rigid body and the suppression of "false targets" caused by the fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 This is a flow chart of Example 1 of the present invention.

[0058] Figure 2 This is the Hough transform principle diagram.

[0059] Figure 3 It is the pulse compression result of radar echo signal of multiple cycles of plasma sheath-enclosed target according to the embodiment of the present invention.

[0060] Figure 4 This is the result of directly performing coherent accumulation on a multi-period radar echo model in an embodiment of the present invention.

[0061] Figure 5 It is the coherent accumulation result of the plasma sheath covering the target based on the improved keystone in the embodiment of the present invention. DETAILED DESCRIPTION

[0062] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0063] The basic concept of the embodiment of the present invention is as follows:

[0064] The plasma sheath with fluid characteristics changes the target characteristics of the target to be measured, forming a composite target of a fluid-encapsulated rigid body. When the composite target is detected, the composite modulation effect of the plasma sheath on the generated echo signal causes the failure of the coherent accumulation of multi-cycle echo signals. The embodiment of the present invention extracts the intra-pulse Doppler frequency of the echo coupling of the plasma sheath-encapsulated target, reveals the generation mechanism of the false target through multi-domain feature analysis, and on this basis, constructs a phase compensation function and improves the scale transformation factor to achieve effective coherent accumulation of multi-cycle echo signals of the plasma sheath-encapsulated target.

[0065] Embodiment 1,

[0066] A plasma sheath-coated target coherent accumulation method based on improved keystone, such as Figure 1 As shown, the following steps are included:

[0067] Step 1: Establish the radar echo model Echo(t q ,t):

[0068] Enter the complex reflection coefficient R at each reference point of the target m , m is the reference point number of the target surface m = 1, 2, 3...M, obtain the amplitude attenuation and phase modulation information of the echo signal at each reference position of the plasma sheath-enclosed target; input the actual target movement speed V, the target initial distance R0, the speed of light c, the number of echo signal cycles q = 1, 2, 3...Q during modeling, calculate the time delay τ0 of the target initial distance, the target echo delay τ of each cycle q ; Input the velocity component v at each reference point of the plasma sheath m , carrier frequency f c, calculate the Doppler frequency component f of the echo signal coupling at each reference point dm ; Input pulse width T p , bandwidth B, calculate sampling frequency Fs, modulation frequency k of echo signal; input repetition period T r , combined pulse width T p , determine the time series t, slow time series t q Based on the above parameters, according to the linear frequency modulation pulse signal form, the radar echo model Echo (t q ,t):

[0069]

[0070] j represents an imaginary number.

[0071] The present invention solves the echo signal of the target covered by the plasma sheath by establishing a radar echo model of Q cycles of the target covered by the plasma sheath, providing a basis for extracting multi-domain features of the echo signal and revealing the mechanism of "false target" generation.

[0072] Step 2: Extract the intra-pulse Doppler frequency f of the radar echo signal of the target covered by the plasma sheath di and velocity fuzzy number W: radar echo model Echo(t q ,t), the echo signal is processed by Wigner transform to obtain the time-frequency curve ξ(t,f) of the echo signal:

[0073]

[0074] CT represents the sum of all cross terms, f represents the frequency, and δ() represents the impulse function;

[0075] The time-frequency curve ξ(t,f) is converted to polar coordinates using Hough transform to achieve effective accumulation of the energy of the time-frequency curve ξ(t,f). The peak value is searched for the accumulated result to obtain the peak coordinates (ρ i ,θ i ), calculate all measurable intrapulse Doppler frequencies f by peak coordinates di :

[0076]

[0077] Where l represents the image width after Hough transform.

[0078] For the repetition period T r Find the reciprocal and get the repetition frequency f r , take all measurable intrapulse Doppler frequencies f dipeak value, search for the maximum intrapulse Doppler frequency, and combine the repetition period T r , and obtain the velocity fuzzy number W of the radar target.

[0079] The present invention obtains the intrapulse Doppler frequency f by Wegener Hoff processing. di , that is, echo signal coupling; the velocity ambiguity number W of the radar target is calculated based on the frequency f, which is used to construct the intra-pulse Doppler frequency compensation function and the scaling factor t u Provide parameter support.

