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

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-jamming 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 method for generating radar anti-jamming waveforms based on a multi-time scale coupling network.

Background technique

Waveform design is a very basic work in the process of radar development, including the selection of signal waveforms and the optimization of related parameters, as well as the optimization of matching processing weights. There is a big gap between different types of waveform design methods, but for MIMO radar, sidelobe suppression and waveform orthogonality are always the focus of waveform design.

Orthogonal waveforms of MIMO radars are divided into frequency-classified orthogonal waveforms and coded orthogonal waveforms. If only the frequency-classified orthogonal waveforms or coded orthogonal waveforms are used, when there are many subarrays of the MIMO radar, the difference between the subarrays will be reduced. Orthogonality will be reduced, which affects the detection of MIMO radars. At the same time, in order to obtain lower autocorrelation side lobes in frequency-classified orthogonal waveforms, a large number of pulses are required, so the coherent processing period is relatively long, which is not conducive to the measurement of high-speed targets.

According to the jamming principle of the repeater jammer, the intercepting receiver needs to accurately extract the frequency, phase, amplitude and pulse position information of the radar transmitted signal to interfere with the radar. The MIMO radar transmit waveform of the present invention has high parameter freedom and low signal space radiation power, and increasing the jammer to accurately extract the radar signal frequency, phase and pulse position information brings great difficulty. The waveform design of the present invention combines the orthogonality of the waveform and the anti-interference ability. On the basis of the chirp pulse train, a phase encoding with a coding length of M is carried out within a single pulse, and random agility of frequency and pulse position is carried out between pulses. After the waveform is optimized by genetic algorithm, the frequency, phase and pulse position of the waveform are The pulse position is random, which makes the waveform have the ability to resist transponder interference while ensuring the orthogonality of the waveform.

In the echo signal processing, the traditional signal processing is to use the echo signal as a narrowband signal, perform matched filtering on the echo pulses of each subarray at the same time, and then obtain the distance and speed information of the target through coherent accumulation and constant false alarm processing. The echo processing of broadband modulated signals by traditional narrowband signal processing methods requires complex phase compensation between pulses. In addition, when the target is in a high-speed motion state and the displacement exceeds one range resolution unit in the coherent processing period, the traditional narrowband echo processing error is large. Aiming at the problem that the error of the narrowband processing algorithm is relatively large, the present invention adopts a broadband signal fuzzy function matching algorithm based on multiple time scales to improve the measurement accuracy of the target distance and speed.

SUMMARY OF THE INVENTION

The invention provides a method for generating radar anti-jamming waveforms based on a multi-time scale coupling network. In view of the shortcomings of the above-mentioned background technology, the orthogonality and anti-jamming properties of waveforms are comprehensively considered, and a radar anti-jamming method based on a multi-time scale coupling network is provided. In the method for generating interference waveform, the present invention uses genetic algorithm to optimize the parameters of the waveform, and obtains better orthogonality and anti-interference ability.

The present invention provides the following technical solutions: a method for generating radar anti-jamming waveforms based on a multi-time scale coupling network, the main contents of which include the generation of transmit waveforms and the processing of echo signals, including the following steps:

Step 1: Build a mathematical model of the MIMO radar transmit waveform, give the time-frequency relationship diagram of the array transmit signal, and obtain the coding parameters that need to be optimized for waveform design;

Step 2: Construct the waveform optimization cost function according to the orthogonality principle of MIMO radar waveform design, optimize the coding parameters with genetic algorithm, and construct the MIMO radar transmit waveform;

Step 3: Combining with the principle of broadband signal matching filtering, the beamforming and target distance and speed information extraction processing procedures of the MIMO radar of the present invention are given;

Step 4: According to the broadband signal ambiguity function theory, generate a set of matched filter reference signals while generating the MIMO radar transmit waveform, design a multi-time-scale coupling network hardware system, and generate a corresponding set of matched filter benchmarks while generating the radar transmit signal Signal.

