阅读说明：本技术 一种基于频谱综合的多方位匹配信号生成方法 (Multi-azimuth matching signal generation method based on spectrum synthesis ) 是由 郭良帅 魏飞鸣 李亚军 张润俊 于 2020-04-07 设计创作，主要内容包括：本发明公开了一种基于频谱综合的多方位匹配信号生成方法,包括对目标在多个匹配探测方位上的信号进行频谱分量合成,设计一种对多个方位探测角度均有较好的探测性能的发射波形,用于雷达探测,极大的提升雷达预警探测能力,具有适应性强、观点新颖,极大的提高了雷达系统探测预警能力,为目标探测及反隐身设计提供有效技术手段。(The invention discloses a multi-azimuth matching signal generation method based on spectrum synthesis, which comprises the steps of carrying out spectrum component synthesis on signals of a target in a plurality of matching detection directions, designing a transmitting waveform with better detection performance on a plurality of direction detection angles, being used for radar detection, greatly improving the radar early warning detection capability, having strong adaptability and novel viewpoint, greatly improving the detection early warning capability of a radar system, and providing an effective technical means for target detection and anti-stealth design.)

1. A multi-azimuth matching signal generation method based on spectrum synthesis is characterized by comprising the following steps:

step S1, transmitting a conventional radar detection signal, and acquiring target time domain scattering echo signals under different azimuth detection angles;

step S2, extracting envelope information of the target time domain scattering echo, extracting frequency spectrum information from the envelope information by using time domain transformation, obtaining target frequency domain response characteristics under different azimuth detection angles, and providing data for target baseband frequency response;

step S3, performing frequency spectrum component synthesis on the envelope information of the target time domain scattering echo signal under different azimuth detection angles by using an inclusion method on a time domain scattering frequency spectrum to obtain comprehensive frequency spectrum signals under all azimuth detections;

step S4, performing time-frequency transformation on the comprehensive frequency spectrum signal to a time domain to obtain a time domain scattering signal; and performing time reversal on the time domain scattering signal to obtain a matched and conjugated time domain signal, performing power matching on the time domain scattering signal and the conventional radar detection signal to obtain a time domain emission signal, and detecting the time domain emission signal as an emission signal.

2. The method for generating multi-azimuth matching signal based on spectrum synthesis as claimed in claim 1, wherein said step S1 comprises:

and acquiring time domain scattering echoes of the narrow pulse envelope modulation high-frequency carrier signals under different azimuth detection angles by using a time domain simulation modeling method to obtain the target time domain scattering echo signals under different azimuth detection angles.

3. The method of claim 2, wherein the narrow-pulse-envelope modulated high-frequency carrier signal is a gaussian modulated pulse signal.

4. The method for generating multi-azimuth matched signals based on spectrum synthesis as claimed in claim 3, wherein said simulation modeling method is a time domain bounce ray method.

5. The method for generating multi-azimuth matching signal based on spectrum synthesis as claimed in claim 4, wherein said step S2 comprises: and extracting the envelope information of the target time domain scattering echo by adopting a radar digital signal intermediate frequency method, and extracting the frequency spectrum information from the envelope information by utilizing a wavelet transformation method.

6. The method for generating multi-azimuth matching signal based on spectrum synthesis as claimed in any one of claims 1 to 5, wherein said step S3 comprises: and accumulating and adding the frequency spectrum components in the frequency spectrum information under each azimuth detection angle in a complex number field to obtain the comprehensive frequency spectrum signal.

7. The method for generating multi-azimuth matching signal based on spectrum synthesis as claimed in claim 1, wherein said step S4 further comprises: and detecting the target based on a time reversal process, wherein the detection process is as follows:

step S4.1, the radar transmitter gives a first transmitting signal S (t);

step S4.2, the first emission signal S (t) passes through a forward transmission channel h₁(t) forming a target detection waveformIn the formulaRepresenting a convolution and then with the target response function h₀(t) acting to form a time domain scattered signalThe time domain scattered signal is a counter-propagating signal h₂(t) after obtaining a primary echo received signal at the radar receiver

S4.3, performing time reversal on the primary echo receiving signal y (t), and performing energy matching with the primary transmitting signal S (t) to form a secondary transmitting signal y (-t);

step S4.4, the second emission signal y (-t) passes through the forward transmission channel h same as the step S4.2₁(t), objective response function h₀(t), reverse transport channel h₂After (t), a secondary echo received signal is formed

Technical Field

The invention relates to the technical field of radar detection signal matching generation, in particular to a multi-azimuth matching signal generation method based on frequency spectrum synthesis.

