CN114527430A - Frequency-agile anti-interference signal coherent accumulation method for frequency block coding - Google Patents

Frequency-agile anti-interference signal coherent accumulation method for frequency block coding Download PDF

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CN114527430A
CN114527430A CN202210113566.XA CN202210113566A CN114527430A CN 114527430 A CN114527430 A CN 114527430A CN 202210113566 A CN202210113566 A CN 202210113566A CN 114527430 A CN114527430 A CN 114527430A
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frequency
distance
pulse
signals
velocity
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李亚超
王宇
王家东
张盼
张鹏
张磊
郭亮
张志军
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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
    • G01S7/28—Details of pulse systems
    • G01S7/282—Transmitters
    • 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
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/292—Extracting wanted echo-signals
    • 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
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/295—Means for transforming co-ordinates or for evaluating data, e.g. using computers
    • 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
    • G01S7/36—Means for anti-jamming, e.g. ECCM, i.e. electronic counter-counter measures
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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Abstract

The invention provides a coherent accumulation method of a frequency-agile anti-interference signal of frequency block coding, which improves the freedom degree of a waveform and solves the problem that the frequency-agile signal in the prior art can not be subjected to coherent accumulation or generates a pseudo peak after accumulation. The method comprises the following implementation steps: firstly, carrying out frequency block coding on pulse signals; then preprocessing the echo signal of each pulse after frequency coding, and performing speed traversal processing on each preprocessed echo signal; then carrying out coherent projection processing on the signals traversed by each speed; and finally, accumulating all the signals after the phase-coherent projection to realize the phase-coherent accumulation of the frequency agile anti-interference signals. The invention increases the agile degree of freedom of the agile frequency conversion anti-interference waveform, realizes the coherent accumulation of the agile frequency conversion anti-interference waveform, and effectively improves the anti-interference performance and the target detection performance of the agile frequency conversion system radar.

Description

Frequency-agile anti-interference signal coherent accumulation method for frequency block coding
Technical Field
The invention belongs to the technical field of radar, and relates to a frequency block coded frequency agile frequency conversion anti-interference signal coherent accumulation method, which can be used in the fields of radar anti-interference, target detection and the like.
Background
The frequency agility radar is a pulse radar, and transmits agility frequency signals, and carrier frequencies of the signals can be agility randomly in a certain range or jump rapidly according to a designed rule. The frequency agility radar can reduce the interception probability of an interference machine due to the rapid change of parameters of agility signals transmitted by the frequency agility radar, and effectively inhibit cross-pulse forwarding type deception interference and narrow-pulse aiming suppression type interference; meanwhile, the frequency hopping bandwidth of the frequency agile signal transmitted by the frequency agile radar is large, and the instantaneous narrow bandwidth can be synthesized into a large bandwidth, so that the distance resolution of the radar can be improved, and the target detection precision of the radar can be improved. In conclusion, the frequency agile radar has a very wide application prospect in the fields of radar anti-interference and target detection.
At present, signal processing in a frequency agile radar system is mostly realized by adopting a non-coherent technology, because the principle is simple and the engineering is easy to realize, but the gain of the non-coherent accumulation has certain loss compared with the coherent accumulation, and the target detection of the radar is not facilitated. Meanwhile, due to the phase coherent removal characteristic among the frequency agile signals, the conventional coherent accumulation methods such as Moving Target Detection (MTD) and FFT fast algorithm are difficult to apply.
In order to solve the problem, the Monauspicious east et al provides a phase-coherent accumulation method of frequency-hopping waveforms among pulses in a coherent accumulation target detection method published in the modern radar of 2020, which is based on a variable period method. The method utilizes the phase non-coherent nature generated by the frequency agility between the repeated frequency offset compensation pulses, so that the traditional FFT fast algorithm can be adopted when the pulse accumulation is carried out in the post-processing. The method has the disadvantages that a specific carrier frequency and a specific repetition frequency hopping sequence need to be designed, the waveform freedom degree is low, and the method is easy to be intercepted by an interference machine, so that the interference confrontation of the frequency agile radar is not facilitated.