Preferably, the main modeling process of the MIMO radar anti-jamming composite modulation signal is as follows:

Assuming that the MIMO radar has L sub-arrays, the number of pulses in one CPI is N, and the phase encoding with code length M is used in each pulse. Now the mathematical model of the signal transmitted by the th sub-array is given:

为第n个子脉冲的载波，

μ为调频斜率，

为第n个子脉冲的第m个码元，从发射信号的数学模型可知，波形优化参数为

用向量表示记为

Ω＝[ξ₁,ξ₂,L,ξ_N]、

In the above formula, T _r is the average pulse period of the sub-pulse, ΔT _r is the minimum pulse jump interval, t _p is the pulse width, _ts is the phase encoding symbol width,

is the carrier of the nth sub-pulse,

μ is the frequency modulation slope,

is the m-th symbol of the n-th sub-pulse. From the mathematical model of the transmitted signal, the waveform optimization parameters are

represented by a vector as

Ω=[ξ ₁ ,ξ ₂ ,L,ξ _N ],

In the waveform parameters, the number of phase coding bits in each pulse is M bits, and each symbol is a quaternary code; the minimum range of frequency jump between pulses is Δf=1/t _p to ensure the orthogonality between pulses; The inter-pulse interval of each pulse also randomly jumps within a range, which increases the anti-interference performance of the signal.

Preferably, in the MIMO radar anti-jamming waveform optimization method, the method for constructing the waveform optimization cost function is specifically:

The orthogonality of the MIMO radar is reflected in the auto-correlation and cross-correlation performance of the transmitted signals between the sub-arrays. In the present invention, the transmitted signals are required to have lower auto-correlation side lobe peaks and cross-correlation peaks, so the peak side lobe level is adopted. Criterion (PSL) for quadrature waveform design:

In the above formula, s _p (t) and s _q (t) are the transmitted signals of different subarrays. When p=q, c _pq (τ) is the autocorrelation function of the transmitted signal; when p≠q, c _pq (τ) is the cross-correlation function of the transmission signal, the present invention takes the phase encoding matrix of the transmission waveform, the frequency encoding sequence of the carrier wave and the pulse position agility sequence as the optimization variable, and the peak sidelobe ratio of the transmission signal is used as the cost function, and is established as follows Optimizing the model:

The optimized parameters of the model are discrete phase, frequency and pulse position coding. Genetic algorithm can be used to optimize the model to obtain MIMO orthogonal waveforms that meet the conditions.

Preferably, the MIMO radar broadband ambiguity function waveform separation and beamforming results:

Considering that in the transceiver co-located MIMO radar system, the number of transmitting and receiving antenna elements is P and Q, respectively, the transmitting and receiving are uniform linear arrays, and the distances between transmitting and receiving antennas are d _t and d _r respectively. , the target arrival direction is

Definition _sk (t) represents the transmit signal of the mth transmit antenna element, s=[s ₁ (t), s ₂ (t), L, s _P (t)] represents the transmit signal vector, M transmit signals After space propagation, the synthetic signal reaching the target at the slant range R (corresponding to the rth distance unit) and the azimuth θ is:

In the formula, ξ ₁ is the propagation attenuation factor, assuming that the transmitted signals for each sub-array are the same, ω=(cv)/(c+v) is the scale parameter, and τ _k is the kth (k=1, 2, L, M) The delay difference of the signal transmitted by the array element relative to the reference array element can be expressed as:

来表示，因此目标处合成信号为：The above formula τ _k is only related to the layout of the antenna and has nothing to do with the motion state of the target. The fixed time delay τ _k can be used

to represent, so the synthesized signal at the target is:

为发射信号导向矢量，

为目标处接收信号向量，可表示为

其中τ₀＝2R₀/(c-v)；In the above formula

Steering vector for the transmitted signal,

is the received signal vector at the target, which can be expressed as

where τ ₀ =2R ₀ /(cv);

The signal r(t) is reflected by the target of a certain RCS, and the signal received by the qth receiving antenna is:

为第q个天线相位差，令式中ξ₁ξ₂＝ξ，将式(1)代入式(8)，则第q个接收天线的回波为：In the formula,

is the phase difference of the qth antenna, let ξ ₁ ξ ₂ =ξ in the formula, and substitute formula (1) into formula (8), then the echo of the qth receiving antenna is:

The received signal vector is x(t)=[x ₁ (t), x ₂ (t), L, x _Q (t)], the matrix form of equation (9) is as follows:

x(t)=ξb(θ _r )α ^T (θ _t )s[ω(t-τ ₀ )](10)

