CN104267379B - A kind of active radar and passive radar based on Waveform Design works in coordination with anti-interference method - Google Patents

Abstract

A kind of active radar and passive radar based on Waveform Design of this invention works in coordination with anti-interference method, belongs to Anti-jamming Technology for Radar field, and it is particularly to technology of radar waveform design.This invention uses active radar and passive radar cooperative work mode, utilize the echo information of passive radar detecting real-time, interference is detected and identifies, and estimate the relevant parameter of interference, Active Radar utilizes the interference information that passive radar provides, the transmitted waveform that design is optimum, and echo information is processed, thus there is the effect of the capacity of resisting disturbance that amount of calculation is little, real-time is high, improve radar under complicated electromagnetic interference environment.

Description

A Cooperative Anti-Jamming Method for Active and Passive Radar Based on Waveform Design

technical field

The invention belongs to the technical field of radar anti-jamming, and in particular relates to radar waveform design technology.

Background technique

Modern radars work in complex electromagnetic interference environments, and must have effective anti-interference capabilities to survive on the battlefield. With the development of radar jamming technology, especially the emergence of active deception jamming technology based on digital radio frequency memory (DRFM), it has brought great challenges to the accuracy of radar target detection and the stability of target tracking. Radar anti-jamming technology is facing with increasing difficulties. There are many types of radar active deception jamming, and a large jamming effect can be obtained with a low interference-to-signal ratio gain, which makes it difficult for the radar to detect and track the real target correctly, and seriously reduces the detection and tracking performance of the radar.

Traditional radars are easily intercepted and copied by jammers due to their fixed transmission waveforms, so they are easily interfered and affect the detection of real targets. Waveform design is one of the effective measures for radar anti-jamming. In recent years, some scholars have used the advantages of active radar to change the transmission waveform to counter deception jamming through the waveform design method. However, these studies are all aimed at a single radar, and the range of a single radar is small, and the real-time performance of a single radar to obtain interference and target parameters is poor, so the anti-interference ability in the rapidly changing and complex electromagnetic interference environment is limited. . Li Shizhong et al. proposed a method of suppressing deceptive false target interference by using an active and passive radar network configured in different places. The measurement information of the pitch angle can be used to identify and eliminate false target interference by point-trace correlation method, which can improve the detection and tracking performance of active and passive radar under false target interference, see [Li Shizhong, Wang Guohong, Xu Haiquan et al. The active/passive radar configured in different places resists multiple false target interference. Fire Power and Command and Control, 2013, 38(5): 10-13]. However, this method processes the interference at the data processing level, which increases the resource consumption of the radar, and has a high probability of misidentifying false targets.

Contents of the invention

In view of the defects existing in the background technology, the present invention adopts the cooperative working mode of active and passive radars, uses the echo information detected by the passive radars in real time, detects and identifies the interference, and estimates the relevant parameters of the interference. The active radar utilizes the interference provided by the passive radar Information, design the optimal transmission waveform, and process the echo information, so as to achieve a small amount of calculation, high real-time performance, and improve the anti-interference ability of the radar in complex electromagnetic interference environments.

The present invention provides a kind of active-passive radar cooperative anti-jamming method based on waveform design, and it comprises the following steps:

Step 1. Passive radar jamming detection

The active and passive radars work at the same time. The active radar continuously emits pulse signals, and both the active and passive radars continuously receive the radar echo signals and process the echo signals. The passive radar detects a specific area in real time. After the radar echo of , the interference is detected using the binary hypothesis detection theory:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\end{array}\right.$

Among them, x(t) represents the signal received by the passive radar, n(t) represents the additive Gaussian white noise, s(t) represents the echo signal of the real target, and J(t) represents the interference signal generated after the jammer intercepts the radar signal; H ₀ and H ₁ respectively represent the two hypothesis test results of non-existence and existence of interference signal J(t);