The patent application with the application publication number of CN109164421A and the name of a target detection method based on a two-dimensional reconstruction algorithm discloses a frequency agile signal coherent accumulation method based on the two-dimensional reconstruction algorithm. The method constructs a distance-speed two-dimensional joint dictionary matrix corresponding to an echo, and adopts an OMP algorithm (orthogonal matching pursuit algorithm) to carry out sparse reconstruction on distance and speed information of a target, so that a coherent accumulation result of a frequency agile signal is obtained. The method has the disadvantages that the problem of grid mismatch is easily caused by the need of grid division of the detected distance-speed area, and at the moment, a false peak is caused by a large error between a real target parameter and each point, so that the radar target detection performance is influenced.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a coherent accumulation method of frequency block coded frequency agile frequency conversion anti-interference signals, is used for solving the problem that the frequency agile frequency conversion signals in the prior art cannot be subjected to coherent accumulation or generate pseudo peaks after accumulation, and simultaneously improves the waveform freedom.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
(1) carrying out frequency block coding on the pulse signals:
averagely dividing frequency agile signals generated by a frequency agile radar in coherent processing time into M groups, wherein each group comprises N pulses, and carrying out frequency coding on carrier frequency of each pulse to obtain a set F consisting of M groups of frequency coding pulses, wherein M is more than or equal to 2,n is more than or equal to 8, and the carrier frequency of the mth group nth frequency coding pulse in the F is Fmn＝f0+gmnΔf，m＝1,2,...,M，n＝1,2,...,N，f0Is the reference carrier frequency, Δ f is the minimum hop interval, gmnThe frequency coding value of the nth frequency coding pulse of the mth group is coded, and the pulse frequency coding values g with the same pulse sequence number are arranged among all the pulse groups1,n～gM,nAre different from each other, i.e. g1,n～gM,nTraversing all integers from 1 to M;
(2) preprocessing the echo signal of each frequency-coded pulse:
(2a) acquiring echo signals s of each frequency coding pulse reflected by a targetmn(t), the echo signal set corresponding to the frequency encoding pulse set F is s ═ s1,s2,...,sm,...,sMIn which s ismFor echo signals of the m-th group of frequency-coded pulses, sm＝{sm1(t),sm2(t),...,smn(t),...,smN(t)}，smn(t) is the echo signal of the mth group nth frequency coding pulse, and t is the fast time;
(2b) for each echo signal smn(t) pulse-compressing the signal s 'at the peak value after each pulse compression'mnDiscretizing into D high-resolution distance unit signals, constructing distance and phase compensation terms corresponding to each high-resolution distance unit signal, and obtaining M groups of distance and phase compensation terms
Figure BDA0003495578690000021
Wherein s ismThe signal at the corresponding post-pulse compression peak value is s'm＝{s'm1,s'm2,...,s'mn,...,s'mN}，s'mThe corresponding distance phase compensation term is
Figure BDA0003495578690000022
D is the serial number of the high-resolution distance unit;
(2c) and (3) performing distance traversal processing on the signal at the peak after each pulse pressure:
will each beMultiplying a distance phase compensation item of each pulse signal on each high-resolution distance unit by a signal at a corresponding pulse pressure post-peak value to obtain M groups of distance traversed two-dimensional time domain signals sr ═ { sr ═1,sr2,...,srm,...,srMWhere sr ismFor the m-th group of two-dimensional time domain signals after pulse distance traversal, srm＝{srm1(d),srm2(d),...,srmn(d),...,srmN(d)}，srmn(d) Traversing the nth pulse distance for the mth group of pulse distances;
(3) performing speed traversal processing on the two-dimensional time domain signal after each distance traversal:
the dimension of the N discretized signals on each high-resolution distance unit in each pulse is called a velocity dimension, the length of the signal on each velocity dimension is filled with zero to 2MN, and the velocity dimension FFT processing is carried out on the signals to obtain M sets of distance time domain velocity frequency domain signals Sv ═ { Sv ═ after velocity traversal1,Sv2,...,Svm,...,SvMIn which, SvmFor the distance time domain velocity frequency domain signal Sv after the mth group signal velocity traversalm＝{Svm1(k),Svm2(k),...,Svmd(k),...,SvmD(k)}，Svmd(k) A distance time domain velocity frequency domain signal after traversing the signal velocity on the mth group of the mth high resolution distance unit, where k is 1, 2.
