CN104515982A

CN104515982A - Bistatic airborne radar clutter compensation method and device based on derivative updating

Info

Publication number: CN104515982A
Application number: CN201410745210.3A
Authority: CN
Inventors: 文珺; 赵进创; 邹星星; 宋玲; 许京伟
Original assignee: Guangxi University
Current assignee: Guangxi University
Priority date: 2014-12-08
Filing date: 2014-12-08
Publication date: 2015-04-15

Abstract

The invention discloses a bistatic airborne radar clutter compensation method and device based on derivative updating. The method includes receiving echo signals of bistatic airborne radar, and calculating sum of transceiving distances of a Kth to-be-detected distance door of the echo signals; calculating pitching angle cosine in a main lobe direction according to the sum of the transceiving distances of the Kth to-be-detected distance door; calculating self-adaptive weight vector of derivative updating according to receiving distance or the pitching angle in the main lobe direction; compensating the echo signals according to the self-adaptive weight vector. Processing based on derivative updating is realized under a bistatic condition; after the method is utilized to compensate echo data, distance dependence of the bistatic airborne radar can be lowered effectively, so that ground moving target detection performance of space-time self-adaptive processing is greatly improved, and working efficiency of radar detection is improved greatly.

Description

Double-base airborne radar clutter compensation method and device based on derivative updating

Technical Field

The invention relates to the technical field of radar communication, in particular to a double-base airborne radar clutter compensation method and device based on derivative updating.

Background

The transmitter system and the receiver system of the double-base airborne radar are installed on different airborne platforms, and compared with a common single airborne radar, the double-base airborne radar has the advantages of being rich in acquired information, long in action distance, high in safety, strong in anti-interference capability, good in anti-interception performance and the like.

However, the radar echo space-time two-dimensional power spectrum of the dual-airborne radar receiving end has the defects: 1. there is a severe distance dependence; 2. there are significant differences in the shapes of different configurations of the carrier. The above problems cause the traditional ground moving target detection performance to be seriously reduced, that is, the ground clutter cannot be effectively inhibited, so that the ground moving target is difficult to detect.

Disclosure of Invention

The invention provides a method and a device for compensating clutter of a double-base airborne radar based on derivative updating, aiming at solving the problem that the clutter of the ground cannot be effectively inhibited during communication of the double-base airborne radar in the prior art.

The method comprises the following steps:

receiving echo signals of the double-base airborne radar, and calculating the sum of the receiving and sending distances of the Kth range gate to be detected of the echo signals;

calculating the cosine of the receiving pitch angle in the main lobe direction according to the sum of the receiving and transmitting distances of the Kth distance gate to be detected;

calculating a self-adaptive weight vector updated by a derivative according to the receiving distance or the pitch angle in the main lobe direction;

and compensating the echo signal according to the self-adaptive weight vector.

According to the clutter compensation method of the bistatic airborne radar based on derivative updating, processing based on derivative updating is achieved under the bistatic condition, after echo data are compensated through the method, the distance dependency of the bistatic airborne radar can be effectively reduced, the ground moving target detection performance of space-time self-adaptive processing is greatly improved, and the working efficiency of radar detection is greatly improved.

The device, comprising:

the first calculation module is used for receiving echo signals of the double-base airborne radar and calculating the sum of the receiving and transmitting distances of the Kth range gate to be detected of the echo signals;

the second calculation module is used for calculating the cosine of the receiving pitch angle in the main lobe direction according to the sum of the receiving and sending distances of the Kth distance gate to be detected;

the third calculation module is used for calculating the self-adaptive weight vector updated by the derivative according to the receiving distance or the pitch angle in the main lobe direction;

and the signal compensation module is used for compensating the echo signal according to the self-adaptive weight vector.

The double-base airborne radar clutter compensation device based on derivative updating realizes processing based on derivative updating under the double-base condition, and can effectively reduce the distance dependence of the double-base airborne radar after the echo data is compensated by using the method, thereby greatly improving the ground moving target detection performance of space-time self-adaptive processing and greatly improving the working efficiency of radar detection.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic flow chart of a method according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an apparatus according to an embodiment of the present invention.

Detailed Description

The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.

As shown in fig. 1, the method includes:

step S101: receiving echo signals of the double-base airborne radar, and calculating the sum of the receiving and sending distances of the Kth range gate to be detected of the echo signals;

specifically, the sum R of the receiving and transmitting distances of the Kth distance door to be detected is calculated according to the following formula_s(k)R：

L is the distance between the transmitting and receiving carriers, R_s(k)For the Kth distance to be detected from the door, H_RTo receive the flying height of the carrier, H_TTo transmit the flying height of the carrier, H_HFor height of detection point, σ_RThe horizontal deflection angle of a connecting line between the speed direction of the receiving carrier and the two machines;

simplifying the above equation yields:

solving the above equation to obtain:

wherein,B＝L²-(H_R-H_T)²。

step S102: calculating the cosine of the receiving pitch angle in the main lobe direction according to the sum of the receiving and transmitting distances of the Kth distance gate to be detected;

specifically, the cosine of the received pitch angle in the main lobe direction is calculated according to the following formula

Step S103: calculating a self-adaptive weight vector updated by a derivative according to the receiving distance or the pitch angle in the main lobe direction;

step S104: and compensating the echo signal according to the self-adaptive weight vector.

