JP4553387B2 - Weight calculation method, weight calculation device, adaptive array antenna, and radar device - Google Patents

Description

  The present invention relates to a weight calculation method suitable for detecting a reflected signal from a target by suppressing unnecessary waves by weight control, a weight calculation device using the weight method, and an adaptive array antenna employing the weight calculation device And a radar apparatus incorporating the adaptive array antenna.

  In recent years, in order to further improve the target detection accuracy, pulse radar apparatuses have incorporated an adaptive array antenna to perform so-called adaptive null steering. This adaptive null steering performs weight control on the phase and amplitude of the received signal in the adaptive array antenna, and the received combined beam is set so that the directivity in the direction in which an unwanted wave such as an interference wave arrives becomes zero (null). It is a process to form. The adaptive array antenna used for such applications properly forms the received combined beam even in an environment where a large number of delayed signals arrive or an environment where unnecessary waves such as clutter and jamming waves exist. It is required to perform weight control as shown.

  Therefore, a weight control method that employs a space-time adaptive signal processing (STAP) method is attracting attention in an adaptive array antenna. This space-time adaptive signal processing (STAP) system can improve SINR (Signal to Interference plus Noise Ratio), and can form a good beam with a directivity in the arrival direction of unwanted waves close to zero. Has characteristics.

  In the space-time adaptive signal processing (STAP) system, the following processing is performed. First, a target reflected signal is received by a plurality (M) of antennas (element antennas, that is, channels) arranged in an array, and the received signal is converted into a range (distance) cell (range) corresponding to the received pulse width. cell) is stored in the corresponding cell positions of all the processing range cells formed in a predetermined length on the time axis. Then, from the stored data, the covariance matrix is calculated from the data of the range cell excluding the range cell that is assumed to contain the target signal (referred to as the processing applied range cell), that is, the cell that is assumed to be formed only from unnecessary waves. To do. Finally, the beam combining circuit performs weight control on the antenna reception signal with the adaptive weight calculated based on the covariance matrix.

  In weight control in this space-time adaptive signal processing method, weight calculation for each range cell is performed in a weight calculation circuit in order to calculate adaptive weight. For this weight calculation, an MWF (Multistage Wiener Filter) method is known as one method (see Non-Patent Document 1).

However, Appendix A (page 2956, APPENDIX A: A LOW COMPLEXITY BLOCKING MATRIX) of the above-mentioned Non-Patent Document 1 shows the calculation time of the method by eigenvalue decomposition when calculating the null matrix B _n for making the unnecessary wave direction zero. Although a shortening method is described, there is no description regarding performance (SINR characteristics) when the method is applied. Therefore, a method of calculating a null matrix B _n of each stage by conventional eigenvalue decomposition, using the method of shortening the calculation time listed in Appendix A of the non-patent document 1, a null matrix B _n of each processing stage The calculation time and the SINR characteristics were compared for the methods for calculating. As a result, it was confirmed that when the method for reducing the calculation time was used, the calculation time was shortened as compared with the method for calculating the null matrix B _n by normal eigenvalue decomposition, but the performance deteriorated.
IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 44, NO. 7, NOVEMBER 1998 “A Multistage Representation of the Wiener Filter Based on Orthogonal Projections”

  As described above, in the spatio-temporal adaptive signal processing method based on the weight control of the adaptive array antenna used in the conventional radar apparatus, when calculating the weight for making the unnecessary wave direction zero, it takes a relatively long time for the null matrix. There was no effective means for shortening the calculation while suppressing the performance deterioration of the SINR characteristic.

  The present invention has been made in view of the above problems, and in the space-time adaptive signal processing system based on weight control, when calculating a weight for making the unnecessary wave direction zero, calculation of a null matrix that requires a relatively long time is performed. It is an object of the present invention to provide a weight calculation method, a weight calculation device, an adaptive array antenna, and a radar device that can be shortened while suppressing performance degradation of SINR characteristics.