(4) Carrying out coherent projection processing on the distance time domain speed frequency domain signal after each speed traversal:
(4a) rewriting the distance time domain speed frequency domain signal after each speed traversal:
make the fast time after rewriting be
Figure BDA0003495578690000031
And will be
Figure BDA0003495578690000032
Substituting the signals into the distance time domain velocity frequency domain signals after traversing each velocity to obtain M groups of rewritten distance time domain velocity frequency domain signals Sv '═ { Sv'1,Sv'2,...,Sv'm,...,Sv'MWhere Δ r is the distance high resolution,
Figure BDA0003495578690000033
c is light velocity, Sv'mFor the mth set of rewritten range time domain velocity frequency domain signals,
Figure BDA0003495578690000034
the distance time domain velocity frequency domain signal is rewritten on the mth group kth velocity resolution unit;
(4b) for each rewritten distance time domain velocity frequency domain signal
Figure BDA0003495578690000035
Performing distance dimension FFT processing to obtain M groups of rewritten distance frequency domain signals;
(4c) and constructing a speed phase compensation item corresponding to each rewritten distance frequency domain signal:
constructing a speed phase compensation item corresponding to each rewritten distance frequency domain signal to obtain M groups of speed compensation phase items (phi)1,φ2,...,φm,...,φMIn which is phimFor the m-th set of velocity phase compensation terms, phim＝{φm1(fr),φm2(fr),...,φmk(fr),...,φm2MN(fr)}，φmk(fr) Velocity phase compensation term for the mth set of kth velocity units, frIs the range frequency;
(4d) and performing coherent projection processing on each rewritten distance frequency domain signal:
multiplying each rewritten distance frequency domain signal by the corresponding speed phase compensation term, and transforming the multiplied signals to a distance time domain through distance dimension IFFT processing to obtain M groups of coherent projected signals ss ═ { ss ═1,ss2,...,ssm,...,ssMWhere, ssmFor the mth group of signals after the coherent projection,
Figure BDA0003495578690000041
the signal after the coherent projection on the mth group kth speed resolution unit;
(4e) and accumulating all the signals after the phase-coherent projection to realize the phase-coherent accumulation of the frequency agile anti-interference signals.
Compared with the prior art, the invention has the following advantages:
according to the invention, the frequency block coding processing is carried out on the frequency agile signal, the limitation on the pulse carrier frequency hopping mode is smaller, and the mode of restricting repetition frequency agile is not needed, so that the waveform freedom degree is higher, the signal is not easy to be intercepted by an interference machine, and the anti-interference performance of the frequency agile signal is improved; meanwhile, the invention performs distance speed traversal in the pulse group on the frequency-agile frequency conversion signals after the frequency block coding, and coherent accumulation among the pulse groups, so that no grid division is needed, thereby solving the problem that the accumulation result has false peaks due to grid mismatch in the prior art.
Drawings
FIG. 1 is a flow chart of an implementation of the present invention;
FIG. 2 is a graph of the results of coherent accumulation of agile frequency anti-interference signals using the present invention;
FIG. 3 is a diagram of the results of coherent accumulation of agile frequency anti-interference signals using a two-dimensional reconstruction algorithm;
FIG. 4 is a diagram showing the result of coherent accumulation of the agile anti-interference signals by the variable period method.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
Referring to fig. 1, the present invention includes the steps of:
step 1) carrying out frequency block coding on the pulse signals:
dividing frequency agile signals generated by a frequency agile radar in a coherent processing time into M groups averagely, wherein each group comprises N pulses, and performing frequency coding on carrier frequency of each pulse to obtain a set F consisting of M groups of frequency coding pulses, wherein in the embodiment, M is 32, N is 64, and carrier frequency of the mth group of nth frequency coding pulses in F is Fmn＝f0+gmnΔf，m＝1,2,...,M，n＝1,2,...,N，f0Is the carrier frequency reference, Δ f is the minimum hop interval, gmnThe frequency coding value of the nth frequency coding pulse of the mth group is coded, and the pulse frequency coding values g with the same pulse sequence number are arranged among all the pulse groups1,n～gM,nAre different from each other, i.e. g1,n～gM,nTraversing all integers from 1 to M;
after frequency block coding is carried out on the frequency agile signals, N pulse signals in each group are processed, then pulse inter-group coherent accumulation is carried out on results after M groups of processing, and at the moment, pulse frequency coding values g are generated among M groups of results1,n～gM,nTraversing all integers within 1-M, ensuring the coherence of the signals processed between pulse groups at the position of a target point, and enabling the target point to be accumulated, but not the target point, so as to highlight the target and realize the purpose of target detection.
