CN115792850A - Airborne rotating antenna radar clutter suppression and target energy focusing method and device based on improved STAP and storage medium - Google Patents
Airborne rotating antenna radar clutter suppression and target energy focusing method and device based on improved STAP and storage medium Download PDFInfo
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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
Technical Field
The invention relates to the technical field of radars, in particular to an airborne rotating antenna radar clutter suppression and target energy focusing method based on an improved STAP, a computer device and a storage medium.
Background
The airborne radar is one of the most important sensors in modern battlefields, and can realize the functions of target detection, remote early warning, battlefield perception, command operation and the like. When an airborne radar searches, detects and tracks targets, the main beam irradiation direction of the radar needs to be changed continuously so as to realize all-directional coverage search of an airspace. The main methods for changing the irradiation direction of the main beam of the radar are mechanical scanning and electronic scanning, which have respective advantages and disadvantages. The mechanical scanning phased array is an important antenna configuration form in the radar, and can well combine the advantages of mechanical scanning and electronic scanning, so that the mechanical scanning phased array is widely applied in reality. But as the radar mode of operation involves mechanical scanning, there is antenna rotation and they are therefore collectively referred to as airborne rotating antenna radars.
When the airborne radar works, the airborne radar scans and irradiates beams, so that strong ground clutter echoes are inevitably received because the beams irradiate the ground, and the target detection performance of the radar is adversely affected. Due to the fact that the speeds of the ground scatterer to the radar platform in different directions are different, the clutter spectrum is widened, and the clutter represents strong space-time coupling. The airborne rotating antenna radar can cause echo Doppler frequency broadening due to the movement of a radar platform relative to a scattering point, and the Doppler effect is also brought by the rotation of the antenna, so that the Doppler broadening phenomenon is aggravated. Rotation of the antenna can also cause problems such as variations in clutter characteristics, inaccurate angle measurements, etc., which can present difficulties and challenges to clutter suppression and effective target detection for radar systems. How to effectively suppress clutter is the central importance of signal processing when the airborne radar works normally.
Interpretation of terms:
space-time Adaptive Processing (STAP);
number of Doppler channels (n) across ADCs )；
Signal-to-noise ratio (SNR);
signal-to-filter-plus-noise ratio (SCNR);
disclosure of Invention
Aiming at the problems of clutter influence and the like faced by a radar, and the problems of clutter characteristic change, inaccurate angle measurement and the like brought by the rotation of an antenna in the existing airborne radar technology, the invention provides a radar clutter suppression and target energy focusing method, a computer device and a storage medium for an airborne rotating antenna based on an improved STAP.
In one aspect, an embodiment of the present invention includes an improved STAP-based airborne rotating antenna radar clutter suppression and target energy focusing method, including:
acquiring working parameters of an airborne rotating antenna radar; the working parameters comprise antenna rotating speed, array element spacing, pulse repetition period, azimuth angles of scattering points and array surfaces, pitch angles of the scattering points and the array surfaces and signal wavelength;
acquiring a rotation disturbance matrix, a space guide vector and a time domain guide vector according to the working parameters;
acquiring a space-time guide vector according to the rotation disturbance matrix, the space guide vector and the time domain guide vector;
acquiring an echo data matrix;
and performing STAP processing on the space-time guiding vector and the echo data matrix to obtain a processing result.
Further, the obtaining a rotational disturbance matrix, a spatial steering vector and a time-domain steering vector according to the working parameters includes:
according to the formula
Establishing the rotation disturbance matrix;
wherein M is the rotational perturbation matrix, β is a rotational phase factor,
w is the rotation speed of the antenna, d is the spacing between array elements, T is the pulse repetition period, theta is the azimuth angle between the scattering point and the array surface,
Scattering points and array surface pitch angles are provided, lambda is the signal wavelength, and N and K are the dimensions of the rotation disturbance matrix.
Further, the obtaining of the rotational disturbance matrix, the spatial steering vector and the temporal steering vector according to the working parameters includes:
according to the formula
Establishing the space steering vector;
wherein S is s As said spatial steering vector, f s Is the normalized spatial frequency.
Further, the obtaining a rotational disturbance matrix, a spatial steering vector and a time-domain steering vector according to the working parameters includes:
according to the formula
Establishing the time domain steering vector;
wherein S is t For the time domain steering vector, f d Is the normalized doppler frequency.
Further, the obtaining a space-time steering vector according to the rotational disturbance matrix, the space steering vector and the time-domain steering vector includes:
according to the formula
Acquiring the space-time guide vector;
wherein S is r For said spatio-temporal steering vector, S s As the space steering vector, S t And M is the rotation disturbance matrix.
Further, the acquiring the echo data matrix includes:
obtaining a target echo matrix x t A clutter matrix c and a noise matrix n;
according to the formula X = X t + c + n determines the echo data matrix X.