Under the constant false alarm condition, the passive radar discriminates the interference detection results. If no interference is detected, the active radar chooses to transmit a conventional pulse signal at the next moment; if interference is detected, skip to step 2 to identify and parameterize the interference estimate;

Step 2. Passive radar jamming identification and parameter estimation

2.1. Interference identification

The waveform information transmitted by the active radar and the radar echo information received by the active and passive radar can be expressed as a K-dimensional function through information fusion in is the parameter set related to the target and interference signal, A is the amplitude set composed of the target and interference signal, ω is the frequency set composed of the target and interference signal, is the azimuth angle set composed of the target and interference, θ is the elevation angle set composed of the target and interference, and f _d is the Doppler set composed of the target and interference; feature extraction is performed on the fused signal, that is, the signal is processed by multiple type of nonlinear transformation, the transformed signal can be expressed as: Among them, S _q =f(R ₁ ,R ₂ ,…R _k ),k≤K, R _k represents the kth characteristic parameter of signal S _q ; for each transformed signal characteristic parameter, the interference type based on neural network is adopted Classification algorithms identify disturbances, at least one of which successfully identifies the disturbance type;

2.2. Parameter estimation

After the interference is identified and classified, according to the type of interference, the corresponding parameters are estimated by the multi-channel estimation method or the maximum likelihood method. The parameters mainly include: the amplitude, Doppler and time delay of the interference signal and the target signal;

Step 3. According to the interference type and interference parameters obtained by the passive radar in step 2, select the appropriate waveform design criteria, construct the corresponding cost function, and then select the optimal waveform design algorithm to calculate the optimal solution set for the cost function, using The obtained optimal solution set constructs the optimal waveform;

Step 4. The active radar transmits the optimal waveform pulse signal obtained in step 3, receives the echo signal at the same time, and performs matched filter processing and Doppler processing on the echo signal, and then performs anti-interference evaluation. If the evaluation effect is good, the detection The results are output and displayed. If the effect is not good, data processing anti-interference measures are used to eliminate interference, and the detection results are output and displayed.

In the step 2.1, Fourier transform, fractional Fourier transform, short-time Fourier transform and matching transformation are simultaneously performed on the fused signals, and then feature extraction is performed on the respective transformed signals.

In the step 3, select the maximum signal-to-noise ratio criterion or the minimum criterion of stopband interference energy to construct the corresponding cost function, then use the conjugate gradient algorithm or the loop iterative algorithm to calculate the optimal solution of the cost function, and then construct the optimal waveform .

The advantages of a kind of active-passive radar cooperative anti-jamming method based on waveform design of the present invention: 1, increased the power range of radar; 3. By transmitting different waveforms, interference can be suppressed after conventional signal processing, which reduces the burden of radar data processing.

Description of drawings

Fig. 1 is a technical architecture diagram of the present invention;

Figure 2 is a flowchart of waveform design.

Figure 3 is a comparison diagram of the simulation results of the Doppler spectrum of the radar echo under the speed deception jamming, using the fixed waveform transmitted by a single active radar and the waveform transmitted after the coordinated waveform design of the active and passive radar.

Figure 3-1 in Figure 3 is the Doppler spectrum of a single active radar after echo processing; Figure 3-2 is the Doppler spectrum of an active and passive radar after echo processing.

detailed description

The specific implementation of the present invention is described below by taking speed deception interference as an example, and the steps are as follows:

Step 1 Passive radar jamming detection

The active and passive radars work at the same time, the active radar continuously emits pulse signals, and both the active and passive radars continuously receive the radar echo signals and process the echo signals. Passive radar detects a specific area in real time. After receiving the radar echo reflected by the target, it uses the binary hypothesis detection theory to detect interference:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; ,</span>$

Among them, x(t) represents the signal received by the passive radar, n(t) represents the additive Gaussian white noise, s(t) represents the echo signal of the real target, and J(t) represents the interference signal generated after the jammer intercepts the radar signal; H ₀ and H ₁ represent the two hypothesis test results of the absence and existence of the interference signal J(t) respectively.

