CN114764136A - Radar anti-interference waveform generation method based on multi-time scale coupling network - Google Patents

Radar anti-interference waveform generation method based on multi-time scale coupling network Download PDF

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CN114764136A
CN114764136A CN202110027839.4A CN202110027839A CN114764136A CN 114764136 A CN114764136 A CN 114764136A CN 202110027839 A CN202110027839 A CN 202110027839A CN 114764136 A CN114764136 A CN 114764136A
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signal
waveform
transmitting
pulse
radar
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熊清
胡文
赵月
董浩
姚翼荣
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Jiangsu Yunhefeng Intelligent Technology Co ltd
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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

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

The invention relates to the technical field of radar signal processing, and discloses a radar anti-interference waveform generation method in a multi-time scale coupling network. The invention aims to design an MIMO radar waveform with better orthogonality and anti-jamming capability, a reference signal of broadband matched filtering is generated by a multi-time scale coupling network, and a processing method of an echo is given; the transmit waveforms between each subarray of the MIMO radar are required to satisfy orthogonality, so that the transmit waveforms between each subarray can be distinguished at a receiving end through matched filtering.

Description

Radar anti-interference waveform generation method based on multi-time scale coupling network
Technical Field
The invention relates to the technical field of radar signal processing, in particular to a radar anti-interference waveform generation method based on a multi-time scale coupling network.
Background
The waveform design is a very basic work in the radar development process, and comprises the selection of signal waveforms and the optimization of related parameters, and also comprises the optimization of matching processing weights. Different types of waveform design modes have a large gap, but for the MIMO radar, the orthogonality of the sidelobe suppression and the waveform is always the focus of the waveform design.
Orthogonal waveforms of the MIMO radar are divided into frequency-division orthogonal waveforms and coding-type orthogonal waveforms, if only frequency-division orthogonal waveforms or coding-type orthogonal waveforms are considered, when a plurality of sub-arrays of the MIMO radar are used, orthogonality among the sub-arrays is reduced, and target detection of the MIMO radar is affected. Meanwhile, if the frequency-division orthogonal waveform needs to obtain lower autocorrelation sidelobes, the number of pulses is more, so that the coherent processing period is longer, and the measurement of a high-speed target is not facilitated.
According to the interference principle of a forwarding jammer, the interception receiver can interfere the radar only by accurately extracting the frequency, phase, amplitude and pulse position information of a signal transmitted by the radar. The MIMO radar has high parameter freedom degree of transmitting waveform and low signal space radiation power, and increases the difficulty brought by the interference machine to accurately extract the frequency, phase and pulse position information of the radar signal. The waveform design of the invention jointly considers the orthogonality and the anti-interference capability of the waveform. On the basis of a linear frequency modulation pulse train, phase coding with the coding length of M is carried out in a single pulse, random agility of frequency and pulse positions is carried out among the pulses, and after the waveform is optimized through a genetic algorithm, the frequency, the phase and the pulse positions of the waveform have randomness, so that the waveform has the capability of resisting transfer type interference while the orthogonality of the waveform is ensured.
In echo signal processing, the traditional signal processing is to use an echo signal as a narrow-band signal, perform matched filtering on each subarray echo pulse at the same time, and obtain distance and speed information of a target through coherent accumulation and constant false alarm processing. The echo processing of the broadband modulation signal by the traditional narrowband signal processing method needs complex phase compensation between pulses. In addition, when the target is in a high-speed motion state and the displacement exceeds one distance resolution unit in the coherent processing period, the processing error is larger according to the traditional narrow-band echo. Aiming at the problem of large error of a narrow-band processing algorithm, the invention adopts a multi-time scale-based broadband signal fuzzy function matching algorithm to improve the measurement precision of the target distance and speed.
Disclosure of Invention
The invention provides a radar anti-interference waveform generation method based on a multi-time scale coupling network, aiming at the defects in the background technology, the orthogonality and the anti-interference performance of the waveform are comprehensively considered, and the radar anti-interference waveform generation method based on the multi-time scale coupling network is provided.