Background

The backward radar scattering echo (RCS) of the low observable target in a high-frequency area is weaker, the target scattering echo amplitude is greatly reduced, and the conventional detection means cannot effectively detect and identify the low observable target; namely, with high requirements on detection sensitivity and identification accuracy, the conventional radar high-frequency detection signal cannot meet the requirements on early warning and identification of low observable targets. And the radar scattering echo difference of the low observable target under different azimuth angles is large, the matched detection waveform (matched detection signal) cannot cover a plurality of azimuth detection angles, and the early warning and detection radar cannot meet the requirement of real-time and accurate detection of the stealth target.

Disclosure of Invention

The invention aims to provide a multi-azimuth matching signal generation method based on spectrum synthesis, which is used for solving the problems of low radar scattering echo and poor identification precision of low observable targets in the prior art and achieving the purpose of providing technical means and data support for detection and identification of the low observable targets.

In order to solve the problems, the invention is realized by the following technical scheme:

a multi-azimuth matching signal generation method based on spectrum synthesis comprises the following steps:

step S1, transmitting a conventional radar detection signal, and acquiring target time domain scattering echo signals under different azimuth detection angles;

step S2, extracting envelope information of the target time domain scattering echo, extracting frequency spectrum information from the envelope information by using time domain transformation, obtaining target frequency domain response characteristics under different azimuth detection angles, and providing data for target baseband frequency response;

step S3, performing frequency spectrum component synthesis on the envelope information of the target time domain scattering echo signal under different azimuth detection angles by using an inclusion method on a time domain scattering frequency spectrum to obtain comprehensive frequency spectrum signals under all azimuth detections;

step S4, performing time-frequency transformation on the comprehensive frequency spectrum signal to a time domain to obtain a time domain scattering signal; and performing time reversal on the time domain scattering signal to obtain a matched and conjugated time domain signal, performing power matching on the time domain scattering signal and the conventional radar detection signal to obtain a time domain emission signal, and detecting the time domain emission signal as an emission signal.

Preferably, the step S1 includes: and acquiring time domain scattering echoes of the narrow pulse envelope modulation high-frequency carrier signals under different azimuth detection angles by using a time domain simulation modeling method to obtain the target time domain scattering echo signals under different azimuth detection angles.

Preferably, the narrow pulse envelope modulation high frequency carrier signal is a gaussian modulation pulse signal.

Preferably, the simulation modeling method is a time domain bounce ray method.

Preferably, the step S2 includes: and extracting the envelope information of the target time domain scattering echo by adopting a radar digital signal intermediate frequency method, and extracting the frequency spectrum information from the envelope information by utilizing a wavelet transformation method.

Preferably, the step S3 includes: and accumulating and adding the frequency spectrum components in the frequency spectrum information under each azimuth detection angle in a complex number field to obtain the comprehensive frequency spectrum signal.

Preferably, the step S4 further includes: and detecting the target based on a time reversal process, wherein the detection process is as follows:

step S4.1, the radar transmitter gives a first transmitting signal S (t);

step S4.2, the first emission signal S (t) passes through a forward transmission channel h₁(t) forming a target detection waveformIn the formulaRepresenting a convolution and then with the target response function h₀(t) acting to form a time domain scattered signalThe time domain scattered signal is a counter-propagating signal h₂(t) after obtaining a primary echo received signal at the radar receiver

S4.3, performing time reversal on the primary echo receiving signal y (t), and performing energy matching with the primary transmitting signal S (t) to form a secondary transmitting signal y (-t);

step S4.4, the second emission signal y (-t) passes through the forward transmission channel h same as the step S4.2₁(t), objective response function h₀(t), reverse transport channel h₂After (t), a secondary echo received signal is formed

The invention has the following advantages:

the multi-azimuth matching design technology based on spectrum synthesis utilizes the weak sensitivity of the target resonance time domain waveform to the detection direction and the small difference of the resonance spectrum distribution in different directions to perform matching synthesis on the time domain scattering waveform of the target in different directions to obtain radar detection signals (time domain emission signals), so that the detection capability of a radar system can be effectively improved.

