CN115792850A - Airborne rotating antenna radar clutter suppression and target energy focusing method and device based on improved STAP and storage medium - Google Patents

Abstract

The invention discloses an improved STAP-based airborne rotating antenna radar clutter suppression and target energy focusing method, a computer device and a storage medium. According to the invention, the rotation disturbance matrix is added to the space-time steering vector, the STAP processing is carried out on the space-time steering vector and the echo data matrix, the clutter in the obtained processing result is suppressed, and the clutter suppression effect basically consistent with that of the traditional STAP is obtained. The invention is widely applied to the technical field of radars.

Description

Clutter Suppression and Target Energy Focusing of Airborne Rotating Antenna Radar Based on Improved STAP Method, device and storage medium

technical field

The invention relates to the technical field of radar, in particular to an airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP, a computer device and a storage medium.

Background technique

Airborne radar is one of the most important sensors on the modern battlefield. It can realize functions such as target detection, long-range early warning, battlefield awareness, and command operations. When airborne radar searches, detects and tracks targets, it needs to constantly change the irradiation direction of the main beam of the radar to achieve all-round coverage of the airspace. The main methods of changing the irradiation direction of the radar main beam are mechanical scanning and electronic scanning, which have their own advantages and disadvantages. Mechanical scanning phased array is an important antenna configuration form in radar. It can well combine the advantages of mechanical scanning and electronic scanning, so it is also widely used in reality. Whenever the radar working mode involves mechanical scanning, there is antenna rotation, so they are collectively referred to as airborne rotating antenna radar.

When the airborne radar is working, it will inevitably receive strong ground clutter echoes due to the beam irradiating the ground, which will have a negative impact on the target detection performance of the radar. Due to the different speeds of ground scatterers towards different directions of the radar platform, the clutter spectrum will be broadened, and the clutter shows strong spatio-temporal coupling. Airborne rotating antenna radar will cause echo Doppler frequency broadening due to the movement of the radar platform relative to the scattering point, and the rotation of the antenna will also bring about the Doppler effect, which will intensify the Doppler broadening phenomenon. The rotation of the antenna will also bring many problems, such as changes in clutter characteristics, inaccurate angle measurement, etc., which will bring difficulties and challenges to radar system clutter suppression and effective target detection. How to effectively suppress clutter is the most important thing in signal processing when airborne radar works normally.

Explanation of terms:

Space-time Adaptive Processing (STAP);

The number of across-Doppler channels (The number of across-Doppler channels, n _ADCs );

Signal-to-noise ratio (SNR);

Signal-to-clutter-plus-noise ratio (signal-to-clutter-plus-noise ratio, SCNR);

Contents of the invention

In view of the current airborne radar technology, on the basis of the clutter influence faced by the radar itself, the clutter characteristics change and inaccurate angle measurement caused by the rotation of the antenna further bring about clutter to the radar system In view of the difficulties and challenges brought about by suppression and target detection, the object of the present invention is to provide a method for suppressing radar clutter and focusing energy of a target on an airborne rotating antenna based on an improved STAP, a computer device and a storage medium.

On the one hand, the embodiment of the present invention includes an airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP, including:

Obtaining the working parameters of the airborne rotating antenna radar; the working parameters include antenna rotation speed, array element spacing, pulse repetition period, azimuth angle between scattering point and array surface, pitch angle between scattering point and array surface, and signal wavelength;

Obtaining a rotation perturbation matrix, a spatial steering vector and a time domain steering vector according to the working parameters;

obtaining a spatiotemporal steering vector according to the rotation perturbation matrix, the spatial steering vector, and the temporal steering vector;

Obtain the echo data matrix;

STAP processing is performed on the space-time steering vector and the echo data matrix to obtain a processing result.

Further, said obtaining the rotation perturbation matrix, space steering vector and time domain steering vector according to the working parameters includes:

According to the formula

establishing the rotation perturbation matrix;

w为天线转速，d为阵列元间距、T为脉冲重复周期、θ为散射点与阵列表面方位角、

为散射点与阵列表面俯仰角，λ为信号波长，N和K为所述旋转扰动矩阵的维度。Wherein, M is the rotation perturbation matrix, β is the rotation phase factor,

w is the rotational speed of the antenna, d is the distance between array elements, T is the pulse repetition period, θ is the azimuth angle between the scattering point and the array surface,

is the pitch angle between the scattering point and the array surface, λ is the signal wavelength, and N and K are the dimensions of the rotation perturbation matrix.

Further, said obtaining the rotation perturbation matrix, space steering vector and time domain steering vector according to the working parameters includes:

建立所述空间导向向量；According to the formula

establishing said spatial steering vector;

Wherein, S _s is the spatial steering vector, and f _s is the normalized spatial frequency.

Further, said obtaining the rotation perturbation matrix, space steering vector and time domain steering vector according to the working parameters includes:

建立所述时域导向向量；According to the formula

establishing said time-domain steering vector;

Wherein, S _t is the time-domain steering vector, and f _d is the normalized Doppler frequency.

Further, the obtaining a space-time steering vector according to the rotation perturbation matrix, the space steering vector and the time domain steering vector includes:

获取所述时空导向向量；According to the formula

Obtain the space-time steering vector;

Wherein, S _r is the space-time steering vector, S _s is the space steering vector, S _t is the time-domain steering vector, and M is the rotation disturbance matrix.

Further, said acquiring the echo data matrix includes:

Obtain target echo matrix x _t , clutter matrix c and noise matrix n;

The echo data matrix X is determined according to the formula X= _xt +c+n.