  In order to solve the above-described problem, the weight calculation method according to the present invention provides a target reflected signal of a radar pulse received via an antenna for a plurality of processing range cells having a length corresponding to a predetermined distance on the time axis. The received combined beam is stored in the corresponding cell position according to the reception timing, and the arrival direction of the unwanted wave is zero with respect to the arrival direction of the target reflected signal using the values stored in the plurality of processing range cells. Is a weight calculation method for calculating a weight for the phase and amplitude of the received signal to form the signal, and makes the arrival direction of the unnecessary wave zero with respect to the direction matrix with respect to the arrival direction of the target reflected signal. The method of calculating a weight null matrix for each of the processing stages or in stages within the processing stage is characterized.

  In addition, the weight calculation device according to the present invention provides a target reflected signal of a radar pulse received via an antenna in accordance with a reception timing with respect to a plurality of processing range cells having a length corresponding to a predetermined distance on the time axis. Using the storage means stored in the corresponding cell position and the values stored in the plurality of processing range cells, a reception combined beam is formed so that the arrival direction of the unnecessary wave is zero with respect to the arrival direction of the target reflected signal. Calculating means for calculating a weight for the phase and amplitude of the received signal, and a weight null matrix for making the arrival direction of the unnecessary wave zero with respect to the direction matrix for the arrival direction of the target reflected signal And changing means for changing the calculation method for each processing stage or stepwise within the processing stage.

  An adaptive array antenna according to the present invention is an adaptive array antenna in which a plurality of element antennas are arranged in an array, and the target reflected signal of a radar pulse is received by being directed in an arbitrary direction. At a corresponding cell position along the reception timing for a plurality of processing range cells having a length corresponding to a predetermined distance on the time axis, and using the values stored in the plurality of processing range cells, the target reflected signal A direction matrix for the direction of arrival of the target reflected signal when calculating the weight for the phase and amplitude of the received signal to form a received combined beam so that the direction of arrival of unwanted waves is zero with respect to the direction of arrival of On the other hand, a calculation method of a weight null matrix for making the arrival direction of the unnecessary wave zero becomes processing stage or processing Stage uptake adaptive weights obtained by stepwise change, and forming a received composite beam performs wait control for said target reflected signal by said adaptive weights.

  The radar apparatus according to the present invention includes a plurality of element antennas arranged in an array, receives a target reflection signal of a radar pulse by being directed in an arbitrary direction, and applies the given adaptive weight to the target reflection signal. An adaptive array antenna that performs weight control to form a received combined beam and the target reflected signal are stored in corresponding cell positions according to reception timing for a plurality of processing range cells having a length corresponding to a predetermined distance on the time axis. And using the values stored in the plurality of processing range cells, the phase of the received signal for forming a received combined beam so that the arrival direction of the unwanted wave becomes zero with respect to the arrival direction of the target reflected signal, and When calculating the adaptive weight for the amplitude, the arrival direction of the unnecessary wave is set to zero with respect to the direction matrix for the arrival direction of the target reflected signal. Weight calculation apparatus for generating the adaptive weight by changing the calculation method of the weight null matrix for each processing stage or stepwise in the processing stage, and weight control is performed by the adaptive array antenna And a signal processing device for detecting a target from the target reflection signal.

  That is, in the weight calculation method according to the present invention, a weight null matrix calculation method for setting the arrival direction of the unnecessary wave to zero with respect to the direction matrix with respect to the arrival direction of the target reflected signal is set for each processing stage. In addition, by changing in stages within the processing stage, it is possible to increase the calculation time and to suppress the degradation of SINR.

  As described above, the weight calculation apparatus according to the present invention uses the weight calculation method according to the present invention that can reduce the processing amount, so that the time for weight calculation can be shortened.

  As described above, the adaptive array antenna according to the present invention employs the weight calculation circuit according to the present invention capable of shortening the time for weight calculation, so that a good combined beam can be formed in a short time.

  Since the radar apparatus of the present invention incorporates the adaptive array antenna of the present invention capable of forming a combined beam in a short time as described above, the target can be quickly captured.