According to the multi-azimuth matching signal generation method based on spectrum synthesis, provided by the invention, aiming at the problems that the scattering echo difference of a target under different azimuth angles is large, the matched detection waveform cannot cover a plurality of azimuth detection angles, and the early warning and detection radar cannot meet the requirement of real-time and accurate detection of a stealth target. The method carries out frequency spectrum component synthesis on signals of the target in a plurality of matched detection directions, designs a transmitting waveform with better detection performance on a plurality of direction detection angles, is used for radar detection, greatly improves the radar early warning detection capability, has strong adaptability and novel view, greatly improves the detection early warning capability of a radar system, and provides an effective technical means for target detection and anti-stealth design.

Drawings

Fig. 1 is a flowchart of a multi-azimuth matching signal generation method based on spectrum synthesis according to an embodiment of the present invention;

fig. 2 is a schematic diagram illustrating a signal time reversal principle according to an embodiment of the present invention.

Detailed Description

The multi-azimuth matching signal generation method based on spectrum synthesis according to the present invention will be described in detail with reference to fig. 1-2 and the following detailed description. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise scale for the purpose of facilitating and distinctly aiding in the description of the embodiments of the present invention. To make the objects, features and advantages of the present invention comprehensible, reference is made to the accompanying drawings. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the implementation conditions of the present invention, so that the present invention has no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

With reference to fig. 1 and fig. 2, the present embodiment provides a method for generating a multi-azimuth matching signal based on spectrum synthesis, including:

and step S1, transmitting a conventional radar detection signal, and acquiring target time domain scattering echo signals under different azimuth detection angles. Preferably, in this embodiment, the step S1 includes: and acquiring time domain scattering echoes of the narrow pulse envelope modulation high-frequency carrier signals under different azimuth detection angles by using a time domain simulation modeling method to obtain the target time domain scattering echo signals under different azimuth detection angles. The narrow pulse envelope modulation high-frequency carrier signal is a Gaussian modulation pulse signal. The simulation modeling method (frequency domain simulation modeling method) is a time domain bounce ray method (TD-SBR).

TD-SBR borrows the concept of frequency domain GO, using a series of closely connected tubes to simulate the propagation of electromagnetic waves as they strike a target surface. Let the starting point of the ray be r₀(x₀,y₀,z₀) The direction vector of ray propagation is s(s)_x,s_y,s_z) Then, the equation of the straight line where the ray is located:

r(x,y,z)＝r₀(x₀,y₀,z₀)+s(s_x,s_y,s_z)t (1)

where t is the time factor and r (x, y, z) is the beam propagation position at time t.

The directions of reflection and refraction of the rays are given by Snell's theorem. The (i + 1) th intersection r of the ray and the object_i+1The field intensity can be measured through the ith intersection point r of the ray tube and the target body_iThe field strength of which is:

E(r_i+1)＝(DF)_i·()_i·E(r_i)·e-^j·phase(2)

in the formula, E (r)_i+1) Is r_i+1The value of the electric field at (phase) k | r_i+1-r_i+1I is the phase change caused by the path, (DF)_iAnd ()_iAre respectively r_iScattering factor and reflection coefficient matrix.

In the formula, ρ₁,ρ₂Are respectively r_iTwo main curvature radiuses of the wave front of the ray tube are located, and s is the propagation distance of the ray. Reflection coefficient matrix ()_iCan be determined by media parameters. For the frequency domain simulation modeling method, the far field radiation of the tube is given by the physical optical integration of the tube at the last reflection of the target surface, i.e.

In the formula (I), the compound is shown in the specification,is angular frequencyThe value of the electric field at the r position.Is angular frequencyThe value of the electric field at the r' position. Z₀Is the spatial wave impedance, j is the imaginary unit and k is the wave number.Is the unit scattering direction vector.Is the unit normal component at the corresponding location.Are the corresponding magnetic field components. r' is a position describing factor of the target surface.

The time domain bounce ray method is derived from a frequency domain bounce ray method, and for a linear time-invariant system, a frequency domain functionAnd the time domain function F (r, t) have the following fourier transform relationship:

for an ideal metal target, the time-domain scattering electric field representation according to boundary condition equation (4) is:

magnetic field of frequency domainThe phase in (1) is separated and can be expressed as:

in the formula I_GOFor the distance traveled by the ray during the path tracing,is a unit direction vector of incidence, r₀The intersection of the incident ray with the target surface,is the frequency domain magnetic field amplitude. Compared with the frequency domain method, the time domain bounce ray method considers the phase difference caused by the path which is passed by the ray after multiple reflections on the target surface. Will be provided with(c is the speed of light) and the formula (4) bring the time domain scattering electric field into the formula (6) as follows:

according to equation (5), (8) can be simplified as:

in the formula (I), the compound is shown in the specification,in order to be the total time delay,the derivative of time t. And performing related accumulation and superposition on the time domain scattering echo signals of different paths (namely under different azimuth detection angles) by using a time reversal algorithm to finally complete the time domain scattering echo signals of the narrow pulse source ultra-electric large-size target.