Step 2) preprocessing the echo signal of each frequency-coded pulse, comprising the following steps:
step 2a) obtaining the echo signal of each frequency coding pulse reflected by a single target, wherein the echo signal set corresponding to the frequency coding pulse set F is s ═ s1,s2,...,sm,...,sMIn which s ismFor echo signals of the m-th group of frequency-coded pulses, sm＝{sm1(t),sm2(t),...,smn(t),...,smN(t)}，smn(t) is the echo signal of the mth group of nth frequency encoding pulses, smnThe expression of (t) is:
Figure BDA0003495578690000051
where t is the fast time, rect (-) is a rectangular function,
Figure BDA0003495578690000052
for time delay, R is the radial distance of the individual target relative to the radar, v is the radial velocity of the individual target relative to the radar, and c is the lightSpeed, tn(m-1) N + N) T is the slow time, T is the pulse repetition period, P is the pulse width, j is the imaginary unit, and γ is the chirp rate;
step 2b) for each echo signal smn(t) performing pulse compression processing, wherein the peak value after the pulse pressure of each echo signal is positioned
Figure BDA0003495578690000053
Where, and without taking into account envelope walking within the pulse group, smThe signal at the corresponding pulse-compressed peak value is s'm＝{s'm1,s'm2,...,s'mn,...,s'mN}，s'mnThe expression of (c) is:
Figure BDA0003495578690000054
for the signals at the peak value after the compression of the M groups of pulses, the distance traversal range is the maximum unambiguous detection range of the radar signals: for a random frequency agile signal, the distance traversal range is DeltaR,
Figure BDA0003495578690000055
meanwhile, the division of the range resolution unit is in accordance with the step frequency theoretical resolution, if the theoretical resolution is low, the target accumulation sidelobe is still high after the traversal is performed by using the dense division, and the resolution cannot be obviously improved, so that the theoretical resolution is required to be attached when the range resolution unit interval is set, so that the theoretical optimal accumulation effect is achieved, and meanwhile, the calculation resources are saved; since the distance resolution of the frequency agile signal is deltar,
Figure BDA0003495578690000056
accordingly, the range Δ R can be divided into D high resolution range units,
Figure BDA0003495578690000057
thus compressing the signal s 'at the post-peak value per pulse'mnDiscretizing into D high-resolution range unit signalsEstablishing distance phase compensation items corresponding to each high-resolution distance unit signal to obtain M groups of distance phase compensation items
Figure BDA0003495578690000061
Wherein the m-th group of signals s 'paired at post-pulse pressure peak'mThe corresponding distance phase compensation term is
Figure BDA0003495578690000062
The expression of (a) is:
Figure BDA0003495578690000063
wherein D is 1,2, and D is a high-resolution distance unit serial number;
step 2c) distance traversing processing is carried out on the signal at the peak value after each pulse pressure:
multiplying the distance phase compensation item of each pulse signal on each high-resolution distance unit with the signal at the corresponding pulse pressure post-peak value to obtain M groups of distance traversed two-dimensional time domain signals sr ═ { sr ═1,sr2,...,srm,...,srMWhere sr ism＝{srm1(d),srm2(d),...,srmn(d),...,srmN(d) Is a two-dimensional time domain signal after the mth group of pulse distance traversal, srmn(d) For the m-th group of the two-dimensional time domain signals after the n pulse distance traversal, srmn(d) The expression of (a) is:
Figure BDA0003495578690000064
step 3) performing speed traversal processing on the two-dimensional time domain signal after each distance traversal:
at a central frequency f0Calculating a maximum unambiguous speed interval Δ V:
Figure BDA0003495578690000065
in which the negative sign indicates that the target is moving in the direction of the radar and prf is the pulse repetitionFrequency, velocity resolution of
Figure BDA0003495578690000066
Uniformly dividing the maximum unambiguous velocity interval delta V into 2MN velocity resolution units, calling the dimensionality of N discretized signals on each high resolution distance unit in each pulse as a velocity dimension, zero-filling the length of the signals on each velocity dimension to 2MN, and performing velocity dimension FFT processing on the signals to obtain M sets of distance time domain velocity frequency domain signals Sv ═ { Sv ═ after velocity traversal1,Sv2,...,Svm,...,SvMIn which Sv ism＝{Svm1(k),Svm2(k),...,Svmd(k),...,SvmD(k)}，SvmFor the distance time domain velocity frequency domain signal Sv after the mth group signal velocity traversalmd(k) Is a distance time domain velocity frequency domain signal Sv after the signal velocity on the mth group of high resolution distance units is traversedmd(k) The expression of (a) is:
Figure BDA0003495578690000071
wherein, k is 1,2, and 2MN is a speed resolution unit serial number;
at this time, in each pulse group, the target is located at (v)1,r1) Therein is disclosed
Figure BDA0003495578690000072
Is the speed unit at which the object is located,
Figure BDA0003495578690000073
a distance unit where the target is located; however, because the phase is not coherent due to the frequency agility in the pulse group, the main lobe of each pulse group is widened and the amplitude is reduced by using the coherent accumulation result obtained by the IFFT processing during the speed traversal, and the target cannot be highlighted, so that a plurality of pulse group signals are required to perform coherent accumulation between the pulses, thereby highlighting the target and realizing target detection.