  As described above, according to the present invention, in the space-time adaptive signal processing method based on weight control, when calculating the weight for making the unnecessary wave direction zero, the calculation of the null matrix that requires a relatively long time can be performed. It is possible to provide a weight calculation method, a weight calculation device, an adaptive array antenna, and a radar device that can be shortened while suppressing performance deterioration.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, an MWF (Multistage Wiener Filter) method as one method of weight calculation described in Non-Patent Document 1 will be described.

In the MWF system, when the direction matrix in the arrival direction of the received signal X is A, the complex amplitude vector is S, and the thermal noise given by the mean 0 and variance σ ₂ is n, the received signal X is expressed by the following equation (1). It is represented by

X = A · S + n (1)
When a target signal is received by M element antennas #m (m: 1 to M) arranged in an array with an interval dx, the wavelength of the received frequency signal is λ (Λ), and D arrivals A steering vector a (θd) that determines the arrival direction of the target signal d (d: 1 to D) is expressed by the following equation (2).

Further, the direction matrix Aθ for the spatial sequence is expressed by the following equation (3).

Therefore, the steering vector a (fd) that determines the arrival direction of the target signal d is expressed by the following equation (4).

From this, the direction matrix Af for the time series is expressed by the following equation (5).

で表される時空間ステアリングベクトルａ（θd,fd）を用いて、下記（７）式で与えられる。

Therefore, the direction matrix A (θ, f) is expressed by the following equation (6).

Using the spatio-temporal steering vector a (θd, fd) expressed by

Here, in the weight calculation in the MWF, as described in Non-Patent Document 1, a null matrix B _n must be calculated at each stage. Normally, this null matrix B _n is calculated by performing eigenvalue decomposition of the input vector h _n to each stage and using orthogonality of the eigenvectors, but generally requires much calculation time. FIG. 1 shows a processing flow of the weight calculation method in the MWF described in Non-Patent Document 1.

In the processing shown in FIG. 1, forward recursion (backward regression) and backward recursion (backward regression) are performed in a plurality of processing stages. Here, B _i = null (h _i ) indicates a blocking matrix (a null matrix that is all zero when B and h are multiplied). As a method for calculating the null matrix B _n , Non-Patent Document 1 describes that singular value decomposition and QR decomposition may be used, and further, Appendix A describes a method for efficiently calculating by reducing the amount of calculation. By using the method, the calculation time can be greatly reduced as compared with a method of performing normal eigenvalue decomposition. However, as described above, when the method for reducing the calculation time is used, the calculation time is shortened as compared with the method for calculating the null matrix B _n by the normal eigenvalue decomposition, but the performance deteriorates.

As an example, calculates a method for calculating a null matrix B _n of each stage by eigenvalue decomposition, a null matrix B _n of each stage using the method of shortening the calculation time listed in Appendix A of the non-patent document 1 The results of confirming the calculation time and SINR characteristics with the method are shown in FIGS. As can be seen from the figure, when the method for reducing the calculation time is used, the calculation time is shortened as compared with the method for calculating the null matrix B _n by eigenvalue decomposition, but the performance deteriorates.

Therefore, the weight calculation method according to the present invention is described in Appendix A of Non-Patent Document 1, a null matrix calculation method for each processing stage or stepwise with respect to the processing stage. Method, Method by Singular Value Decomposition, Method by QR Decomposition, Method by Effective Inverse Covariance (ECI: Effective Covariance Inverse, eg I-h _n · h _n ^ H, where I is a unit matrix, H is a complex conjugate transpose ) To obtain weights.

As described above, the weight calculation method of the present invention changes the calculation method of the null matrix B _n for each processing stage, or changes the calculation method of the null matrix B _n step by step with respect to the processing stage. It is possible to increase the speed and suppress degradation of SINR.

  As described above, the weight calculation apparatus according to the present invention uses the weight calculation method according to the present invention that can reduce the processing amount, so that the time for weight calculation can be shortened.

  As described above, the adaptive array antenna according to the present invention employs the weight calculation circuit according to the present invention capable of shortening the time for weight calculation, so that a good combined beam can be formed in a short time.

