CN114660558A - Improved keystone-based coherent accumulation method, system, equipment and storage medium for plasma sheath cladding target - Google Patents

Improved keystone-based coherent accumulation method, system, equipment and storage medium for plasma sheath cladding target Download PDF

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CN114660558A
CN114660558A CN202210308106.2A CN202210308106A CN114660558A CN 114660558 A CN114660558 A CN 114660558A CN 202210308106 A CN202210308106 A CN 202210308106A CN 114660558 A CN114660558 A CN 114660558A
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target
frequency
intra
plasma sheath
pulse
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白博文
刘彦明
丁懿
牛戈钊
李小平
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Xidian University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4021—Means for monitoring or calibrating of parts of a radar system of receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4052—Means for monitoring or calibrating by simulation of echoes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

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Abstract

The invention discloses a method, a system, equipment and a storage medium for coherent accumulation of a plasma sheath coating target based on an improved keystone, wherein the coherent accumulation method specifically comprises the following steps: establishing a multi-period radar echo model of a plasma sheath coated target; extracting the intra-pulse Doppler frequency of the target multicycle radar echo signal coated by the plasma sheath; constructing an intra-pulse Doppler frequency compensation function, and determining a scale transformation factor; performing cyclic compensation through an intra-pulse Doppler frequency compensation function, and performing energy focusing on all compensation results to obtain frequency domain representation of the compensated pulse compression result; and transforming the compensated pulse compression result frequency domain representation to obtain a coherent accumulation result Y, and obtaining the initial distance and the movement speed of the target through peak value search. The method estimates the movement speed and the initial distance by peak value search, remarkably improves the energy gain of a true target, and realizes the detection of the hypersonic aircraft.

Description

Improved keystone-based coherent accumulation method, system, equipment and storage medium for plasma sheath cladding target
Technical Field
The invention belongs to the technical field of radar target detection, and relates to a coherent accumulation method, a coherent accumulation system, coherent accumulation equipment and a coherent accumulation storage medium for a plasma sheath coated target based on an improved keystone.
Background
When the hypersonic aircraft flies near space at a speed of more than 10Ma, air molecules in a stagnation area are subjected to the action of aerodynamic thermal ionization to form plasma, and the plasma and the aircraft move relatively to form a plasma sheath. Because the plasma sheath is an electromagnetic medium consisting of a large number of charged particles, when a target covered by the plasma sheath is detected, the phenomena of amplitude attenuation, phase distortion, Doppler frequency component increase and the like are generated by radar echo, so that the traditional target detection algorithm is mismatched, a false target appears in a one-dimensional distance image, and the reliable detection of the hypersonic aircraft is seriously influenced.
The existing research mainly aims at inhibiting the traditional false targets generated by time delay, asynchronous interference, surrounding, ghost images and the like, but the false target generated by a plasma sheath is greatly different from the traditional target, the false target stably exists in each period of echo, and meanwhile, the high-speed motion characteristic of the hypersonic velocity target enables the phenomenon of walking of a span-off unit to occur, so that the coherent accumulation of the hypersonic velocity aircraft is further influenced. Therefore, there is no effective suppression technique for coherent accumulation of the multi-cycle echo signal of the target covered by the plasma sheath.
Disclosure of Invention
In order to solve the problems, the invention provides a coherent accumulation method of a plasma sheath coated target based on an improved keystone, which is used for coherent accumulation of multi-cycle echo signals of the plasma sheath coated target moving at a constant speed, and estimation of a moving speed and an initial distance is carried out through peak value search, so that the energy gain of a true target is improved, the detection of a hypersonic aircraft is realized, and the problems in the prior art are solved.
It is a second object of the present invention to provide an improved keystone plasma sheath coating target coherent accumulation system.
A third object of the present invention is to provide an electronic apparatus.
It is a fourth object of the present invention to provide a computer storage medium.
The invention adopts the technical scheme that a plasma sheath coating target coherent accumulation method based on improved keystone comprises the following steps:
step1, establishing a multi-period radar echo model of the plasma sheath covering target;
step2, extracting the intra-pulse Doppler frequency f of the target multicycle radar return signal covered by the plasma sheathdi；
Step3, constructing an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000011
Intra-pulse based Doppler frequency compensation function
Figure BDA0003566520550000012
Scale transformation factor t of improved keystone algorithmu；
Step4, performing pulse compression processing and Fourier transform on the radar echo signal of the target multi-cycle covered by the plasma sheath to obtain a distance domain representation y (t) of the pulse compression resultqF) by means of an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000021
For y (t)qAnd f) performing cyclic compensation, performing energy focusing on all compensation results, and obtaining a frequency domain representation y of the compensated pulse compression resultcom(tqF), effectively suppressing decoys;
step5, based on the scale transformation factor tuAnd characterizing the frequency domain of the compensated pulse compression result by sinc interpolation processingcom(tqAnd f) carrying out transformation to obtain a coherent accumulation result Y, and obtaining the initial distance and the movement speed of the target through peak value search.
