JP4986284B2 - 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 calculation method, and an adaptive array employing the weight calculation device. The present invention relates to an antenna 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 at the adaptive array antenna, and the received combined beam is made 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. Therefore, it is required to perform weight control.

  Therefore, a weight control method that employs a space-time adaptive signal processing (STAP) method is attracting attention in an adaptive array antenna. This spatio-temporal adaptive signal processing (STAP) system can improve SINR (Signal to Interference plus Noise Ratio), and can perform good beam formation with directivity in the arrival direction of unnecessary 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 antennas (element antennas, that is, channels) arranged in a plurality (M) of arrays, 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 so as to be continuous with 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 using 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. A multistage Wiener Filter (MWF) method is known as one method for this weight calculation (see Non-Patent Document 1).

However, although Non-Patent Document 1 describes a weight calculation method for setting the direction of unnecessary waves to zero, in order to derive the optimum weight by reducing the analysis stages in order according to the order of the matrix, the calculation is performed. It was necessary to speed up.
IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 44, NO. 7, NOVEMBER 1998 “A Multistage Representation of the Wiener Filter Based on Orthogonal Projections” IEEE Proceedings of the 2000 Antenna Applications Symposium, Sep. 20-22, 2000 “Efficient Architectures for Implementing Adaptive Algorithms”

  As described above, in the spatio-temporal adaptive signal processing method using adaptive array antenna weight control used in conventional radar equipment, a calculation amount corresponding to the matrix order is required when calculating the weight to make the unnecessary wave direction zero. Met.

  The present invention has been made in view of the above problems, and in the spatio-temporal adaptive signal processing method based on weight control, when calculating weights to make the unnecessary wave direction zero, the amount of calculation is greatly increased while maintaining substantial accuracy. An object of the present invention is to provide a weight calculation method that can be reduced to a minimum, and to provide a weight calculation device, an adaptive array antenna, and a radar device that employ this weight calculation method.

  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. A weight calculation method for calculating weights for the phase and amplitude of the received signal in a plurality of processing stages in a stepwise manner to form any one of the plurality of processing stages in the process of calculating the weights The jump number is determined on the basis of an allowable loss value obtained in advance with respect to the jump stage number of the processing stage. It is characterized in.

  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 weights for the phase and amplitude of the received signal in stages at a plurality of processing stages, wherein the calculating means is an arbitrary one of the plurality of processing stages in the process of calculating the weights. The number of stages to be skipped is determined based on the allowable loss value obtained in advance with respect to the number of stages to skip the processing stage. And wherein the Rukoto.

  The adaptive array antenna according to the present invention forms a received combined beam in an arbitrary direction by arranging a plurality of element antennas in an array and controlling the phase of each of the plurality of antenna elements based on an adaptive weight. An adaptive array antenna that receives a target reflected signal of a radar pulse by the received combined beam, wherein the adaptive weight is configured to send the target reflected signal to a plurality of processing range cells having a length corresponding to a predetermined distance on a time axis. On the other hand, it is stored in the corresponding cell position according to the reception timing, and using the values stored in the plurality of processing range cells, reception synthesis is performed so that the arrival direction of the unnecessary wave becomes zero with respect to the arrival direction of the target reflected signal. Weights for the phase and amplitude of the received signal for forming a beam are calculated in stages at a plurality of processing stages, In the process of calculating the weight, the weight is calculated by executing skipping of any stage among the plurality of processing stages, and the number of skipped stages is an allowable loss calculated in advance with respect to the number of skipped stages of the processing stage. It is determined based on a value.

  The radar apparatus according to the present invention forms a reception combined beam in an arbitrary direction by arranging a plurality of element antennas in an array and controlling the phase of each of the plurality of antenna elements based on an adaptive weight, An adaptive array antenna that receives a target reflected signal of a radar pulse by the received composite beam, and the target reflected signal corresponding to a plurality of processing range cells having a length corresponding to a predetermined distance on the time axis in accordance with the reception timing The reception for forming a reception composite beam that is stored in a cell position and uses the values stored in the plurality of processing range cells so that an arrival direction of an unnecessary wave becomes zero with respect to an arrival direction of the target reflected signal Weight calculation for generating adaptive weights by calculating weights for signal phase and amplitude in stages at multiple processing stages And a signal processing device for detecting a target from the target reflected signal received by the adaptive array antenna, wherein the weight calculation device is configured to select any of the plurality of processing stages in the process of calculating the weight. Stage skipping is executed, and the number of skipped stages is determined based on an allowable loss value obtained in advance with respect to the number of skipped stages of the processing stage.