Further, performing STAP processing on the space-time steering vector and the echo data matrix to obtain a processing result, including:

Obtain the weight vector of the spatio-temporal two-dimensional optimal processor;

Process the space-time steering vector and the echo data matrix according to the formula y=W _optr ^H X to obtain the processing result; wherein, y is the processing result, W _optr is the weight vector, and X is the The echo data matrix is described above, and the superscript H represents the Hermitian transpose operation.

Further, said obtaining the weight vector of the spatio-temporal two-dimensional optimal processor includes:

Determine the weight vector according to the formula W _optr = μR ^-1 S _r ;

Wherein, W _optr is the weight vector, S _r is the space-time steering vector, R is the covariance matrix of the echo data matrix, and μ is a constant.

On the other hand, the embodiment of the present invention also includes a computer device, including a memory and a processor, the memory is used to store at least one program, and the processor is used to load the at least one program to execute the highly programmable program in the embodiment. Scalable stateless alerting approach.

On the other hand, the embodiment of the present invention also includes a storage medium, which stores a processor-executable program, and the processor-executable program is used to implement the high scalability in the embodiment when executed by the processor. Stateless alerting method.

The beneficial effects of the present invention are: the airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP in the embodiment, by obtaining the rotating disturbance matrix corresponding to the rotational speed of the radar antenna, adding the rotating disturbance matrix to the space-time guidance On the vector, the STAP processing is performed on the space-time steering vector and the echo data matrix, and the clutter in the obtained processing result is suppressed, and the clutter suppression effect basically consistent with the traditional STAP can be obtained. On the other hand, the clutter Accurate matching with the characteristics of the target echo can compensate for the Doppler spectrum broadening effect caused by antenna rotation while performing clutter suppression, and realize clutter suppression and energy focusing. Compared with traditional STAP, in terms of energy focusing It has significant advantages. After the clutter is suppressed, the output signal-to-noise ratio will not be affected by the rotation of the antenna, and the signal-to-noise ratio will be kept stable without decreasing, so as to achieve the purpose of improving the traditional STAP. It has universal applicability and good practical application value.

Description of drawings

Fig. 1 is the schematic diagram of the principle of improving the traditional STAP in the embodiment;

Fig. 2 is a schematic diagram of modeling the working scene of the airborne rotating array antenna radar in the embodiment;

Fig. 3 is the schematic diagram that takes any row of array element of antenna in the embodiment to analyze;

FIG. 4 is a diagram showing the variation of the number of cross-Doppler channels with the rotational speed of the antenna and the number of antenna array elements caused by the rotation of the antenna in the embodiment;

Fig. 5 (a) is the range Doppler diagram of the echo received by the first array element in the embodiment, Fig. 5 (b) is the range Doppler diagram of the echo received by the 32nd array element, Fig. 5 (c) is the range Doppler diagram of the echo received by the 64th array element, and Fig. 5(d) is a schematic diagram of the Doppler channel where the main clutter center of the echo received by each array element of the antenna is located;

Figure 6(a) is a schematic diagram of the main clutter center distribution corresponding to each antenna unit when n _a =0rpm in the embodiment, and Figure 6(b) is the main clutter center distribution corresponding to each antenna unit when n _a =160rpm in the embodiment schematic diagram;

Fig. 7 (a) is the clutter suppression effect obtained by using the traditional STAP and a partial enlarged view, and Fig. 7 (b) is the clutter suppression effect obtained by using the improved STAP in the embodiment and a partial enlarged view;

Fig. 8(a), Fig. 8(b), Fig. 8(c) and Fig. 8(d) respectively show that when the rotational speed of the antenna is n _a = 0rpm, _na = 40rpm, _na = 90rpm and _na = 160rpm, the traditional Schematic diagram of the comparison of the energy focusing capabilities of STAP and the improved STAP in the examples;

Fig. 9 is a flow chart of an airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP in an embodiment.

Detailed ways

Practice has shown that STAP can make full use of the spatial and Doppler information of the transmitted echo clutter received by the airborne radar during the target detection process. According to the coupling characteristics of frequency, an optimal clutter suppression method is designed to adaptively form a zero notch matching clutter and jamming signals, which can significantly improve the clutter suppression and target detection performance of airborne radar.

The STAP method can be mainly divided into the following two types: the full-dimensional space-time adaptive processing method, and the dimension-reduced space-time adaptive processing method. Full-dimensional space-time adaptive signal processing uses more degrees of freedom to suppress clutter, which can achieve the optimal processing effect, but too many processing dimensions will also greatly increase the amount of calculation, which cannot meet the actual time processing requirements. Bring difficulties to project realization. In most cases, the dimensionality of the clutter subspace is significantly smaller than the dimensionality of the entire space. The full-dimensional STAP used for clutter suppression has the possibility of dimensionality reduction. Dimensionality reduction STAP (such as auxiliary channel reception method (ACR), joint domain positioning method (JDL), multi-dimensional channel joint adaptive processing method (M-CAP), etc.) can greatly reduce the amount of calculation, but the processing effect will not be optimal, only quasi-optimal processing can be achieved, and the performance is close to the optimal full-dimensional STAP .

The STAP used in this embodiment is improved and is different from the current full-dimensional STAP or dimension-reduced STAP. The current full-dimensional STAP or dimension-reduced STAP can be collectively referred to as traditional STAP. In order to better observe the processing effect of STAP before and after improvement, the STAP used in this example can be regarded as an improvement on the basis of full-dimensional STAP, and it is also compared with traditional full-dimensional STAP when demonstrating the effectiveness of the method .