Further, in Step1, the plasma sheath covers the target radar Echo model Echo (t)qAnd t) is given by the following formula:
Figure BDA0003566520550000022
wherein R ismThe complex reflection coefficients at each reference point of the target are shown, M is the serial number M of the reference points on the surface of the target, wherein M is 1, 2 and 30Time delay, τ, representing the initial distance of the targetqRepresenting target echo time delay of each period, wherein the number Q of echo signal periods is 1, 2 and 3dmDoppler frequency component, f, representing the coupling of the echo signals at each reference pointcRepresenting the carrier frequency.
Further, at Step2, the intra-pulse Doppler frequency fdiThe obtaining method comprises the following steps:
based on a radar echo model with a target multi-period covered by a plasma sheath, processing an echo signal by adopting Weiganer transformation to obtain a time-frequency curve xi (t, f) of the echo signal:
Figure BDA0003566520550000023
wherein R ismThe complex reflection coefficients of the target at the reference points are shown, M is the serial number M of the target surface reference points, i.e. 1, 2 and 3cRepresenting the carrier frequency, fdmRepresenting the Doppler frequency component of the echo signal coupling at each reference point, k representing the modulation frequency of the echo signal, t representing the time sequence, CT representing the sum form of all cross terms, and δ () representing the impulse function;
converting the time-frequency curve xi (t, f) to polar coordinates by Hough transformation to realize effective accumulation of energy of the time-frequency curve xi (t, f), and performing peak value search on the accumulation result to obtain peak value coordinates (rho)i,θi) Calculating all measurable intra-pulse Doppler frequencies f by peak coordinatesdi：
Figure BDA0003566520550000024
Where l denotes an image width after hough transform, and Fs denotes a sampling frequency.
Further, in Step3, the intra-pulse doppler frequency compensation function
Figure BDA0003566520550000031
Determined according to the following formula:
Figure BDA0003566520550000032
wherein I is the doppler frequency I extracted at the ith 1, 2, 3.. I;
the scale transformation factor tuDetermined according to the following formula:
Figure BDA0003566520550000033
wherein, tqRepresents a slow time sequence; the scale transformation factor tuThe traditional scale factor mismatch condition is eliminated.
Further, Step4 specifically includes:
based on the carrier frequency fcPulse width TpActual moving speed V of target and initial distance R of target0A matched filter h (t) is provided, and the matched filter h (t) and the radar Echo signal Echo (t)qT) performing convolution output to obtain a pulse compression result y (t)q,t)：
Figure BDA0003566520550000034
Wherein, fdvA Doppler frequency component corresponding to the actual moving speed V of the target, B a frequency bandwidth, and tauqRepresenting target echo time delay, tau, of each cycle0A time delay representing an initial distance of the target;
for the pulse compression result y (t)qT) performing Fourier transform to obtain a pulse compression resultFrequency domain characterization y (t)qF) by means of an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000035
For y (t)qF) carrying out cyclic compensation, wherein each compensation eliminates the influence generated by the intra-pulse Doppler frequency; energy focusing is carried out on all compensation results to obtain the frequency domain representation y of the compensated pulse compression resultcom(tq,f)。
Further, Step5 specifically includes:
by a scale transformation factor tuAnd pulse compression results frequency domain characterization ycom(tqAnd f) realizing the correction of the walking of the cross-distance unit through sinc interpolation processing to obtain a virtual time axis transformation result ycom(tu,f)：
Figure BDA0003566520550000036
Wherein, η (t)u) For the velocity blur elimination term, fcRepresenting carrier frequency, f frequency, tqRepresenting a slow time sequence, wherein the number Q of echo signal cycles is 1, 2 and 3.
For ycom(tuF) performing an inverse Fourier transform to obtain a pulse compression result y associated with the virtual timecom(tuT), to ycom(tuT) carrying out multi-period coherent accumulation to obtain a coherent accumulation result Y of multi-period echoes;
carrying out peak value search on the coherent accumulation result Y, and obtaining an estimated initial distance R through a peak value coordinateestiAnd estimating the velocity of motion Vesti。
Further, the velocity blur elimination term η (t)u) Determined according to the following equation:
Figure BDA0003566520550000041
wherein, W represents the speed measurement fuzzy number;for the repetition period TrCalculating the reciprocal to obtain the repetition frequency frTaking all measurable intra-pulse Doppler frequencies fdiSearching for the maximum intra-pulse Doppler frequency in combination with the repetition frequency frAnd solving the speed measurement fuzzy number W of the radar target.