The invention provides the following technical scheme: the radar anti-interference waveform generating method based on the multi-time scale coupling network mainly comprises the steps of generating a transmitting waveform and processing an echo signal, and comprises the following steps of:
the method comprises the following steps: constructing a mathematical model of the transmitting waveform of the MIMO radar, giving a time-frequency relation graph of the array transmitting signal, and obtaining coding parameters needing to be optimized in waveform design;
step two: constructing a waveform optimization cost function according to the waveform design orthogonality principle of the MIMO radar, optimizing coding parameters by using a genetic algorithm, and constructing an MIMO radar transmitting waveform;
step three: combining the broadband signal matching filtering principle to provide the beam forming and target range and speed information extraction processing process of the MIMO radar;
step four: according to the broadband signal fuzzy function theory, a group of matched filtering reference signals are generated while MIMO radar transmitting waveforms are generated, a multi-time scale coupling network hardware system is designed, and a corresponding group of matched filtering reference signals are generated while radar transmitting signals are generated.
Preferably, the main modeling process of the MIMO radar anti-interference composite modulation signal is as follows:
the MIMO radar is provided with L sub-arrays, the number of pulses in one CPI is N, phase coding with the code length of M is adopted in each pulse, and a mathematical model of a signal transmitted by the first sub-array is given:
Figure BDA0002890978560000031
in the above formula, TrIs the average pulse period, Δ T, of the sub-pulsesrIs the minimum pulse position jump interval, tpIs the pulse width, tsIn order to phase encode the symbol width,
Figure BDA0002890978560000032
is the carrier of the nth sub-pulse,
Figure BDA0002890978560000033
mu is the frequency-modulated slope of the frequency,
Figure BDA0002890978560000034
for the mth code element of the nth sub-pulse, the waveform optimization parameter is as follows from the mathematical model of the transmitted signal
Figure BDA0002890978560000035
Expressed as a vector
Figure BDA0002890978560000036
Ω＝[ξ1,ξ2,L,ξN]、
Figure BDA0002890978560000037
In the waveform parameters, the number of phase encoding bits in each pulse is M bits, and each code element is a four-phase code; the minimum range of frequency jump between pulses is 1/tpEnsuring orthogonality among pulses; the pulse interval of each pulse also jumps randomly within a range, and the anti-interference performance of the signal is improved.
Preferably, the method for optimizing the anti-interference waveform of the MIMO radar specifically includes:
the orthogonality of the MIMO radar is shown in the autocorrelation and cross-correlation performance of signals transmitted among subarrays, and the signals transmitted in the invention are required to have lower autocorrelation side lobe peak values and cross-correlation peak values, so the peak side lobe level criterion (PSL) is adopted to carry out orthogonal waveform design:
Figure BDA0002890978560000038
Figure BDA0002890978560000039
in the above formula, sp(t) and sq(t) is the transmission signal of different subarrays, when p is q, cpq(τ) is an autocorrelation function of the transmitted signal; when p ≠ q, cpq(tau) is the cross-correlation function of the emission signal, the invention takes the phase coding matrix of the emission waveform, the frequency coding sequence of the carrier wave and the pulse position agility sequence as optimization variables, takes the peak value and the sidelobe ratio of the emission signal as a cost function, and establishes the following optimization model:
Figure BDA0002890978560000041
the optimization parameters of the model are discrete phase, frequency and pulse position codes, and the model can be optimized by adopting a genetic algorithm to obtain an MIMO orthogonal waveform meeting the conditions.
