JP2006078269A - Radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently suppress both clutter and interference even in an environment with the main lobe clutter having strong intensity or the interference. <P>SOLUTION: The clutter is suppressed by MTI 12, 22 relative to each received signal by a main antenna 11 and an auxiliary antenna 12, and furthermore the clutter is sufficiently suppressed by executing DFT by DFT circuits 13, 23. and then, an SLC operation is executed by using the same filter bank signal to a main CH and an auxiliary CH in SLC circuits 30 to 3M-1. Consequently, clutter components of input signals of the main CH and the auxiliary CH are suppressed sufficiently on a frequency axis by the MTI and the DFT, and the SLC operation is executed after making an interference signal component dominant, to thereby suppress surely even the interference component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radar apparatus equipped with an SLC (Sidelobe Cancellation) that suppresses clutter and interference in a main lobe and interference environment.

  In an SLC mounted in a conventional radar apparatus, the antenna sensitivity in the interference arrival direction is set to 0 (a null point is formed) using a signal from an auxiliary antenna having a gain higher than the side lobe of the main antenna (for example, non-patent) Reference 1). However, in practice, when the SLC is operated when the beam output includes clutter larger than the interference level in the main lobe and the interference environment, the SLC operates to reduce the main lobe clutter, and the interference is Cannot be suppressed.

  As a countermeasure, there is a method of performing an SLC operation after suppressing clutter by MTI (see Non-Patent Document 2). This method uses data between PRI (Pulse Repetition Intervals) of a plurality of pulse hits for each of a main CH (Channel) signal obtained by the main antenna and an auxiliary CH signal obtained by the auxiliary antenna. Then, after suppressing the main lobe clutter by MTI (Moving Target Indicator), the SLC process is performed to suppress the main lobe clutter and the interference in the interference environment.

According to this method, in the case of a clutter having a relatively low intensity, the interference is suppressed by the SLC in the subsequent stage because the clutter is suppressed by the MTI. However, in the case of a clutter with a very strong intensity, there is a problem that the MTI cannot completely suppress the clutter, and as a result, the clutter and the interference cannot be sufficiently suppressed.
IEICE, “Revised Radar Technology”, pp. 295-296 Alfonso Farina, “Antenna-Based Signal Processing Techniques for Radar Systems”, Artech House, pp. 170-176 (1992) Nobuyoshi Kikuma, "Adaptive signal processing by array antenna", Science and Technology Publishing (1999), pp. 67-86 Nobuyoshi Kikuma, "Adaptive signal processing by array antenna", Science and Technology Publishing (1999), pp. 35-37, 98-99 Patent registration number P1816548: Adaptive antenna device

  As described above, in the conventional SLC-equipped radar apparatus, even if the main lobe clutter is suppressed by the SLC after suppressing the main lobe clutter by the MTI, if the strong main lobe clutter exists, the MTI suppresses the interference. As a result, there was a problem that neither clutter nor interference could be sufficiently suppressed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radar apparatus that can sufficiently suppress both clutter and disturbance even in a strong main lobe clutter or interference environment.

  In order to solve the above problems, the present invention is configured as follows.

  (1) MTI processing means for removing clutter of the main channel signal output from the main antenna and the auxiliary antenna signal output from the auxiliary antenna by MTI (Moving Target Indicator) processing, and after the MTI processing Filter bank processing means for suppressing clutter in a plurality of filter banks by DFT (Discrete Fourier Transform) processing or FFT (Fast Fourier Transform) processing for each of the main channel signal and auxiliary channel signal of SLC processing means for suppressing interference signals by performing SLC (Sidelobe Cancellation) of the main channel signal and auxiliary channel signal in a set of processing results for each filter bank.

  In the radar apparatus having the configuration of (1), DFT is performed after MTI on the input signals of the main CH and auxiliary CH, and after the clutter is sufficiently suppressed, the same filter bank signal for the main CH and auxiliary CH is used. , SLC operation is performed. Therefore, the clutter components of the input signals of the main CH and auxiliary CH are sufficiently suppressed on the frequency axis by MTI and DFT, and the SLC operation is performed with the disturbing signal components dominant, so that the disturbing components are also reliably suppressed. be able to.