A modified keystone-based plasma sheath coating target coherent accumulation system comprises
The radar echo model establishing module is used for establishing a multi-period radar echo model of the plasma sheath coated target;
an intra-pulse Doppler frequency extraction module for extracting the intra-pulse Doppler frequency f of the echo signal of the multi-period radar with the plasma sheath covering the targetdi；
A compensation function construction module for constructing an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000042
Intra-pulse based Doppler frequency compensation function
Figure BDA0003566520550000043
Construction of the Scale transformation factor tu；
The compensation module is used for performing pulse compression processing and Fourier transform on the radar echo signal of the plasma sheath coating target in multiple cycles to obtain a distance domain representation y (t) of a pulse compression resultqF) by means of an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000044
For y (t)qAnd f) performing multi-channel parallel compensation, performing energy focusing on the compensation result, and obtaining the frequency domain representation y of the compensated pulse compression resultcom(tq,f)；
A coherent accumulation module for scaling the input signal based on the scale conversion factor tuAnd characterizing the frequency domain of the compensated pulse compression result by sinc interpolation processingcom(tqF) carrying out transformation to obtain a coherent accumulation result Y based on an improved keystone algorithm, and obtaining the initial distance and the movement speed of the target through peak value search。
An electronic device, which adopts the method to realize the plasma sheath coating target coherent accumulation.
A computer storage medium having stored therein at least one program instruction that is loaded and executed by a processor to implement the above-described plasma sheath coating target coherent accumulation method.
The invention has the beneficial effects that:
(1) aiming at a plasma sheath coating target moving at a constant speed, the invention effectively improves the energy gain of a true target and the energy ratio of the true/false target by an intra-pulse Doppler frequency multi-channel parallel compensation mode, and can effectively inhibit a radar echo one-dimensional range profile false target.
(2) The invention improves the scale transformation factor based on the intra-pulse Doppler frequency component, solves the problem that the traditional keystone algorithm is not matched, realizes effective coherent accumulation of multi-period echo signals, and remarkably improves the energy gain of a true target by combining intra-pulse Doppler frequency cyclic compensation.
(3) Because the plasma sheath has fluid characteristics, the method provided by the invention is suitable for coherent accumulation of multi-cycle radar echoes of a complex target with a rigid body coated by the fluid and suppression of 'false targets' generated by the fluid.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flowchart of example 1 of the present invention.
Fig. 2 is a hough transform schematic.
Figure 3 shows the result of pulse compression of a radar echo signal for multiple cycles of coating a target with a plasma sheath according to an embodiment of the present invention.
FIG. 4 shows the result of coherent accumulation directly performed on a multi-period radar echo model according to an embodiment of the present invention.
FIG. 5 shows the target coherent accumulation of plasma sheath coating based on the modified keystone of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The basic concept of the embodiment of the invention is as follows:
the plasma sheath with the fluid characteristic changes the target characteristic of the target to be detected to form a complex target of a fluid-coated rigid body, and when the complex target is detected, the plasma sheath generates a complex modulation effect of echo signals, so that the multi-cycle echo signal coherent accumulation fails. The embodiment of the invention extracts the coupled intra-pulse Doppler frequency of the target echo coated by the plasma sheath, discloses a generation mechanism of a false target through multi-domain characteristic analysis, and on the basis, constructs a phase compensation function and improves a scale transformation factor to realize effective coherent accumulation of the target multi-period echo signal coated by the plasma sheath.
In the case of the example 1, the following examples are given,
a method for coherent accumulation of a target sheath cladding plasma based on modified keystone, as shown in fig. 1, comprising the steps of:
step1, establishing a plasma sheath coating target radar Echo model Echo (t)q,t)：
Inputting complex reflection coefficient R at each reference point of targetmM is a target surface reference point serial number M1, 2, 3.. M, and amplitude attenuation and phase modulation information of an echo signal at each reference position of a target coated by a plasma sheath are obtained; inputting actual moving speed V and initial distance R of target during modeling0C, speed of light, c, backThe number Q of wave signal cycles is 1, 2, 30Target echo time delay tau of each periodq(ii) a Velocity component v at each reference point of the input plasma sheathmCarrier frequency fcCalculating the Doppler frequency component f of echo signal coupling at each reference pointdm(ii) a Input pulse width TpCalculating a sampling frequency Fs and a modulation frequency k of an echo signal; input repetition period TrCombined pulse width TpDetermining a time sequence t, a slow time sequence tq(ii) a Based on the parameters, a radar Echo model Echo (t) of a target with a plasma sheath covering Q periods is established according to a linear frequency modulation pulse signal formq,t)：
Figure BDA0003566520550000061
j represents an imaginary number.
The invention solves the echo signal of the target coated by the plasma sheath by establishing a radar echo model with the plasma sheath coating the target for Q periods, and provides a basis for carrying out extraction of multi-domain characteristics of the echo signal and disclosure of a generation mechanism of a false target.