Further, the performing STAP processing on the spatio-temporal steering vector and the echo data matrix to obtain a processing result includes:
acquiring a weight vector of a space-time two-dimensional optimal processor;
according to the formula y = W optr H Processing the space-time guiding vector and the echo data matrix by X to obtain the processing result; wherein y is the result of the treatment, W optr And for the weight vector, X is the echo data matrix, and the superscripted H represents Hermitian transposition operation.
Further, the obtaining of the weight vector of the space-time two-dimensional optimal processor comprises:
according to the formula W optr ＝μR -1 S r Determining the weight vector;
wherein, W optr Is the weight vector, S r R is the covariance matrix of the echo data matrix, and mu is a constant.
In another aspect, embodiments of the present invention also include a computer apparatus including a memory for storing at least one program and a processor for loading the at least one program to perform a high scalability stateless alert method in an embodiment.
In another aspect, embodiments of the present invention also include a storage medium having stored therein a processor-executable program, which when executed by a processor, is configured to perform a high-scalability stateless alerting method in an embodiment.
The beneficial effects of the invention are: according to the airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP, the rotating disturbance matrix corresponding to the rotating speed of the radar antenna is obtained, the rotating disturbance matrix is added to the space-time guiding vector, STAP processing is carried out on the space-time guiding vector and the echo data matrix, clutter in an obtained processing result is suppressed, a clutter suppression effect basically consistent with that of a traditional STAP can be obtained, on the other hand, accurate matching of characteristics of the clutter and the target echo can be achieved, doppler spectrum broadening influence caused by antenna rotation can be compensated while clutter suppression is carried out, clutter suppression and energy focusing are achieved, compared with the traditional STAP, the method has the advantages in energy focusing, the output signal-to-noise ratio is not affected by antenna rotation after clutter suppression, the signal-to-noise ratio is kept stable and not reduced, the purpose of improving the traditional STAP is achieved, and the method has general applicability and good practical application value.
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Fig. 1 is a schematic diagram of an embodiment of an improvement of a conventional STAP;
FIG. 2 is a schematic diagram for modeling an operating scene of an airborne rotary array antenna radar in an embodiment;
FIG. 3 is a schematic diagram of an embodiment of analyzing any array element of an antenna;
FIG. 4 is a diagram of the variation of the number of cross-Doppler channels caused by the rotation of the antenna with the number of antenna elements and the number of antenna rotation speed in the embodiment;
fig. 5 (a) is a range-doppler plot of echoes received by the first array element in the embodiment, fig. 5 (b) is a range-doppler plot of echoes received by the 32 th array element, fig. 5 (c) is a range-doppler plot of echoes received by the 64 th array element, and fig. 5 (d) is a schematic diagram of a doppler channel in which the center of a main clutter of echoes received by each array element of the antenna is located;
FIG. 6 (a) shows n in example a Fig. 6 (b) is a schematic diagram of the distribution of the dominant clutter centers corresponding to each antenna unit when =0rpm, in the embodiment, n a The schematic distribution diagram of the main clutter center corresponding to each antenna unit when =160 rpm;
fig. 7 (a) is a clutter suppression effect and a partial magnified view obtained using a conventional STAP, and fig. 7 (b) is a clutter suppression effect and a partial magnified view obtained using a modified STAP in an embodiment;
FIG. 8(a), FIG. 8 (b), FIG. 8 (c) and FIG. 8 (d) show the number of antenna revolutions n a ＝0rpm、n a ＝40rpm、n a =90rpm and n a Energy focusing capability of the conventional STAP and the improved STAP in the examples is compared with a schematic diagram at 160 rpm;
fig. 9 is a flowchart of an airborne rotating antenna radar clutter suppression and target energy focusing method based on the improved STAP in the embodiment.
Detailed Description
Practice shows that the STAP can fully utilize the space and Doppler information of the transmitted echo clutter received by the airborne radar in the target detection process. According to the coupling characteristic of frequency, an optimal clutter suppression method is designed, zero trapped waves matched with the clutter and the interference signals are formed in a self-adaptive mode, and clutter suppression and target detection performance of the airborne radar can be improved remarkably.
STAP methods can be mainly classified into the following two types: a full-dimensional space-time adaptive processing method and a reduced-dimensional space-time adaptive processing method. The clutter is suppressed by using more degrees of freedom in full-dimensional space-time adaptive signal processing, so that the optimal processing effect can be achieved, but the calculated amount is greatly increased due to excessive processing dimensions, the actual time processing requirement cannot be met, and the difficulty is brought to engineering implementation. In most cases, the dimension of the clutter subspace is obviously smaller than that of the whole space, the full-dimensional STAP for clutter suppression has the possibility of dimension reduction, and the dimension reduction STAP (such as an auxiliary channel receiving method (ACR), a joint domain positioning method (JDL), a multi-dimensional channel joint adaptive processing method (M-CAP) and the like) can greatly reduce the calculated amount, but can cause that the processing effect cannot reach the optimum, only can achieve the quasi-optimum processing, and the performance approaches to the optimum full-dimensional STAP.
