阅读说明：本技术 基于虚拟信道化的多雷达对抗方法和系统 (Multi-radar countermeasure method and system based on virtual channelization ) 是由 刘佳琪 高路 白锦良 江志烨 秦鹏 刘洪艳 李虎 曹阳 刘成国 徐锋 王上月 于 2020-04-21 设计创作，主要内容包括：本发明涉及一种多雷达对抗方法和系统,该方法包括：对接收的雷达射频信号进行分频并与分频本振信号混频后获得分频中频信号,对该分频中频信号的脉冲前沿进行频率检测,得到脉冲起始频率；对雷达信号的分频中频信号进行宽窄带判断,得到宽带信号或者窄带信号的宽窄带判断结果；根据宽窄带判断结果,对于宽带信号计算宽带信号中心频率；根据宽窄带判断结果,对于窄带信号根据脉冲起始频率来确定本振信号频率范围并切换至对应本振信号；对于宽带信号则根据宽带信号中心频率来确定本振信号频率范围并切换至对应本振信号；该本振信号与雷达射频信号混频后生成中频雷达信号,再根据中频雷达信号生成雷达干扰信号。(The invention relates to a multi-radar countermeasure method and a system, wherein the method comprises the following steps: carrying out frequency division on a received radar radio frequency signal, mixing the frequency division radio frequency signal with a frequency division local oscillator signal to obtain a frequency division intermediate frequency signal, and carrying out frequency detection on the leading edge of a pulse of the frequency division intermediate frequency signal to obtain a pulse starting frequency; carrying out wideband and narrowband judgment on the frequency division intermediate frequency signal of the radar signal to obtain a wideband and narrowband judgment result of a wideband signal or a narrowband signal; calculating the center frequency of the broadband signal according to the judgment result of the broadband and narrowband; determining a local oscillator signal frequency range according to the pulse starting frequency for the narrow-band signal and switching to a corresponding local oscillator signal according to the wide-band and narrow-band judgment result; determining a local oscillator signal frequency range according to the broadband signal center frequency for the broadband signal and switching to a corresponding local oscillator signal; the local oscillator signal and the radar radio frequency signal are mixed to generate an intermediate frequency radar signal, and then a radar interference signal is generated according to the intermediate frequency radar signal.)

1. A multi-radar countermeasure method based on virtual channelization, the method comprising the steps of:

s1, carrying out frequency division on the received radar radio frequency signal, mixing the frequency divided radar radio frequency signal with a frequency division local oscillator signal to obtain a frequency division intermediate frequency signal, and carrying out frequency detection on the pulse leading edge of the frequency division intermediate frequency signal to obtain a pulse starting frequency;

s2, performing wideband and narrowband judgment on the frequency-division intermediate-frequency signal of the radar signal to obtain a wideband or narrowband judgment result;

s3, calculating the center frequency of the broadband signal according to the judgment result of the broadband and narrowband;

s4, determining a local oscillation signal frequency range of the narrow-band signal according to the pulse starting frequency and switching to a corresponding local oscillation signal according to the wide-band and narrow-band judgment result; determining a local oscillator signal frequency range according to the broadband signal center frequency for the broadband signal and switching to a corresponding local oscillator signal; the local oscillator signal and the radar radio frequency signal are mixed to generate an intermediate frequency radar signal, and then a radar interference signal is generated according to the intermediate frequency radar signal.

2. The virtual channelization based multi-radar countermeasure method of claim 1, the method further comprising:

when the next detection window arrives, stopping sending the current radar interference signal, simultaneously detecting whether a new radar radio frequency signal is received, if the new radar radio frequency signal is not received in the detection window, continuing to send the current radar interference signal until the next detection window arrives or the total interference duration is over; if a new radar radio frequency signal is received in the interception window, the new radar radio frequency signal is detected again by using the steps S1-S4 and a radar interference signal is generated, and then the radar interference signal which is currently in an effective state is alternately transmitted until the next interception window arrives or the total interference duration is over.

3. The virtual channelization-based multi-radar impedance matching method as claimed in claim 1 or 2, wherein the pulse start frequency of the leading edge of the pulse of the divided intermediate frequency signal is calculated in step S1 by the following formula:

wherein, Delta theta is the phase difference of two adjacent sampling points of the frequency division intermediate frequency signal, and the sampling time is t_s。

4. The virtual channelization-based multi-radar countermeasure method according to claim 1 or 2, wherein the step S3 includes:

calculating the bandwidth of the wideband signal as B₂If the pulse starting frequency of the broadband signal is f, when the broadband signal is positively frequency-modulated, the central frequency f of the broadband signal is_OIs composed ofWhen the broadband signal is negative frequency modulation, the central frequency f of the broadband signal_OIs composed of

5. The multi-radar impedance matching method based on virtual channelization of claim 1 or 2, wherein in step S4, the local oscillator signal frequency range is determined and switched to the corresponding local oscillator signal by:

for narrow band signals, when the measured pulse start frequency f is satisfiedIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range of the frequency difference value of each stage of local oscillation signal is 800MHz-1 GHz;

for wideband signals, when the calculated center frequency f of the wideband signal_OSatisfy the requirement ofIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range is 800MHz-1GHz for the frequency difference of each stage of local oscillation signals.