Step2, extracting the intra-pulse Doppler frequency f of the echo signal of the target radar coated by the plasma sheathdiAnd speed measurement fuzzy number W: radar Echo model Echo (t) based on target Q periods coated by plasma sheathqT), processing the echo signal by adopting wigner transformation to obtain a time-frequency curve xi (t, f) of the echo signal:
Figure BDA0003566520550000062
CT denotes the sum form of all cross terms, f denotes frequency, δ () denotes impulse function;
converting the time-frequency curve xi (t, f) to polar coordinates by Hough transform to realize effective accumulation of energy of the time-frequency curve xi (t, f), and performing peak value search on the accumulation result to obtain peak value coordinates (rho)i,θi) Calculating all measurable intra-pulse Doppler frequencies f by peak coordinatesdi：
Figure BDA0003566520550000063
Where l represents the image width after hough transform.
For the repetition period TrCalculating the reciprocal to obtain the repetition frequency frTaking all measurable intra-pulse Doppler frequencies fdiSearching for the maximum intra-pulse Doppler frequency, the simultaneous repetition period TrAnd solving the speed measurement fuzzy number W of the radar target.
The invention obtains the intra-pulse Doppler frequency f by Weiganhoff processingdiI.e. echo signal coupling; calculating the speed measurement fuzzy number W of the radar target based on the frequency f to construct an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000064
And a scale factor tuProviding parametric support.
Step3, constructing the intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000071
And a scale factor tu：
Determining the frequency f corresponding to the time domain based on the time sequence t, and coupling all measurable intra-pulse Doppler frequencies f according to the radar echodiModulating the frequency k, constructing an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000072
The following were used:
Figure BDA0003566520550000073
i is the ith extracted doppler frequency, I1, 2, 3.. I; combined frequency f, plasma sheath covering meshIntra-pulse doppler frequency f of radar echo signaldiCarrier frequency fcConstructing the scale transformation factor tuThe following:
Figure BDA0003566520550000074
the invention provides a basis for effectively inhibiting the false target generated by the plasma sheath by constructing the intra-pulse Doppler frequency compensation function. The traditional scale factor mismatching situation is eliminated by constructing the scale transformation factor, and a basis is provided for realizing coherent accumulation of the plasma sheath coated target multi-cycle echo signals.
Step4, solving the frequency domain representation y of the compensated pulse compression resultcom(tq,f)：
Based on the carrier frequency fcPulse width TpActual target speed V and initial target distance R0A matched filter h (t) is provided, and the matched filter h (t) and the radar Echo signal Echo (t)qT) performing convolution output to obtain a pulse compression result y (t)q,t)：
Figure BDA0003566520550000075
Wherein f isdvAnd a doppler frequency component corresponding to the actual moving speed V of the target.
For the pulse compression result y (t)qAnd t) performing Fourier transform (FFT) to obtain frequency domain representation y (t) of pulse compression resultqF) using an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000076
For y (t)qF) carrying out I times of compensation, carrying out energy focusing on the compensation result, and obtaining the frequency domain representation y of the compensated pulse compression resultcom(tq,f)：
Figure BDA0003566520550000077
By solving for the pulse compression result y (t)qT), one-dimensional range profile characteristics of the plasma sheath wrapped target are obtained, revealing that the "false target" is formed by intra-pulse doppler frequencies. Frequency domain characterization y (t) of pulse compression results based on a compensation function constructed by intra-pulse Doppler frequencyqAnd f) carrying out cyclic compensation, wherein the influence generated by the intra-pulse Doppler frequency is eliminated once in each compensation (after the intra-pulse Doppler frequency is eliminated, the distance measured by the target is positioned at a real position), and carrying out energy focusing on all compensation results, so that the energy gain of a real target is improved, the energy ratio of a real target to a false target is improved, and the effective inhibition of the false target is realized.
Step5, realizing coherent accumulation y of multi-period echoes based on improved keystone algorithmcom(tu,f)：
By a scale transformation factor tuAnd pulse compression results frequency domain characterization ycom(tqAnd f) realizing the correction of the walking of the cross-distance unit through sinc interpolation processing to obtain a virtual time axis transformation result ycom(tu,f)：
Figure BDA0003566520550000081
Wherein, eta (t)u) For the velocity ambiguity elimination term, the phenomenon of walking of the span-off unit can be effectively solved by utilizing the formula to convert through a virtual time axis.
For ycom(tuF) performing an inverse Fourier transform to obtain a pulse compression result y associated with the virtual timecom(tuT), to ycom(tuT) carrying out multi-period coherent accumulation to obtain coherent accumulation result Y of multi-period echo, carrying out peak value search on coherent accumulation result Y, and obtaining estimated initial distance R through peak value coordinatesestiAnd estimating the velocity of motion Vesti。
The method solves the problem that the scale conversion factors of the traditional keystone algorithm are not matched based on the scale conversion factors after intra-pulse Doppler frequency improvement, performs virtual time axis conversion on the pulse compression frequency domain representation of the multi-cycle echo signals by utilizing the improved scale factors, solves the problem of the walking of a span unit caused by overhigh target movement speed, realizes effective coherent accumulation of the multi-cycle echoes of the plasma sheath coated target, can estimate the movement speed and the initial distance of the target by peak value extraction, and lays a foundation for reliable detection, even stable tracking and the like of the hypersonic target in the near space.