The energy detection algorithm is used to detect the interference, that is, the envelope detection is performed on the received echo signal. If the echo is detected within a CPI (the selection of the number of pulses ensures that the target amplitude remains unchanged within a CPI). If the signal amplitude suddenly increases to more than twice, it is judged as interference, otherwise it is considered as no interference.

The active radar selects the transmission waveform according to the result of the interference detection of the passive radar. If the passive radar detects that there is no interference, then jump to step 4, and the active radar chooses to transmit a conventional pulse signal at the next moment; if it detects that there is interference, then jump to step 2 Disturbances are identified and parameter estimated.

Step 2 Passive radar jamming identification and parameter estimation

2.1. Interference identification

The waveform information transmitted by the active radar and the radar echo information received by the active and passive radars can be expressed as a 3-dimensional function S _r =f(A,ω,f _d ) through information fusion, where A,ω,f _d are related to the target and The parameter set related to the interference signal, A is the amplitude set composed of the target and interference, ω is the frequency set composed of the target and interference, and f _d is the Doppler set composed of the target and interference. Feature extraction is performed on the fused signal, that is, the signal is subjected to Fourier transform, fractional Fourier transform, short-time Fourier transform and matching transformation at the same time. After the Fourier transform, it is transformed into the frequency domain, that is, the characteristic function S _q =FT(S _r ), where FT(·) represents the Fourier transform. For speed jamming, due to the influence of the number of quantization bits of the jammer, there will be many harmonic components in the frequency domain of the jamming, and the speed deception jamming Doppler is obviously different from other jamming Dopplers, so the selection of harmonic parameters and multiple Puller two parameters as characteristic parameters. The interference type identification algorithm based on neural network can identify the interference as speed deception interference.

2.2. Parameter estimation

After identifying the jamming as speed deception jamming, the multi-channel estimation method is used to estimate the amplitude and Doppler parameters of the target and jamming. The received signal passes through M channels at the same time, and each channel is connected to a matched filter, that is, the received signal is sequentially processed with the current transmission pulse and the first m (m=1,2,...,M) transmission pulses for matched filter processing, and then multiple The Doppler processing can estimate the amplitude and Doppler information of the target and interference in the channel.

Step 3 Active Radar Waveform Design

After knowing that the interference is velocity deception interference, choose to transmit inter-pulse phase encoding waveform in the next coherent processing interval, and the phase of each pulse is obtained by optimizing the design. The specific design is as follows: select the minimum stop-band interference energy criterion as the waveform design The optimization criterion is to set a stop band near each target; use the parameters of the target and interference obtained by the real-time estimation of passive radar, such as the amplitude of the target and interference, Doppler, etc., to construct the corresponding optimization problem; choose the cyclic iterative algorithm to solve The optimization problem obtains the optimal solution set, which is the initial phase of each transmitted pulse in the next coherent processing interval.

Step 4 Active Radar Transmit Waveform Selection

The active radar has the ability to transmit different waveforms, and the transmitted waveform is determined by the result of passive radar interference detection in step 1. If the passive radar detects that there is no spoofing interference, the active radar chooses to transmit a conventional pulse signal, such as a simple pulse signal or a simple chirp, etc.; if the passive radar detects that there is spoofing interference, the active radar chooses to transmit a designed pulse waveform, That is, the waveform designed in step 3. In addition, in step 5, if the evaluation effect of the active radar after the anti-jamming effect evaluation is good, the active radar chooses to keep transmitting the designed pulse waveform.

Step 5 Active Radar Echo Signal Processing

When the passive radar does not detect interference, the active radar transmits a conventional pulse signal, and the active radar outputs and displays the detection results after performing matched filter processing and Doppler processing; if the passive radar detects interference, the active radar transmits a designed pulse, and perform matched filtering and Doppler processing on the received echo signal, and evaluate the anti-jamming effect on the processing result at the same time. If the effect is good, the detection result will be output and displayed. If the effect is not good, use the dot trace correlation algorithm from the data level Eliminate interference, and output and display the detection results after processing.