现考虑第q个接收天线的接收回波的宽带匹配处理，由式(10)可得第q个接收通道回波信号为：b(θ _r ) in equation (10) is the steering vector of the receiving antenna,

Now consider the broadband matching processing of the received echo of the qth receiving antenna, the echo signal of the qth receiving channel can be obtained from equation (10) as:

Now perform broadband matched filtering on the echo signal of the qth receiving antenna. According to the theory of broadband ambiguity function, it can be known that the reference signal of the pth transmit channel is:

The matching output of the qth receiving channel receiving the signal of the pth transmitting channel is:

The above formula T is the duration of the burst. According to the orthogonality of the transmitted signal, only the signal of the pth transmit channel in the transmitted signal vector has an output, and the matching output can be simplified as:

From the above formula, when ω=η _m , τ ₀ =ξ _m , the matched filter has the maximum output, and the maximum output of the matched filter is recorded as

After the echo signal passes through the broadband matching network, the distance and speed information of the target can be obtained, and then the azimuth angle of the target can be obtained through beamforming. The output of the beamforming is:

为宽带匹配滤波的输出，τ₀与ω为目标的时延和多普勒频率，当

时，上式有最大值，此时目标方向为：In formula (15),

is the output of the broadband matched filter, τ ₀ and ω are the target delay and Doppler frequency, when

When , the above formula has a maximum value, and the target direction is:

对应的相位处的波形的幅度值，这些幅度值产生了一系列的子脉冲，每个

的持续时间是由雷达的带宽所决定的；脉冲时序控制模块改变脉冲之间的脉冲周期，实现波形脉位捷变调制；通过多路DDS电路后可以产生MIMO雷达正交波形，产生MIMO雷达正交波形后，一路信号给MIMO雷达发射天线，一路作为多时间尺度耦合网络电路的输入，产生回波信号的宽带匹配滤波的参考信号；Preferably, the broadband echo matching signal is generated while the radar transmit signal is generated, and the output of the quadrature waveform is generated by the DDS waveform generator according to the frequency and phase coding sequence.

The amplitude values of the waveform at the corresponding phases that produce a series of sub-pulses, each

The duration is determined by the bandwidth of the radar; the pulse timing control module changes the pulse period between the pulses to realize the waveform pulse position agile modulation; after multiple DDS circuits, the MIMO radar quadrature waveform can be generated, and the MIMO radar positive waveform can be generated. After the waveform is crossed, one signal is sent to the MIMO radar transmitting antenna, and the other is used as the input of the multi-time scale coupling network circuit to generate a broadband matched filter reference signal of the echo signal;

The essence of the broadband matching network is to find the maximum value of the two-dimensional ambiguity function of the echo signal. When the transmitting signal is generated at the transmitting end, the reference signal of the broadband matching network is also generated. The purpose of the multi-time scale coupling network is to generate a set of transmissions for each sub-array. The signal group in which the signal is jointly shifted in time and frequency is used for the broadband matched filtering of the echo signal; in the multi-time scale coupling circuit part, the transmission signal delay τ _k of each sub-array is set as the reception of the kth distance gate Then, all Doppler frequencies are matched and filtered in the kth range gate to realize the broadband pulse pressure processing of the echo signal of the kth range gate.

The present invention has the following beneficial effects:

The purpose of the invention is to design a MIMO radar waveform with good orthogonality and anti-interference ability, use a multi-time scale coupling network to generate a reference signal of broadband matched filtering, and provide a processing method for the echo; The transmit waveforms between the sub-arrays should satisfy the orthogonality, so that the transmit waveforms between the sub-arrays can be distinguished by matched filtering at the receiving end.

On the basis of linear frequency modulation, the waveform of the invention performs intrapulse phase encoding on the pulse train, and the inter-pulse frequency and pulse position are jointly agile, so that the waveform has better orthogonality and anti-interference performance, and the echo signal adopts a broadband signal. According to the matched filtering theory, matched filtering is performed on the echo signal to distinguish the echo signals of each transmitting channel, and finally the distance, speed and angle information of the target are obtained by combining with digital beamforming.

The invention is characterized in that when the transmitter generates a composite modulated transmission signal, a reference signal group of broadband signal matching filtering is generated through a multi-time scale coupling network, and the signal of each receiving channel can be subjected to broadband matching filtering to obtain the speed and distance of the target. , compared with the traditional echo signal processing method, the processing complexity of the echo signal is greatly reduced, and the target detection accuracy is high.