Step 4) carrying out coherent projection processing on the distance time domain speed frequency domain signal after traversing each speed, comprising the following steps:
when the inter-pulse coherent accumulation is performed between different pulse groups via the intra-pulse group, due to the influence of speed, the target is located on different distance resolution units, and the inter-pulse coherent accumulation cannot be directly performed, so that the positions of the targets between different pulse groups need to be aligned in distance by adopting coherent projection processing, and the coherent projection processing can be quickly realized by performing FFT processing on signals on each speed resolution unit and performing phase compensation on the signals in a frequency domain;
step 4a) rewriting the distance time domain velocity frequency domain signal after each velocity traversal:
make the fast time after rewriting be
Figure BDA0003495578690000074
And will be
Figure BDA0003495578690000075
Substituting the signals into the distance time domain velocity frequency domain signals after traversing each velocity to obtain M groups of rewritten distance time domain velocity frequency domain signals Sv '═ { Sv'1,Sv'2,...,Sv'm,...,Sv'MTherein of
Figure BDA0003495578690000076
Sv'mFor the mth set of rewritten range time domain velocity frequency domain signals,
Figure BDA0003495578690000077
for the distance time domain velocity frequency domain signal after rewriting on the mth group kth velocity resolution unit,
Figure BDA0003495578690000078
the expression of (a) is:
Figure BDA0003495578690000079
step 4b) for each rewritten distance time domain velocity frequency domain signal
Figure BDA0003495578690000081
Performing distance dimension FFT processing to obtain M groups of rewritten distance frequency domain signals;
step 4c) constructing a velocity phase compensation term corresponding to each rewritten distance frequency domain signal:
according to each rewritten distance frequency domain signal, constructing a speed phase compensation item corresponding to the distance frequency domain signal to obtain M groups of speed compensation phase items { phi1,φ2,...,φm,...,φMIn which phim＝{φm1(fr),φm2(fr),...,φmk(fr),...,φm2MN(fr)}，φmFor the m-th set of velocity phase compensation terms, phimk(fr) A velocity phase compensation term, phi, for the mth set of kth velocity unitsmk(fr) The expression of (a) is:
Figure BDA0003495578690000082
in the formula (f)rIs the range frequency;
step 4d) carrying out coherent projection processing on each rewritten distance frequency domain signal:
multiplying each rewritten distance frequency domain signal by the corresponding speed phase compensation term, and transforming the multiplied signals to a distance time domain through distance dimension IFFT processing to obtain M groups of coherent projected signals ss ═ { ss ═1,ss2,...,ssm,...,ssMTherein of
Figure BDA0003495578690000083
ssmFor the mth group of signals after the coherent projection,
Figure BDA0003495578690000084
for the coherent projected signal on the mth set of kth velocity resolution cells,
Figure BDA0003495578690000085
the expression of (c) is:
Figure BDA0003495578690000086
after phase-coherent projection, the target is located at (v) in the signal matrix of each pulse groupk,rd) Therein is disclosed
Figure BDA0003495578690000087
Is the speed unit at which the object is located,
Figure BDA0003495578690000088
the distance unit of the target, the target position (v) in the mth pulse groupk,rd) The coherent projected signal can be expressed as:
Figure BDA0003495578690000091
step 4e) accumulating all the signals after the coherent projection, and realizing coherent accumulation of the frequency agile anti-interference signals:
because the pulse groups have the same pulse sequence number pulse frequency code g1,n～gM,nTraversing all integers from 1 to M, so that when the signals after the phase-coherent projection of each pulse group are added, the phases of the signals at the same slow time are coherent, and therefore, the signal of the position of the target point after the accumulation between the pulses can be represented as:
Figure BDA0003495578690000092
after the M groups of signals after the phase-coherent projection are accumulated, the signal at the target position is equivalent to the sum of the accumulated N groups of phase-coherent signals with the length of M, and a target peak value appears at the point; the non-target point position is non-coherent in phase during the accumulation of the pulse groups, and a fixed peak value cannot be formed after the accumulation in the pulse groups, so that each accumulation between the pulse groups is a random value, and the amplitude value at the non-target point finally approaches to zero after the accumulation of a plurality of groups, thereby highlighting the target and realizing the target detection.