6. The virtual channelization-based multi-radar countermeasure method of claim 1 or 2, wherein the generating a radar jamming signal from the intermediate frequency radar signal comprises:

1) establishing a target scattering point model to output coordinates of a target scattering point and a target centroid in a target coordinate system;

2) converting coordinates of scattering points and a target centroid in a target coordinate system into a radar coordinate system through a coordinate transformation matrix, wherein the coordinate transformation matrix comprises a precession angle and a micromotion period which represent micromotion characteristics;

3) calculating the centroid instantaneous slant distance between the centroid of the target and the radar and the scattering point instantaneous slant distance between each scattering point and the radar, and calculating the micro-motion distance of each scattering point according to the centroid instantaneous slant distance and the scattering point instantaneous slant distance;

4) generating a baseband interference signal based on micro characteristic modulation according to the micro distance of the scattering point;

5) and generating an intermediate frequency interference signal according to the received intermediate frequency radar signal and the baseband interference signal modulated based on the inching characteristic.

7. A multi-radar countermeasure system based on virtual channelization, comprising: the device comprises a radar signal frequency division module, a local oscillator signal generation module, a first frequency mixer, a second frequency mixer and a control module;

the input end of the first mixer is connected to the output end of the radar signal frequency division module, and the output end of the first mixer is connected to the control module; the radar radio frequency signal is subjected to frequency division through the radar signal frequency division module and then is subjected to frequency mixing with a frequency division local oscillator signal through the first frequency mixer, so that a frequency division intermediate frequency signal is obtained;

the control module is used for: carrying out frequency detection on the pulse leading edge of the frequency-divided intermediate-frequency signal to obtain a pulse starting frequency; carrying out wideband and narrowband judgment on the frequency division intermediate frequency signal of the radar signal to obtain a wideband and narrowband judgment result of a wideband signal or a narrowband signal; calculating the center frequency of a broadband signal for the broadband signal according to the judgment result of the broadband and narrowband; according to the judgment result of the wide and narrow bands, determining the frequency range of a local oscillation signal for the narrow band signal according to the pulse starting frequency and controlling a local oscillation signal generation module to switch to the corresponding local oscillation signal; determining a local oscillator signal frequency range according to the broadband signal center frequency and controlling a local oscillator signal generating module to switch to a corresponding local oscillator signal for the broadband signal;

the input end of the second frequency mixer is connected with the output end of the local oscillator signal generation module and the receiving end of the radar radio frequency signal, and the output end of the second frequency mixer is connected to the control module; the local oscillator signal and the radar radio frequency signal generate an intermediate frequency radar signal after passing through a second frequency mixer, and the control module generates a radar interference signal according to the intermediate frequency radar signal.

8. The virtual channelization-based multi-radar countermeasure system of claim 7, wherein the control module is further configured to: when the next detection window arrives, stopping sending the current radar interference signal, simultaneously detecting whether a new radar radio frequency signal is received, if the new radar radio frequency signal is not received in the detection window, continuing to send the current radar interference signal until the next detection window arrives or the total interference duration is over; if a new radar radio frequency signal is received in the interception window, detecting the initial pulse frequency again for the new radar radio frequency signal and generating a radar interference signal, and then alternately transmitting the radar interference signal in the effective state at present until the next interception window arrives or the total interference duration is over.

9. The multi-radar countermeasure system based on virtual channelization of claim 7 or 8, wherein the local oscillator signal generating module includes multiple local oscillator signal generating units, and each local oscillator signal generating unit is connected with a local oscillator control switch, and the control module controls output of each local oscillator signal respectively to implement local oscillator signal switching.

10. The virtual channelization-based multi-radar countermeasure system of claim 7 or 8, wherein the master control module determines the local oscillator signal frequency range and switches to the corresponding local oscillator signal by:

for narrow band signals, when the measured pulse start frequency f is satisfiedIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range of the frequency difference value of each stage of local oscillation signal is 800MHz-1 GHz;

for wideband signals, when the calculated center frequency f of the wideband signal_OSatisfy the requirement ofIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range is 800MHz-1GHz for the frequency difference of each stage of local oscillation signals.

Technical Field

The invention relates to an electronic radar countermeasure technology, in particular to a multi-radar countermeasure method and system based on virtual channelization.

Background

With the development of high-resolution broadband imaging radar, networking radar, bistatic radar and distributed coherent radar, the working modes and signal forms of the radar are diversified, so that the electromagnetic environment faced by active electronic interference is more and more complex.