And step S2, extracting envelope information of the target time domain scattering echo, extracting frequency spectrum information from the envelope information by using time domain transformation, obtaining target frequency domain response characteristics under different azimuth detection angles, and providing data for target baseband frequency response.

Preferably, the step S2 includes: and extracting the envelope information of the target time domain scattering echo by adopting a radar digital signal intermediate frequency method, and extracting the frequency spectrum information from the envelope information by utilizing a wavelet transformation method.

When Fourier transform of ψ (t) satisfies C_ψ＝∫_R|ψ(ω)|²When/| ω | d ω < ∞, we call ψ (ω) as a mother wavelet function. After the mother wavelet psi (omega) is subjected to expansion and translation, a wavelet sequence psi can be obtained_a,b(t), then the continuous wavelet transform of an arbitrary function is defined as

Where a is a scale factor and b is a translation factor. Wavelet inverse transform

The wavelet transform can be expressed in the frequency domain as:

the wavelet transform has several properties:

in practical application, the wavelet transform can be expressed in a discrete form, and the sampling period is T, so that the wavelet transform can be obtained

The essence of the wavelet transform is to project the signal onto a series of wavelet basis functions, i.e. to approximate the signal with a series of wavelet basis functions. The wavelet transform is a time scale analysis method, overcomes the defect that the window function of the STFT cannot be changed, and can effectively focus the instantaneous structure of a signal. The basic wavelet psi (t) can be seen as the impulse response of a band-pass filter, which generates the functional family psi by panning and warping_a,b(t)。ψ_a,bThe window area determined by (t) is the same as the window area determined by ψ (t), but the shape is different. When a increases, i.e. a broadened window function is selected, the bandwidth decreases, and_a,b(t) the center of the window moves towards the low-frequency direction, so that the requirement of higher frequency resolution at the low frequency is met; when a is reduced, a compressed window function is selected, the bandwidth is increased, and the requirement of higher time resolution at high frequency is met.

And step S3, performing frequency spectrum component synthesis on the envelope information of the target time domain scattering echo signal under different azimuth detection angles on the time domain scattering frequency spectrum by using an inclusion method to obtain comprehensive frequency spectrum signals under all azimuth detections. Preferably, the step S3 includes: and accumulating and adding the frequency spectrum components in the frequency spectrum information under each azimuth detection angle in a complex number field to obtain the comprehensive frequency spectrum signal.

The invention adopts an inclusion method to develop matching detection signal design based on spectrum synthesis, and the specific steps are as follows:

① extracting the time domain envelope waveform of the target by adopting the radar digital signal intermediate frequency technology;

② obtaining target frequency spectrum response distribution by time-frequency transformation technology in S2;

③ using an inclusion method to carry out frequency spectrum component synthesis, specifically, accumulating and adding the frequency spectrum components of each direction in a plurality of domains, then carrying out time-frequency inverse transformation on the obtained frequency spectrum distribution to a time domain, and obtaining a matched time domain emission waveform after normalization;

④ repeatedly using ①, ②, ③ operations until an optimal signal-to-noise ratio is reached;

step S4, performing time-frequency transformation on the comprehensive frequency spectrum signal to a time domain to obtain a time domain scattering signal; and performing time reversal on the time domain scattering signal to obtain a matched and conjugated time domain signal, performing power matching on the time domain scattering signal and the conventional radar detection signal to obtain a time domain transmitting signal, ensuring the consistency of power energy of a transmitter, and performing a new round of detection by using the time domain transmitting signal as a transmitting signal (a new radar detection signal).

The time-frequency transform (time-frequency transform method) adopted in the step S4 is a wavelet transform technique. The wavelet transform window is an adjustable time-frequency window, a short window is used at high frequency, the central frequency is increased, the time resolution is increased, a wide window is used at low frequency, the bandwidth is narrowed, the central frequency is reduced, the frequency resolution is increased, namely, signals are observed at different scales, the signals are analyzed at different resolutions, the idea of multi-resolution analysis is fully embodied, and the method is consistent with the characteristics of time-varying and non-stable signals. And the wavelet transformation has linear characteristic and does not generate cross interference terms.