Description of drawings

Fig. 1 is the schematic diagram of the lth subarray transmission signal of the present invention;

Fig. 2 is the time-frequency relation diagram of the MIMO radar transmit waveform of the present invention;

Fig. 3 is the echo signal processing flow chart of the present invention;

FIG. 4 is a diagram of a multi-time scale coupling network waveform generation system diagram of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Please refer to Figure 1. The generation method of radar anti-jamming waveform based on multi-time scale coupling network, the main content of radar anti-jamming waveform generation method based on multi-time scale coupling network, including the generation of transmit waveform and the processing of echo signal, including the following step:

Step 1: Build a mathematical model of the MIMO radar transmit waveform, give the time-frequency relationship diagram of the array transmit signal, and obtain the coding parameters that need to be optimized for waveform design;

Step 2: Construct the waveform optimization cost function according to the orthogonality principle of MIMO radar waveform design, optimize the coding parameters with genetic algorithm, and construct the MIMO radar transmit waveform;

Step 3: Combining with the principle of broadband signal matching filtering, the beamforming and target distance and speed information extraction processing procedures of the MIMO radar of the present invention are given;

Step 4: According to the broadband signal ambiguity function theory, generate a set of matched filter reference signals while generating the MIMO radar transmit waveform, design a multi-time-scale coupling network hardware system, and generate a corresponding set of matched filter benchmarks while generating the radar transmit signal Signal.

The main modeling process of MIMO radar anti-jamming composite modulation signal is as follows:

Assuming that the MIMO radar has L sub-arrays, the number of pulses in one CPI is N, and the phase encoding with code length M is used in each pulse. Now the mathematical model of the signal transmitted by the th sub-array is given:

为第n个子脉冲的载波，

μ为调频斜率，

为第n个子脉冲的第m个码元，从发射信号的数学模型可知，波形优化参数为

用向量表示记为

Ω＝[ξ₁,ξ₂,L,ξ_N]、

In the above formula, T _r is the average pulse period of the sub-pulse, ΔT _r is the minimum pulse jump interval, t _p is the pulse width, _ts is the phase encoding symbol width,

is the carrier of the nth sub-pulse,

μ is the frequency modulation slope,

is the m-th symbol of the n-th sub-pulse. From the mathematical model of the transmitted signal, the waveform optimization parameters are

represented by a vector as

Ω=[ξ ₁ ,ξ ₂ ,L,ξ _N ],

In the waveform parameters, the number of phase coding bits in each pulse is M bits, and each symbol is a quaternary code; the minimum range of frequency jump between pulses is Δf=1/t _p to ensure the orthogonality between pulses; The inter-pulse interval of each pulse also randomly jumps within a range, which increases the anti-interference performance of the signal.

The waveform optimization method of MIMO radar anti-jamming, the method of constructing the waveform optimization cost function is as follows:

The orthogonality of the MIMO radar is reflected in the auto-correlation and cross-correlation performance of the transmitted signals between the sub-arrays. In the present invention, the transmitted signals are required to have lower auto-correlation side lobe peaks and cross-correlation peaks, so the peak side lobe level is adopted. Criterion (PSL) for quadrature waveform design:

In the above formula, s _p (t) and s _q (t) are the transmitted signals of different subarrays. When p=q, c _pq (τ) is the autocorrelation function of the transmitted signal; when p≠q, c _pq (τ) is the cross-correlation function of the transmission signal, the present invention takes the phase encoding matrix of the transmission waveform, the frequency encoding sequence of the carrier wave and the pulse position agility sequence as the optimization variable, and the peak sidelobe ratio of the transmission signal is used as the cost function, and is established as follows Optimizing the model:

The optimized parameters of the model are discrete phase, frequency and pulse position coding. Genetic algorithm can be used to optimize the model to obtain MIMO orthogonal waveforms that meet the conditions.