The conventional interference countermeasure method has insufficient capability to combat multiple radars. For example, the multi-radar countermeasure generally adopts a channelized detection guided local oscillator selection method, each channel covers a certain frequency band, and in order to cope with the multi-radar, the coverage bandwidth of the general channel is narrow, which is about 100MHz or less, so that a plurality of channels are needed to cover the whole frequency band. The channel and the local oscillator have a corresponding relationship, for example, the channel 1 selects the local oscillator 1, the channel 2 corresponds to the local oscillator 2, and the channel n corresponds to the local oscillator n. And each channel judges whether the channel has a signal or not through the detector, the detector judges that the channel has the signal when the output level of the detector is high, and the detector judges that no signal exists when the output level is low. And selecting the local oscillator according to the corresponding relation between the channel and the local oscillator when the signal exists. Multiple channels need to be set up, resulting in an overall increase in complexity. And when the signal frequency is between adjacent channels, both channels output detection, or the detection high level is jittered on both channels, so that the local oscillation selection based on the channel detection has an unstable phenomenon.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a method and a system for multi-radar countermeasure based on virtual channelization, aiming at one or more of the above defects in the prior art, and realizing instantaneous coverage of a frequency band by forming virtual channelization through multiple local oscillators, thereby improving the countermeasure effect of active electronic interference.

In order to solve the technical problem, the invention provides a multi-radar countermeasure method based on virtual channelization, which comprises the following steps:

s1, carrying out frequency division on the received radar radio frequency signal, mixing the frequency divided radar radio frequency signal with a frequency division local oscillator signal to obtain a frequency division intermediate frequency signal, and carrying out frequency detection on the pulse leading edge of the frequency division intermediate frequency signal to obtain a pulse starting frequency;

s2, performing wideband and narrowband judgment on the frequency-division intermediate-frequency signal of the radar signal to obtain a wideband or narrowband judgment result;

s3, sorting the broadband signals according to the broadband and narrowband judgment result to calculate the central frequency of the broadband signals;

s4, determining a local oscillation signal frequency range of the narrow-band signal according to the pulse starting frequency and switching to a corresponding local oscillation signal according to the wide-band and narrow-band judgment result; determining a local oscillator signal frequency range according to the broadband signal center frequency for the broadband signal and switching to a corresponding local oscillator signal; the local oscillator signal and the radar radio frequency signal are mixed to generate an intermediate frequency radar signal, and then a radar interference signal is generated according to the intermediate frequency radar signal.

In the multi-radar countermeasure method based on virtual channelization according to the present invention, preferably, the method further includes: when the next detection window arrives, stopping sending the current radar interference signal, simultaneously detecting whether a new radar radio frequency signal is received, if the new radar radio frequency signal is not received in the detection window, continuing to send the current radar interference signal until the next detection window arrives or the total interference duration is over; if a new radar radio frequency signal is received in the interception window, the new radar radio frequency signal is detected again by using the steps S1-S4 and a radar interference signal is generated, and then the radar interference signal which is currently in an effective state is alternately transmitted until the next interception window arrives or the total interference duration is over.

In the multi-radar impedance matching method based on virtual channelization according to the present invention, preferably, the step S1 calculates the pulse start frequency of the leading edge of the pulse of the divided intermediate frequency signal by the following formula:

wherein, Delta theta is the phase difference of two adjacent sampling points of the frequency division intermediate frequency signal, and the sampling time is t_s。

In the multi-radar countermeasure method based on virtual channelization according to the present invention, preferably, the step S3 includes:

calculating the bandwidth of the wideband signal as B₂If the pulse starting frequency of the broadband signal is f, when the broadband signal is positively frequency-modulated, the central frequency f of the broadband signal is_OIs composed ofWhen the broadband signal is negative frequency modulation, the central frequency f of the broadband signal_OIs composed of

In the multi-radar impedance matching method based on virtual channelization according to the present invention, preferably, in step S4, the local oscillator signal frequency range is determined and switched to the corresponding local oscillator signal by:

for narrow band signals, when the measured pulse start frequency f is satisfiedIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range of the frequency difference value of each stage of local oscillation signal is 800MHz-1 GHz;

for wideband signals, when the calculated center frequency f of the wideband signal_OSatisfy the requirement ofIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range is 800MHz-1GHz for the frequency difference of each stage of local oscillation signals.

In the multi-radar countermeasure method based on virtual channelization according to the present invention, preferably, the generating a radar interference signal according to the intermediate frequency radar signal includes:

1) establishing a target scattering point model to output coordinates of a target scattering point and a target centroid in a target coordinate system;

2) converting coordinates of scattering points and a target centroid in a target coordinate system into a radar coordinate system through a coordinate transformation matrix, wherein the coordinate transformation matrix comprises a precession angle and a micromotion period which represent micromotion characteristics;

3) calculating the centroid instantaneous slant distance between the centroid of the target and the radar and the scattering point instantaneous slant distance between each scattering point and the radar, and calculating the micro-motion distance of each scattering point according to the centroid instantaneous slant distance and the scattering point instantaneous slant distance;

4) generating a baseband interference signal based on micro characteristic modulation according to the micro distance of the scattering point;

5) and generating an intermediate frequency interference signal according to the received intermediate frequency radar signal and the baseband interference signal modulated based on the inching characteristic.