The STAP used in this embodiment is improved, and is different from the current full-dimensional STAP or reduced-dimensional STAP, and the current full-dimensional STAP or reduced-dimensional STAP and other technologies can be collectively referred to as a conventional STAP. In order to better observe the processing effect of the STAP before and after improvement, the STAP used in the embodiment can be regarded as being improved on the basis of the full-dimensional STAP, and the method effectiveness demonstration is compared with the traditional full-dimensional STAP.
The conventional STAP can well solve the clutter suppression problem of an airborne fixed antenna radar, but the antenna rotation condition is not considered, so that the Doppler broadening and the diffusion problem caused by the antenna rotation cannot be solved. Doppler broadening and diffusion bring adverse effects to clutter suppression and target energy focusing of an airborne rotating antenna system, and further the signal-to-noise ratio after clutter suppression is low, and the low signal-to-noise ratio can cause target detection performance of a radar to be reduced.
In view of the disadvantages of the conventional STAP, the idea of improving the conventional STAP in this embodiment is shown in fig. 1, and includes: the method comprises the steps of firstly modeling a working scene of the airborne rotating antenna radar, analyzing radar echo signal characteristics, comparing the signal characteristics with the signal characteristics of a conventional fixed antenna radar to obtain a rotating disturbance matrix which is directly related to the rotating speed under the rotating condition, and adding the disturbance matrix corresponding to the rotating speed to a space-time guide vector for STAP (space-time adaptive programming), so that the improvement of the traditional STAP is realized, the influence of the rotation of the antenna can be counteracted, and clutter suppression and target capability focusing are better realized.
The STAP improved by the idea shown in fig. 1 can well offset the influence of antenna rotation, can realize accurate matching of target information, and avoid the influence of cross-doppler effect caused by antenna rotation, so that the target is not dispersed into multiple targets, and further the signal-to-noise ratio of the target is reduced and the detection performance of the target of the radar is reduced.
The following describes a modified concept shown in fig. 1. The improved idea shown in fig. 1 is to realize clutter suppression and target energy focusing of an airborne rotating antenna radar by improving STAP, and includes the following steps:
and 5, performing clutter suppression and target capability focusing by using the improved STAP, and comparing to show the effectiveness of the steps 1-4.
Referring to fig. 1, step 1 specifically includes: and modeling the working scene of the airborne rotating antenna radar system, and solving a radar receiving echo signal model.
In step 1, the working scene modeling of the airborne rotating array antenna radar is shown in fig. 2. Assuming that the radar antenna is a planar array with M rows and N columns, the unit spacing is d, the antenna array rotates at an angular speed w, the radar platform flies linearly at a speed v, the platform height h, and at an initial moment, the included angle theta between the flying direction of the platform and the planar direction of the antenna is y . The ground scattering units which are equidistant to the radar platform are distributed in a distance ring, and the ring is divided into P scattering units. And taking one of the scattering units for signal modeling analysis, and marking as a scattering point p. The initial range from p to radar is R p (with respect to the array element of row 1, column 1) the azimuth angle is θ p Angle of pitch is
So the radiation cone angle psi of the airborne rotary array antenna radar p The cosine value of
Since the size of the antenna is much smaller than the radar distance to p, the azimuth and elevation angles of the elements of the antenna plane to p can be considered approximately the same at the same time. Thus, the distance from p to the nth column element of the mth row of the antenna is
Wherein, M =1,2, \8230, M; n =1,2, ·, N. Suppose that the antenna is wound around the nth 0 Array element is rotated, the above formula can be rewritten as
Wherein
Is the mth line n 0 Distance of column elements to p, i.e.
Due to the motion of the radar platform and the rotation of the antenna, at the time t, the distance from the m-th row and n-column array elements of the radar to p is
Wherein v is pr The radial velocity of the radar platform towards the scattering point p,
when the time t is short, the antenna rotation angle Δ θ p Wt is very small and can be regarded as theta p An infinitesimal quantity of (c). Thus, the first order Taylor expansion of formula (2) can be expressed as
In the formula (3), are defined
Is the radial velocity of the nth array element towards p when the antenna rotates.