The MIMO radar broadband ambiguity function waveform separation and beamforming results:

Considering that in the transceiver co-located MIMO radar system, the number of transmitting and receiving antenna elements is P and Q, respectively, the transmitting and receiving are uniform linear arrays, and the distances between transmitting and receiving antennas are d _t and d _r respectively. , the target arrival direction is

Definition _sk (t) represents the transmit signal of the mth transmit antenna element, s=[s ₁ (t), s ₂ (t), L, s _P (t)] represents the transmit signal vector, M transmit signals After space propagation, the synthetic signal reaching the target at the slant range R (corresponding to the rth distance unit) and the azimuth θ is:

In the formula, ξ ₁ is the propagation attenuation factor, assuming that the transmitted signals for each sub-array are the same, ω=(cv)/(c+v) is the scale parameter, and τ _k is the kth (k=1, 2, L, M) The delay difference of the signal transmitted by the array element relative to the reference array element can be expressed as:

来表示，因此目标处合成信号为：The above formula τ _k is only related to the layout of the antenna and has nothing to do with the motion state of the target. The fixed time delay τ _k can be used

to represent, so the synthesized signal at the target is:

为发射信号导向矢量，

为目标处接收信号向量，可表示为

其中τ₀＝2R₀/(c-v)；In the above formula

Steering vector for the transmitted signal,

is the received signal vector at the target, which can be expressed as

where τ ₀ =2R ₀ /(cv);

The signal r(t) is reflected by the target of a certain RCS, and the signal received by the qth receiving antenna is:

为第q个天线相位差，令式中ξ₁ξ₂＝ξ，将式(1)代入式(8)，则第q个接收天线的回波为：In the formula,

is the phase difference of the qth antenna, let ξ ₁ ξ ₂ =ξ in the formula, and substitute formula (1) into formula (8), then the echo of the qth receiving antenna is:

The received signal vector is x(t)=[x ₁ (t), x ₂ (t), L, x _Q (t)], the matrix form of equation (9) is as follows:

x(t)=ξb(θ _r )α ^T (θ _t )s[ω(t-τ ₀ )] (10)

现考虑第q个接收天线的接收回波的宽带匹配处理，由式(10)可得第q个接收通道回波信号为：b(θ _r ) in equation (10) is the steering vector of the receiving antenna,

Now consider the broadband matching processing of the received echo of the qth receiving antenna, the echo signal of the qth receiving channel can be obtained from equation (10) as:

Now perform broadband matched filtering on the echo signal of the qth receiving antenna. According to the theory of broadband ambiguity function, it can be known that the reference signal of the pth transmit channel is:

The matching output of the qth receiving channel receiving the signal of the pth transmitting channel is:

The above formula T is the duration of the burst. According to the orthogonality of the transmitted signal, only the signal of the pth transmit channel in the transmitted signal vector has an output, and the matching output can be simplified as:

From the above formula, when ω=η _m , τ ₀ =ξ _m , the matched filter has the maximum output, and the maximum output of the matched filter is recorded as

After the echo signal passes through the broadband matching network, the distance and speed information of the target can be obtained, and then the azimuth angle of the target can be obtained through beamforming. The output of the beamforming is:

为宽带匹配滤波的输出，τ₀与ω为目标的时延和多普勒频率，当

时，上式有最大值，此时目标方向为：In formula (15),

is the output of the broadband matched filter, τ ₀ and ω are the target delay and Doppler frequency, when

When , the above formula has a maximum value, and the target direction is:

对应的相位处的波形的幅度值，这些幅度值产生了一系列的子脉冲，每个

的持续时间是由雷达的带宽所决定的；脉冲时序控制模块改变脉冲之间的脉冲周期，实现波形脉位捷变调制；通过多路DDS电路后可以产生MIMO雷达正交波形，产生MIMO雷达正交波形后，一路信号给MIMO雷达发射天线，一路作为多时间尺度耦合网络电路的输入，产生回波信号的宽带匹配滤波的参考信号；While generating the radar transmission signal, a broadband echo matching signal is generated. The output of the quadrature waveform is generated by the DDS waveform generator according to the frequency and phase coding sequence.