The invention also provides a multi-radar countermeasure system based on virtual channelization, which comprises: the device comprises a radar signal frequency division module, a local oscillator signal generation module, a first frequency mixer, a second frequency mixer and a control module;

the input end of the first mixer is connected to the output end of the radar signal frequency division module, and the output end of the first mixer is connected to the control module; the radar radio frequency signal is subjected to frequency division through the radar signal frequency division module and then is subjected to frequency mixing with a frequency division local oscillator signal through the first frequency mixer, so that a frequency division intermediate frequency signal is obtained;

the control module is used for: carrying out frequency detection on the pulse leading edge of the frequency-divided intermediate-frequency signal to obtain a pulse starting frequency; carrying out wideband and narrowband judgment on the frequency division intermediate frequency signal of the radar signal to obtain a wideband and narrowband judgment result of a wideband signal or a narrowband signal; calculating the center frequency of a broadband signal for the broadband signal according to the judgment result of the broadband and narrowband; according to the judgment result of the wide and narrow bands, determining the frequency range of a local oscillation signal for the narrow band signal according to the pulse starting frequency and controlling a local oscillation signal generation module to switch to the corresponding local oscillation signal; determining a local oscillator signal frequency range according to the broadband signal center frequency and controlling a local oscillator signal generating module to switch to a corresponding local oscillator signal for the broadband signal;

the input end of the second frequency mixer is connected with the output end of the local oscillator signal generation module and the receiving end of the radar radio frequency signal, and the output end of the second frequency mixer is connected to the control module; the local oscillator signal and the radar radio frequency signal generate an intermediate frequency radar signal after passing through a second frequency mixer, and the control module generates a radar interference signal according to the intermediate frequency radar signal.

In the multi-radar countermeasure system based on virtual channelization according to the present invention, preferably, the control module is further configured to: when the next detection window arrives, stopping sending the current radar interference signal, simultaneously detecting whether a new radar radio frequency signal is received, if the new radar radio frequency signal is not received in the detection window, continuing to send the current radar interference signal until the next detection window arrives or the total interference duration is over; if a new radar radio frequency signal is received in the interception window, detecting the initial pulse frequency again for the new radar radio frequency signal and generating a radar interference signal, and then alternately transmitting the radar interference signal in the effective state at present until the next interception window arrives or the total interference duration is over.

In the multi-radar countermeasure system based on virtual channelization according to the present invention, preferably, the control module calculates a pulse start frequency of a pulse leading edge of the divided intermediate frequency signal by the following formula:

wherein, Delta theta is the phase difference of two adjacent sampling points of the frequency division intermediate frequency signal, and the sampling time is t_s。

In the multi-radar countermeasure system based on virtual channelization according to the present invention, preferably, the local oscillation signal generating module includes multiple local oscillation signal generating units, and each local oscillation signal generating unit is connected with a local oscillation control switch, and the control module controls output of each local oscillation signal to implement local oscillation signal switching.

In the multi-radar countermeasure system based on virtual channelization according to the present invention, preferably, the main control module determines the local oscillation signal frequency range and switches to the corresponding local oscillation signal by:

for narrow band signals, when the measured pulse start frequency f is satisfiedIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range of the frequency difference value of each stage of local oscillation signal is 800MHz-1 GHz;

for wideband signals, when the calculated center frequency f of the wideband signal_OSatisfy the requirement ofIf so, selecting the ith local oscillation signal; wherein f is_iThe frequency of the ith local oscillator signal is represented by i, the value range of i is 1,2, …, m is the number of the local oscillator signals, B₁The value range is 800MHz-1GHz for the frequency difference of each stage of local oscillation signals.

In the multi-radar countermeasure system based on virtual channelization according to the present invention, preferably, the main control module generates a radar interference signal from the intermediate frequency radar signal by:

1) establishing a target scattering point model to output coordinates of a target scattering point and a target centroid in a target coordinate system;

2) converting coordinates of scattering points and a target centroid in a target coordinate system into a radar coordinate system through a coordinate transformation matrix, wherein the coordinate transformation matrix comprises a precession angle and a micromotion period which represent micromotion characteristics;

3) calculating the centroid instantaneous slant distance between the centroid of the target and the radar and the scattering point instantaneous slant distance between each scattering point and the radar, and calculating the micro-motion distance of each scattering point according to the centroid instantaneous slant distance and the scattering point instantaneous slant distance;

4) generating a baseband interference signal based on micro characteristic modulation according to the micro distance of the scattering point;

5) and generating an intermediate frequency interference signal according to the received intermediate frequency radar signal and the baseband interference signal modulated based on the inching characteristic.

The multi-radar countermeasure method and the system based on virtual channelization have the following beneficial effects: the invention adopts multiple local oscillators to cover a certain waveband frequency range to form virtual channelization, selects a corresponding channel according to a frequency measurement result, and realizes multi-radar countermeasure through instantaneous coverage of a frequency band, thereby improving the multi-radar countermeasure performance in a complex signal environment and further improving the countermeasure effect of active electronic interference.