  That is, in the weight calculation method according to the present invention, the calculation time is calculated by skipping a plurality of processing stages in the weight calculation method for making the arrival direction of the unwanted wave zero with respect to the arrival direction of the target reflected signal. Can be speeded up.

  As described above, the weight calculation apparatus according to the present invention uses the weight calculation method capable of reducing the processing amount, so that the time for weight calculation can be reduced.

  As described above, the adaptive array antenna according to the present invention employs the weight calculation circuit 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 an adaptive array antenna 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 spatio-temporal adaptive signal processing method based on weight control, the calculation amount is greatly reduced while maintaining substantial accuracy when calculating the weight to make the unnecessary wave direction zero. A weight calculation method, a weight calculation device, an adaptive array antenna, and a radar device can be provided.

  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 of the arrival direction of the received signal X is A, the complex amplitude vector is S, the average is 0, and the thermal noise given by the variance σ ² is n, the received signal X is expressed by the following equation (1): It is represented by

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).

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

The weight calculation in the MWF is described in Non-Patent Document 1. Table 1 and FIG. 1 show a processing flow and a processing configuration of the weight calculation method in the MWF described in Non-Patent Document 1.

  That is, Table 1 shows the processing contents of forward regression and backward regression in weight calculation, and FIG. 1 shows a conventional configuration when the processing contents shown in Table 1 are executed in a plurality of processing stages. Is shown. As shown in FIG. 1, conventionally, the calculation is performed in order one by one. For this reason, the matrix order of the blocking matrix B is reduced only one dimension at a time for one stage. Therefore, a large amount of calculation is required as a whole.

  In contrast, FIG. 2 shows an example of a processing configuration when the present invention is applied. In the processing configuration shown in FIG. 2, the weight calculation is performed by skipping one processing stage. Compared with the conventional method shown in FIG. 1, the number of stages to be calculated is reduced from five to three, and it is clear that the calculation time can be increased.

  Here, when M = 8, N = 8, and the number of sample data 64, the relationship between the number of stages to be skipped (deleted) and the SINR characteristic when calculating the blocking matrix B is shown in FIG. As can be seen from FIG. 3, if the number of rows to be deleted (the number of stages to jump) L is about 4 (that is, a 3-stage jump), SINR characteristics substantially equivalent to those of the conventional method are obtained.

Furthermore, according to Non-Patent Document 2, the following equation (8) related to the blocking matrix B

Is O (N _TOTAL ² K) times (N _total is the order of the matrix, where M × N, K is the number of sample data). Therefore, in the calculation specifications M = 8, N = 8, and the number of sample data 64, the total calculation amount of the equation (8) related to the blocking matrix B according to the conventional method for five stages shown in FIG.
4096 + 4032 + 3968 + 3904 + 3840 = 19840 times
It becomes. On the other hand, according to the configuration of the present invention shown in FIG.
4096 +3968 +3840 = 11904 times
Thus, the calculation amount is about 0.6 times, and it can be seen that the calculation amount can be greatly reduced even when one stage is skipped by the present invention.

  Note that the number and order of the jumping stages are not limited to the example shown here, and can be arbitrarily set. However, specifically, the number of stages to jump is determined as shown in FIG.

  In FIG. 4, when the device scale is first determined from the required space and the number of time channels (step S1), the relationship between the number of stages jumping over and the SINR characteristic is obtained by simulation, and the loss for the number of stages jumping over from this SINR characteristic is calculated. Confirm (step S2). Subsequently, the number of stages that jumps is determined from the allowable value α [dB] of loss (step S3), and a circuit corresponding to the number of stages that jumps is mounted on the actual machine (step S4).

  Therefore, according to the weight calculation method of the present invention, since the weight is determined by skipping a plurality of processing stages, the calculation time can be increased.