The amplitude values of the waveform at the corresponding phases that produce a series of sub-pulses, each

The duration is determined by the bandwidth of the radar; the pulse timing control module changes the pulse period between the pulses to realize the waveform pulse position agile modulation; after multiple DDS circuits, the MIMO radar quadrature waveform can be generated, and the MIMO radar positive waveform can be generated. After the waveform is crossed, one signal is sent to the MIMO radar transmitting antenna, and the other is used as the input of the multi-time scale coupling network circuit to generate a broadband matched filter reference signal of the echo signal;

The essence of the broadband matching network is to find the maximum value of the two-dimensional ambiguity function of the echo signal. When the transmitting signal is generated at the transmitting end, the reference signal of the broadband matching network is also generated. The purpose of the multi-time scale coupling network is to generate a set of transmissions for each sub-array. The signal group in which the signal is jointly shifted in time and frequency is used for the broadband matched filtering of the echo signal; in the multi-time scale coupling circuit part, the transmission signal delay τ _k of each sub-array is set as the reception of the kth distance gate Then, all Doppler frequencies are matched and filtered in the kth range gate to realize the broadband pulse pressure processing of the echo signal of the kth range gate.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1. based on the radar anti-jamming waveform generation method of multi-time scale coupling network, its main content comprises the generation of transmission waveform and the processing of echo signal, it is characterized in that: comprise the following steps: Step 1: Build a mathematical model of the MIMO radar transmit waveform, give the time-frequency relationship diagram of the array transmit signal, and obtain the coding parameters that need to be optimized for waveform design; Step 2: Construct the waveform optimization cost function according to the orthogonality principle of MIMO radar waveform design, optimize the coding parameters with genetic algorithm, and construct the MIMO radar transmit waveform; Step 3: Combining with the principle of broadband signal matching filtering, the beamforming and target distance and speed information extraction processing procedures of the MIMO radar of the present invention are given; Step 4: According to the broadband signal ambiguity function theory, generate a set of matched filter reference signals while generating the MIMO radar transmit waveform, design a multi-time-scale coupling network hardware system, and generate a corresponding set of matched filter benchmarks while generating the radar transmit signal Signal. 2. the radar anti-jamming waveform generation method based on multi-time scale coupling network according to claim 1, is characterized in that: described MIMO radar anti-jamming composite modulation signal, its main modeling process is as follows: Assuming that the MIMO radar has L sub-arrays, the number of pulses in one CPI is N, and the phase encoding with code length M is used in each pulse. Now the mathematical model of the signal transmitted by the th sub-array is given:

In the above formula, T _r is the average pulse period of the sub-pulse, ΔT _r is the minimum pulse jump interval, t _p is the pulse width, _ts is the phase encoding symbol width,

is the carrier of the nth sub-pulse,

μ is the frequency modulation slope,

is the m-th symbol of the n-th sub-pulse. From the mathematical model of the transmitted signal, the waveform optimization parameters are

represented by a vector as

Ω=[ξ ₁ ,ξ ₂ ,L,ξ _N ],

In the waveform parameters, the number of phase coding bits in each pulse is M bits, and each symbol is a quaternary code; the minimum range of frequency jump between pulses is Δf=1/t _p to ensure the orthogonality between pulses; The inter-pulse interval of each pulse also randomly jumps within a range, which increases the anti-interference performance of the signal. 3. the radar anti-jamming waveform generation method based on multi-time scale coupling network according to claim 2, is characterized in that: described MIMO radar anti-jamming waveform optimization method, the method for constructing waveform optimization cost function is specifically: The orthogonality of the MIMO radar is reflected in the auto-correlation and cross-correlation performance of the transmitted signals between the sub-arrays. In the present invention, the transmitted signals are required to have lower auto-correlation side lobe peaks and cross-correlation peaks, so the peak side lobe level is adopted. Criterion (PSL) for quadrature waveform design:

In the above formula, s _p (t) and s _q (t) are the transmitted signals of different subarrays. When p=q, c _pq (τ) is the autocorrelation function of the transmitted signal; when p≠q, c _pq (τ) is the cross-correlation function of the transmission signal, the present invention takes the phase encoding matrix of the transmission waveform, the frequency encoding sequence of the carrier wave and the pulse position agility sequence as the optimization variable, and the peak sidelobe ratio of the transmission signal is used as the cost function, and is established as follows Optimizing the model:

The optimized parameters of the model are discrete phase, frequency and pulse position coding. Genetic algorithm can be used to optimize the model to obtain MIMO orthogonal waveforms that meet the conditions. 4. the radar anti-jamming waveform generation method based on multi-time scale coupling network according to claim 3, is characterized in that: described MIMO radar wideband ambiguity function waveform separation and beamforming result: Considering that in the transceiver co-located MIMO radar system, the number of transmitting and receiving antenna elements is P and Q, respectively, the transmitting and receiving are uniform linear arrays, and the distances between transmitting and receiving antennas are d _t and d _r respectively. , the target arrival direction is