[0080] Step 3: Construct the intrapulse Doppler frequency compensation function and the scaling factor t u :

[0081] Based on the time series t, the frequency f corresponding to the time domain is determined, and the total measurable intrapulse Doppler frequency f coupled with the radar echo is calculated. di , modulation frequency k, construct the intrapulse Doppler frequency compensation function as follows:

[0082]

[0083] i is the i-th extracted Doppler frequency, i=1, 2, 3...I; the combined frequency f, the intrapulse Doppler frequency f of the radar echo signal of the plasma sheath-enclosed target di , carrier frequency f c , construct the scale transformation factor t u as follows:

[0084]

[0085] The present invention provides a basis for effectively suppressing the "false target" generated by the plasma sheath by constructing an intrapulse Doppler frequency compensation function. The conventional scale factor mismatch is eliminated by constructing a scale transformation factor, providing a basis for realizing the coherent accumulation of multi-cycle echo signals of the plasma sheath-enclosed target.

[0086] Step 4, solve the frequency domain representation y of the compensated pulse compression result com (t q ,f):

[0087] Based on the carrier frequency f c , pulse width T p , target actual speed V, target initial distance R0, set the matched filter h(t), match the matched filter h(t), radar echo signal Echo(t q ,t) is convolved and output to obtain the pulse compression result y(t q ,t):

[0088]

[0089] Among them, f dv Indicates the Doppler frequency component corresponding to the actual moving speed V of the target.

[0090] The pulse compression result y(t q ,t) is transformed by Fourier transform (FFT) to obtain the frequency domain representation of the pulse compression result y(t q ,f), using the intrapulse Doppler frequency compensation function For y(t q ,f) Perform compensation once, focus the compensation result, and obtain the frequency domain representation of the pulse compression result after compensation y com (t q ,f):

[0091]

[0092] By solving the pulse compression result y(t q ,t), the one-dimensional range image characteristics of the plasma sheath covering the target were obtained, revealing that the "false target" was formed by the intrapulse Doppler frequency. Based on the compensation function constructed by the intrapulse Doppler frequency, the frequency domain characterization of the pulse compression result y(t q ,f) Perform cyclic compensation, each compensation eliminates the influence of the intra-pulse Doppler frequency (after the intra-pulse Doppler frequency is eliminated, the measured distance of the target is at the real position), and all compensation results are energy focused, which improves the energy gain of the real target, improves the energy ratio of the real / false target, and realizes the effective suppression of the false target.

[0093] Step 5: Coherent accumulation of multi-period echoes based on the improved keystone algorithm com (t u ,f):

[0094] According to the scaling factor t u Frequency domain characterization of pulse compression results com (t q ,f), through the sinc interpolation process, the correction of the movement of the cross-distance unit is realized, and the virtual time axis transformation result y is obtained com (t u ,f):

[0095]

[0096] Among them, η(t u ) is the velocity blur elimination term. By using the above formula and converting through the virtual time axis, the phenomenon of moving across distance units can be effectively solved.

[0097] Forcom (t u ,f) Perform inverse Fourier transform to obtain the pulse compression result y related to virtual time com (t u ,t), for y com (t u ,t) Perform multi-cycle coherent accumulation to obtain the coherent accumulation result Y of the multi-cycle echo, perform peak search on the coherent accumulation result Y, and obtain the estimated initial distance R through the peak coordinates esti and estimated motion speed V esti .

[0098] The present invention solves the problem of mismatch of scale transformation factors of the traditional Keystone algorithm based on the improved scale transformation factor of the intrapulse Doppler frequency. By utilizing the improved scale factor, the pulse compression frequency domain representation of the multi-cycle echo signal is transformed into a virtual time axis, which solves the cross-distance unit movement caused by the excessively high target movement speed, realizes the effective coherent accumulation of multi-cycle echoes of the plasma sheath-covered target, and estimates the movement speed and initial distance of the target through peak extraction, laying a foundation for reliable detection and even stable tracking of hypersonic targets in near space.