Assuming that the radar transmits a signal of
Where u (t) is the complex envelope of the modulated signal, w 0 Is an angular frequency of wherein
Is the initial phase. The mth row and nth column array elements of the antenna receive the echo signal reflected from the scattering unit p
Wherein A is p τ is the delay time of the echo, which is the complex amplitude of the echo signal reflected from p. Time delay of signal from radar to p is
Wherein r is p In order to be the instantaneous tilting distance,
and c is the speed of light. The time required for the signal to return from p to the radar is
So that the total delay is
Thus, after the signal is transmitted at time t, the echo signal is received at a time t
Substituting the formula (4) into an echo signal expression to obtain
Wherein
Is a pulse scale factor. Due to the fact that
Therefore, it is not only easy to use
(5) The formula can be simplified approximately as follows:
wherein,
in order to take account of the time delay of the two-way transmission from the m-th row and n-th column of the radar antenna to p, w dpn Is the doppler frequency of the echo signal and,
according to formula (7), w dpn Is composed of two parts, wherein
Indicating the Doppler shift, f, caused by the radar platform moving in the p direction dpnr Indicating the doppler shift caused by the rotation of the antenna,
indicating the radar operating wavelength.
The value of (c) is small and negligible. The result of down-conversion of the echo signal is therefore:
wherein A is p0 ＝A p e jφ . Dividing the time t into a fast time t and a slow time t k I.e. by
T is the pulse repetition period, K =1,2, \8230, and K is the number of pulses. Fast time phase term
Small and negligible. Therefore, it is possible to
The echo is subjected to waveform matching filtering to obtain
Where x (τ) l -τ 0 ) Is a range ambiguity function of the echo signal,
only the range-ring echo in which the scatter point p is located, i.e. x (τ), is taken into account l -τ 0 ) =1, so equation (8) can be rewritten as:
as can be seen from equation (9), the horizontal rotation angular velocity of the antenna does not affect the phase relationship of the echo signals of the respective reception channels in the elevation direction, and therefore, only the case of the horizontal line array is considered. Therefore, at this time, the above formula can be rewritten as
Wherein
In order to be the amplitude of the signal,
the additional phase caused by the rotation of the antenna is denoted as the rotating phase factor. It is composed ofWherein N =1,2, \ 8230, N; k =1,2, \8230;, K.
Referring to fig. 1, step 2 specifically includes: through radar echo signal characteristic analysis, the method is compared with echoes in a traditional fixed antenna radar scene, and a disturbance matrix which is directly related to the rotation speed of the antenna and is added in the echoes can be extracted.
The formula of the echo signal model (10) obtained by modeling in the step 1 can be expressed in a matrix form as follows:
wherein s is p An echo data matrix, s, representing scattering points p tp And s sp Respectively a time domain guide vector and a space domain guide vector when the airborne radar antenna does not rotate,
can be used to represent the echo signal characteristics of an airborne stationary antenna. The superscript (T) represents the matrix transpose operation. As shown in equation (11), a perturbation matrix M is generated due to the rotation of the antenna p . According to formula (14), M p Related to the rotation speed of the antenna, the pulse repetition period, the array element spacing, the angle of the scattering point to the array surface, and the wavelength of the signal. It is embodied as a linear phase modulation in the spatial and temporal domains. When the antenna is not rotating, M p Is an all-one matrix of dimension NxK, thisAt that time have
Namely M p The method does not bring influence, and the rationality of matrix decomposition of the signal model is proved.
Referring to fig. 1, step 3 specifically includes: the method comprises the steps of analyzing the cross-Doppler condition of the airborne rotary antenna radar, and analyzing factors influencing the number of cross-Doppler channels and adverse effects brought by the cross-Doppler channel condition.
Suppose that the airborne planar array antenna is wound by the nth c The array elements rotate. The rotation speed of the antenna is n a (revolutions per minute, rpm). The angular velocity of the antenna is thus
Any row of elements of the antenna is taken for analysis, as shown in fig. 3. The doppler difference is greatest across the array as the antenna rotates. Let the antenna at t 0 Transmitting signals at time t 1 Receiving echo at the moment, and the rotation angle of the antenna is a = w (t) 1 -t 0 ) = w Δ t. Since Δ t is very small and the antenna size is much smaller than the distance between the radar and the scattering point, the azimuth angle θ in time Δ t p And a pitch angle
Respectively, are approximately constant. The walking distances of two end point array elements are respectively delta l 1 ＝(n c -1)da＝(n c -1) dw Δ t and Δ l N ＝(n c -N)da＝(n c -N) dw Δ t. The resulting phase differences are respectively
And
the doppler shifts of the echo signals are therefore:
and
so that the frequency difference between the two end array elements is
Both traditional pulse doppler Processing (PD) and spreading factor method (EFA) require fourier transformation of the pulse data to obtain a doppler channel bandwidth of
Wherein f is r K is the number of points in the slow time FFT for the pulse repetition frequency. Thus, the number of cross-Doppler channels (n) caused by antenna rotation ADcs ) Is composed of
Where round () represents the operation rounded to the nearest integer. From the formula (37), n ADCs The method is related to the number of antenna elements, the rotation speed of the antenna, the number of slow time FFT points, the distance between array element units, the azimuth angle and the pitch angle of a radar to a scattering point, the signal wavelength and the pulse repetition frequency.