Definition _sk (t) represents the transmit signal of the mth transmit antenna element, s=[s ₁ (t), s ₂ (t), L, s _P (t)] represents the transmit signal vector, M transmit signals After space propagation, the synthetic signal reaching the target at the slant range R (corresponding to the rth distance unit) and the azimuth θ is:

In the formula, ξ ₁ is the propagation attenuation factor, assuming that the transmitted signals for each sub-array are the same, ω=(cv)/(c+v) is the scale parameter, and τ _k is the kth (k=1, 2, L, M) The delay difference of the signal transmitted by the array element relative to the reference array element can be expressed as:

The above formula τ _k is only related to the layout of the antenna and has nothing to do with the motion state of the target. The fixed time delay τ _k can be used

to represent, so the synthesized signal at the target is:

In the above formula

Steering vector for the transmitted signal,

is the received signal vector at the target, which can be expressed as

where τ ₀ =2R ₀ /(cv); The signal r(t) is reflected by the target of a certain RCS, and the signal received by the qth receiving antenna is:

In the formula,

is the phase difference of the qth antenna, let ξ ₁ ξ ₂ =ξ in the formula, and substitute formula (1) into formula (8), then the echo of the qth receiving antenna is:

The received signal vector is x(t)=[x ₁ (t), x ₂ (t), L, x _Q (t)], the matrix form of equation (9) is as follows: x(t)=ξb(θ _r )α ^T (θ _t )s[ω(t-τ ₀ )] (10) b(θ _r ) in equation (10) is the steering vector of the receiving antenna,

Now consider the broadband matching processing of the received echo of the qth receiving antenna, the echo signal of the qth receiving channel can be obtained from equation (10) as:

Now perform broadband matched filtering on the echo signal of the qth receiving antenna. According to the theory of broadband ambiguity function, it can be known that the reference signal of the pth transmit channel is:

The matching output of the qth receiving channel receiving the signal of the pth transmitting channel is:

The above formula T is the duration of the burst. According to the orthogonality of the transmitted signal, only the signal of the pth transmit channel in the transmitted signal vector has an output, and the matching output can be simplified as:

From the above formula, when ω=η _m , τ ₀ =ξ _m , the matched filter has the maximum output, and the maximum output of the matched filter is recorded as

After the echo signal passes through the broadband matching network, the distance and speed information of the target can be obtained, and then the azimuth angle of the target can be obtained through beamforming. The output of the beamforming is:

In formula (15),

is the output of the broadband matched filter, τ ₀ and ω are the target delay and Doppler frequency, when

When , the above formula has a maximum value, and the target direction is:

5. The method for generating radar anti-jamming waveforms based on a multi-time scale coupling network according to claim 4, characterized in that: said generating the radar transmit signal simultaneously generates a broadband echo matching signal, and the output of the quadrature waveform is determined by the DDS The waveform generator generates each

The amplitude values of the waveform at the corresponding phases that produce a series of sub-pulses, each

The duration is determined by the bandwidth of the radar; the pulse timing control module changes the pulse period between pulses to realize the waveform pulse position agile modulation; after multiple DDS circuits, the MIMO radar quadrature waveform can be generated, and the MIMO radar positive waveform can be generated. After the waveform is crossed, one signal is sent to the MIMO radar transmitting antenna, and the other is used as the input of the multi-time scale coupling network circuit to generate the reference signal of the broadband matched filter of the echo signal; The essence of the broadband matching network is to find the maximum value of the two-dimensional ambiguity function of the echo signal. When the transmitting signal is generated at the transmitting end, the reference signal of the broadband matching network is also generated. The purpose of the multi-time scale coupling network is to generate a set of transmissions for each sub-array. The signal group in which the signal is jointly shifted in time and frequency is used for the broadband matched filtering of the echo signal; in the multi-time scale coupling circuit part, the transmission signal delay τ _k of each sub-array is set as the reception of the kth distance gate Then, all Doppler frequencies are matched and filtered in the kth range gate to realize the broadband pulse pressure processing of the echo signal of the kth range gate.

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