[0099] Embodiment 2,

[0100] The plasma sheath-enclosed target coherent accumulation method based on the improved keystone is the same as that in Example 1, wherein the plasma sheath-enclosed target radar echo model Echo (t q ,t), including the following steps:

[0101] 2.1) Calculate radar signal parameters:

[0102] Using the bandwidth B, calculate the sampling frequency Fs = 10*B; using the sampling frequency Fs, pulse width T p , Repeat period T r , determine the time series t = 1:1 / Fs:(T r -T p / 2); using pulse width T r , the number of echo signal cycles q = 1, 2, 3....Q, the slow time series is determined as follows:

[0103] t q =(q-1)×T r

[0104] Using pulse width T p , bandwidth B, and determine the modulation frequency of the echo signal as follows:

[0105] k=B / T p

[0106] 2.2) Calculate radar echo delay parameters and coupled Doppler frequency:

[0107] Using the target initial distance R0, the target actual movement speed V during modeling, the speed of light c, and the repetition period T r , calculate the radar echo initial distance delay τ0 = 2 × R0 / c, each cycle target echo delay τ q =2×(R0-V×t q ) / c; using the velocity component v at each reference point of the plasma sheath m , speed of light c, carrier frequency f c , calculate the intrapulse Doppler frequency component f coupled with the echo signal dm =2×v m ×f c / c;

[0108] 2.3) Establish the radar echo model Echo(t q ,t): According to the radar signal parameters, radar echo delay parameters, and coupled Doppler frequency, the radar echo signal Echo (t q ,t) are as follows:

[0109]

[0110] The above formula represents the echo signal of the qth period when the plasma sheath covers the target.

[0111] Embodiment 3,

[0112] The plasma sheath-encapsulated target coherent accumulation method based on the improved keystone is the same as that in Embodiment 1-2, wherein the extraction of the intrapulse Doppler frequency f of the radar echo signal of the plasma sheath-encapsulated target in step S2 is di and the speed measurement fuzzy number W, including the following steps:

[0113] 3.1) Calculate the Wigner transform result of the radar echo of the plasma sheath covering the target: Based on the Wigner transform, the radar echo signal Echo (t q ,t) for processing:

[0114]

[0115] Wherein, h represents the delay amount when the echo signal is autocorrelated, and ()* represents the conjugate processing of the echo signal. * Represents the conjugate of the echo signal; the time-frequency curve ξ(t,f) of the echo signal is obtained by the above formula:

[0116]

[0117] 3.2) Energy accumulation of time-frequency curve based on Hough transform: Figure 2 As shown, the time-frequency curve is processed using Hough transform and polar coordinate transformation is performed:

[0118] tcosθ+fsinθ=ρ ρ≥0,0≤θ≤π

[0119] Line f = f c +f dm Each point on +kt corresponds to a curve in polar coordinates, and the curves corresponding to all points on the straight line intersect at one point in polar coordinates, forming an energy peak.

[0120] 3.3) Extract all measurable intrapulse Doppler frequencies f di :

[0121] Perform peak search on the accumulated results to obtain the peak coordinates (ρ i ,θ i ), calculate all measurable intrapulse Doppler frequencies f by peak coordinates di :

[0122]

[0123] Where l represents the image width after Hough transform.

[0124] 3.4) Estimate the maximum velocity fuzzy number W:

[0125] Using the repetition period T r , and get the repetition frequency f r =1 / T r ; Take all measurable intrapulse Doppler frequencies f di The peak value f dmax , combined with the repetition frequency f r , estimate the maximum velocity fuzzy number W:

[0126] W = floor[2×f dmax / f r ].

[0127] Embodiment 4,

[0128] The plasma sheath-coated target coherent accumulation method based on the improved keystone is the same as that in Embodiment 1-3, wherein the step S3 described in constructing the intrapulse Doppler frequency compensation function and the scaling factor t u , including the following steps:

[0129] 4.1) Constructing the intrapulse Doppler frequency compensation function

[0130] Based on the time series t, determine the frequency domain sequence f corresponding to the time domain, and all measurable intra-pulse Doppler frequencies f coupled by radar echoes di , modulation frequency k, construct the intrapulse Doppler frequency compensation function as follows:

[0131]

[0132] The phase compensation function can solve the "false target" phenomenon caused by the Doppler frequency of the plasma sheath.

[0133] 4.2) Constructing the scale transformation factor t u :

[0134] Combined frequency f (frequency domain sequence), intrapulse Doppler frequency f of the radar echo signal of the plasma sheath covering the target di , carrier frequency f c , construct the scale transformation factor t u as follows:

[0135]

[0136] The improved scale transformation factor eliminates the scale transformation factor mismatch phenomenon caused by the intrapulse Doppler frequency, providing support for solving the cross-distance unit movement phenomenon. The traditional scale factor does not contain the intrapulse Doppler frequency. The present invention improves the traditional scale transformation factor, redesigns the scale factor, and solves the problem of scale transformation factor mismatch in the traditional keystone algorithm.