The technical effects of the invention are further explained by simulation experiments as follows:
1. simulation conditions and content
1 point target is arranged according to a receiver coordinate system in a ground scene, a simulation test is carried out on the same computer by using MATLAB R2017a, a coherent accumulation simulation test is respectively carried out on echoes of the frequency agile anti-interference signal by using a variable period method and a two-dimensional reconstruction algorithm in the prior art, and the parameters of the simulation test for obtaining the echoes are set as follows: the total number of pulse groups M is 32, the total number of pulses N in one pulse group is 64, and the carrier frequency reference f016GHz, the minimum frequency hopping interval Δ f is 60MHz, the radial distance R of the target relative to the radar is 201.24m, and the radial speed v of the target relative to the radar is 22 m/s;
simulation 1, carrying out a coherent accumulation simulation experiment on the echo of the frequency agile anti-interference signal of the invention, wherein the result is shown in fig. 2;
simulation 2, performing a coherent accumulation simulation experiment on the echo of the frequency agile anti-interference signal by using a two-dimensional reconstruction algorithm, wherein the result is shown in fig. 3;
and 3, performing a coherent accumulation simulation experiment on the echo of the frequency agile anti-interference signal by using a variable period method, wherein the result is shown in fig. 4.
2. And (3) simulation result analysis:
referring to fig. 2, it can be seen from the coherent accumulation result obtained by the present invention that the detected target distance is 201.3m, the speed is 21.97m/s, and the requirements of distance resolution and speed resolution under the condition of the simulation experiment of the present invention are satisfied;
referring to fig. 3, as can be seen from the results of coherent accumulation of echoes of the agile frequency anti-interference signals by using a two-dimensional reconstruction algorithm, because the problem of grid mismatch occurs under the simulation experiment condition of the present invention, the real parameters of the target do not fall on the preset grid, a plurality of pseudo peaks other than the real target occur;
referring to fig. 4, it can be seen from the result of performing coherent accumulation on the echo of the agile frequency anti-interference signal by using the variable period method, that the target echo cannot perform coherent accumulation because the phase non-coherence between pulses due to frequency agility cannot be compensated by using the heavy frequency coherent difference because the heavy frequency is not changed under the simulation experiment condition of the present invention;
in summary, the coherent accumulation result obtained by the method can obtain an accurate target detection result, no pseudo peak exists, and the problem of grid mismatch may occur when the coherent accumulation is performed by using a two-dimensional reconstruction algorithm, so that the pseudo peak is generated and the target detection performance is influenced, thereby demonstrating that the target detection performance of the method is better; meanwhile, when the phase-coherent accumulation is carried out by using the variable period method, because the repetition frequency coherent difference is needed to compensate the non-coherent phase, when the repetition frequency agility mode does not meet the condition or the repetition frequency is unchanged, the phase-coherent accumulation cannot be carried out, so that the target detection fails.