In the case of the example 2, the following examples are given,
the coherent accumulation method of the target covered by the plasma sheath based on the improved keystone is the same as that of the embodiment 1, wherein the Echo model Echo (t) of the target covered by the plasma sheath is established as described in Step1qT), comprising the following steps:
2.1) calculating radar signal parameters:
calculating the sampling frequency Fs (10 × B) by using the frequency bandwidth B; using the sampling frequency Fs, pulse width TpRepetition period TrDetermining the time sequence T as 1:1/Fs (T)r-Tp2); by pulse width TrAnd determining a slow time sequence by using the number Q of echo signal cycles as 1, 2 and 3.
tq＝(q-1)×Tr
By pulse width TpAnd a frequency bandwidth B, wherein the modulation frequency of the echo signal is determined as follows:
k＝B/Tp
2.2) calculating radar echo time delay parameters and coupling Doppler frequency:
using the initial distance R of the target0Actual movement speed V, light speed c and repetition period T of target during modelingrCalculating the initial distance delay tau of the radar echo0＝2×R0C, target echo time delay tau of each periodq＝2×(R0-V×tq) C; using the velocity component v at each reference point of the plasma sheathmLight speed c, carrier frequency fcCalculating the coupled intra-pulse Doppler frequency component f of the echo signaldm＝2×vm×fc/c；
2.3) establishing a plasma sheath cladding target radar Echo model Echo (t)qT): establishing a radar Echo signal Echo (t) according to the radar signal parameter, the radar Echo time delay parameter and the coupling Doppler frequencyqT) is as follows:
Figure BDA0003566520550000091
the above equation represents the echo signal of the qth period of the target coated by the plasma sheath.
In the case of the embodiment 3, the following examples,
coherent accumulation method for target wrapped by plasma sheath based on improved keystone, as in embodiment 1-2, wherein step S2 is performed to extract the intra-pulse doppler frequency f of radar echo signal of target wrapped by plasma sheathdiAnd a speed measurement fuzzy number W, comprising the following steps:
3.1) calculating the Wegener transformation result of the echo of the target radar coated by the plasma sheath: radar Echo signal Echo (t) based on wigner transformationqAnd t) processing:
Figure BDA0003566520550000092
where h represents a delay amount when the echo signal is subjected to the autocorrelation processing, and () represents the echo signal being subjected to the conjugation processing. Echo*Representing the conjugate of the echo signal; and obtaining a time-frequency curve xi (t, f) of the echo signal according to the formula:
Figure BDA0003566520550000093
3.2) carrying out energy accumulation on the time-frequency curve based on Hough transform: as shown in fig. 2, the time-frequency curve is processed by hough transform, and polar coordinate transform is performed:
tcosθ+fsinθ＝ρ ρ≥0,0≤θ≤π
straight line f ═ fc+fdmEach point on + kt corresponds to a curve in polar coordinates,curves corresponding to all points on the straight line intersect at one point in the polar coordinate, and an energy peak value is formed.
3.3) extracting all measurable intra-pulse Doppler frequencies fdi：
Carrying out peak value search on the accumulation result to obtain a peak value coordinate (rho)i,θi) Calculating all measurable intra-pulse Doppler frequencies f by peak coordinatesdi：
Figure BDA0003566520550000094
Where l represents the image width after hough transform.
3.4) estimating the maximum speed measurement fuzzy number W:
using repetition period TrObtaining a repetition frequency fr＝1/Tr(ii) a Taking all measurable intra-pulse Doppler frequencies fdiPeak value f ofdmaxCombined with repetition frequency frEstimating the maximum speed measurement fuzzy number W:
W＝floor[2×fdmax/fr]。
in the case of the example 4, the following examples are given,
the method for coherent accumulation of target covered by plasma sheath based on improved keystone is the same as that of embodiments 1-3, wherein the step S3 is to construct the intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000101
And a scale factor tuThe method comprises the following steps:
4.1) construction of an Intra-pulse Doppler frequency Compensation function
Figure BDA0003566520550000102
Determining a frequency domain sequence f corresponding to a time domain based on the time sequence t, and coupling all measurable intra-pulse Doppler frequencies f according to radar echoesdiModulating the frequency k, constructing an intra-pulse Doppler frequency compensation function
Figure BDA0003566520550000103
The following were used:
Figure BDA0003566520550000104
the phase compensation function may account for "false target" phenomena caused by the doppler frequency of the plasma sheath.
4.2) construction of the Scale transformation factor tu：
Combined frequency f (frequency domain sequence), intra-pulse Doppler frequency f of target radar echo signal covered by plasma sheathdiCarrier frequency fcConstructing the scale transformation factor tuThe following were used:
Figure BDA0003566520550000105
the improved scale transformation factor eliminates the phenomenon that the intra-pulse Doppler frequency causes the mismatching of the scale transformation factor, and provides support for solving the problem of the cross-distance unit walking phenomenon. The traditional scale factor does not contain intra-pulse Doppler frequency, the invention improves the traditional scale transformation factor, redesigns the scale factor and solves the problem that the scale transformation factor of the traditional keystone algorithm is not matched.