  Since the radar apparatus of the present invention incorporates the adaptive array antenna of the present invention capable of forming a combined beam in a short time as described above, the target can be quickly captured. In particular, when applied to an aperture synthesis radar apparatus, as described above, an adaptive array antenna is incorporated to form a composite beam in a short time, so that the target shape can be quickly grasped.

Here, when the calculation method of the null matrix B _n is changed in stages with respect to the processing stage (M = 8, N = 8, the number of sample data is 64, and the null matrix calculation is performed by eigenvalue decomposition up to n stages. FIG. 4 shows an example of SINR characteristics in the case of using the (n−1) stage and subsequent null matrix calculation as the method described in Appendix A of Non-Patent Document 1. As is apparent from FIG. 4, by applying the present invention, it is possible to suppress degradation of SINR characteristics.

  FIG. 5 is a schematic block diagram of a weight calculation apparatus in space-time adaptive signal processing to which the present invention is applied. In FIG. 5, reference numeral 11 denotes an adaptive array antenna that receives the target reflected signal of the radar pulse by M antenna elements. Each element output of the antenna 11 is received and detected by the receiving unit 12 and prepared in the data storage unit 13. The processing range cell having a length corresponding to the predetermined distance is stored in the corresponding cell position along the reception timing.

  Here, part of the antenna element output is sent to the reference signal estimation unit 14 and used as a reference for the amplitude and phase of the received signal. The excitation unit 16 periodically excites the reference signal estimation unit 14 and the reference signal generation unit 15 to estimate and generate a reference signal for weight calculation of each range cell corresponding to a predetermined distance.

  The accumulated data in the data accumulating unit 13 is sent to the spatiotemporal adaptive signal processing unit 17. The spatio-temporal adaptive signal processing unit 17 calculates a covariance matrix from the data of the range cell excluding the range cell that is assumed to include the target signal, that is, the cell data that is assumed to be formed only from unnecessary waves, in the weight calculation circuit 171. Calculate. Finally, the beam combining circuit 172 performs weight control on the antenna reception signal with the adaptive weight calculated based on the covariance matrix to obtain output data.

In the weight control in the space-time adaptive signal processing system having the above-described configuration, the weight calculation circuit 171 performs weight calculation for each range cell in order to calculate the adaptive weight. Weight calculation method described above in the weight calculation circuit 171, that is, the calculation method of the null matrix B _n for each processing stage, or adopt a method for stepwise changing the calculation method of the null matrix B _n to the processing stage To do. As a result, it is possible to increase the calculation time and suppress the deterioration of SINR.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows the flow of a process of the weight calculation method in MWF described in the nonpatent literature 1. The figure which shows the SINR characteristic of each of the method by the eigenvalue decomposition | disassembly described in the nonpatent literature 1, and the method described in the appendix A. It is a comparison of calculation time between the method based on eigenvalue decomposition described in Non-Patent Document 1 and the method described in Appendix A. As an example of the present invention, the null matrix calculation is performed up to n stages using a method based on eigenvalue decomposition, and the null matrix calculation after the (n−1) stage is set to the method described in Appendix A of Non-Patent Document 1. The figure which shows a SINR characteristic. The block diagram which shows schematic structure of the weight calculation part in the space-time adaptive signal processing which is embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Adaptive array antenna, 12 ... Reception part, 13 ... Data storage part, 14 ... Reference signal estimation part, 15 ... Reference signal generation part, 16 ... Excitation part, 17 ... Space-time adaptive signal processing part, 171 ... Weight calculation circuit 172, a beam synthesis circuit.

Claims (8)