Traditional STAP can solve the clutter suppression problem of airborne fixed antenna radar very well, but it does not consider the situation of antenna rotation, so it cannot solve the problem of Doppler broadening and dispersion caused by antenna rotation. However, Doppler broadening and diffusion will adversely affect the clutter suppression and target energy focusing of the airborne rotating antenna system, which will lead to a low signal-to-noise ratio after clutter suppression, and the low signal-to-noise ratio will lead to radar target detection Performance drops.

In view of the shortcomings of traditional STAP, the improvement idea of traditional STAP in this embodiment is shown in Figure 1, including: first, modeling the working scene of the airborne rotating antenna radar, analyzing the characteristics of the radar echo signal, and combining with the conventional fixed antenna Comparing the signal characteristics of the radar, it is concluded that under the rotation condition, there will be an additional rotation disturbance matrix directly related to the rotation speed, and the disturbance matrix corresponding to the rotation speed is added to the space-time steering vector used for STAP to realize the traditional Improvements to STAP to counteract the effects of antenna rotation for better clutter suppression and targeting capability focus.

The STAP improved by the idea shown in Figure 1 can well offset the influence of antenna rotation, can achieve accurate matching of target information, and avoid the influence of the cross-Doppler effect caused by antenna rotation, so that the target does not As for being dispersed into multiple targets, the signal-to-noise ratio of the target is reduced and the detection performance of the radar target is reduced.

The idea of improvement shown in FIG. 1 will be described below. The improvement idea shown in Figure 1 is to realize the clutter suppression and target energy focusing of the airborne rotating antenna radar by improving the STAP, including the following steps:

Step 1, modeling the working scene of the airborne rotating antenna radar system;

Step 2, through the analysis and comparison of radar echo signal characteristics, extract the rotation disturbance matrix;

Step 3, analyze the factors that affect the number of cross-Doppler channels and the adverse effects that will be brought in the case of cross-Doppler channels;

Step 4, according to the principle of STAP, add the rotation perturbation matrix to realize the improvement of the traditional STAP;

Step 5, use the improved STAP to suppress clutter and focus on target capabilities, and compare the effectiveness of steps 1-4.

Steps 1-5 are described below.

step 1

Referring to Figure 1, step 1 is specifically: modeling the working scene of the airborne rotating antenna radar system, and obtaining the radar receiving echo signal model.

所以机载旋转阵列天线雷达的辐射圆锥角ψ_p的余弦值是

In step 1, the modeling of the airborne rotating array antenna radar working scene is shown in Figure 2. Assuming that the radar antenna is a planar array with M rows and N columns, the element spacing is d, the antenna array rotates at an angular velocity w, the radar platform flies in a straight line at a velocity v, and the platform height is h. At the initial moment, the angle between the platform flight direction and the antenna plane direction is θ _y . The ground scattering units equidistant from the radar platform are distributed in a distance ring, and the ring is divided into P scattering units. Take one of the scattering units for signal modeling and analysis, and record it as the scattering point p. The initial range from p to the radar is R _p (relative to the array element at row 1 and column 1), the azimuth angle is θ _p , and the elevation angle is

So the cosine value of the radiation cone angle ψ _p of the airborne rotating array antenna radar is

Since the size of the antenna is much smaller than the distance from the radar to p, it can be approximately considered that the azimuth and elevation angles of each array element on the antenna plane to p are the same at the same time. Therefore, the distance from p to the nth row and nth column of the antenna is

其中

是第m行第n₀列阵元到p的距离,即

由于雷达平台的运动和天线的旋转，在t时刻，雷达第m行n列阵元到p的距离为Wherein, m=1,2,...,M; n=1,2,...,N. Assuming that the antenna rotates around the n _0th array element, the above formula can be rewritten as

in

is the distance from the n _0th column array element in the mth row to p, that is

Due to the movement of the radar platform and the rotation of the antenna, at time t, the distance from the array element in the nth row of the radar to p is

当时间t较短时，天线旋转角Δθ_p＝wt非常小，可视为θ_p的无穷小量。因此，(2)式的一阶泰勒展开可表示为where v _pr is the radial velocity of the radar platform towards the scattering point p,

When the time t is short, the antenna rotation angle Δθ _p =wt is very small, which can be regarded as an infinitesimal quantity of θ _p . Therefore, the first-order Taylor expansion of (2) can be expressed as

为天线旋转时第n列阵元朝向p的径向速度。In (3), define

is the radial velocity of the nth array element towards p when the antenna rotates.

其中u(t)为调制信号的复包络，w₀为角频率，其中

为初始相位。则天线第m行第n列阵元接收到从散射单元p反射的回波信号为

其中A_p为从p反射的回波信号的复振幅，τ为回波的延迟时间。信号从雷达到p的时延为

其中r_p为瞬时倾斜距离，

c为光速。信号从p返回到雷达所需要的时间是

所以总延迟为

Suppose the signal emitted by the radar is

where u(t) is the complex envelope of the modulating signal, w ₀ is the angular frequency, where

is the initial phase. Then, the echo signal reflected from the scattering unit p received by the array element in the mth row and the nth column of the antenna is

Where A _p is the complex amplitude of the echo signal reflected from p, and τ is the delay time of the echo. The time delay of the signal from the radar to p is

where r _p is the instantaneous slope distance,

c is the speed of light. The time it takes for the signal to return from p to the radar is

So the total delay is

Therefore, after the signal is sent at time t, the time at which the echo signal is received is

Substituting (4) into the echo signal expression, we get

为脉冲比例因子。由于

所以

in

is the pulse scaling factor. because

so

(5) can be approximated and simplified as:

为不考虑天线旋转时，从雷达天线第m行第n列阵元到p的双向传输延迟时间，w_dpn为回波信号的多普勒频率，in,

In order not to consider the antenna rotation, the two-way transmission delay time from the nth row of the radar antenna to p, _wdpn is the Doppler frequency of the echo signal,

表示雷达平台向p方向移动引起的多普勒频移，f_dpnr表示天线旋转引起的多普勒频移，

表示雷达工作波长。

的值很小，可以忽略不计。所以回波信号下变频后的结果为:

其中A_p0＝A_pe^jφ。将时间t分为快时间t和慢时间t_k，即

T为脉冲重复周期，k＝1,2,…,K为脉冲个数。快时间相位项

很小，可以忽略不计。所以

It can be known from formula (7) that w _dpn consists of two parts, where

Indicates the Doppler frequency shift caused by the movement of the radar platform to the p direction, f _dpnr indicates the Doppler frequency shift caused by the antenna rotation,

Indicates the radar operating wavelength.

The value of is small and can be ignored. Therefore, the result after the echo signal is down-converted is:

where A _p0 =A _p e ^jφ . Divide time t into fast time t and slow time t _k , namely

T is the pulse repetition period, k=1, 2,..., K is the number of pulses. fast time phase term

Small enough to be ignored. so

Perform waveform matching filtering on the echo, and then get

只考虑散点p所在的那个距离环回波，即x(τ_l-τ₀)＝1，因此(8)式可改写为:where x(τ _l -τ ₀ ) is the range ambiguity function of the echo signal,

Only consider the distance loop echo where the scattered point p is located, that is, x(τ _l -τ ₀ )=1, so formula (8) can be rewritten as:

It can be seen from formula (9) that the angular velocity of the horizontal rotation of the antenna does not affect the phase relationship of the echo signals of each receiving channel in the elevation direction, so only the case of the horizontal linear array is considered. Therefore, the above formula can be rewritten as

为幅度，

为天线旋转引起的附加相位，记为旋转相位因子。其中n＝1,2,…,N；k＝1,2,…,K。in

for the magnitude,

is the additional phase caused by the rotation of the antenna, denoted as the rotation phase factor. where n=1,2,...,N; k=1,2,...,K.

step 2

Referring to Figure 1, step 2 is specifically: through the analysis of the characteristics of the radar echo signal, compare it with the echo in the traditional fixed antenna radar scene, and extract a disturbance matrix directly related to the antenna rotation speed in the echo .

The echo signal model (10) modeled in step 1 can be expressed in matrix form as follows:

可以用来表示机载固定天线的回波信号特性。上标(T)表示矩阵转置运算。由(11)式可知，由于天线旋转的存在，会产生一个扰动矩阵M_p。由(14)式可知，M_p与天线的转速、脉冲重复周期、阵列元间距、散射点与阵列表面的角度以及信号的波长有关。它具体表现为在空间和时间域的线性相位调制。当天线不旋转时，M_p是一个N×K维的全一矩阵，此时就有

即M_p不会带来影响，这也印证了本方法将信号模型进行矩阵分解的合理性。Among them, s _p represents the echo data matrix of scattering point p, s _tp and s _sp are the time domain steering vector and the air domain steering vector when the airborne radar antenna does not rotate, respectively,

It can be used to represent the echo signal characteristics of the airborne fixed antenna. A superscript (T) denotes a matrix transpose operation. It can be known from formula (11) that due to the existence of antenna rotation, a perturbation matrix M _p will be generated. It can be seen from formula (14) that M _p is related to the rotational speed of the antenna, the pulse repetition period, the spacing between array elements, the angle between the scattering point and the array surface, and the wavelength of the signal. It is embodied as linear phase modulation in space and time domain. When the antenna does not rotate, M _p is a N×K dimensional all-one matrix, at this time there is

That is, M _p will not have an impact, which also confirms the rationality of this method to decompose the signal model into a matrix.

step 3

Referring to Figure 1, step 3 specifically includes: analyzing the cross-Doppler situation of the airborne rotating antenna radar, analyzing the factors that affect the number of cross-Doppler channels, and the adverse effects that will be caused by the cross-Doppler channel situation.

取天线任意一排阵元进行分析，如图3所示。天线旋转时阵列两端的多普勒差最大。设天线在t₀时刻发射信号，在t₁时刻接收回波，天线旋转角度为a＝w(t₁-t₀)＝wΔt。由于Δt非常小，且天线尺寸远小于雷达与散射点之间的距离，因此在时间Δt中方位角θ_p和俯仰角

分别近似恒定。两个端点阵元的走动距离分别为Δl₁＝(n_c-1)da＝(n_c-1)dwΔt和Δl_N＝(n_c-N)da＝(n_c-N)dwΔt。由此产生的相位差分别为

和

Assume that the airborne planar array antenna rotates around the n _cth array element. The rotational speed of the antenna is _na (revolutions per minute, rpm). So the angular velocity of the antenna is

Take any array element of the antenna for analysis, as shown in Figure 3. The Doppler difference at both ends of the array is greatest when the antenna is rotated. Assuming that the antenna transmits a signal at time t ₀ and receives an echo at time t ₁ , the rotation angle of the antenna is a=w(t ₁ -t ₀ )=wΔt. Since Δt is very small and the antenna size is much smaller than the distance between the radar and the scattering point, the azimuth angle θ _p and the elevation angle

are approximately constant. The walking distances of the two end point array elements are Δl ₁ =(n _c -1)da=(n _c -1)dwΔt and Δl _N =(n _c -N)da=(n _c -N)dwΔt respectively. The resulting phase difference is

and

和

所以两端数组元素之间的频率差是

Therefore, the Doppler frequency shift of the echo signal is:

and

So the frequency difference between the array elements at both ends is

其中f_r为脉冲重复频率，K为慢时间FFT中的点数。因此，天线旋转引起的跨多普勒通道数(n_ADcs)为Both the traditional pulse Doppler processing (PD) and the expansion factor method (EFA) need to perform Fourier transform on the pulse data, and the obtained Doppler channel bandwidth is