In the case of the example 5, the following examples were conducted,
modified keystone-based method for coherent accumulation of plasma sheath coating target as in embodiments 1-4, wherein the solution of the compensated pulse compression result frequency domain characterization y described in step S4com(tqF), comprising the steps of:
5.1) setting a matched filter h (t):
according to pulse width TpCarrier frequency fcModulating frequency k, and setting a matched filter as follows by combining a linear frequency modulation signal form:
Figure BDA0003566520550000106
5.2) pulse compression result y (t)qT): radar Echo signal Echo (t) using matched filterqAnd t) performing pulse compression processing to obtain a distance dimension characterization as follows:
Figure BDA0003566520550000107
as can be seen from the above equation, the peak position of the sa function is subject to fdmDifferent intra-pulse doppler frequencies affect the peak position on the one-dimensional range image.
5.3) solving the frequency domain representation y of the compensated pulse compression resultcom(tq,f)：
For the pulse compression result y (t)qAnd t) performing Fourier transform (FFT) to obtain frequency domain representation of the pulse pressure result:
Figure BDA0003566520550000111
using phase compensation functions
Figure BDA0003566520550000112
Performing multichannel parallel compensation on the frequency domain representation of the pulse pressure result:
Figure BDA0003566520550000113
the above formula can further be expressed as:
Figure BDA0003566520550000114
when the measurable intra-pulse Doppler frequency f in the compensation functiondiDoppler frequency component f coupled in echodmWhen the same, the above formula can eliminate the influence of the intra-pulse Doppler frequency, and f is only equal to the initial position R of the target0Actual movement speed V of target and slow time sequence tqCorrelation, independent of the intra-pulse doppler frequency. When I times of compensation and energy focusing are carried out, the energy gain of the real target is improved.
In the case of the example 6, it is shown,
the method for coherent accumulation of the target sheath cladding plasma based on the improved keystone, as in embodiments 1-5, wherein the improved keystone algorithm based on step S5 implements coherent accumulation of multi-cycle echoes, comprising the following steps:
6.1) construction of the velocity ambiguity resolution term η (t)u)：
Using scale transformation factor tuMeasuring the speed fuzzy number W, and constructing a speed fuzzy elimination term eta (t)u) As follows:
Figure BDA0003566520550000115
6.2) completing the transformation of the virtual time axis:
using a velocity blur elimination term η (t)u) And the compensated pulse compression result frequency domain characterization ycom(tqF), correction of the walking across distance units by sinc interpolation processing:
Figure BDA0003566520550000116
when the above-mentioned scale transformation factors are matched, the inverse fourier transform of the correction result can be expressed as:
Figure BDA0003566520550000117
6.3) carrying out coherent accumulation on the transformation result of the virtual time shaft: transformation result y using virtual time axiscom(tcT), total number of cycles Q of echo signal, to ycom(tcT) fourier transform (FFT) along the periodic axis:
Figure BDA0003566520550000121
x represents a frequency domain sequence of fourier transform, and corresponds to the number of cycles Q.
6.4) estimating the initial distance and the movement speed of the target:
searching peak energy of the coherent accumulation result to obtain peak coordinates (r, u), combining the total period number Q and the repetition period TrSpeed of light c, carrier frequency fcObtaining an estimated nominal initial distance R from the peak coordinates according to the following equationestiEstimated velocity of motion Vesti：
Figure BDA0003566520550000122
Figure BDA0003566520550000123
t denotes the time series, r denotes the coordinates, and t (r) is the r-th value in the t series.
In the examples of the tests, the following tests were carried out,
the design method of the plasma sheath coating target coherent accumulation method based on the improved keystone is the same as that of the examples 1-6.
Simulation conditions and contents:
the method adopts CFD flow field simulation data of a reentry vehicle RAM-C, sets the state of a far-field target vehicle as a state of facing the radar, and sets the initial distance R between the target and a wave gate010km, the carrier frequency f of the transmitted radar signalc9.5GHz, bandwidth B10M, pulse width Tp10us, repeat period Tr100us, sampling frequency Fs 30M, light speed c 3 × 108m/s, the number of cycles Q is 128, the flying height H is 30km, and the flying speed V is 25 mach (mach 1 is 340 m/s).
Simulation results and analysis:
FIG. 3 shows the pulse compression result obtained by performing the pulse compression processing and Fourier transform on the radar echo signal of the plasma sheath covering the target for multiple periods according to the embodiment of the invention. It can be seen from the figure that the echo signal is coupled with the intra-pulse Doppler frequency component, so that the existing radar signal processing method is invalid, and the phenomenon of false target of the radar echo one-dimensional range profile is caused. The three peak positions on the one-dimensional distance image are 10220m, 10540m and 11074m respectively, wherein the distance between the true target and the farthest false target of the corresponding true target at the position of 11074m is 857m, and the energy of the farthest false target is higher than that of the true target, which seriously affects the accurate detection of the true target.