  FIG. 5 is a block diagram showing an embodiment of a weight calculation apparatus according to the present invention. In FIG. 5, reference numeral 11 denotes a CPU (arithmetic processing unit), which is connected to a program storage ROM 13, a data input / output interface (I / O) 14, and a temporary data storage RAM 15 through a bus 12. The ROM 13 stores an MWF weight calculation program based on the method of calculating the weight by skipping the number of processing stages according to the present invention. When the processing start is instructed, the CPU 11 loads the program from the ROM 13 and inputs / outputs data. Data is acquired via the interface 14 and temporarily stored in the RAM 15. The data is appropriately read from the RAM 15, and the MWF weight calculation processing based on the method of calculating the weight by skipping the number of processing stages according to the present invention is obtained. The weight calculation result is output from the interface 14.

  Since the weight calculation apparatus of the present invention having the above configuration uses the weight calculation method according to the present invention that can reduce the processing amount, the time for weight calculation can be shortened. Therefore, this weight calculation device is employed in an adaptive array antenna to calculate weights for input / output of individual antenna elements. According to this, since the time for calculating the weight is shortened, it is possible to form a good synthesized beam in a short time.

  Incidentally, adaptive array antennas are employed in radar devices such as a synthetic aperture radar device for capturing a target. Therefore, since the combined beam can be formed in a short time by employing the weight calculation device of the present invention for the adaptive array antenna as described above, the radar device using this antenna has a target. It becomes possible to capture more quickly. In particular, when applied to an aperture synthesis radar apparatus, a synthetic beam is formed in an adaptive array antenna in a short time as described above, so that the target shape can be quickly grasped.

  As an example of the radar apparatus, FIG. 6 shows a schematic block configuration diagram of a radar apparatus in which a weight calculation apparatus in space-time adaptive signal processing to which the present invention is applied is incorporated. In FIG. 6, reference numeral 21 denotes an adaptive array antenna that receives a target reflected signal of a radar pulse with M antenna elements. Each element output of the antenna 21 is received and detected by the receiving unit 22 and sent to the data storage unit 23. In the data storage unit 23, a storage area corresponding to a processing range cell having a length corresponding to a predetermined distance is prepared in advance, and input data is sequentially stored in a storage area at a corresponding cell position according to the reception timing.

  Here, a part of the antenna element output is sent to the reference signal estimation unit 24 and used as a reference for the amplitude and phase of the received signal. The excitation unit 26 periodically excites the reference signal estimation unit 24 and the reference signal generation unit 25 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 accumulation unit 23 is sent to the spatiotemporal adaptive signal processing unit 27. The spatio-temporal adaptive signal processing unit 27 uses the weight calculation circuit 271 to generate a covariance matrix from data of a range cell excluding a range cell that is assumed to include a target signal, that is, a cell that is assumed to be formed only from unnecessary waves. Calculate. Finally, the beam combining circuit 272 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 spatio-temporal adaptive signal processing system having the above configuration, the weight calculation circuit 271 performs weight calculation for each range cell in order to calculate the adaptive weight. This weight calculation circuit 271 employs the weight calculation method described above, that is, a method of calculating weights by skipping a plurality of processing stages. As a result, the calculation time can be increased.

  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 components 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 block diagram which shows the conventional structure in the case of performing the processing content shown in Table 1 in a some processing stage. The block diagram which shows the structure in the case of performing in the process stage which applied this invention to the processing content shown in Table 1. FIG. The characteristic view which shows the SINR characteristic with respect to the reduced number of rows at the time of using the weight calculation method which concerns on this invention. The flowchart which shows the process sequence for determining the number of interleaving stages in this invention. The block diagram which shows one Embodiment of the weight calculation apparatus which concerns on this invention. The schematic block block diagram of the radar apparatus in which the weight calculation apparatus in the space-time adaptive signal processing to which this invention was applied was incorporated.

Explanation of symbols

  11 ... CPU, 12 ... bus, 13 ... ROM for program storage, 14 ... data input / output interface, 15 ... RAM for temporary storage of data, 21 ... adaptive array antenna, 22 ... receiver, 23 ... data storage, 24 ... reference Signal estimation unit 25. Reference signal generation unit 26. Excitation unit 27 27 Spatio-temporal adaptive signal processing unit 271 Weight calculation circuit 272 Beam synthesis circuit

Claims (6)