Drawings

FIG. 1 is a flow chart of a virtual channelization based multi-radar countermeasure method in accordance with a preferred embodiment of the present invention;

FIG. 2 is a control timing diagram of a virtual channelization based multi-radar countermeasure method in accordance with a preferred embodiment of the present invention;

FIG. 3 is a schematic diagram of a target coordinate system in a perturbation signal generation process based on micro-motion feature modulation according to a preferred embodiment of the present invention;

fig. 4 is a schematic block diagram of a virtual channelization based multi-radar countermeasure system in accordance with a preferred embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Fig. 1 is a flowchart of a multi-radar countermeasure method based on virtual channelization according to a preferred embodiment of the present invention. As shown in fig. 1, the embodiment provides a virtual channelization-based multi-radar countermeasure method, which includes the following steps:

first, in step S1, a frequency detection step is performed to perform frequency division on a received radar radio frequency signal and mix the frequency divided radar radio frequency signal with a frequency division local oscillator signal to obtain a frequency division intermediate frequency signal, and perform frequency detection on a pulse leading edge of the frequency division intermediate frequency signal to obtain a pulse start frequency. The frequency of the frequency division local oscillation signal is fixed, and the value range is 500-800M.

The frequency measurement of the frequency division signal is to measure the intermediate frequency IQ signal of the radar radio frequency signal frequency division, then to calculate the frequency by first-order phase difference, and to improve the frequency measurement precision by multiple accumulation and averaging. The method has the characteristics of small operand, high frequency measurement speed and capability of meeting the requirement of quickly switching local oscillators.

Specifically, in order to perform frequency measurement on the leading edge of a radar signal pulse, a frequency division intermediate frequency signal IQ signal needs to be acquired and processed to obtain phase information. Suppose the pulse start frequency of the frequency-divided intermediate frequency signal is f and the sampling time is t_sThen, the I, Q components of the collected divided intermediate frequency signal are respectively:

I(n)＝Acos(2πfnt_s+φ) (1)

Q(n)＝Asin(2πfnt_s+φ) (2)

wherein n is a sampling point sequence, and the nth sampling point time is (n-1) t_sPhi is the initial phase of the frequency division intermediate frequency signal;

then the instantaneous phase of the signal can be found to be:

by solving the phase difference between two adjacent sampling points of the frequency division intermediate frequency signal, the pulse starting frequency can be solved as follows:

where Δ θ is a phase difference between two adjacent sampling points of the divided intermediate frequency signal, θ (n +1) is a phase of the n +1 th sampling point, and θ (n) is a phase of the nth sampling point, which can be obtained based on I, Q signals of the divided intermediate frequency signal of each sampling point.

Subsequently, in step S2, a wideband/narrowband determination is performed to perform a wideband/narrowband determination on the frequency-divided intermediate frequency signal of the radar signal, and a result of the wideband/narrowband determination on the wideband signal or the narrowband signal is obtained. In the step, the signal type can be judged by setting a threshold, when the signal bandwidth is larger than the threshold, the signal type is considered to belong to a broadband signal, and when the signal bandwidth is smaller than the threshold, the signal type is considered to belong to a narrowband signal, and the threshold is generally set to be 50 MHz. In this step, a bandwidth and a bandwidth flag may be set, where the narrowband signal time flag is 0 and the wideband signal time flag is 1.

Subsequently, in step S3, a wideband signal center frequency calculation step is performed to calculate a wideband signal center frequency for the wideband signal based on the wideband-narrowband determination result. In the step, the bandwidth of the broadband signal is calculated to be B₂If the pulse starting frequency of the broadband signal is f, when the broadband signal is positively frequency-modulated, the central frequency f of the broadband signal is_OIs composed ofWhen the broadband signal is negative frequency modulation, the central frequency f of the broadband signal_OIs composed of

Subsequently, in step S4, a local oscillator signal switching step is performed, in which, according to the wide-narrow band determination result, a local oscillator signal frequency range is determined for the narrow-band signal according to the pulse start frequency and is switched to a corresponding local oscillator signal; and for the broadband signal, determining a local oscillation signal frequency range according to the central frequency of the broadband signal and switching to a corresponding local oscillation signal. The local oscillator signal and the radar radio frequency signal are mixed to generate an intermediate frequency radar signal, and then a radar interference signal is generated according to the intermediate frequency radar signal.

Preferably, the system has m local oscillator signals, and the frequency difference of each local oscillator signal is B₁，B₁The value range is 800MHz-1 GHz. That is, f₂＝f₁+B₁，f₃＝f₁+2B₁，……，f_m＝f₁+(m-1)B₁。f₁Is approximately in the SCX band range.

For narrow band signals, when the measured pulse start frequency f is satisfiedIf so, selecting the ith local oscillation signal; wherein f is_iThe value range of i is 1,2, …, and m is the number of local oscillation signals.

For wideband signals, when the calculated center frequency f of the wideband signal_OSatisfy the requirement ofIf so, selecting the ith local oscillation signal; wherein f is_iThe value range of i is 1,2, …, and m is the number of local oscillation signals.

The steps in the above method may be implemented by table lookup.

Taking specific wave band as an example, 5 local oscillators are adopted to cover a certain frequency range to form virtual channelization, five local oscillators are initialized, and the frequency difference value of each stage of local oscillator signal is B₁Setting five local oscillators to f respectively at 800MHz₁、f₂、f₃、f₄And f₅. For narrow-band signals, measured directly by the signal pulse headThe pulse starting frequency controls local oscillator switching, and for broadband signals, the central frequency of the broadband signals controls the local oscillator switching, so that the local oscillator is ensured to be in the center of the frequency of the broadband signals.