[0137] Embodiment 5,

[0138] The plasma sheath-coated target coherent accumulation method based on the improved keystone is the same as that in Embodiment 1-4, wherein the frequency domain representation y of the pulse compression result after solving the compensation in step S4 is com (t q ,f), including the following steps:

[0139] 5.1) Set the matched filter h(t):

[0140] According to the pulse width T p , carrier frequency f c , modulation frequency k, combined with the linear frequency modulation signal form, set the matching filter as follows:

[0141]

[0142] 5.2) Pulse compression result y(t q ,t): Use matched filter to filter the radar echo signal Echo(t q,t) is subjected to pulse compression processing, and the distance dimension representation is obtained as follows:

[0143]

[0144] From the above formula, we can see that the peak position of the sa function is affected by f dm Different intrapulse Doppler frequencies will affect the peak position on the one-dimensional range image.

[0145] 5.3) Solve the frequency domain representation of the compensated pulse compression result y com (t q ,f):

[0146] The pulse compression result y(t q ,t) Perform Fourier transform (FFT) to obtain the frequency domain representation of the pulse pressure result:

[0147]

[0148] Using the phase compensation function Multi-channel parallel compensation of the frequency domain representation of pulse pressure results:

[0149]

[0150] The above formula can be further expressed as:

[0151]

[0152] When the measurable intrapulse Doppler frequency f in the compensation function di The Doppler frequency component f coupled to the echo dm At the same time, the above formula can eliminate the influence of the intrapulse Doppler frequency, and f is only related to the target's initial position R0, the target's actual movement speed V, and the slow time series t q The energy gain of the real target is improved through I compensation and energy focusing.

[0153] Embodiment 6,

[0154] The plasma sheath-coated target coherent accumulation method based on improved keystone is the same as that in embodiments 1-5, wherein the coherent accumulation of multi-cycle echoes based on the improved keystone algorithm described in step S5 includes the following steps:

[0155] 6.1) Construct the velocity ambiguity elimination term η(t u ):

[0156] Using the scaling factor t u , speed measurement fuzzy number W, construct speed fuzzy elimination term η(t u ) is as follows:

[0157]

[0158] 6.2) Complete the transformation of the virtual timeline:

[0159] Using the velocity ambiguity elimination term η(t u ), frequency domain representation of the compensated pulse compression result y com (t q ,f), correction of cross-distance unit movement is achieved through sinc interpolation processing:

[0160]

[0161] When the scale transformation factors in the above formula match, the inverse Fourier transform of the correction result can be expressed as:

[0162]

[0163] 6.3) Coherently accumulate the transformation results of the virtual time axis: Use the transformation result y of the virtual time axis com (t c ,t), the total number of echo signal cycles Q, for y com (t c ,t) Perform Fourier transform (FFT) along the periodic axis:

[0164]

[0165] x represents the frequency domain sequence of Fourier transform, corresponding to the number of cycles Q.

[0166] 6.4) Target initial distance and movement speed estimation:

[0167] Perform peak energy search on the coherent accumulation results to obtain the peak coordinates (r,u), combined with the total number of cycles Q and the repetition period T r , speed of light c, carrier frequency f c , the estimated initial distance R is obtained by the peak coordinate according to the following formula esti , estimated motion speed V esti :

[0168]

[0169]

[0170] t represents the time series, r represents the coordinate, and t(r) is the rth value in the t sequence.

[0171] Test example,

[0172] The design method of the plasma sheath-coated target coherent accumulation method based on the improved keystone is the same as that of Example 1-6.

[0173] Simulation conditions and contents:

[0174] The present invention adopts the CFD flow field simulation data of the reentry vehicle RAM-C, sets the far-field target vehicle state to fly head-on to the radar, the target initial distance from the wave gate R0 = 10km, and the radar signal carrier frequency f is transmitted. c =9.5GHz, bandwidth B = 10M, pulse width T p =10us, repetition period T r =100us, sampling frequency Fs=30M, speed of light c=3×10 8 m / s, the number of cycles Q=128, the flight altitude H=30km, and the flight speed V=25 Mach (1 Mach=340m / s).