Where _fr is the pulse repetition frequency and K is the number of points in the slow-time FFT. Therefore, the number of cross-Doppler channels (n _ADcs ) caused by antenna rotation is

Among them, round() represents the operation of rounding to the nearest integer. It can be seen from equation (37) that n _ADCs is related to the number of antenna elements, antenna rotation speed, number of slow-time FFT points, element spacing, azimuth and elevation angles from the radar to the scattering point, signal wavelength, and pulse repetition frequency.

得到

此时(15)可以写成

When the main beam direction is the normal direction of the array antenna, that is, θ _p =90° and

get

At this point (15) can be written as

Set the radar working parameters as shown in Table 1, and observe the variation of n _ADCs with the antenna speed and the number of antenna elements through simulation.

Table 1 Radar system operating parameters

parameter value Number of antenna array columns (N) 64 Number of pulses in one CPI (K) 32 Wavelength (λ) 0.1m Pulse repetition frequency (f_r) 6000Hz Radar platform speed (v) 120m/s Height of radar platform (h) 1000m Antenna rotation speed (n_a) 0,90,160rpm Input noise-to-noise ratio (CNR_i) 90dB Input signal-to-noise ratio (SNR_i) 20dB

Fig. 4 is a diagram showing the variation of n _ADCs with the rotational speed of the antenna and the number of antenna array elements. It can be seen from Figure 4 that n _ADCs increases with the increase of the antenna rotation speed and the number of antenna elements. When the number of antenna elements is 64, if the antenna speed n _a <20rpm, the number of cross-Doppler channels is 0, if n _a >130rpm, n _ADCs = 3, if continue to increase the antenna speed or the number of antenna array elements, n _ADCs will continue to expand. It is not difficult to understand that when the antenna does not rotate, the movement of each antenna element to the same scattering point is the same, so the distance Doppler spectrum of the received echo at each element is roughly the same, and the Doppler spectrum of the main clutter center Channels are also the same. Next, observe the change of the range Doppler spectrum when the antenna rotates through the simulation results. It can be seen from the parameters set by the system that when the antenna does not rotate, that is, when _na =0rpm, the target is located in the 24th Doppler channel, and the main clutter center is located in the 30th Doppler channel.

In order to better explain the Doppler frequency shift and dispersion phenomenon, take the antenna rotation speed as 90rpm, and n _ADCs is equal to 2 at this time. Fig. 5 is a range Doppler diagram of echoes received by some array elements when _na = 90rpm. Specifically, Fig. 5(a) is the range-Doppler diagram of the echo received by the first array element, Fig. 5(b) is the range-Doppler diagram of the echo received by the 32nd array element, and Fig. 5(c) It is the range Doppler diagram of the echo received by the 64th array element, and Fig. 5(d) shows the Doppler channel where the main clutter center of the echo received by each array element of the antenna is located.

It can be seen from Fig. 5 that when the antenna rotation speed n _a =90rpm, the echoes received by different array elements have different distances from the Doppler spectrum, and the Doppler channel at the center of the main clutter is shifted and becomes no longer uniform. The antenna element closest to the rotation axis has the smallest rotation speed, and its main clutter center remains unchanged in the 30th Doppler channel, as shown in Figure 5(b). As the antenna unit gets closer to the two ends of the antenna, the linear velocity of the array element increases gradually, and the main clutter center shifts to the 29th channel and the 31st channel respectively, as shown in Fig. 5(a) and 5(c). This is because It is caused by the movement directions of the array elements at both ends of the antenna being opposite. Similarly, by changing the rotational speed of the antenna, the Doppler channel information of the main clutter center corresponding to each antenna unit at different rotational speeds can be obtained, as shown in FIG. 6 .

Specifically, when the antenna does not rotate, that is, when n _a =0rpm, the distribution of main clutter centers corresponding to each antenna unit is shown in Figure 6(a), and all main clutter centers are in the Doppler channel 30, which means The same applies to other speed cases where n _ADCs =0. At this time, there is no offset and spread on the Doppler spectrum, and the influence of antenna rotation can be ignored at this time, and the processing effect of using the traditional STAP and the improved STAP is equivalent. On the contrary, if the antenna rotation speed is increased to 160rpm, the influence of the antenna rotation speed on the cross-Doppler channel will be more serious, as shown in Fig. 6(b), at this time n _ADCs =3.

step 4

Referring to Figure 1, step 4 is specifically: according to the STAP principle, under the condition of keeping the target power unchanged, the output signal power is minimized, that is, the power of the clutter is minimized, and the clutter suppression is completed while protecting the integrity of the target. The antenna rotation speed when the radar is working is used as prior knowledge, and the corresponding disturbance matrix is obtained, which is added to the space-time steering vector to realize the improvement of the traditional STAP.