Preferably, the MIMO radar broadband ambiguity function waveform separation and beamforming result:
considering that in a transmitting-receiving co-located MIMO radar system, the number of array elements of a transmitting antenna and the number of array elements of a receiving antenna are respectively P and Q, the transmitting and the receiving are both uniform linear arrays, and the spacing between the array elements of the transmitting antenna and the receiving antenna is respectively dtAnd drThe target arrival direction is
Figure BDA0002890978560000042
Definition sk(t) denotes the transmitted signal of the mth transmitting antenna element, s ═ s1(t),s2(t),L,sP(t)]Representing a transmitting signal vector, wherein M transmitting signals are propagated through space, and a composite signal of the M transmitting signals reaching a target located at an oblique distance R (corresponding to an R-th distance unit) and in an azimuth direction theta is as follows:
Figure BDA0002890978560000043
xi in the formula1For propagation attenuation factor, let the transmit signal be the same for each subarray, ω ═ c-v)/(c + v) is the scale parameter, τkThe delay difference of the signal transmitted for the kth (k ═ 1,2, L, M) array element with respect to the reference array element can be expressed as:
Figure BDA0002890978560000044
above formula taukFixed time delay tau, dependent only on antenna layout and not on the state of motion of the targetkCan use
Figure BDA0002890978560000045
Thus the composite signal at the target is:
Figure BDA0002890978560000051
in the above formula
Figure BDA0002890978560000052
In order to transmit a signal steering vector,
Figure BDA0002890978560000053
the vector of the received signal at the target can be expressed as
Figure BDA0002890978560000054
Wherein tau is0＝2R0/(c-v)；
The signal r (t) is reflected by a target of a certain RCS, and the signal received by the qth receiving antenna is:
Figure BDA0002890978560000055
in the formula (I), the compound is shown in the specification,
Figure BDA0002890978560000056
for the q-th antenna phase difference, let xi in the equation1ξ2When equation (1) is substituted for equation (8), the echo of the qth receiving antenna is:
Figure BDA0002890978560000057
the received signal vector is x (t) ═ x1(t),x2(t),L,xQ(t)]The matrix form of equation (9) is as follows:
x(t)＝ξb(θr)αT(θt)s[ω(t-τ0)](10)
b (θ) in formula (10)r) In order to receive the antenna steering vector,
Figure BDA0002890978560000058
now, considering the wideband matching process of the reception echo of the q-th receiving antenna, the q-th reception channel echo signal obtained from equation (10) is:
Figure BDA0002890978560000059
now, the q-th receiving antenna echo signal is subjected to broadband matching filtering, and the reference signal of the p-th transmitting channel is known by the broadband fuzzy function theory as follows:
Figure BDA00028909785600000510
the matching output of the qth receiving channel receiving the pth transmitting channel signal is:
Figure BDA0002890978560000061
the above formula T is the burst duration, and it can be known from the orthogonality of the transmitted signals that only the signal of the pth transmission channel in the transmitted signal vector is output, and the matching output can be simplified as:
Figure BDA0002890978560000062
from the above formula, when ω ═ ηm，τ0＝ξmThe maximum output of the matched filter is recorded as
Figure BDA0002890978560000063
The echo signal can obtain the distance and speed information of the target after passing through the broadband matching network, and then the azimuth angle of the target can be obtained through beam forming, wherein the output of the beam forming is as follows:
Figure BDA0002890978560000064
in the formula (15), the reaction mixture is,
Figure BDA0002890978560000065
for the output of the broadband matched filtering, τ0Time delay and Doppler frequency targeted to ω when
Figure BDA0002890978560000066
Then, the above equation has a maximum value, where the target direction is:
Figure BDA0002890978560000067
preferably, the generation of radar emission signal and the generation of broadband echo matching signal are simultaneously carried out, and the output of orthogonal waveform is generated by DDS waveform generator according to frequency and phase coding sequence
Figure BDA0002890978560000068
Amplitude values of the waveform at the corresponding phases, which amplitude values generate a series of sub-pulses, each of which
Figure BDA0002890978560000069
The duration of (c) is determined by the bandwidth of the radar; the pulse time sequence control module changes the pulse period between pulses to realize waveform pulse position agility modulation; after the MIMO radar orthogonal waveform is generated, one path of signal is sent to an MIMO radar transmitting antenna, and the other path of signal is used as the input of a multi-time scale coupling network circuit to generate a reference signal of broadband matched filtering of an echo signal;
the broadband matching network is essentially used for searching the maximum value of a two-dimensional fuzzy function of an echo signal, a reference signal of the broadband matching network is generated while a transmitting end generates a transmitting signal, and the purpose of the multi-time scale coupling network is to generate a group of signal groups of each subarray transmitting signal which are jointly shifted in time and frequency and used for broadband matching filtering of the echo signal; in the multi-time scale coupling circuit part, the transmitting signal delay tau of each sub-array is setkAnd performing matched filtering on all Doppler frequencies in the kth range gate to obtain a received signal of the kth range gate, and performing broadband pulse pressure processing on an echo signal of the kth range gate.