[0175] Simulation results and analysis:

[0176] Figure 3 The embodiment of the present invention only performs pulse compression processing and Fourier transform on the radar echo signal of the plasma sheath-encapsulated target for multiple periods to obtain the pulse compression result. As can be seen from the figure, the existing radar signal processing method fails due to the coupling of the echo signal with the intra-pulse Doppler frequency component, resulting in the "false target" phenomenon in the one-dimensional range image of the radar echo. The three peak positions on the one-dimensional range image are 10220m, 10540m and 11074m, respectively. The real target corresponding to the position of 11074m has a distance interval of 857m between the real target and the farthest false target, and the energy of the farthest false target is higher than that of the real target, which seriously affects the accurate detection of the real target.

[0177] Figure 4 This is the result of directly performing coherent accumulation on a multi-period radar echo model according to an embodiment of the present invention. As can be seen from the figure, due to the excessively fast target movement speed and limited bandwidth, the cross-distance unit movement phenomenon occurs, leakage occurs during the energy accumulation process, and coherent accumulation cannot be performed effectively.

[0178] Figure 5 This is the coherent accumulation diagram of the plasma sheath-encapsulated target based on the improved keystone in the present invention. It can be seen from the figure that the Doppler frequency multi-channel parallel compensation method in the present invention solves the problem of cross-distance unit movement caused by the target's excessively high speed, and at the same time significantly improves the energy gain of the true target, and realizes the effective coherent accumulation of multi-cycle echoes of the plasma sheath-encapsulated target; by searching the peak position, the initial distance and movement speed of the target can be estimated.

[0179] If the plasma sheath coating target coherent accumulation method described in the embodiment of the present invention is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the plasma sheath coating target coherent accumulation method described in the embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, ROM, RAM, disk or CD-ROM and other media that can store program codes.

[0180] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A plasma sheath-coated target coherent accumulation method based on improved keystone, characterized in that: The following steps are involved: Step 1, establish a multi-cycle radar echo model of the plasma sheath covering the target; Step 2: Extract the intra-pulse Doppler frequency f of the multi-period radar echo signal of the target covered by the plasma sheath di ; Step 3: Construct the intrapulse Doppler frequency compensation function Wherein, i is the i-th extracted Doppler frequency i=1, 2, 3...I; k represents the modulation frequency of the echo signal; The combined frequency f, the pulse Doppler frequency f of the radar echo signal of the plasma sheath covering the target di , carrier frequency f c , construct the scale transformation factor t of the keystone algorithm u : Among them, t q represents a slow time series; the scale transformation factor t u Eliminates the mismatch of traditional scale factors; Step 4: Pulse compression and Fourier transform are performed on the multi-period radar echo signal of the plasma sheath-encapsulated target to obtain the range domain representation y(t q ,f), through the intrapulse Doppler frequency compensation function For y(t q ,f) Perform cyclic compensation, focus the energy of all compensation results, and obtain the frequency domain representation of the compensated pulse compression result y com (t q ,f),Effectively suppress false targets; Step 5, based on the scale transformation factor t u , the frequency domain representation of the compensated pulse compression result y is obtained by sinc interpolation com (t q ,f) transform to obtain the coherent accumulation result Y, and obtain the initial distance and movement speed of the target through peak search.

2. According to claim 1, a plasma sheath-coated target coherent accumulation method based on improved keystone, characterized in that: In the Step 1, the plasma sheath covers the target radar echo model Echo (t q ,t) see the following formula: Among them, R m represents the complex reflection coefficient at each reference point of the target, m is the reference point number of the target surface m = 1, 2, 3....M, t represents the time series, τ0 represents the time delay of the initial distance of the target, τ q represents the target echo delay of each period, the number of echo signal periods q=1, 2, 3....Q, j represents an imaginary number, f dm represents the Doppler frequency component of the echo signal coupled at each reference point, f c represents the carrier frequency; k represents the modulation frequency of the echo signal, T p Indicates pulse width.

3. According to the plasma sheath coating target coherent accumulation method based on improved keystone in claim 1, it is characterized in that: In Step 2, the intrapulse Doppler frequency f di How to obtain: Based on the multi-period radar echo model of the plasma sheath covering the target, the echo signal is processed by using Wigner transform to obtain the time-frequency curve ξ(t,f) of the echo signal: Among them, R m represents the complex reflection coefficient at each reference point of the target, m is the reference point number of the target surface m = 1, 2, 3....M, f represents the frequency, f c Indicates the carrier frequency, f dm represents the Doppler frequency component coupled to the echo signal at each reference point, k represents the modulation frequency of the echo signal, t represents the time series, CT represents the sum of all cross terms, and δ() represents the impulse function; The time-frequency curve ξ(t,f) is converted to polar coordinates through Hough transform to achieve effective accumulation of the energy of the time-frequency curve ξ(t,f). The peak value is searched for the accumulated result to obtain the peak coordinates (ρ i ,θ i ), calculate all measurable intrapulse Doppler frequencies f by peak coordinates di : Among them, l represents the image width after Hough transform, and Fs represents the sampling frequency.