STAP is a joint processing of one-dimensional spatial adaptive filtering and one-dimensional temporal adaptive filtering. It is based on the criterion of minimum variance and maximum output signal-to-noise ratio with linear constraints, and can output the optimal linear combination, which can adaptively solve the problem of airborne radar clutter suppression. Use NK×1-dimensional W to represent the weight vector of the processor, then W=[w ₁₁ ,…,w _1K ,w ₂₁ ,…,w _2K ,…,w _N1 ,…,w _NK ] ^T , where w _nk is The adaptive weight of the nth array element at the kth pulse echo. The STAP processor can be described as a mathematical optimization problem:

。其中S_s为空间导向向量，S_t为时域导向向量，

为Kronecker积。对于传统旋转天线雷达,有

其中

为归一化空间频率，

为归一化多普勒频率，各参数的含义如图2所示。Wherein R=E[XX ^H ] is the covariance matrix of echo data of NK×NK dimension. The expression of the echo data matrix X is X= _xt +c+n. Among them, x _t is the target echo matrix, c is the clutter matrix, and n is the noise matrix. E[·] represents the statistical expectation. S is the space-time two-dimensional steering vector.

. where S _s is the space steering vector, S _t is the time domain steering vector,

Hoard for Kronecker. For traditional rotating antenna radar, there are

in

is the normalized spatial frequency,

In order to normalize the Doppler frequency, the meaning of each parameter is shown in Figure 2.

If the rotation of the antenna is considered, the space-time steering vector will change accordingly. Combined with the conclusion in step 2, it is known that the change of the space-time steering vector can be reflected in the disturbance matrix. The conclusion in step 2 is the analysis of the p-echo of the scattering point, which is extended to the general case here, that is, the case that is applicable to all the scattering points. The conclusion obtained for a specific scatter point p can also be applied to any scatter point after generalization. For example, after a certain quantity corresponding to a specific scatter point p is removed from the subscript p, it represents a quantity of the same nature applicable to any scatter point. For example, β _p represents the rotation phase factor corresponding to a specific scattering point p, β represents the rotation phase factor corresponding to any scattering point; M _p represents the rotation perturbation matrix corresponding to a specific scattering point p, and M represents the rotation perturbation matrix corresponding to any scattering point.

After extending the analysis of the echo of scattering point p to the general situation, we can get:

为旋转相位因子，表示天线旋转引起的附加相位。如果天线是固定的，即β＝0，此时M是N×K维的全一矩阵，有S_r＝S，将S_r重塑为N K×1维的矩阵。即S_r＝[S_r(1,1),…,S_r(N,1),S_r(1,2),…,S_r(N,K)]^T。where S _r is the space-time steering vector of the airborne rotating antenna radar,

is the rotational phase factor, which represents the additional phase caused by the antenna rotation. If the antenna is fixed, that is, β=0, then M is an N×K-dimensional all-one matrix, and S _r =S, and S _r is reshaped into a NK×1-dimensional matrix. That is, S _r =[S _r (1,1),...,S _r (N,1),S _r (1,2),...,S _r (N,K)] ^T .

Therefore, the weight vector of the spatio-temporal two-dimensional optimal processor is:

W _optr ＝μR ^-1 S _r #(19)

Among them, μ is a constant. The output after final STAP processing can be expressed as:

Where X=x _ij ^T , ij=1,...,NK, superscript (H) means Hermitian transpose, and superscript (*) means complex conjugation.

step 5

Referring to Fig. 1, step 5 is specifically: use the improved STAP to suppress clutter and focus on target capabilities. By comparing the performance with the traditional STAP, the effectiveness of the improved STAP method is highlighted.

The rotation of the antenna causes the offset and spread of the received echo in the Doppler domain, which also causes the spread of the target energy in the range Doppler spectrum. When performing experimental simulation verification, the target point is set in the 24th Doppler channel of the 600th range gate when the antenna does not rotate. When the antenna rotation speed is n _a =90rpm, n _ADCs =2, the traditional STAP cannot compensate the Doppler frequency shift and spread caused by the antenna rotation, and the clutter suppression effect is shown in Figure 7(a). Zoom in on the area close to the target to see the power distribution of the target and the center of the main clutter. Similarly, for the same echo data, the improved STAP method of steps 1-4 is used to process, and the clutter suppression effect and local enlarged map are obtained, as shown in Fig. 7(b). It can be seen from Figure 7 that, except for the main clutter center, the two methods have a good suppression effect on clutter, and the clutter suppression performance is comparable.

From the range Doppler spectrum, the power value of the 600th range unit of the 24th Doppler channel where the target is located can be obtained. Comparing the target power values in Figure 7(a) and Figure 7(b), it can be easily found that due to the Doppler spread caused by the antenna rotation causes energy dispersion, the main clutter center power and target power in Figure 7(a) are both Nearly 10dB lower than that in Figure 6(b). Because the traditional STAP method cannot compensate for the adverse effects of antenna rotation, but the improved STAP method in steps 1-4 can. Therefore, the output SNR value of the improved STAP in steps 1-4 is close to the set input SNR value because the energy of the target is effectively focused. The output signal-to-noise ratio value after traditional STAP is related to n _ADCs . The larger the value of n _ADCs , the more dispersed the target energy is, and the lower the output signal-to-noise ratio is. The reduction of the output signal-to-noise ratio will affect the target detection performance of the radar. In order to analyze the energy focusing capabilities of the two methods at different antenna speeds, the 600th range gate power curve where the target is located is extracted from the range Doppler spectrum processed by the two methods, as shown in Figure 8. Among them, the antenna rotation speed corresponding to Figure 8(a) is n _a =0rpm, the antenna rotation speed corresponding to Figure 8(b) is n _a =40rpm, the antenna rotation speed corresponding to Figure 8(c) is n _a =90rpm, and Figure 8( d) The corresponding antenna rotational speed is n _a =160 rpm.