The invention has the following beneficial effects:
the invention aims to design an MIMO radar waveform with better orthogonality and anti-jamming capability, a reference signal of broadband matched filtering is generated by a multi-time scale coupling network, and a processing method of an echo is given; the transmit waveforms between each subarray of the MIMO radar are required to satisfy orthogonality, so that the transmit waveforms between each subarray can be distinguished at a receiving end through matched filtering.
The waveform of the invention carries out intra-pulse phase coding on the pulse string on the basis of linear frequency modulation, and the inter-pulse frequency and the pulse position are jointly and quickly changed, so that the waveform has better orthogonality and anti-interference performance, the echo signal adopts a broadband signal matching filtering theory, the echo signal is subjected to matching filtering to distinguish the echo signal of each transmitting channel, and finally the distance, the speed and the angle information of a target are obtained by combining digital beam forming.
The invention is characterized in that the transmitter generates a composite modulation transmitting signal, and simultaneously generates a reference signal group of broadband signal matched filtering through a multi-time scale coupling network, and can carry out broadband matched filtering on the signal of each receiving channel to obtain the speed and the distance of a target.
Drawings
FIG. 1 is a schematic diagram of the first sub-array of the present invention;
FIG. 2 is a time-frequency relationship diagram of a transmitting waveform of the MIMO radar of the present invention;
FIG. 3 is a flow chart of echo signal processing according to the present invention;
FIG. 4 is a diagram of a multi-time scale coupling network waveform generation system according to 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 drawings in 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.
Referring to fig. 1, the main contents of the method for generating an anti-interference waveform of a radar based on a multi-time-scale coupling network, the method for generating an anti-interference waveform of a radar based on a multi-time-scale coupling network include the generation of a transmit waveform and the processing of an echo signal, and the method includes the following steps:
the method comprises the following steps: constructing a mathematical model of the transmitting waveform of the MIMO radar, giving a time-frequency relation graph of the array transmitting signal, and obtaining coding parameters needing to be optimized in waveform design;
step two: constructing a waveform optimization cost function according to the waveform design orthogonality principle of the MIMO radar, optimizing coding parameters by using a genetic algorithm, and constructing an MIMO radar transmitting waveform;
step three: combining the broadband signal matching filtering principle to provide the beam forming and target distance and speed information extraction processing process of the MIMO radar;
step four: according to the broadband signal fuzzy function theory, a group of matched filtering reference signals are generated while MIMO radar transmitting waveforms are generated, a multi-time scale coupling network hardware system is designed, and a corresponding group of matched filtering reference signals are generated while radar transmitting signals are generated.
The anti-interference composite modulation signal of the MIMO radar comprises the following main modeling processes:
the MIMO radar is provided with L sub-arrays, the number of pulses in one CPI is N, phase coding with the code length of M is adopted in each pulse, and a mathematical model of a signal transmitted by the first sub-array is given:
Figure BDA0002890978560000081
in the above formula, TrIs the average pulse period, Δ T, of the sub-pulsesrIs the minimum pulse position jump interval, tpIs the pulse width, tsIn order to phase encode the symbol width,
Figure BDA0002890978560000091
is the carrier of the n-th sub-pulse,
Figure BDA0002890978560000092
mu is the frequency-modulated slope of the frequency,
Figure BDA0002890978560000093
for the mth code element of the nth sub-pulse, the waveform optimization parameter is as follows from the mathematical model of the transmitted signal
Figure BDA0002890978560000094
Expressed as a vector
Figure BDA0002890978560000095
Ω＝[ξ1,ξ2,L,ξN]、
Figure BDA0002890978560000096
In the waveform parameters, the number of phase encoding bits in each pulse is M bits, and each code element is a four-phase code; the minimum range of frequency jump between pulses is 1/tpEnsuring orthogonality among pulses; the pulse interval of each pulse also jumps randomly within a range, and the anti-interference performance of the signal is improved.