FIG. 4 shows the result of coherent accumulation directly performed on a multi-period radar echo model according to an embodiment of the present invention. It can be seen from the figure that the phenomenon of walking of the span unit is caused due to the fact that the target moves at an excessively high speed and the frequency bandwidth is limited, leakage is generated in the energy accumulation process, and coherent accumulation cannot be effectively carried out.
Fig. 5 is a coherent accumulation diagram of the target sheath cladding for a plasma based on a modified keystone in accordance with the present invention. The figure shows that the Doppler frequency multi-channel parallel compensation method solves the problem of the walking of the span-off unit caused by overhigh target motion speed, obviously improves the energy gain of a real target, and realizes the effective coherent accumulation of the multi-period echoes of the target coated by the plasma sheath; the initial distance and the movement speed of the target can be estimated by searching the peak position.
The method for coherent accumulation of the target coating of the plasma sheath according to the embodiment of the present invention may be stored in a computer readable storage medium if it is implemented in the form of a software functional module and sold or used as an independent product. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to perform all or part of the steps of the method for coherent accumulation of plasma sheath coating target according to the embodiment of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a U disk, a removable hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A modified keystone-based method for coherent accumulation of a target coated with a plasma sheath comprises the following steps:
step1, establishing a multi-period radar echo model of the plasma sheath coating target;
step2, extracting the intra-pulse Doppler frequency f of the target multicycle radar return signal covered by the plasma sheathdi；
Step3, constructing the intra-pulse Doppler frequency compensation function
Figure FDA0003566520540000013
Intra-pulse based Doppler frequency compensation function
Figure FDA0003566520540000014
Scale transformation factor t of improved keystone algorithmu；
Step4, performing pulse compression processing and Fourier transform on the radar echo signal of the target multi-cycle covered by the plasma sheath to obtain a distance domain representation y (t) of the pulse compression resultqF) by means of an intra-pulse Doppler frequency compensation function
Figure FDA0003566520540000015
For y (t)qAnd f) performing cyclic compensation, performing energy focusing on all compensation results, and obtaining a frequency domain representation y of the compensated pulse compression resultcom(tqF), effectively suppressing decoys;
step5 based on the scaling factor tuAnd characterizing the frequency domain of the compensated pulse compression result by sinc interpolation processingcom(tqAnd f) transforming to obtain the phase contrastAnd accumulating the result Y, and obtaining the initial distance and the movement speed of the target through peak value searching.
2. The improved keystone-based coherent accumulation method for targets sheathed by plasma sheath as claimed in claim 1, wherein in Step1, the plasma sheath is sheathed by target radar Echo model Echo (t)qAnd t) is given by the following formula:
Figure FDA0003566520540000011
wherein R ismThe complex reflection coefficients at each reference point of the target are shown, M is the serial number M of the reference points on the surface of the target, wherein M is 1, 2 and 30Time delay, τ, representing the initial distance of the targetqRepresenting target echo time delay of each period, wherein the number Q of echo signal periods is 1, 2 and 3dmDoppler frequency component, f, representing the coupling of the echo signals at each reference pointcRepresenting the carrier frequency.
3. The method of claim 1, wherein Step2 is performed at an intra-pulse Doppler frequency fdiThe obtaining method comprises the following steps:
based on a radar echo model with a target multi-period covered by a plasma sheath, processing an echo signal by adopting Weiganer transformation to obtain a time-frequency curve xi (t, f) of the echo signal:
Figure FDA0003566520540000012
wherein R ismThe complex reflection coefficients at the reference points of the target are shown, M is the serial number M of the reference points of the surface of the target, wherein M is 1, 2 and 3cRepresenting the carrier frequency, fdmA doppler frequency component representing the coupling of the echo signal at each reference point, k represents the modulation frequency of the echo signal,t represents a time series, CT represents a sum form of all cross terms, δ () represents an impulse function;
converting the time-frequency curve xi (t, f) to polar coordinates by Hough transformation to realize effective accumulation of energy of the time-frequency curve xi (t, f), and performing peak value search on the accumulation result to obtain peak value coordinates (rho)i,θi) Calculating all measurable intra-pulse Doppler frequencies f by peak coordinatesdi：
Figure FDA0003566520540000021
Where l denotes an image width after hough transform, and Fs denotes a sampling frequency.
4. The method of claim 3, wherein the Step3 is an intra-pulse Doppler frequency compensation function
Figure FDA0003566520540000022
Determined according to the following formula:
Figure FDA0003566520540000023
wherein I is the doppler frequency I extracted at the ith 1, 2, 3.. I;
the scale transformation factor tuDetermined according to the following formula:
Figure FDA0003566520540000024
wherein, tqRepresents a slow time sequence; the scale transformation factor tuThe traditional scale factor mismatch condition is eliminated.