Claims (8)

1. A frequency block coded frequency agile frequency conversion anti-interference signal coherent accumulation method is characterized by comprising the following steps:
(1) carrying out frequency block coding on the pulse signals:
dividing frequency agile signals generated by a frequency agile radar in a coherent processing time into M groups averagely, wherein each group comprises N pulses, and carrying out frequency coding on carrier frequency of each pulse to obtain a set F consisting of M groups of frequency coded pulses, wherein M is more than or equal to 2, N is more than or equal to 8, and carrier frequency of the mth group of nth frequency coded pulses in F is Fmn＝f0+gmnΔf，m＝1,2,...,M，n＝1,2,...,N，f0Is the reference carrier frequency, Δ f is the minimum hop interval, gmnThe frequency coding value of the nth frequency coding pulse of the mth group is coded, and the pulse frequency coding values g with the same pulse sequence number are arranged among all the pulse groups1,n～gM,nAre different from each other, i.e. g1,n～gM,nTraversing all integers from 1 to M;
(2) preprocessing the echo signal of each frequency-coded pulse:
(2a) acquiring echo signals s of each frequency coding pulse reflected by a targetmn(t), echo signals corresponding to the frequency coded pulse set FSet of numbers s ═ s1,s2,...,sm,...,sMIn which s ismEncoding the echo signal of the pulse for the mth group of frequencies, sm＝{sm1(t),sm2(t),...,smn(t),...,smN(t)}，smn(t) is the echo signal of the mth group nth frequency coding pulse, and t is the fast time;
(2b) for each echo signal smn(t) pulse-compressing the signal s 'at the peak value after each pulse compression'mnDiscretizing into D high-resolution range unit signals, constructing range and phase compensation terms corresponding to each high-resolution range unit signal, and obtaining M groups of range and phase compensation terms
Figure FDA0003495578680000011
Wherein s ismThe signal at the corresponding post-pulse compression peak value is s'm＝{s'm1,s'm2,...,s'mn,...,s'mN}，s'mThe corresponding distance phase compensation term is
Figure FDA0003495578680000012
D is the serial number of the high-resolution distance unit;
(2c) and (3) performing distance traversal processing on the signal at the peak after each pulse pressure:
multiplying the distance phase compensation item of each pulse signal on each high-resolution distance unit with the signal at the corresponding pulse pressure post-peak value to obtain M groups of distance traversed two-dimensional time domain signals sr ═ { sr ═1,sr2,...,srm,...,srMWhere sr ismFor the m-th group of two-dimensional time domain signals after pulse distance traversal, srm＝{srm1(d),srm2(d),...,srmn(d),...,srmN(d)}，srmn(d) Traversing the nth pulse distance for the mth group of pulse distances;
(3) performing speed traversal processing on the two-dimensional time domain signal after each distance traversal:
discretizing N numbers of pixels per high resolution range bin in each pulseThe dimension of the signal after being transformed is called as a velocity dimension, the length of the signal in each velocity dimension is filled with zero to 2MN, and the velocity dimension FFT processing is carried out on the signals to obtain M sets of distance time domain velocity frequency domain signals Sv ═ { Sv ═ Sv after velocity traversal1,Sv2,...,Svm,...,SvMIn which, SvmFor the distance time domain velocity frequency domain signal Sv after the mth group signal velocity traversalm＝{Svm1(k),Svm2(k),...,Svmd(k),...,SvmD(k)}，Svmd(k) A distance time domain velocity frequency domain signal after traversing the signal velocity on the mth group of the mth high resolution distance unit, where k is 1, 2.
(4) Carrying out coherent projection processing on the distance time domain speed frequency domain signal after each speed traversal:
(4a) rewriting the distance time domain speed frequency domain signal after each speed traversal:
make the fast time after rewriting be
Figure FDA0003495578680000021
And will be
Figure FDA0003495578680000022
Substituting the signals into the distance time domain and velocity frequency domain signals after each velocity traversal to obtain M groups of rewritten distance time domain and velocity frequency domain signals Sv ═ { Sv'1,Sv'2,...,Sv'm,...,Sv'MWhere Δ r is the distance high resolution,
Figure FDA0003495578680000023
c is light velocity, Sv'mFor the mth set of rewritten range time domain velocity frequency domain signals,
Figure FDA0003495578680000024
Figure FDA0003495578680000025
for the distance time domain velocity frequency domain signal after rewriting on the mth group kth velocity resolution unit；
(4b) For each rewritten distance time domain velocity frequency domain signal
Figure FDA0003495578680000026
Performing distance dimension FFT processing to obtain M groups of rewritten distance frequency domain signals;
(4c) and constructing a speed phase compensation item corresponding to each rewritten distance frequency domain signal:
constructing a speed phase compensation item corresponding to each rewritten distance frequency domain signal to obtain M groups of speed compensation phase items (phi)1,φ2,...,φm,...,φMIn which is phimFor the m-th set of velocity phase compensation terms, phim＝{φm1(fr),φm2(fr),...,φmk(fr),...,φm2MN(fr)}，φmk(fr) Velocity phase compensation term for the mth set of kth velocity units, frIs the range frequency;
(4d) and performing coherent projection processing on each rewritten distance frequency domain signal:
multiplying each rewritten distance frequency domain signal by the corresponding speed phase compensation term, and transforming the multiplied signals to a distance time domain through distance dimension IFFT processing to obtain M groups of coherent projected signals ss ═ { ss ═1,ss2,...,ssm,...,ssMWhere, ssmFor the mth group of signals after the coherent projection,
Figure FDA0003495578680000031
Figure FDA0003495578680000032
the signal after the coherent projection on the mth group kth speed resolution unit;
(4e) and accumulating all the signals after the phase-coherent projection to realize the phase-coherent accumulation of the frequency agile anti-interference signals.