Because the invention can dynamically switch to the corresponding local oscillator signal according to the pulse starting frequency of the received signal, the width of each channel can be 800MHz-1GHz, compared with the traditional channelization mode, the invention reduces the number of channels and saves the hardware cost.

More preferably, the method of the present invention further comprises:

when the next detection window arrives, stopping sending the current radar interference signal, simultaneously detecting whether a new radar radio frequency signal is received, if the new radar radio frequency signal is not received in the detection window, continuing to send the current radar interference signal until the next detection window arrives or the total interference duration is over; if a new radar radio frequency signal is received in the interception window, the new radar radio frequency signal is detected again by using the steps S1-S4 and a radar interference signal is generated, and then the radar interference signal which is currently in an effective state is alternately transmitted until the next interception window arrives or the total interference duration is over. The radar interference signal in the effective state at present refers to a radar interference signal detected and generated in the total interference duration at present. The total interference duration is preferably 200us to 2ms, the length of the detection window is about 2-3us, the interval of the detection window is 5-10 us, namely, the detection window is switched every 5-10 us for searching. The existing multi-radar signal countermeasure technology based on channelization needs to process each channel in parallel, that is, the traditional way of the multi-radar signal countermeasure is to confront the multi-radar from the frequency domain, and needs a multipath filter and a detector. The virtual channelization method provided by the invention adopts a frequency domain and time domain combined countermeasure mode, for example, 5 local oscillators are adopted to cover the whole frequency band, each virtual channel covers 800MHz-1GHz, and the number of channels is reduced.

Please refer to fig. 2, which is a control timing diagram of the virtual channelization based multi-radar countermeasure method according to the preferred embodiment of the invention. The ADC trigger signal is a trigger signal generated by an ADC when the intermediate frequency radar signal reaches the control module. When receiving radar radio frequency signalDuring signal generation, the initial pulse frequency can be measured after the pulse leading edge of the intermediate frequency radar signal is 300ns, the wide and narrow band signals can be distinguished when the pulse leading edge of the intermediate frequency radar signal is 800ns, and then the initial pulse frequency or the center frequency of the wide band signal of the radar 1 is judged to determine the frequency f falling into the first local oscillation signal₁And when the coverage range is within the preset range, switching to the first local oscillator signal and generating a first radar interference signal. When the next detection window comes, the initial pulse frequency of the intermediate frequency radar signal is detected again, and when the initial pulse frequency of the new radar 2 or the center frequency of the broadband signal is detected, the frequency f falling into the second local oscillator signal is determined₂And switching to a second local oscillator signal and generating a second radar interference signal. And then, before a new radar signal is received in a new reconnaissance window, the first local oscillator signal and the second local oscillator signal are alternately switched, so that the first radar interference signal and the second radar interference signal are alternately sent.

The invention further adds a jogging feature when generating the radar interference signal. The micro-motion distance of scattering points can be calculated in real time according to a target scattering point model, a baseband interference signal based on micro-motion characteristic modulation is generated according to the micro-motion distance of the scattering points, and an intermediate frequency interference signal is generated according to an intermediate frequency radar signal and the baseband interference signal based on micro-motion characteristic modulation. The intermediate frequency interference signal can be up-converted again, converted to radio frequency and then transmitted. Specifically, the process comprises the steps of:

the method comprises the following steps: and establishing a target scattering point model and outputting coordinates of the target scattering point and the centroid in a target coordinate system.

According to the scattering characteristics of the target radar, a target scattering point model is established to output the coordinates of the target scattering point in a target coordinate system. Fig. 3 is a schematic diagram of a target coordinate system in a process of generating an interference signal based on inching characteristic modulation according to a preferred embodiment of the invention. As shown in the figure, a coordinate system is first established, the target vertex is set as the coordinate origin O, the target symmetry axis is set as the w-axis, and the direction from the target vertex to the target bottom surface is the w-axis forward direction. The u, v axes were selected according to the right hand series. And (3) selecting only the vertex and the bottom surface edge of the target by using a scattering point model of the target, wherein the coordinates of the scattering point are (u, v, w). Assuming a cube with the side length of the target being 1 meter, the scattering points take 8 vertexes A1-A8 of the cube, and the precession center takes the centroid P of the target. The coordinates of the scattering points and the centroid in the target coordinate system are the scattering characteristics of the target (different scattering points of the target are different), and can be preset in the DSP without changing in real time and changing with the frequency and the incident angle of the radio wave.

Step two: and converting coordinates in a target coordinate system of the scattering points and the target centroid into a radar coordinate system through a coordinate transformation matrix, wherein the coordinate transformation matrix comprises a precession angle and a micromotion period which represent micromotion characteristics.

The coordinate transformation matrix adopted in the step comprises a precession angle α and a micromotion period omega, so that the micromotion characteristics of the target are included while the coordinate transformation is carried out.