The target reflected signal of the radar pulse received via the antenna is divided in accordance with the reception timing in a plurality of range cells in the memory space, divided in length corresponding to the reception pulse width along the time axis,
Using said plurality of record values stored Njiseru, except range cell that is assumed to contain a target signal, calculates a covariance matrix from range cell data that is assumed to be formed of only the unnecessary wave, the Using the covariance matrix, a null matrix that represents a weight for the phase and amplitude of the received signal for forming a received combined beam so that the arrival direction of the unwanted wave becomes zero with respect to the arrival direction of the target reflected signal A weight calculation method for calculating by dividing into a plurality of processing stages ,
A plurality of methods having different calculation times are prepared as the null matrix calculation method, and the weight calculation method changes the null matrix calculation method for each processing stage or stepwise within the plurality of processing stages. Calculation method. In the null matrix calculation method, the eigenvalue decomposition method , the singular value decomposition method, the QR decomposition method, and the effective inverse covariance method are used to reduce the calculation time of the eigenvalue decomposition method. The weight calculation method according to claim 1, wherein a method is prepared . Storage means for sequentially storing the target reflected signal of the radar pulse received via the antenna along the reception timing in a plurality of range cells in the memory space, which is divided by a length corresponding to the reception pulse width along the time axis;
Using said plurality of record values stored Njiseru, except range cell that is assumed to contain a target signal, calculates a covariance matrix from range cell data that is assumed to be formed of only the unnecessary wave, the Using the covariance matrix, a null matrix that represents a weight for the phase and amplitude of the received signal for forming a received combined beam so that the arrival direction of the unwanted wave becomes zero with respect to the arrival direction of the target reflected signal A calculation means for dividing the calculation into a plurality of processing stages ;
A plurality of methods having different calculation times are prepared as the null matrix calculation method, and changing means for changing the null matrix calculation method step by step within each of the processing stages or within the plurality of processing stages. The weight calculation apparatus characterized by the above-mentioned. The weight calculation apparatus according to claim 3, wherein the calculation unit calculates the null matrix using a reference signal or an estimated reference signal corresponding to the target reflected signal. In the null matrix calculation method, the eigenvalue decomposition method , the singular value decomposition method, the QR decomposition method, and the effective inverse covariance method are used to reduce the calculation time of the eigenvalue decomposition method. The weight calculation apparatus according to claim 3, wherein a method is prepared . An adaptive array antenna in which a plurality of element antennas are arranged in an array, the direction of which is controlled in an arbitrary direction and a target reflected signal of a radar pulse is received,
The target return signal, being divided by the length of the received pulse width corresponds along the time axis, are memorized along the reception timing to a plurality of range cells in the memory space, using the values stored in said plurality of Les Njiseru Then, a covariance matrix is calculated from range cell data that is assumed to be formed only from unwanted waves, excluding the range cell that is assumed to contain the target signal, and the unwanted wave is calculated with respect to the arrival direction of the target reflected signal. When calculating a null matrix representing a weight with respect to the phase and amplitude of the received signal for forming a received combined beam so that the arrival direction becomes zero by dividing into a plurality of processing stages using the covariance matrix, calculation of the prepared plurality of different schemes of calculating time as calculation method of the null matrix, for each of the processing stages, or stepwise the null matrix within said plurality of processing stages Captures the adaptive weights obtained by changing the method, adaptive array antenna and forming the received combined beam performs wait control for said target reflected signal by said adaptive weights. A plurality of element antennas are arranged in an array, and a target reflected signal of a radar pulse is received by being controlled in an arbitrary direction, and a weighted control is performed on the target reflected signal by a given adaptive weight to form a received combined beam. An adaptive array antenna,
The target return signal, being divided by the length of the received pulse width corresponds along the time axis, are memorized along the reception timing to a plurality of range cells in the memory space, using the values stored in said plurality of Les Njiseru Then, a covariance matrix is calculated from range cell data that is assumed to be formed only from unwanted waves, excluding the range cell that is assumed to contain the target signal, and the unwanted wave is calculated with respect to the arrival direction of the target reflected signal. When calculating a null matrix representing an adaptive weight for the phase and amplitude of the received signal to form a received combined beam so that the arrival direction becomes zero using the covariance matrix divided into a plurality of processing stages. , by preparing a plurality of systems having different computation time as a calculation method of the null matrix, for each of the processing stages, or stepwise the null matrix within said plurality of processing stages A weight calculating unit for generating said adaptive weights to change the calculation method,
A radar apparatus, comprising: a signal processing device that detects a target from a target reflection signal that has been subjected to weight control by the adaptive array antenna.   The radar apparatus according to claim 7, wherein the signal processing device detects a target shape.

Images