A target reflected signal of a radar pulse received via an antenna is stored in a corresponding cell position along 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 values stored in the plurality of processing range cells, with respect to 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 weights in stages in a plurality of processing stages,
The weight is calculated based on the covariance matrix by calculating a covariance matrix from data of cells assumed to be formed only from unnecessary waves by a multistage Wiener Filter (MWF) method. Adaptation weights,
In the process of calculating the weight, a jump related to a specific variable used in the covariance matrix among the plurality of processing stages is executed.
The relationship between the number of stages to jump and the SINR (Signal to Interference plus Noise Ratio) characteristic is obtained in advance based on the equipment scale determined from the required space and the number of time channels. A weight calculation method comprising: obtaining and determining the number of stages that jumps from the allowable value of loss . Storage means for storing a target reflected signal of a radar pulse received via an antenna at a corresponding cell position along a reception timing with respect to a plurality of processing range cells having a length corresponding to a predetermined distance on a time axis;
Using the values stored in the plurality of processing range cells, with respect to 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 Calculating means for calculating weights in stages in a plurality of processing stages;
The calculation means calculates a covariance matrix from data of cells assumed to be formed only from unnecessary waves by the multistage Wiener Filter (MWF) method as the weight, and this covariance An adaptive weight is calculated based on a matrix, and in the process of calculating the weight, a jump related to a specific variable used in the covariance matrix among the plurality of processing stages is executed in advance. Based on the equipment scale determined from the required space and the number of time channels, the relationship between the number of stages to jump and SINR (Signal to Interference plus Noise Ratio) characteristics is obtained, and the loss for the number of stages to jump from this relationship is obtained, weight calculator instrumentation, characterized in that to determine the number of stages jump from the allowable value of the loss .   The weight calculation apparatus according to claim 2, wherein the calculation means calculates the weight using a reference signal or an estimated reference signal corresponding to the target reflection signal. A plurality of element antennas are arranged in an array, and a received combined beam is formed in an arbitrary direction by controlling the phase of each of the plurality of antenna elements based on an adaptive weight, and a target reflection of a radar pulse is generated by the received combined beam. An adaptive array antenna for receiving signals,
A storage means for said target reflected signal is stored in a corresponding cell location along the reception timing for a plurality of processing range cells having a length of a predetermined distance corresponding on the time axis,
Using the values stored in the plurality of processing range cells, with respect to 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 Calculating means for calculating weights in stages in a plurality of processing stages;
The calculation means calculates a covariance matrix from data of cells assumed to be formed only from unnecessary waves by the multistage Wiener Filter (MWF) method as the weight, and this covariance It is assumed that the adaptive weight is calculated based on a matrix, and in the process of calculating the weight, a jump related to a specific variable used for the covariance matrix among the plurality of processing stages is executed in advance. Based on the equipment size determined from the required space and the number of time channels, the relationship between the number of stages to jump and the SINR (Signal to Interference plus Noise Ratio) characteristics is obtained, and the loss for the number of stages to jump is obtained from this relationship. , Ada, characterized in that to determine the number of stages jump based on the allowable value of the loss Restorative array antenna. A plurality of element antennas are arranged in an array, and a received combined beam is formed in an arbitrary direction by controlling the phase of each of the plurality of antenna elements based on an adaptive weight, and a target reflection of a radar pulse is generated by the received combined beam. An adaptive array antenna for receiving signals;
The target reflected signal is stored in 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 values stored in the plurality of processing range cells are used. Weighting with respect to the phase and amplitude of the received signal for forming a received combined beam so that the direction of arrival of unwanted waves is zero with respect to the direction of arrival of the target reflected signal in a plurality of processing stages. A weight calculation device for generating the adaptive weight in
A signal processing device for detecting a target from a target reflected signal received by the adaptive array antenna,
The weight calculation device calculates a covariance matrix from the data of a cell that is assumed to be formed only from unnecessary waves, using the multistage Wiener Filter (MWF) method as the weight. The adaptive weight is calculated based on a variance matrix, and in the process of calculating the weight, a jump related to a specific variable used in the covariance matrix among the plurality of processing stages is executed. The relationship between the number of stages to jump and the SINR (Signal to Interference plus Noise Ratio) characteristic is obtained in advance based on the equipment scale determined from the required space and the number of time channels. determined, and characterized by determining the number of stages jump based on the allowable value of the loss That the radar device. The radar apparatus according to claim 5 , wherein the signal processing device detects a target shape.

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