The coordinate transformation matrix specifically comprises the following steps:

where α is the precession angle, β is ω t, ω is the inching period, t is time, the precession angle α and the inching period ω are both preset, do not change with time, and are related to the target characteristic.

Therefore, the coordinates of the respective scattering points and the centroid in the target coordinate system can be converted into the radar coordinate system in this step by the following formula:

wherein u, v and w are coordinates in a target coordinate system, X, Y and Z are coordinates in a radar coordinate system, α is a precession angle, β is ω t, ω is a micro-motion period, and t is time.

Step three: and calculating the centroid instantaneous slant distance between the centroid of the target and the radar and the scattering point instantaneous slant distance between each scattering point and the radar, and calculating the micro-motion distance of each scattering point according to the centroid instantaneous slant distance and the scattering point instantaneous slant distance.

In the process of target movement, firstly, the instantaneous slant distance of the target centroid P and radar, namely the centroid instantaneous slant distance R is calculated_PThen, according to the coordinate transformation matrix and the sight line shielding, calculating the instantaneous slant range of each scattering point and the radar, namely the centroid instantaneous slant rangeAnd the difference of the slope distances of each scattering point is calculated as the vernier distance.

The slope distance of the precession center, namely the centroid instantaneous slope distance between the target centroid and the radar is as follows:

the instantaneous slope distance of the scattering point between the ith scattering point and the radar is as follows:

the micro-motion distance of the ith scattering point is:

in the above formula, R_PIs the centroid instantaneous slant distance between the target centroid and the radar,is the instantaneous slope distance, X, of the scattering point between the ith scattering point and the radar_P、Y_p、Z_PAs coordinates of the center of mass of the target in the radar coordinate system, X_r、Y_r、Z_rFor the coordinates of the radar in the radar coordinate system, is the coordinate of the ith scattering point of the target in the radar coordinate system.

Step four: and generating a baseband interference signal based on the micro characteristic modulation according to the micro distance of the scattering point.

According to the imaging principle of the inverse synthetic aperture radar, a baseband interference signal is generated by phase modulation of each scattering point due to micromotion, namely:

the interference signal contains n scattering points. Wherein, Δ R_iThe micro-motion distance of the ith scattering point is the coordinate transformation matrix T. n is the number of scattering points, k is the chirp rate, f_cIs the center frequency, c is the speed of light, and t is the time. In the formula 2. delta.R_iThe/c embodies the delay processing. Where k is the ramp frequency obtained by measuring the intermediate frequency radar signal, f_cThe center frequency is the measured center frequency of the medium frequency radar signal.

Step five: and generating an intermediate frequency interference signal according to the intermediate frequency radar signal and the baseband interference signal modulated based on the inching characteristic.

The intermediate frequency interference signal generated in the step is:

J(t)＝IF(t)*S(t)；

if (t) is intermediate frequency radar signal, s (t) is baseband interference signal modulated based on jogging feature.

f₀Is the initial frequency of the received intermediate frequency radar signal and k is the chirp rate of the received intermediate frequency radar signal.

The invention adopts a real-time calculation technology of the micro-motion characteristic modulation parameter, wherein the micro-motion characteristic modulation parameter is the micro-motion distance between a target scattering point and a target precession center relative to a radar. On the basis of establishing a target scattering point model, coordinate transformation is carried out according to track information, radar position information and micro-motion characteristic information (micro-motion period, precession angle and precession center) to realize real-time resolving of micro-motion characteristic modulation parameters of a target. In addition, the invention also combines the baseband interference modulation signal optimization generation technology, and the baseband interference modulation signal can be generated by the micro-motion distance of all scattering points according to the inverse synthetic aperture radar deskew principle. And the baseband modulation is carried out on the intermediate frequency signal to realize the generation of the interference signal with the inching characteristic. The baseband signal modulation algorithm adopted by the micro-motion interference modulation signal greatly simplifies the complexity of interference signal generation and improves the efficiency of interference signal generation.

Based on the same inventive concept, the invention also provides a multi-radar countermeasure system based on virtual channelization. Referring to fig. 4, a schematic block diagram of a virtual channelization based multi-radar countermeasure system is shown according to a preferred embodiment of the present invention. As shown in fig. 4, the virtual channelization based multi-radar countermeasure system includes: the radar signal frequency division module 100, the local oscillator signal generation module 200, the first mixer 300, the second mixer 400 and the control module 500.

The radar rf signal input in the system can be divided into two paths and input to the radar signal frequency dividing module 100 and the second mixer 400, respectively.

The input end of the first mixer 300 is connected to the output end of the radar signal frequency dividing module 100, and is also connected to the frequency-dividing local oscillator signal, and the output end of the first mixer 300 is connected to the control module 500. The radar radio frequency signal is subjected to frequency division through the radar signal frequency division module 100 and then is mixed with the frequency division local oscillation signal through the first mixer 300, so that a frequency division intermediate frequency signal is obtained.

The radar signal frequency dividing module 100 preferably includes a filtering and amplifying unit 110, a frequency dividing unit 120, and a low-pass filtering unit 130, wherein the filtering and amplifying unit is configured to filter and amplify the radar radio frequency signal. The frequency dividing unit 120 is configured to divide the frequency of the amplified radar radio frequency signal. For example, a frequency divider is used to divide the radar rf signal by N, where N may be 8, 16, 32, etc. The low pass filter unit 130 is configured to perform low pass filtering on the frequency-divided signal, and then input the frequency-divided signal to the first mixer 300.