The method for optimizing the anti-interference waveform of the MIMO radar specifically comprises the following steps:
the orthogonality of the MIMO radar is shown in the autocorrelation and cross-correlation performance of signals transmitted among subarrays, and the signals transmitted in the invention are required to have lower autocorrelation side lobe peak values and cross-correlation peak values, so the peak side lobe level criterion (PSL) is adopted to carry out orthogonal waveform design:
Figure BDA0002890978560000097
Figure BDA0002890978560000098
in the above formula, sp(t) and sq(t) is the transmission signal of different sub-arrays, when p is q, cpq(τ) is an autocorrelation function of the transmitted signal; when p ≠ q, cpq(tau) is the cross-correlation function of the emission signal, the invention takes the phase coding matrix of the emission waveform, the frequency coding sequence of the carrier wave and the pulse position agility sequence as optimization variables, takes the peak value and the sidelobe ratio of the emission signal as a cost function, and establishes the following optimization model:
Figure BDA0002890978560000101
the optimization parameters of the model are discrete phase, frequency and pulse position codes, and the model can be optimized by adopting a genetic algorithm to obtain an MIMO orthogonal waveform meeting the conditions.
The MIMO radar broadband fuzzy function waveform separation and beam forming result is as follows:
considering that in a transmitting-receiving co-located MIMO radar system, the numbers of transmitting antenna array elements and receiving antenna array elements are respectively P and Q, the transmitting and receiving are both uniform linear arrays, and the array element distances of the transmitting antenna and the receiving antenna are respectively dtAnd drThe target arrival direction is
Figure BDA0002890978560000102
Definition sk(t) denotes the transmitted signal of the mth transmitting antenna element, s ═ s1(t),s2(t),L,sP(t)]Representing a transmitting signal vector, wherein M transmitting signals are propagated through space, and a composite signal of the M transmitting signals reaching a target located at an oblique distance R (corresponding to an R-th distance unit) and in an azimuth direction theta is as follows:
Figure BDA0002890978560000103
xi in the formula1For propagation attenuation factor, let the transmit signal be the same for each subarray, ω ═ c-v)/(c + v) is the scale parameter, τkThe delay difference of the signal transmitted for the kth (k ═ 1,2, L, M) array element with respect to the reference array element can be expressed as:
Figure BDA0002890978560000104
above formula taukFixed time delay tau, dependent only on antenna layout and independent of target motionkCan use
Figure BDA0002890978560000105
Thus the composite signal at the target is:
Figure BDA0002890978560000106
in the above formula
Figure BDA0002890978560000111
In order to transmit a signal steering vector,
Figure BDA0002890978560000112
the vector of the received signal at the target can be expressed as
Figure BDA0002890978560000113
Wherein tau is0＝2R0/(c-v)；
The signal r (t) is reflected by a target of a certain RCS, and the signal received by the qth receiving antenna is:
Figure BDA0002890978560000114
in the formula (I), the compound is shown in the specification,
Figure BDA0002890978560000115
for the q-th antenna phase difference, let xi in the equation1ξ2When equation (1) is substituted for equation (8), the echo of the qth receiving antenna is:
Figure BDA0002890978560000116
the received signal vector is x (t) ═ x1(t),x2(t),L,xQ(t)]The matrix form of equation (9) is as follows:
x(t)＝ξb(θr)αT(θt)s[ω(t-τ0)] (10)
b (θ) in the formula (10)r) In order to receive the antenna steering vector,
Figure BDA0002890978560000117
now consider the wideband matching process of the received echo for the q-th receive antenna, equation(10) The q-th receiving channel echo signal can be obtained as follows:
Figure BDA0002890978560000118
now, the q-th receiving antenna echo signal is subjected to broadband matching filtering, and the reference signal of the p-th transmitting channel is known by the broadband fuzzy function theory as follows:
Figure BDA0002890978560000119