When the main beam direction is the normal direction of the array antenna, i.e. theta p =90 ° and
to obtain
At this time (15) can be written as
Setting the radar operating parameters as shown in Table 1, by simulationObservation of n ADCs The change rule of the antenna rotation speed and the antenna array element number is followed.
TABLE 1 Radar System operating parameters
| Parameter(s) | Value of |
| Antenna array column number (N) | 64 |
| Number of pulses in one CPI (K) | 32 |
| Wavelength (lambda) | 0.1m |
| Pulse repetition frequency (f) r ) | 6000Hz |
| Radar platform velocity (v) | 120m/s |
| Radar platform height (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 shows n ADCs The variation with the rotation speed of the antenna and the number of the antenna elements. As can be seen from FIG. 4, n ADCs As the antenna speed and the number of antenna elements increase. When the number of antenna elements is 64, if the antenna rotates at n a <20rpm, number of Doppler channels crossing 0, if n a >130rpm，n ADCs =3, if continue to increase antenna rotation speed or number of antenna array elements, n ADCs The expansion will continue. It will be appreciated that when the antenna is not rotating, the movement of each antenna element to the same scattering point is the same, so that the range-doppler spectrum of the received echoes at each element is approximately the same, and the doppler channel at the centre of the main clutter is the same. The change of the distance Doppler spectrum when the antenna rotates is observed through a simulation result. From the parameters set by the system, when the antenna is not rotating, n is a At =0rpm, the target is located at the 24 th doppler channel and the center of the dominant clutter is located at the 30 th doppler channel.
To better explain the Doppler shift and diffusion phenomena, the antenna speed is taken to be 90rpm, where n is ADCs Equal to 2. FIG. 5 is n a =90rpm, some array elements receive the range-doppler plot of the echoes. Specifically, fig. 5 (a) is a range-doppler diagram of the echo received by the first array element, fig. 5 (b) is a range-doppler diagram of the echo received by the 32 th array element, fig. 5 (c) is a range-doppler diagram of the echo received by the 64 th array element, and fig. 5 (d) is a doppler channel in which the center of the main clutter of the echo received by each array element of the antenna is located.
As can be seen from fig. 5, when the antenna speed n is high a When the speed is not less than 90rpm, the echo distance Doppler spectrums received by different array elements are different, and the Doppler channels at the centers of the main clutter deviate and are not unified any more. The antenna element closest to the rotation axis has the smallest rotation linear velocity, and its main clutter center remains not moving in the 30 th doppler channel, as shown in fig. 5 (b). Along with the antenna units approaching to the two ends of the antenna, the linear velocity of the array elements increases gradually and the main clutterThe center shifts to the 29 th and 31 th channels, respectively, as shown in fig. 5 (a) and 5 (c), which is caused by the opposite moving directions of the two end elements of the antenna. Similarly, by changing the rotation speed of the antenna, the main clutter center doppler channel information corresponding to each antenna unit under different rotation speeds can be obtained as shown in fig. 6.
In particular when the antenna is not rotating, i.e. n a The same applies to n, where the distribution of the centers of the main clutter corresponding to each antenna element is as shown in fig. 6 (a), and all the centers of the main clutter are within the doppler channel 30 when =0rpm ADCs Other speed cases of = 0. At this time, there is no shift or dispersion in the doppler spectrum, and the effect of antenna rotation is not considered, so that the processing effect of the conventional STAP is equivalent to that of the improved STAP. Conversely, if the antenna speed is increased to 160rpm, the influence of the antenna speed on the cross-Doppler channel condition is more serious, as shown in FIG. 6 (b), where n is ADCs ＝3。
Referring to fig. 1, step 4 specifically includes: according to the STAP principle, under the condition of keeping the target power unchanged, the output signal power is minimized, namely the power of the clutter is minimized, and the clutter suppression is completed while the target integrity is protected. And taking the rotation speed of the antenna when the radar works as priori knowledge to obtain a corresponding disturbance matrix, and adding the disturbance matrix to the space-time steering vector to realize the improvement of the traditional STAP.
STAP is a joint process of one-dimensional spatial domain adaptive filtering and one-dimensional time domain adaptive filtering. The method is based on the linear constraint minimum variance and the maximum output signal-to-noise ratio criterion, can output the optimal linear combination, and can self-adaptively solve the clutter suppression problem of the airborne radar. Representing the weight vector of the processor by W of dimension N K × 1, W = [ W = [ [ W ] 11 ,…,w 1K ,w 21 ,…,w 2K ,…,w N1 ,…,w NK ] T Wherein w is nk And the adaptive weight of the nth array element at the kth pulse echo is obtained. The STAP processor can be described as a mathematical optimization problem:
wherein R = E [ XX ] H ]Is a covariance matrix of echo data of dimensions N K × N K. The expression of the echo data matrix X is X = X t + c + n. Wherein x is t The target echo matrix, c the clutter matrix and n the noise matrix. E [. C]Indicating a statistical expectation. S is a space-time two-dimensional steering vector.