The time-reversed focusing characteristic in said step S4 is closely related to its space-time matched filtering characteristic. The time domain echo spectrum obtained through time reversal contains more target resonance spectrums, and the energy of the resonance spectrums can be effectively improved by carrying out relevant modulation at a transmitting end, so that higher signal-to-noise ratio/signal-to-noise ratio is obtained, and data support is provided for detection application.

The concept of time reversal is extended from phase conjugation in optics. The specific method is that a signal is transmitted at a transmitting end, and after the signal is received by a receiving array element through a propagation medium, the time domain signal is subjected to time reversal and energy normalization and then is sent out again through the same medium. If the scattering channel is reciprocal, the spread due to multipath of the channel can be compensated without any a priori knowledge of the propagation environment, so that the time-reversed newly transmitted signal reaches a space-time focus at the original source location. Through time reversal, the transmit waveform can be adjusted to match the scattering characteristics of the propagation medium and the target, thereby improving the echo signal-to-noise ratio.

In radar detection, a radar echo signal of a point target is a time delay copy of a transmission waveform with weighted amplitude. In the presence of multipath, using ray theory, the channel transfer function can be modeled as

In the formula: n represents the number of multipaths; a is_nAnd τ_nRespectively representing the attenuation amplitude and the time delay corresponding to the nth path. If the relative position and posture of the radar and the target are unchanged and the size of the transmitted pulse relative to the target is narrow, the target can be regarded as the superposition of scattered echoes of a plurality of parts of the target, so that the superposition can be equivalent to a multipath channel effect, and the echo amplitude a of each part of the target is not considered at first_nThe time-varying characteristic is such that the resonance frequency characteristic contained in the envelope of the echo signal is not taken into account. After the time reversal technology is adopted, the scattered echoes at different positions are accumulated and superposed at a certain time to form a strong echo peak value, and the anti-stealth capability is improved.

The step S4 further includes: the target detection is performed based on a time reversal process (time reversal detection model), which is as follows, as shown in fig. 2:

step S4.1, the radar transmitter gives a first transmitting signal S (t);

step S4.2, the first emission signal S (t) passes through a forward transmission channel h₁(t) forming a target detection waveformIn the formulaRepresenting a convolution and then with the target response function h₀(t) acting to form a time domain scattered signalThe time domain scattered signal is a counter-propagating signal h₂(t) after obtaining a primary echo received signal at the radar receiver

S4.3, performing time reversal on the primary echo receiving signal y (t), and performing energy matching with the primary transmitting signal S (t) to form a secondary transmitting signal y (-t);

step S4.4, the second emission signal y (-t) passes through the forward transmission channel h same as the step S4.2₁(t), objective response function h₀(t), reverse transport channel h₂After (t), a secondary echo received signal is formed

The secondary echo receiving signal z (t) and the forward transmission channel h₁(t), objective response function h₀(t), reverse transport channel h₂And (t) is a conjugate relation, the signal characteristics are the same, multipath energy components caused by multiple components of the target are accumulated, energy and signal-to-noise ratio improvement can be formed, and the more complex the target is, the more the components are, the more the performance improvement is obvious.

Therefore, the multi-azimuth matching design technology based on spectrum synthesis in the embodiment utilizes the weak sensitivity of the target resonance time domain waveform to the detection azimuth, the difference of the resonance spectrum distribution in different azimuths is small, and the radar detection signals (time domain emission signals) obtained by matching and synthesizing the time domain scattering waveforms in different azimuths of the target can effectively improve the detection capability of the radar system.

The multi-azimuth matching signal generation method based on spectrum synthesis provided by the embodiment has the advantages that the scattering echo difference of the target under different azimuth angles is large, the matching detection waveform cannot cover a plurality of azimuth detection angles, and the early warning and detection radar cannot meet the requirements of real-time and accurate detection of the stealth target. The invention carries out frequency spectrum component synthesis on time domain scattering echo signals of a target on a plurality of azimuth detection angles, designs a transmitting waveform with better detection performance on a plurality of azimuth detection angles, is used for radar detection, greatly improves the radar early warning detection capability, has strong adaptability and novel view, greatly improves the detection early warning capability of a radar system, and provides an effective technical means for target detection and anti-stealth design.

It should be noted that the apparatuses and methods disclosed in the embodiments herein can be implemented in other ways. The apparatus embodiments described above are merely illustrative, and for example, the flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments herein. In this regard, each block in the flowchart or block diagrams may represent a module, a program, or a portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.