the matching output of the qth receiving channel receiving the pth transmitting channel signal is:
Figure BDA00028909785600001110
the above formula T is the burst duration, and it can be known from the orthogonality of the transmitted signals that only the signal of the pth transmission channel in the transmitted signal vector is output, and the matching output can be simplified as:
Figure BDA0002890978560000121
in the above formula, when ω ═ ηm，τ0＝ξmWhen the matched filter has the maximum output, the maximum output of the matched filter is recorded as
Figure BDA0002890978560000122
The echo signal can obtain the distance and speed information of the target after passing through the broadband matching network, and then the azimuth angle of the target can be obtained through beam forming, wherein the output of the beam forming is as follows:
Figure BDA0002890978560000123
in the formula (15), the reaction mixture is,
Figure BDA0002890978560000124
for the output of the broadband matched filtering, τ0Time delay and Doppler frequency targeted to ω when
Figure BDA0002890978560000125
Then, the above equation has a maximum value, where the target direction is:
Figure BDA0002890978560000126
generating radar emission signal and broadband echo matching signal, and generating orthogonal waveform output by DDS waveform generator according to frequency and phase code sequence
Figure BDA0002890978560000127
Amplitude values of the waveform at the corresponding phases, which amplitude values generate a series of sub-pulses, each of which
Figure BDA0002890978560000128
Is determined by the bandwidth of the radar; the pulse time sequence control module changes the pulse period between pulses to realize waveform pulse position agility modulation; after the MIMO radar orthogonal waveform is generated, one path of signal is sent to an MIMO radar transmitting antenna, and the other path of signal is used as the input of a multi-time scale coupling network circuit to generate a reference signal of broadband matched filtering of an echo signal;
the broadband matching network is essentially used for searching the maximum value of a two-dimensional fuzzy function of an echo signal, a reference signal of the broadband matching network is generated while a transmitting end generates a transmitting signal, and the purpose of the multi-time scale coupling network is to generate a group of signal groups of each subarray transmitting signal which are jointly shifted in time and frequency and used for broadband matching filtering of the echo signal; in the multi-time scale coupling circuit part, the transmitting signal delay tau of each sub-array is setkFor the received signal of the kth range gate, and then at the kth rangeAnd performing matched filtering on all Doppler frequencies in the gate to realize the broadband pulse pressure processing on the echo signal of the kth range gate.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (5)

1. The radar anti-interference waveform generation method based on the multi-time scale coupling network mainly comprises the steps of transmitting waveform generation and echo signal processing, and is characterized in that: the method comprises the following steps:
the method comprises the following steps: constructing a mathematical model of the transmitting waveform of the MIMO radar, giving a time-frequency relation graph of array transmitting signals, and obtaining coding parameters needing to be optimized in waveform design;
step two: constructing a waveform optimization cost function according to the waveform design orthogonality principle of the MIMO radar, optimizing coding parameters by using a genetic algorithm, and constructing an MIMO radar transmitting waveform;
step three: combining the broadband signal matching filtering principle to provide the beam forming and target distance and speed information extraction processing process of the MIMO radar;
step four: according to the broadband signal fuzzy function theory, a group of matched filtering reference signals are generated while MIMO radar transmitting waveforms are generated, a multi-time scale coupling network hardware system is designed, and a corresponding group of matched filtering reference signals are generated while radar transmitting signals are generated.