. Wherein S s As a space steering vector, S t Is a time-domain steering vector and is,
is the product of Kronecker. For the conventional rotating antenna radar, there are
Wherein
In order to normalize the spatial frequencies of the signals,
for normalizing the doppler frequency, the meaning of the parameters is shown in fig. 2.
The space-time steering vector changes accordingly if the antenna rotation is taken into account. In conjunction with the conclusions in step 2, it is known that the change in the space-time steering vector can be reflected in the perturbation matrix. The conclusion in step 2 is an analysis of the echoes of the scattering points pbroth, which is generalized here to the general case, i.e. applicable for all scattering points. The conclusion drawn for a particular scattering point p can also be applied to any scattering point after generalization, for example, a certain amount corresponding to a particular scattering point p is removed by subscript p to indicate an amount of the same property that is applied to any scattering point. For example, beta p The rotating phase factor corresponding to a specific scattering point p is represented, and beta represents the rotating phase factor corresponding to any scattering point; m p And representing a rotation disturbance matrix corresponding to a specific scattering point p, and M represents a rotation disturbance matrix corresponding to any scattering point.
After the analysis of the p-echo of the scattering point is generalized to a general case, the following results can be obtained:
wherein S r Is the space-time guiding vector of the airborne rotating antenna radar,
to rotate the phase factor, the additional phase caused by the antenna rotation is indicated. If the antenna is fixed, i.e. β =0, then M is a full matrix of dimensions N × K, with S r = S, mixing S r Reshaping into an NKx 1 dimensional matrix. Namely S r ＝[S r (1,1),…,S r (N,1),S r (1,2),…,S r (N,K)] T 。
So the weight vector of the space-time two-dimensional optimal processor is:
W optr ＝μR -1 S r #(19)
where μ is a constant. The final post-STAP processed output can be expressed as:
wherein X = X ij T Ij =1, \ 8230, NK, superscript (H) denotes Hermitian transpose, superscript (#) denotes complex conjugation.
Referring to fig. 1, step 5 specifically includes: clutter suppression and target capability focusing are performed using the improved STAP. The effectiveness of the STAP method is remarkably improved by comparing the performance with that of the traditional STAP.
Rotation of the antenna results in a shift and spread of the received echoes over the doppler domain, which also results in a spread of the target energy over the range-doppler spectrum. Experimental simulation verification is performed by setting the target point in the 24 th doppler channel of the 600 th range gate when the antenna does not rotate. When the antenna rotation speed is n a At =90rpm, n ADCs =2, the conventional STAP cannot compensate for doppler shift and dispersion caused by antenna rotation, and the clutter suppression effect is shown in fig. 7 (a). A portion near the target region is enlarged to observe the power distribution of the target and the center of the primary clutter. Also, for the same echo data, the clutter suppression effect and the partial enlargement are obtained using the modified STAP method of steps 1 to 4, as shown in fig. 7 (b). As can be seen from fig. 7, except for the center of the main clutter, the two methods have good clutter suppression effect and comparable clutter suppression performance.
The power value of the 600 th range cell of the 24 th Doppler channel where the target is located can be obtained from the range-Doppler spectrum. Comparing the target power values of fig. 7 (a) and 7 (b), it can be easily found that the main clutter center power and the target power of fig. 7 (a) are both approximately 10dB lower than those of fig. 6 (b) due to the energy dispersion caused by the doppler spread caused by the antenna rotation. Since the conventional STAP method cannot compensate for the adverse effect of the antenna rotation, the improved STAP method in steps 1-4 can. Thus, the output signal-to-noise ratio after the improved STAP in steps 1-4 is close to the set input signal-to-noise ratio, since the energy of the target is effectively focused. The output signal-to-noise ratio after the conventional STAP is n ADCs Related to, n ADCs The larger the value, the more dispersed the target energy, and the lower the output signal-to-noise ratio, which will affect the target detection performance of the radar. In order to analyze the energy focusing capability of the two methods at different antenna rotation speeds, a 600 th range gate power curve of the target is extracted from the range-doppler spectra processed by the two methods, as shown in fig. 8. Where, the antenna rotation speed corresponding to fig. 8 (a) is n a =0rpm, and the antenna rotation speed corresponding to fig. 8 (b) is n a =40rpm, and the antenna rotation speed corresponding to fig. 8 (c) is n a =90rpm, and the antenna rotation speed corresponding to fig. 8 (d) is n a ＝160rpm。
And marking the power value of the 24 th Doppler channel where the target is positioned by using the data cursor. As can be seen from fig. 8 (a), when the antenna is not rotated, the doppler spectrum is not shifted and spread at this time, and the target energy is not spread, so the processing effect of the two methods is the same, and the target energy value is equal for the same echo data. As can be seen from FIGS. 8 (b), 8 (c) and 8 (d), as n goes a The target power value after the improved STAP can be kept about 20dB, while the target power value after the traditional STAP is gradually reduced. When the target power value is reduced to a certain degree, it is more susceptible to noise, and the target is easily submerged in the noise. The reduction in target energy results in a reduction in output signal-to-noise ratio, which in turn adversely affects target detection.