Claims (3)

1. active radar and passive radar based on Waveform Design works in coordination with an anti-interference method, and the method includes:

Step 1, passive radar Interference Detection

Active radar and passive radar works simultaneously, and Active Radar is constantly to emission pulse signal, and active radar and passive radar the most constantly receives radar and returns Echo-signal is also processed by ripple signal, and passive radar carries out detecting real-time to specific region, is receiving the thunder of target reflection After reaching echo, use dualism hypothesis etection theory that interference is detected:

$\left\{\begin{array}{c}{H}_0:x\left(t\right)=s\left(t\right)+n\left(t\right)\\ H_1:x\left(t\right)=s\left(t\right)+J\left(t\right)+n\left(t\right)\end{array}\right.$

Wherein, x (t) represents that passive radar receives signal, and n (t) represents additive white Gaussian noise, and s (t) is real goal echo-signal, J (t) The interference signal generated after intercepting and capturing radar signal for jammer；H₀、H₁Represent that interference signal J (t) does not exists and has two kinds respectively Hypothesis testing result；

Under the conditions of CFAR, interference detection results is differentiated by passive radar, if be not detected by interference, Active Radar under One moment selected to launch general pulse signal；If be detected that there is interference, then interference is identified by jump procedure 2 and parameter is estimated Meter；

Step 2, passive radar disturbance ecology and parameter estimation

Step 2.1, disturbance ecology

Shape information and the radar return information of active radar and passive radar reception that Active Radar is launched can be expressed as a K through information fusion Dimension functionWhereinBeing the parameter set relevant with target and interference signal, A is The amplitude collection that target and interference are constituted, ω is target and disturbs the frequency set constituted,The azimuth set constituted for target and interference, θ is target and the angle of pitch set of interference composition, f_dThe Doppler's collection constituted for target and interference；Signal after merging is carried out spy Levying extraction, signal carries out polytype nonlinear transformation the most simultaneously, transformed rear signal is all represented by: Wherein S_q=f (R₁,R₂,…R_k), k≤K, R_kRepresent signal S_qKth category feature parameter；Signal characteristic after each conversion is joined Number uses interference type sorting algorithm based on neutral net to be identified interference, and at least one of which can successfully identify interference class Type；

Step 2.2, parameter estimation

After interference is identified classification, for interference type, by the multichannel estimation technique or maximum likelihood method, it is carried out accordingly Parameter estimation, its parameter specifically includes that interference signal and the amplitude of echo signal, Doppler and time delay；

Step 3, the interference type obtained according to passive radar in step 2 and interference parameter, select suitable Waveform Design criterion, Constructing corresponding cost function, then select the Waveform Design algorithm of optimum to calculate the disaggregation making cost function optimum, utilization is tried to achieve Optimal solution set construct optimum waveform；

The optimum waveform pulse signal that step 4, Active Radar step of transmitting 3 obtain, receives echo-signal simultaneously, and believes echo Number carry out matched filtering process and doppler processing, then carry out anti-jamming evaluation, if testing result well, is carried out defeated by Evaluated effect Going out display, effect is bad then uses data to process interference protection measure rejecting interference, and testing result is carried out output display.

A kind of active radar and passive radar based on Waveform Design works in coordination with anti-interference method, it is characterised in that described Step 2.1 carries out Fourier transformation, Fourier Transform of Fractional Order, Short Time Fourier Transform and coupling to the signal after merging simultaneously Conversion, then carries out feature extraction to signal after each transformation into itself.

A kind of active radar and passive radar based on Waveform Design works in coordination with anti-interference method, it is characterised in that institute State and step 3 selects maximum signal noise ratio principle or stopband interfering energy minimum criteria construct corresponding cost function, then utilize conjugation Gradient algorithm or loop iteration algorithm calculate the optimal solution of this cost function, reconstruct out optimum waveform.