2. The method for generating radar anti-jamming waveforms based on multi-time scale coupling network according to claim 1, wherein: the anti-interference composite modulation signal of the MIMO radar comprises the following main modeling processes:
the MIMO radar is provided with L sub-arrays, the number of pulses in one CPI is N, phase coding with the code length of M is adopted in each pulse, and a mathematical model of a signal transmitted by the first sub-array is given:
Figure FDA0002890978550000011
in the above formula, TrIs the average pulse period, Δ T, of the sub-pulsesrIs the minimum pulse position jump interval, tpIs the pulse width, tsIn order to phase encode the symbol width,
Figure FDA0002890978550000012
is the carrier of the nth sub-pulse,
Figure FDA0002890978550000013
mu is the frequency-modulated slope of the frequency,
Figure FDA0002890978550000014
for the mth code element of the nth sub-pulse, the waveform optimization parameter is as follows from the mathematical model of the transmitted signal
Figure FDA0002890978550000015
Expressed as a vector
Figure FDA0002890978550000016
Ω＝[ξ1,ξ2,L,ξN]、
Figure FDA0002890978550000017
In the waveform parameters, the number of phase encoding bits in each pulse is M bits, and each code element is a four-phase code; the minimum range of frequency jump between pulses is 1/tpEnsuring orthogonality among pulses; the pulse interval of each pulse also jumps randomly within a range, and the anti-interference performance of the signal is improved.
3. The method for generating radar anti-jamming waveforms based on multi-time scale coupling network according to claim 2, wherein: the MIMO radar anti-interference waveform optimization method specifically comprises the following steps of:
the orthogonality of the MIMO radar is shown in the autocorrelation and cross-correlation performance of signals transmitted among subarrays, and the signals transmitted in the invention are required to have lower autocorrelation side lobe peak values and cross-correlation peak values, so the peak side lobe level criterion (PSL) is adopted to carry out orthogonal waveform design:
Figure FDA0002890978550000021
Figure FDA0002890978550000022
in the above formula, sp(t) and sq(t) is the transmission signal of different sub-arrays, when p is q, cpq(τ) is an autocorrelation function of the transmitted signal; when p ≠ q, cpq(tau) is the cross-correlation function of the emission signal, the invention takes the phase coding matrix of the emission waveform, the frequency coding sequence of the carrier wave and the pulse position agility sequence as optimization variables, takes the peak value and the sidelobe ratio of the emission signal as a cost function, and establishes the following optimization model:
Figure FDA0002890978550000023
the optimization parameters of the model are discrete phase, frequency and pulse position codes, and the model can be optimized by adopting a genetic algorithm to obtain an MIMO orthogonal waveform meeting the conditions.
4. The method for generating radar anti-jamming waveforms based on multi-time scale coupling network according to claim 3, wherein: the MIMO radar broadband fuzzy function waveform separation and beam forming result is as follows:
considering that in a transmitting-receiving co-located MIMO radar system, the number of array elements of a transmitting antenna and the number of array elements of a receiving antenna are respectively P and Q, the transmitting and the receiving are both uniform linear arrays, and the spacing between the array elements of the transmitting antenna and the receiving antenna is respectively dtAnd drThe target arrival direction is
Figure FDA0002890978550000031
Definition sk(t) denotes the transmitted signal of the mth transmitting antenna element, s ═ s1(t),s2(t),L,sP(t)]Representing a transmitting signal vector, wherein M transmitting signals are propagated through space, and a composite signal of the M transmitting signals reaching a target located at an oblique distance R (corresponding to an R-th distance unit) and in an azimuth direction theta is as follows:
Figure FDA0002890978550000032
xi in the formula1For propagation attenuation factor, let the transmit signal be the same for each subarray, ω ═ c-v)/(c + v) is the scale parameter, τkThe delay difference of the signal transmitted for the kth (k ═ 1,2, L, M) array element with respect to the reference array element can be expressed as:
Figure FDA0002890978550000033
above formula taukFixed time delay tau, dependent only on antenna layout and not on the state of motion of the targetkCan use
Figure FDA0002890978550000034
Thus the composite signal at the target is:
Figure FDA0002890978550000035
in the above formula
Figure FDA0002890978550000036
In order to transmit a signal steering vector,
Figure FDA0002890978550000037
the vector of the received signal at the target can be expressed as
Figure FDA0002890978550000038
Wherein tau is0＝2R0/(c-v)；
The signal r (t) is reflected by a target of a certain RCS, and the signal received by the qth receiving antenna is:
Figure FDA0002890978550000041
in the formula (I), the compound is shown in the specification,
Figure FDA0002890978550000042
for the q-th antenna phase difference, let xi in the equation1ξ2When equation (1) is substituted for equation (8), the echo of the qth receiving antenna is:
Figure FDA0002890978550000043
the received signal vector is x (t) ═ x1(t),x2(t),L,xQ(t)]The matrix form of equation (9) is as follows:
x(t)＝ξb(θr)αT(θt)s[ω(t-τ0)] (10)
b (θ) in the formula (10)r) In order to receive the antenna steering vector,
Figure FDA0002890978550000044
now, considering the wideband matching process of the reception echo of the q-th receiving antenna, the q-th reception channel echo signal obtained from equation (10) is:
Figure FDA0002890978550000045
now, the q-th receiving antenna echo signal is subjected to broadband matching filtering, and the reference signal of the p-th transmitting channel is known by the broadband fuzzy function theory as follows:
Figure FDA0002890978550000046
the matching output of the qth receiving channel receiving the pth transmitting channel signal is:
Figure FDA0002890978550000047
the above formula T is the burst duration, and it can be known from the orthogonality of the transmitted signals that only the signal of the pth transmission channel in the transmitted signal vector is output, and the matching output can be simplified as:
Figure FDA0002890978550000051
from the above formula, when ω ═ ηm，τ0＝ξmWhen the matched filter has the maximum output, the maximum output of the matched filter is recorded as
Figure FDA0002890978550000052
The echo signal can obtain the distance and speed information of the target after passing through the broadband matching network, and then the azimuth angle of the target can be obtained through beam forming, wherein the output of the beam forming is as follows:
Figure FDA0002890978550000053
in the formula (15), the reaction mixture is,
Figure FDA0002890978550000054
for the output of the broadband matched filtering, τ0Time delay and Doppler frequency targeted to ω when
Figure FDA0002890978550000055
Then, the above equation has a maximum value, where the target direction is:
Figure FDA0002890978550000056
5. the method for generating radar anti-jamming waveforms based on multi-time scale coupling network according to claim 4, wherein: the said radar emission signal is generated and the broadband echo matching signal is generated at the same time, the output of the orthogonal waveform is generated by DDS waveform generator according to the frequency and phase code sequence
Figure FDA0002890978550000057
Amplitude values of the waveform at the corresponding phases, which amplitude values produce a series of sub-pulses, each of which is a pulse of a pulse width
Figure FDA0002890978550000058
The duration of (c) is determined by the bandwidth of the radar; the pulse time sequence control module changes the pulse period between pulses to realize waveform pulse position agility modulation; through a plurality of DDS circuits, MIMO radar positive signals can be generatedAfter orthogonal waveforms of the MIMO radar are generated, one path of signals are sent to an MIMO radar transmitting antenna, and the other path of signals are used as the input of a multi-time scale coupling network circuit to generate a reference signal of broadband matched filtering of echo signals;
the broadband matching network is essentially used for searching the maximum value of a two-dimensional fuzzy function of an echo signal, a reference signal of the broadband matching network is generated while a transmitting end generates a transmitting signal, and the purpose of the multi-time scale coupling network is to generate a group of signal groups of each subarray transmitting signal which are jointly shifted in time and frequency and used for broadband matching filtering of the echo signal; in the multi-time scale coupling circuit part, the transmitting signal delay tau of each sub-array is setkAnd performing matched filtering on all Doppler frequencies in the kth range gate to obtain a received signal of the kth range gate, and performing broadband pulse pressure processing on an echo signal of the kth range gate.
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