In conclusion, through performance comparison between the conventional STAP and the improved STAP, it is not difficult to find that clutter suppression performances of the two methods are basically consistent, but the improved STAP has a remarkable advantage in the aspect of energy focusing, an output signal-to-noise ratio is not influenced by antenna rotation after clutter suppression, the signal-to-noise ratio is kept stable and not reduced, and the method has an important significance for radar target detection after the STAP.
In the embodiment, based on the principle of steps 1-5, an airborne rotating antenna radar clutter suppression and target energy focusing method based on an 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 comprises the following steps:
s1, acquiring working parameters of an airborne rotating antenna radar;
s2, acquiring a rotation disturbance matrix, a space guide vector and a time domain guide vector according to the working parameters;
s3, acquiring a space-time guide vector according to the rotation disturbance matrix, the space guide vector and the time domain guide vector;
s4, acquiring an echo data matrix;
and S5, performing STAP processing on the time-space steering vector and the echo data matrix to obtain a processing result.
Steps S1 to S5 are designed based on the principle of steps 1 to 5, in particular, equations (17) to (20).
In step S1, the obtained working parameters comprise the rotation speed w of the antenna, the spacing d of the array elements, the pulse repetition period T, the azimuth angle theta between the scattering point and the array surface, and the pitch angle between the scattering point and the array surface
And a signal wavelength lambda.
In step S2, the rotational disturbance matrix M is calculated based on equation (18).
In step S2, based on
Calculating to obtain a space guide vector S s 。
In step S2, based on
Calculating to obtain a time domain guide vector S t 。
In step S3, by
And calculating to obtain a space-time guiding vector S. Wherein,
the Kronecker product operation is performed.
In step S4, a target echo matrix x is obtained t Clutter matrix c and noise matrix n according to the formula X = X t And + c + n to obtain an echo data matrix X.
In step S5, the formula R = E [ XX [ ] is firstly passed H ]The covariance matrix R of the echo data matrix X is calculated by setting a constant mu according to the formula (19) W optr ＝μR -1 S r And calculating to obtain a weight vector W of the space-time two-dimensional optimal processor optr According to formula (20) that
And calculating to obtain a processing result y.
According to the principle of the steps 1-5, the echo data matrix X is processed by executing the steps S1-S5, clutter in the obtained processing result y is suppressed, and a clutter suppression effect basically consistent with that of a traditional STAP can be obtained, the steps S1-S5 have remarkable advantages in the aspect of energy focusing on the basis, the output signal-to-noise ratio can be prevented from being influenced by antenna rotation after clutter suppression, the signal-to-noise ratio is kept stable and not reduced, and the method has important significance for radar target detection after the STAP.
The high-extensibility stateless alarm method in the embodiment may be implemented by writing a computer program for implementing the high-extensibility stateless alarm method in the embodiment, writing the computer program into a computer device or a storage medium, and executing the high-extensibility stateless alarm method in the embodiment when the computer program is read out to run, thereby implementing the same technical effect as the high-extensibility stateless alarm method in the embodiment.
It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature or indirectly fixed or connected to the other feature. Furthermore, the descriptions of upper, lower, left, right, etc. used in the present disclosure are only relative to the mutual positional relationship of the constituent parts of the present disclosure in the drawings. As used in this disclosure, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, unless defined otherwise, all technical and scientific terms used in this example have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in the description of the embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this embodiment, the term "and/or" includes any combination of one or more of the associated listed items.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one type of element from 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 ("e.g.," such as "or the like") provided with this embodiment is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.
It should be recognized that embodiments of the present invention can be realized and implemented by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer readable memory. The methods may be implemented in a computer program using standard programming techniques, including a non-transitory computer-readable storage medium configured with the computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner, according to the methods and figures described in the detailed description. Each program may be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) 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 a programmed application specific integrated circuit for this purpose.
Further, operations of processes described in this embodiment can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The processes described by the present embodiments (or variations and/or combinations thereof) may be performed under the control of one or more computer systems configured with executable instructions and may be implemented as code (e.g., executable instructions, one or more computer programs, or one or more applications) collectively executed on one or more processors, by hardware, or combinations thereof. The computer program includes a plurality of instructions executable by one or more processors.