Step S105: and carrying out full-dimensional STAP processing on the compensated echo signal, and carrying out moving target detection on the processed echo signal.

As shown in fig. 2, the apparatus includes:

the first calculation module 10 is configured to receive an echo signal of the dual-base airborne radar, and calculate a sum of transceiving distances of a kth range gate to be detected of the echo signal;

the second calculation module 20 is configured to calculate the cosine of the receiving pitch angle in the main lobe direction according to the sum of the receiving and sending distances of the kth distance gate to be detected;

a third calculating module 30, configured to calculate an adaptive weight vector updated by the derivative according to the receiving distance or the pitch angle in the main lobe direction;

and the signal compensation module 40 is configured to compensate the echo signal according to the adaptive weight vector.

And the signal detection module 50 is configured to perform full-dimensional STAP processing on the compensated echo signal, and perform moving-target detection on the processed echo signal.

In the above technical solution, the first calculating module 10 is specifically configured to:

calculating the sum R of the receiving and transmitting distances of the Kth distance door to be detected according to the following formula_s(k)R：

simplifying the above equation yields:

solving the above equation to obtain:

wherein,B＝L²-(H_R-H_T)²。

the second computing module 20 is specifically configured to

Calculating the cosine of the received pitch angle in the main lobe direction according to the following formula

The technical scheme of the invention is explained in detail as follows:

DBU (derivative update based) method

The DBU is originally used for solving the clutter distance dependency problem of an airborne forward looking array radar, and considers that the distribution characteristic of clutter is a function of the slant range R and changes along with the change of the slant range, and a corresponding STAP weight vector should also beA function of the slope distance. Let reference range gate be r_mThe corresponding STAP weight vector is W_DBU(r_m) Then r is_iWeight vector W corresponding to each range gate_DBU(r_i) The Taylor expansion of (A) is:

if it is considered that r is_i-r_mVery small (relative to r)_mAfter normalization), neglecting the influence of the quadratic term and its higher-order terms above in equation (1), then:

W_DBU(r_i)≈W_DBU(r_m)+(r_i-r_m)W_DBU(r_m)' (2)

W_DBU(r_m)',W_DBU(r_m) ", each represents W_DBU(r_m) The first and second derivatives of (c). And the target range gate pitch angle cosine is used for replacing the pitch distance as a DBU method of updating the variable, and the processing principle is the same as that of the traditional DBU method. From the above expression, it can be known that the adaptive weight vectors are different for different range gates, however, in practical engineering implementation, the clutter covariance matrix is generally statistically and averagely estimated by using the data of one or all range gates received by the radar, and the calculated STAP weight vector is used to perform clutter suppression on the data of the one or all range gates being processed, that is, the optimal weight vectors of all range gates should be the same for the data of the one or all range gates being processed.

Processing NK multiplied by 1(N is the number of antennas, K time domain pulse number) dimensional data X (r) of corresponding range gate by the above weight vector_i) The latter corresponding outputs are:

thus, the adaptive weight vector after transformation of formula (3) no longer changes with the change of the range gate, and the relation of the adaptive weight changing with the distance has been transferred to each unit data, thereby realizing the distance dependency compensation for clutter.

DBU (double base airborne radar) method

The distance and the pitch angle between each target scattering point and the receiver on a range gate to be detected are changed due to the geometrical structure of the double-base airborne radar. Considering that the echo of the double-base airborne radar is only related to the receiving distance and the receiving azimuth angle, the receiving distance or the pitch angle cosine of the receiving main lobe azimuth direction is taken as an updating variable, and the double-base airborne DBU is realized. Because the difference between the sum of the receiving and transmitting distances of the range gates to be detected and the adjacent range gates is a fixed value, and when only the receiving distance is taken as a DBU updating variable, the change of the transmitting distance bears a part of the original fixed distance change, the change of the receiving distance is smaller than the change of the sum of the original receiving and transmitting distances. From the formula (1), it is found that the smaller the variation between adjacent update variables is, the less the information above the second order is discarded, and the closer the processing result is to the optimal processing.