5. The method for the targeted coherent accumulation of sheath-coated plasma based on the modified keystone as claimed in claim 4, wherein Step4 is specifically as follows:
based on the carrier frequency fcPulse width TpActual moving speed V of target and initial distance R of target0A matched filter h (t) is provided, and the matched filter h (t) and the radar Echo signal Echo (t)qT) performing convolution output to obtain a pulse compression result y (t)q,t)：
Figure FDA0003566520540000025
Wherein f isdvA Doppler frequency component corresponding to the actual moving speed V of the target, B a frequency bandwidth, and tauqRepresenting target echo time delay, tau, of each cycle0A time delay representing an initial distance of the target;
for the pulse compression result y (t)qAnd t) performing Fourier transform to obtain frequency domain representation y (t) of pulse compression resultqF) by means of an intra-pulse Doppler frequency compensation function
Figure FDA0003566520540000026
For y (t)qF) carrying out cyclic compensation, wherein each compensation eliminates the influence generated by the intra-pulse Doppler frequency; energy focusing is carried out on all compensation results to obtain the frequency domain representation y of the compensated pulse compression resultcom(tq,f)。
6. The method for coherent accumulation of target coating in plasma sheath based on keystone as claimed in claim 1, wherein said Step5 is specifically:
according to a scale transformation factor tuAnd pulse compression results frequency domain characterization ycom(tqAnd f) realizing the correction of the walking of the cross-distance unit through sinc interpolation processing to obtain a virtual time axis transformation result ycom(tu,f)：
Figure FDA0003566520540000031
Wherein, eta (t)u) For the velocity blur elimination term, fcRepresenting carrier frequency, f frequency, tqRepresenting a slow time sequence, wherein the number Q of echo signal cycles is 1, 2 and 3.
For ycom(tuF) performing an inverse Fourier transform to obtain a pulse compression result y associated with the virtual timecom(tuT), to ycom(tuT) carrying out multi-period coherent accumulation to obtain a coherent accumulation result Y of multi-period echoes;
carrying out peak value search on the coherent accumulation result Y, and obtaining an estimated initial distance R through a peak value coordinateestiAnd estimating the velocity of motion Vesti。
7. The modified keystone-based plasma sheath cladding target coherent accumulation method of claim 6, wherein the velocity ambiguity resolution term η (t) isu) Determined according to the following formula:
Figure FDA0003566520540000032
wherein, W represents the speed measurement fuzzy number; for the repetition period TrCalculating the reciprocal to obtain the repetition frequency frTaking all measurable intra-pulse Doppler frequencies fdiSearching for the maximum intra-pulse Doppler frequency in combination with the repetition frequency frAnd solving the speed measurement fuzzy number W of the radar target.
8. The modified keystone-based plasma sheath-coated target coherent accumulation system, which is characterized in that the modified keystone-based plasma sheath-coated target coherent accumulation method as claimed in claim 1 comprises
The radar echo model establishing module is used for establishing a multi-period radar echo model of the plasma sheath coated target;
an intra-pulse Doppler frequency extraction module for extracting the intra-pulse Doppler frequency f of the echo signal of the multi-period radar with the plasma sheath covering the targetdi；
A compensation function constructing module for constructing intra-pulse Doppler frequency compensation function
Figure FDA0003566520540000033
Intra-pulse based Doppler frequency compensation function
Figure FDA0003566520540000034
Construction of the Scale transformation factor tu；
The compensation module is used for performing pulse compression processing and Fourier transform on the radar echo signal of the plasma sheath coating target in multiple cycles to obtain a distance domain representation y (t) of a pulse compression resultqF) by means of a Doppler frequency compensation function
Figure FDA0003566520540000035
For y (t)qAnd f) carrying out multichannel parallel compensation, carrying out energy focusing on a compensation result, and obtaining a frequency domain representation y of the compensated pulse compression resultcom(tq,f)；
A coherent accumulation module for scaling the input signal based on the scale conversion factor tuAnd characterizing the frequency domain of the compensated pulse compression result by sinc interpolation processingcom(tqAnd f) carrying out transformation to obtain a coherent accumulation result Y based on an improved keystone algorithm, and obtaining the initial distance and the movement speed of the target through peak value search.
9. An electronic device, wherein the plasma sheath coating target coherent accumulation is achieved by the method of any of claims 1-7.
10. A computer storage medium having stored therein at least one program instruction, the at least one program instruction being loaded and executed by a processor to implement the target coherent accumulation method of plasma sheath cladding as recited in any one of claims 1-7.
CN202210308106.2A 2022-03-26 2022-03-26 Improved keystone-based coherent accumulation method, system, equipment and storage medium for plasma sheath cladding target Pending CN114660558A (en)

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CN115685169A (en) * 2022-11-09 2023-02-03 哈尔滨工程大学 Underwater sound weak moving target detection method based on broadband keystone transformation

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115685169A (en) * 2022-11-09 2023-02-03 哈尔滨工程大学 Underwater sound weak moving target detection method based on broadband keystone transformation

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