2. A frequency block coding as claimed in claim 1The coherent accumulation method of the frequency agile anti-interference signals is characterized in that s in the step (2a)mn(t), the expression of which is:
Figure FDA0003495578680000033
wherein rect (-) is a rectangular function,
Figure FDA0003495578680000034
for time delay, R is the radial distance of the individual target relative to the radar, v is the radial velocity of the individual target relative to the radar, tnWhere ((m-1) N + N) T is the slow time, T is the pulse repetition period, P is the pulse width, j is the imaginary unit, and γ is the chirp rate.
3. The coherent accumulation method of frequency-agile frequency-division-coded anti-jamming signals according to claim 1, wherein s 'in step (2 b)'mnAnd an
Figure FDA0003495578680000035
The expressions are respectively:
Figure FDA0003495578680000036
Figure FDA0003495578680000037
in the formula, tnWhere ((m-1) N + N) T is the slow time, T is the pulse repetition period, R is the radial distance of a single target from the radar, v is the radial velocity of a single target from the radar, and j is the imaginary unit.
4. The method of claim 1, wherein the step of performing coherent accumulation of the agile anti-interference signal comprisesSr described in step (2c)mn(d) The expression is as follows:
Figure FDA0003495578680000041
where T is the pulse repetition period, R is the radial distance of the individual target from the radar, v is the radial velocity of the individual target from the radar, and j is an imaginary unit.
5. The method as claimed in claim 1, wherein the Sv in step (3) is a coherent accumulation method of Sv signalsmd(k) The expression is as follows:
Figure FDA0003495578680000042
where T is the pulse repetition period, R is the radial distance of the individual target from the radar, v is the radial velocity of the individual target from the radar, and j is an imaginary unit.
6. The coherent accumulation method for frequency block coded agile anti-interference signals according to claim 1, wherein the step (4a) is performed by
Figure FDA0003495578680000043
The expression is as follows:
Figure FDA0003495578680000044
where T is the pulse repetition period, R is the radial distance of the individual target from the radar, v is the radial velocity of the individual target from the radar, and j is an imaginary unit.
7. The agile frequency reactance of a frequency block coding according to claim 1The coherent integration method of interference signals, characterized in that phi in step (4c)mk(fr) The expression is as follows:
Figure FDA0003495578680000051
wherein j is an imaginary unit,
Figure FDA0003495578680000052
for speed resolution, prf is the pulse repetition frequency and T is the pulse repetition period.
8. The method of claim 1, wherein the step (4d) comprises the step of performing coherent accumulation on the frequency-agile anti-interference signals with the frequency block coding
Figure FDA0003495578680000053
The expression is as follows:
Figure FDA0003495578680000054
wherein T is a pulse repetition period, j is an imaginary unit,
Figure FDA0003495578680000055
for velocity resolution, prf is the pulse repetition frequency, R is the radial distance of the individual target relative to the radar, and v is the radial velocity of the individual target relative to the radar.
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CN114779177A (en) * 2022-06-17 2022-07-22 中国人民解放军空军预警学院 Coherent processing method for frequency diversity waveform
CN115453490A (en) * 2022-11-10 2022-12-09 艾索信息股份有限公司 Coherent accumulation method, device and equipment based on radar signals and storage medium
CN116736240A (en) * 2023-06-25 2023-09-12 中国人民解放军空军预警学院 Compatible method for inter-pulse frequency agility and coherent processing

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CN114779177A (en) * 2022-06-17 2022-07-22 中国人民解放军空军预警学院 Coherent processing method for frequency diversity waveform
CN114779177B (en) * 2022-06-17 2022-09-30 中国人民解放军空军预警学院 Coherent processing method for frequency diversity waveform
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CN116736240A (en) * 2023-06-25 2023-09-12 中国人民解放军空军预警学院 Compatible method for inter-pulse frequency agility and coherent processing
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