If the distance of the kth distance door to be detected is R_S(k)The sum of the received transmission distances is known,the receiving distance equation with respect to the receiving direction main lobe direction (receiving front normal direction) can be obtained as

the formula is simplified to obtain:

it can be seen that the above formula is a sum R of the transceiving distances_s(k)RAnd solving the equation. To obtain R_s(k)RThe mathematical expression of (a) is:

A = L^{2} + 2 H_{R} H_{T} - 2 H_{R}^{2} - - - (7)

B＝L²-(H_R-H_T)² (8)

since the dual base carrier configuration of the present invention is in the rear and front, and the azimuth of the front is counterclockwise, the square root in equation (6) is positive.

Further, the cosine of the received pitch angle with respect to the receiver main lobe direction (along the direction of the normal to the wavefront) can be obtained:

for the sake of convenience of distinction, a method in which the receiver main lobe direction reception distance is used as an update variable is referred to as DBU, and a method in which the receiver main lobe direction pitch angle cosine is used as an update variable is referred to as EDBU. Since the two methods are basically consistent in processing, only the DBU algorithm process using the receiving distance as an update variable is described here.

And after the received echo data DBU of the P range gates are compensated, clutter covariance matrix estimation is carried out to obtain:

wherein:

gamma in the above equation (8)_DBUIs when X_DBU(r_i) Ensuring R for white Gaussian noise_DBUIs a normalized coefficient of the identity matrix. r is_riReceiving slope distance r for ith range gate_rmTo reference the receiving slope distance of the range gate, the most remote range gate is typically selected.

The covariance matrix corresponding to the DBU method is 2NK dimension, the direct SMI algorithm of the echo data, namely the direct STAP processing, is the data covariance matrix corresponding to the NK dimension, the clutter covariance matrix of the NK dimension is estimated and inverted, and the operation amount is o (NK)³Therefore, the DBU method is more computationally intensive than the direct STAP process, and the requirement for an iid (independent and identically distributed) sample is also increased due to the increased dimension of the covariance matrix, which is a problem that the DBU method needs to be improved and needs to be further researched.

The calculation of the adaptive weight vector of the DBU method is obtained by the following criteria:

\{\begin{matrix} \min W_{DBU}^{H} R_{DBU} W_{SBU} \\ st . W_{DBU}^{H} S = 1 \end{matrix} - - - (13)

W_{DBU} = R_{DBU}^{- 1} S / (S^{H} R_{DBU}^{- 1} S) - - - (14)

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in the formula (16)d is the array element spacing, lambda is the wavelength, cos psi_S0Is the receive space cone cosine. In formula (17)f_d0For the Doppler channel frequency, f, to be detected_rIn order to be able to do so at the pulse repetition frequency,is the direct product of Kronecker. The improvement factor for a certain doppler channel is found by the following formula:

CNR is the noise-to-noise ratio, σ, of the input²For noise power, the full-dimensional optimal STAP algorithm is used here, and the dimension-reduced STAP algorithm is not described here again.

While the present invention is susceptible of embodiment in many different forms, there is shown in the drawings, and will be described herein with reference to the accompanying drawings, embodiments of the present invention, which are illustrated in the accompanying drawings, and not intended to limit the invention to the specific forms set forth herein, but rather to limit the invention to the specific forms disclosed, and it will be understood by those skilled in the art that the foregoing and various other changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A double-base airborne radar clutter compensation method based on derivative updating is characterized by comprising the following steps:

and compensating the echo signal according to the self-adaptive weight vector.

2. The method for derivative update based bistatic airborne radar clutter compensation according to claim 1, further comprising:

and carrying out full-dimensional STAP processing on the compensated echo signal, and carrying out moving target detection on the processed echo signal.

3. The method for compensating clutter according to claim 1, wherein the step of calculating the sum of the transmit-receive distances of the kth range gate to be detected of the echo signal specifically comprises:

simplifying the above equation yields:

solving the above equation to obtain:

wherein,B＝L²-(H_R-H_T)²。

4. the method for double-base airborne radar clutter compensation based on derivative update of claim 1, wherein the step of calculating the cosine of the received pitch angle in the mainlobe direction specifically comprises:

5. A double-base airborne radar clutter compensation device based on derivative updating is characterized by comprising:

6. The derivative update based bistatic airborne radar clutter compensation apparatus of claim 5, further comprising:

and the signal detection module is used for carrying out full-dimensional STAP processing on the compensated echo signal and carrying out moving target detection on the processed echo signal.

7. The derivative update-based bistatic airborne radar clutter compensation apparatus according to claim 5, wherein said first calculation module is specifically configured to:

simplifying the above equation yields:

solving the above equation to obtain:

wherein,B＝L²-(H_R-H_T)²。

8. the derivative update-based bistatic airborne radar clutter compensation apparatus according to claim 5, wherein said second calculation module is specifically configured to