4. According to claim 1, a plasma sheath-coated target coherent accumulation method based on improved keystone, characterized in that: The Step 4 is specifically as follows: Based on the carrier frequency f c , pulse width T p , the actual speed of the target V, the initial distance of the target R0, set the matched filter h(t), and the matched filter h(t), the radar echo signal Echo(t q ,t) is convolved and output to obtain the pulse compression result y(t q ,t): Among them, f dv represents the Doppler frequency component corresponding to the actual target velocity V, B represents the bandwidth, τ q represents the target echo delay in each period, τ0 represents the time delay of the target initial distance; The pulse compression result y(t q ,t) is transformed into the frequency domain representation of the pulse compression result y(t q ,f), through the intrapulse Doppler frequency compensation function For y(t q f) Perform cyclic compensation, each compensation eliminates the influence of Doppler frequency in the pulse; perform energy focusing on all compensation results to obtain the frequency domain representation of the pulse compression result after compensation y com (t q ,f).

5. According to the plasma sheath coating target coherent accumulation method based on improved keystone in claim 1, it is characterized in that: The Step 5 is specifically as follows: According to the scaling factor t u Frequency domain characterization of pulse compression results com (t q ,f), through the sinc interpolation processing to achieve the correction of the cross-distance unit movement, the virtual time axis transformation result y com (t u ,f): Among them, η(t u ) is the velocity blur elimination term, f c represents the carrier frequency, f represents the frequency, t q Represents a slow time series, the number of echo signal cycles q = 1, 2, 3....Q; For com (t u ,f) Perform inverse Fourier transform to obtain the pulse compression result y related to virtual time com (t u ,t), for y com (t u ,t) perform multi-cycle coherent accumulation to obtain the coherent accumulation result Y of the multi-cycle echo; Perform peak search on the coherent accumulation result Y and obtain the estimated initial distance R through the peak coordinates esti and estimated motion speed V esti .

6. According to claim 5, a plasma sheath-coated target coherent accumulation method based on improved keystone is characterized in that: The velocity blur elimination term η(t u ) is determined according to the following formula: Where W represents the speed measurement fuzzy number; for the repetition period T r Find the reciprocal and get the repetition frequency f r , take all measurable intrapulse Doppler frequencies f di The peak value of the pulse is searched for the maximum intrapulse Doppler frequency, combined with the repetition frequency f r , and obtain the velocity fuzzy number W of the radar target.

7. A plasma sheath-encapsulated target coherent accumulation system based on improved keystone, characterized in that: A plasma sheath-coated target coherent accumulation method based on improved keystone as claimed in claim 1 is adopted, comprising: A radar echo model building module is used to build a multi-period radar echo model of a target covered by a plasma sheath; The intra-pulse Doppler frequency extraction module is used to extract the intra-pulse Doppler frequency f of the multi-period radar echo signal of the plasma sheath-covered target. di ; Compensation function building module, used to build intrapulse Doppler frequency compensation function Constructing the scaling factor t based on the intrapulse Doppler frequency u ; The compensation module is used to perform pulse compression processing and Fourier transform on the multi-period radar echo signal of the plasma sheath-enclosed target to obtain the distance domain representation y(t q ,f), through the Doppler frequency compensation function For y(t q ,f) Perform multi-channel parallel compensation, focus the energy of the compensation results, and obtain the frequency domain representation of the compensated pulse compression results y com (t q ,f); Coherent accumulation module for scaling factor t u , the frequency domain representation of the compensated pulse compression result y is obtained by sinc interpolation com (t q ,f) transform and obtain the coherent accumulation result Y based on the improved keystone algorithm, and obtain the initial distance and movement speed of the target through peak search.

8. An electronic device, characterized in that: The method described in any one of claims 1 to 6 is used to achieve coherent accumulation of plasma sheath-encapsulated targets.

9. A computer storage medium, characterized in that The storage medium stores at least one program instruction, and the at least one program instruction is loaded and executed by the processor to implement the plasma sheath covering target coherent accumulation method as described in any one of claims 1-6.

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