Use the data cursor to mark the power value of the 24th Doppler channel where the target is located. It can be seen from Figure 8(a) that when the antenna does not rotate, the Doppler spectrum does not shift and spread at this time, and the target energy does not disperse, so the processing effects of the two methods are the same. For the same echo data, the target energy values are equal. From Figure 8(b), Figure 8(c), and Figure 8(d), it can be seen that with the increase of n _a , the target power value after the improved STAP can be maintained at about 20dB, while the target power value after the traditional STAP slowing shrieking. When the target power value is reduced to a certain level, it is more susceptible to the influence of noise, and it is easy to submerge the target in the noise. The reduction of target energy leads to a decrease of the output signal-to-noise ratio, which in turn has an adverse effect on target detection.

In summary, after comparing the performance of traditional STAP and improved STAP, it is not difficult to find that the clutter suppression performance of the two methods is basically the same, but the improved STAP has a significant advantage in energy focusing, which can make the output signal noise after clutter suppression The ratio is not affected by the rotation of the antenna, and the signal-to-noise ratio is kept stable and does not decrease, which is of great significance to the radar target detection after STAP.

In this embodiment, based on the principles of steps 1-5, an airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP is provided. Referring to Fig. 9, the airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP includes the following steps:

S1. Obtain the working parameters of the airborne rotating antenna radar;

S2. Obtain the rotation perturbation matrix, the space steering vector and the time domain steering vector according to the working parameters;

S3. According to the rotation perturbation matrix, the space steering vector and the time domain steering vector, obtain the space-time steering vector;

S4. Obtain the echo data matrix;

S5. Perform STAP processing on the space-time steering vector and the echo data matrix to obtain a processing result.

Steps S1-S5 are designed based on the principles of steps 1-5, especially formulas (17)-(20).

以及信号波长λ。In step S1, the obtained working parameters include antenna rotation speed w, array element spacing d, pulse repetition period T, azimuth angle θ between scattering point and array surface, pitch angle between scattering point and array surface

and the signal wavelength λ.

In step S2, based on formula (18), the rotation disturbance matrix M is calculated.

计算得到空间导向向量S_s。In step S2, based on

Calculate the spatial steering vector S _s .

计算得到时域导向向量S_t。In step S2, based on

Calculate the time-domain steering vector S _t .

计算得到时空导向向量S。其中，

为Kronecker积运算。In step S3, by

Calculate the space-time steering vector S. in,

is the Kronecker product operation.

In step S4, by obtaining the target echo matrix x _t , the clutter matrix c and the noise matrix n, the echo data matrix X is calculated according to the formula X=x _t +c+n.

In _step S5, first calculate the covariance matrix R of the echo data matrix X through the formula R=E[XX ^H ], set a constant μ, and calculate the space ^- _time The weight vector W _optr of the two-dimensional optimal processor, according to formula (20) is

, calculate the processing result y.

According to the principle of steps 1-5, it can be seen that by executing steps S1-S5 to process the echo data matrix X, the clutter in the obtained processing result y is suppressed, and the clutter suppression effect basically consistent with that of traditional STAP can be obtained , steps S1-S5 have significant advantages in energy focusing on this basis, and can make the output signal-to-noise ratio not affected by antenna rotation after clutter suppression, and keep the signal-to-noise ratio stable without decreasing, which is very important for radar targets after STAP Probing is important.

It is possible to write a computer program that executes the highly scalable stateless alarm method in this embodiment, write the computer program into a computer device or a storage medium, and when the computer program is read and run, execute this embodiment The high-scalability stateless alarm method in the present embodiment achieves the same technical effect as the high-scalability stateless alarm method in the embodiment.

It should be noted that, unless otherwise specified, when a feature is called "fixed" or "connected" to another feature, it can be directly fixed and connected to another feature, or indirectly fixed and connected to another feature. on a feature. In addition, descriptions such as up, down, left, and right used in the present disclosure are only relative to the mutual positional relationship of the components of the present disclosure in the drawings. As used in this disclosure, the singular forms "a", "the", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. In addition, unless otherwise defined, all technical and scientific terms used in this embodiment have the same meaning as commonly understood by those skilled in the art. The terms used in the description of this embodiment are only for describing specific embodiments, not for limiting the present invention. The term "and/or" used in this embodiment includes any combination of one or more related listed items.

It should be understood that although the terms first, second, third etc. may be used in the present disclosure to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish elements of the same type from one another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. The use of any and all examples, or exemplary language ("such as", "such as", etc.) provided in the examples is intended merely to better illuminate the examples of the invention and will not cast a shadow on the scope of the invention unless otherwise claimed impose restrictions.

It should be appreciated that embodiments of the invention may be realized or implemented by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer readable memory. The methods can be implemented in a computer program using standard programming techniques - including a non-transitory computer-readable storage medium configured with a computer program, where the storage medium so configured causes the computer to operate in a specific and predefined manner - according to the specific Methods and Figures described in the Examples. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, the programs can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language. Furthermore, the program can be run on an application specific integrated circuit programmed for this purpose.

Furthermore, operations of processes described in this embodiment may be performed in any suitable order unless otherwise indicated by this embodiment or otherwise clearly contradicted by context. The processes described in this embodiment (or variants and/or combinations thereof) can be executed under the control of one or more computer systems configured with executable instructions, and can be executed as code jointly executed on one or more processors (eg, executable instructions, one or more computer programs, or one or more applications), hardware or a combination thereof. The computer program comprises a plurality of instructions executable by one or more processors.