Further, the method may be implemented in any type of computing platform operatively connected to a suitable connection, including but not limited to a personal computer, mini computer, mainframe, workstation, networked or distributed computing environment, separate or integrated computer platform, or in communication with a charged particle tool or other imaging device, or the like. Aspects of the invention may be embodied in 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 write storage medium, RAM, ROM, or the like, such that it may be read by a programmable computer, which when read by the storage medium or device, is operative to configure and operate the computer to perform the procedures described herein. Further, 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 includes instructions or programs that implement 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.
A computer program can be applied to input data to perform the functions described in the present embodiment to convert the input data to generate output data that is stored to a non-volatile memory. The 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 particular visual depictions of physical and tangible objects produced on a display.
The present invention is not limited to the above embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention as long as the technical effects of the present invention are achieved by the same means. The invention is capable of other modifications and variations in its technical solution and/or its implementation, within the scope of protection of the invention.
Claims (10)
1. An improved STAP-based airborne rotary antenna radar clutter suppression and target energy focusing method, wherein the improved STAP-based airborne rotary antenna radar clutter suppression and target energy focusing method comprises the following steps:
acquiring working parameters of an airborne rotating antenna radar; the working parameters comprise antenna rotating speed, array element spacing, pulse repetition period, azimuth angles of scattering points and array surfaces, pitch angles of the scattering points and the array surfaces and signal wavelength;
acquiring a rotation disturbance matrix, a space guide vector and a time domain guide vector according to the working parameters;
acquiring a space-time guide vector according to the rotation disturbance matrix, the space guide vector and the time-domain guide vector;
acquiring an echo data matrix;
and performing STAP processing on the space-time guiding vector and the echo data matrix to obtain a processing result.
2. The improved STAP based airborne rotary antenna radar clutter suppression and target energy focusing method of claim 1, wherein said obtaining a rotational perturbation matrix, a spatial steering vector and a temporal steering vector from said operating parameters comprises:
according to the formula
Establishing the rotation disturbance matrix;
wherein M is the rotational perturbation matrix, β is a rotational phase factor,
w is the rotation speed of the antenna, d is the spacing between array elements, T is the pulse repetition period, theta is the azimuth angle between the scattering point and the array surface,
Scattering points and array surface pitch angles are provided, lambda is the signal wavelength, and N and K are the dimensions of the rotation disturbance matrix.
3. The improved STAP-based airborne rotating antenna radar clutter suppression and target energy focusing method of claim 1, wherein said deriving a rotational perturbation matrix, a spatial steering vector, and a temporal steering vector from said operating parameters comprises:
according to the formula
Establishing the spatial steering vector;
wherein S is s Is the space steering vector, f s To normalize the spatial frequency.
4. The improved STAP-based airborne rotating antenna radar clutter suppression and target energy focusing method of claim 1, wherein said deriving a rotational perturbation matrix, a spatial steering vector, and a temporal steering vector from said operating parameters comprises:
according to the formula
Establishing the time domain steering vector;
wherein S is t For the time domain steering vector, f d Is the normalized doppler frequency.
5. The improved STAP based airborne rotary antenna radar clutter suppression and target energy focusing method of claim 1, wherein said obtaining a spatio-temporal steering vector from said rotational perturbation matrix, said spatial steering vector and said temporal steering vector comprises:
according to the formula
Obtaining the space-time guiding vector;
wherein S is r For said spatio-temporal steering vector, S s As the space steering vector, S t For the time domain steering vector, M isThe perturbation matrix is rotated.
6. The improved STAP-based airborne rotating antenna radar clutter suppression and target energy focusing method of claim 1, wherein said acquiring an echo data matrix comprises:
obtaining a target echo matrix x t A clutter matrix c and a noise matrix n;
according to the formula X = X t + c + n determines the echo data matrix X.
7. An improved-STAP-based airborne rotary antenna radar clutter suppression and target energy focusing method according to claim 6, wherein said STAP processing said spatio-temporal steering vector and said echo data matrix to obtain processing results comprises:
acquiring a weight vector of a space-time two-dimensional optimal processor;
according to the formula y = W optr H X processes the space-time guiding vector and the echo data matrix to obtain a processing result; wherein y is the result of the treatment, W optr And for the weight vector, X is the echo data matrix, and the superscripted H represents Hermitian transposition operation.
8. The improved STAP-based airborne rotating antenna radar clutter suppression and target energy focusing method of claim 7, wherein said obtaining weight vectors for a space-time two-dimensional optimal processor comprises:
according to the formula W optr ＝μR -1 S r Determining the weight vector;
wherein, W optr As the weight vector, S r R is the covariance matrix of the echo data matrix, and μ is a constant.
9. A computer apparatus comprising a memory for storing at least one program and a processor for loading the at least one program to perform the high scalability stateless alert method of any of claims 1-8.
10. A computer readable storage medium having stored therein a processor executable program, wherein the processor executable program when executed by a processor is for performing the high extensibility stateless alerting method of any one of claims 1-8.
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