Preferably, the local oscillation signal generating module 200 includes multiple local oscillation signal generating units, each local oscillation signal generating unit is connected to a local oscillation control switch, and the control module 500 controls output of each local oscillation signal to implement local oscillation signal switching. For example, in this embodiment, the first local oscillator signal generating unit 210, the second local oscillator signal generating unit 220, the third local oscillator signal generating unit 230, the fourth local oscillator signal generating unit 240, and the fifth local oscillator signal generating unit 250 are included, and each local oscillator signal generating unit is connected to a local oscillator control switch. The local oscillation control switch is controlled by the local oscillation control word sent by the control module 500. The frequency of each local oscillator signal generating unit is controlled by a frequency control word sent by the control module 500.

The control module 500 is configured to: carrying out frequency detection on the pulse leading edge of the frequency-divided intermediate-frequency signal to obtain a pulse starting frequency; carrying out wideband and narrowband judgment on the frequency division intermediate frequency signal of the radar signal to obtain a wideband and narrowband judgment result of a wideband signal or a narrowband signal; calculating the center frequency of the broadband signal according to the judgment result of the broadband and narrowband; determining a local oscillator signal frequency range according to the pulse starting frequency for the narrow-band signal and controlling a local oscillator signal generating module to switch to a corresponding local oscillator signal according to the wide-band and narrow-band judgment result; and for the broadband signal, determining the frequency range of the local oscillation signal according to the central frequency of the broadband signal and controlling the local oscillation signal generation module to switch to the corresponding local oscillation signal.

Preferably, the control module 500 may calculate the pulse start frequency of the leading edge of the pulse of the divided intermediate frequency signal by the following formula:

wherein, Delta theta is the phase difference of two adjacent sampling points of the frequency division intermediate frequency signal,sampling time t_s。

Preferably, the control module 500 calculates the bandwidth of the wideband signal as B first₂If the pulse starting frequency of the broadband signal is f, when the broadband signal is positively frequency-modulated, the central frequency f of the broadband signal is_OIs composed ofWhen the broadband signal is negative frequency modulation, the central frequency f of the broadband signal_OIs composed ofThe system may have m local oscillator signals, that is, the local oscillator signal generating module 200 includes m local oscillator signal generating units, and the frequency difference of each local oscillator signal is B₁，B₁The value range is 800MHz-1 GHz. That is, f₂＝f₁+B₁，f₃＝f₁+2B₁，……，f_m＝f₁+(m-1)B₁. For narrow band signals, when the measured pulse start frequency f is satisfiedIf so, selecting the ith local oscillation signal, namely switching to the ith local oscillation signal generating unit; wherein f is_iThe value range of i is 1,2, …, and m is the number of local oscillation signals.

For wideband signals, when the calculated center frequency f of the wideband signal_OSatisfy the requirement ofIf so, selecting the ith local oscillation signal, namely switching to the ith local oscillation signal generating unit; wherein f is_iThe value range of i is 1,2, …, and m is the number of local oscillation signals.

The input end of the second mixer 400 is connected to the output end of the local oscillator signal generating module 200 and the receiving end of the radar radio frequency signal, and the output end of the second mixer 400 is connected to the control module 500. The local oscillator signal and the radar radio frequency signal pass through the second mixer 400 to generate an intermediate frequency radar signal, and the control module 500 generates a radar interference signal according to the intermediate frequency radar signal.

The control module 500 is further configured to: when the next detection window arrives, stopping sending the current radar interference signal, simultaneously detecting whether a new radar radio frequency signal is received, if the new radar radio frequency signal is not received in the detection window, continuing to send the current radar interference signal until the next detection window arrives or the total interference duration is over; if a new radar radio frequency signal is received in the interception window, detecting the initial pulse frequency again for the new radar radio frequency signal and generating a radar interference signal, and then alternately transmitting the radar interference signal in the effective state at present until the next interception window arrives or the total interference duration is over. The radar interference signal in the effective state at present refers to a radar interference signal detected and generated in the total interference duration at present.

It should be understood that the principles of the virtual channelization based multi-radar countermeasure method and system of the present invention are the same, and therefore the detailed description of the embodiments of the virtual channelization based multi-radar countermeasure method is also applicable to the virtual channelization based multi-radar countermeasure system.

In summary, the invention employs multiple local oscillators to cover a frequency range of a certain band to form virtual channelization, selects a corresponding channel according to a frequency measurement result, and implements multi-radar countermeasure by instantaneously covering the frequency band. In addition, the frequency division signal frequency measurement technology and the local oscillator control technology solve the problems of rapid high-precision frequency measurement and rapid local oscillator switching. The traditional frequency measurement mode does not meet the requirement of an interference machine on reaction time. The technology calculates the frequency through a phase difference method, and the method has the characteristics of fast frequency measurement and shortened local oscillation switching time.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.