Further, the method can be implemented in any type of computing platform operably connected to a suitable one, including but not limited to personal computer, minicomputer, main frame, workstation, network or distributed computing environment, stand-alone or integrated computer platform, or communicate with charged particle tools or other imaging devices, etc. Aspects of the invention can be implemented as machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, optically read and/or written storage medium, RAM, ROM, etc., such that they are readable by a programmable computer, when the storage medium or device is read by the computer, can be used to configure and operate the computer to perform the processes described herein. Additionally, the machine-readable code, or portions thereof, may be transmitted over a wired or wireless network. The invention described in this embodiment includes these and other different types of non-transitory computer-readable storage media when such media include instructions or programs for implementing the steps described above in conjunction with a microprocessor or other data processor. The invention also includes the computer itself when programmed according to the methods and techniques described herein.

Computer programs can be applied to input data to perform the functions described in this embodiment, thereby transforming the input data to generate output data stored to non-volatile memory. Output information may also be applied to one or more output devices such as a display. In a preferred embodiment of the invention, the transformed data represents physical and tangible objects, including specific visual depictions of physical and tangible objects produced on a display.

The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above-mentioned implementation, as long as it achieves the technical effect of the present invention by the same means, within the spirit and principles of the present invention, any Any modification, equivalent replacement, improvement, etc., shall be included within the protection scope of the present invention. Various modifications and changes may be made to the technical solutions and/or implementations within the protection scope of the present invention.

Claims (10)

1. a kind of airborne rotating antenna radar clutter suppression based on improved STAP and target energy focusing method, it is characterized in that, described airborne rotating antenna radar clutter suppression based on improved STAP and target energy focusing method comprise: Obtaining the working parameters of the airborne rotating antenna radar; the working parameters include antenna rotation speed, array element spacing, pulse repetition period, azimuth angle between scattering point and array surface, pitch angle between scattering point and array surface, and signal wavelength; Obtaining a rotation perturbation matrix, a spatial steering vector and a time domain steering vector according to the working parameters; obtaining a spatiotemporal steering vector according to the rotation perturbation matrix, the spatial steering vector, and the temporal steering vector; Obtain the echo data matrix; STAP processing is performed on the space-time steering vector and the echo data matrix to obtain a processing result. 2. the airborne rotating antenna radar clutter suppression and the target energy focusing method based on improved STAP according to claim 1, is characterized in that, described according to described operating parameter acquisition rotation perturbation matrix, space steering vector and time domain steering vector, including: According to the formula

establishing the rotation perturbation matrix; Wherein, M is the rotation perturbation matrix, β is the rotation phase factor,

w is the rotational speed of the antenna, d is the distance between array elements, T is the pulse repetition period, θ is the azimuth angle between the scattering point and the array surface,

is the pitch angle between the scattering point and the array surface, λ is the signal wavelength, and N and K are the dimensions of the rotation perturbation matrix. 3. the airborne rotating antenna radar clutter suppression and the target energy focusing method based on improved STAP according to claim 1, is characterized in that, described according to described operating parameter acquisition rotation perturbation matrix, space steering vector and time domain steering vector, including: According to the formula

establishing said spatial steering vector; Wherein, S _s is the spatial steering vector, and f _s is the normalized spatial frequency. 4. the airborne rotating antenna radar clutter suppression and target energy focusing method based on improved STAP according to claim 1, is characterized in that, described according to described operating parameter acquisition rotation perturbation matrix, space steering vector and time domain steering vector, including: According to the formula

establishing said time-domain steering vector; Wherein, S _t is the time-domain steering vector, and f _d is the normalized Doppler frequency. 5. the airborne rotating antenna radar clutter suppression and target energy focusing method based on improved STAP according to claim 1, is characterized in that, described according to described rotating perturbation matrix, described space steering vector and described time domain Orientation vector, to obtain the space-time orientation vector, including: According to the formula

Obtain the space-time steering vector; Wherein, S _r is the space-time steering vector, S _s is the space steering vector, S _t is the time-domain steering vector, and M is the rotation disturbance matrix. 6. the airborne rotating antenna radar clutter suppression and target energy focusing method based on improved STAP according to claim 1, is characterized in that, described acquisition echo data matrix comprises: Obtain target echo matrix x _t , clutter matrix c and noise matrix n; The echo data matrix X is determined according to the formula X= _xt +c+n. 7. the airborne rotating antenna radar clutter suppression and target energy focusing method based on improved STAP according to claim 6, is characterized in that, described space-time steering vector and described echo data matrix are carried out STAP process, Get processing results, including: Obtain the weight vector of the spatio-temporal two-dimensional optimal processor; Process the space-time steering vector and the echo data matrix according to the formula y=W _optr ^H X to obtain the processing result; wherein, y is the processing result, W _optr is the weight vector, and X is the The echo data matrix is described above, and the superscript H represents the Hermitian transpose operation. 8. the airborne rotating antenna radar clutter suppression and target energy focusing method based on improved STAP according to claim 7, is characterized in that, the weight vector of described acquisition time-space two-dimensional optimal processor comprises: Determine the weight vector according to the formula W _optr = μR ^-1 S _r ; Wherein, W _optr is the weight vector, S _r is the space-time steering vector, R is the covariance matrix of the echo data matrix, and μ is a constant. 9. A computer device, characterized in that it comprises a memory and a processor, the memory is used to store at least one program, and the processor is used to load the at least one program to execute any one of claims 1-8 Highly scalable stateless alerting method. 10. A computer-readable storage medium, wherein a processor-executable program is stored, wherein the processor-executable program is used to execute any one of claims 1-8 when executed by a processor. The highly scalable stateless alerting method described above.

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