  (2) For each of the main channel signal output from the main antenna and the auxiliary antenna signal output from the auxiliary antenna, a plurality of signals are obtained by DFT (Discrete Fourier Transform) processing or FFT (Fast Fourier Transform) processing. Filter bank processing means for suppressing clutter in the filter bank, and SLC (Sidelobe Cancellation) processing of the main channel signal and auxiliary channel signal with the set of processing results for each filter bank to suppress interference signals SLC processing means, and the filter bank processing means gives a null to the clutter in the side lobe shape of the filter bank.

  In the radar device having the configuration of (2), instead of the post-MTI DFT processing of (1), the side lobe shape of the filter bank is made to have a null with respect to the clutter, and the clutter is sufficiently suppressed. Since the SLC operation is performed with the disturbing signal component dominant, the disturbing component can be reliably suppressed.

  According to the present invention, it is possible to provide a radar apparatus that can sufficiently suppress both clutter and interference even in a strong main lobe clutter or interference environment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of an SLC-mounted radar apparatus according to the first embodiment of the present invention. In FIG. 1, 11 and 21 are a main antenna and an auxiliary antenna, respectively, using a phased array. The main CH signal Xb and the auxiliary CH signal Xa output from the antennas 11 and 21 have their clutter components suppressed by the MTIs 12 and 22, respectively. The Outputs Xbmti and Xamti of the MTIs 12 and 22 are converted from time domain into M frequency domain signals Xbf0 to XbfM-1 and Xaf0 to XafM-1 by DFT (Discrete Fourier Transform) circuits 13 and 23, respectively. The frequency domain signals on the main CH side and the auxiliary CH side are input to SLC processing circuits 30 to 3M-1 prepared for each same area.

  Each of the SLC circuits 30 to 3M-1 includes a delay circuit A1, amplifiers A2 and A3, a narrowband filter including an adder A4, and a weighting circuit including multipliers A5 and A6 and a subtractor A7. The interference signal input from the side lobe direction of the main antenna 11 is canceled by the interference signal input to the auxiliary antenna 21, thereby suppressing the interference signal for each frequency band by an angular filter. The outputs b1 to bM of the SLC circuits 30 to 3M-1 are extracted as beam outputs for each frequency band.

  In the above configuration, the processing operation of the first embodiment will be described below with reference to FIG.

  The N-pulse received signal from the main antenna 11 shown in FIG. 2A is subjected to MTI processing for each of the L PRI range cells, as shown in FIG. 2B.

Using the post-MTI signal, the DFT shown in FIG.

Of course, this DFT processing may be FFT (Fast Fourier Transform).

  Using the above signals, the SLC process shown in FIG. SLC cancels the interference signal input from the side lobe direction of the main antenna with the interference signal input to the auxiliary antenna. Thereby, the interference signal can be suppressed by the filter in the angular direction.

  FIG. 3 shows an outline of the above processing. That is, as shown in FIG. 3A, it is assumed that strong interference is given and residual clutter is generated even by the MTI process. In this embodiment, as shown in FIG. 3B, DFT processing is performed together with MTI to suppress clutter on the frequency axis, and further, on the spatial axis (angle axis) by SLC as shown in FIG. 3C. ) To form an antenna pattern null and suppress interference.

  As described above, in the radar apparatus according to the first embodiment, the DFT is performed after the MTI on the input signals of the main CH and the auxiliary CH, and after the clutter is sufficiently suppressed, the same filter for the main CH and the auxiliary CH is used. The SLC operation is performed using the bank signal. Therefore, the clutter components of the input signals of the main CH and auxiliary CH are sufficiently suppressed on the frequency axis by MTI and DFT, and the SLC operation is performed with the disturbing signal components dominant, so that the disturbing components are also reliably suppressed. be able to.

  In the present embodiment, the case where the auxiliary antenna is 1CH has been described. However, when the number of disturbances is plural, the auxiliary antenna may be plural CH and the auxiliary antenna to SLC systems may be arranged in parallel. A system in the case of a plurality of auxiliary CHs is shown in FIG. In this case, the outputs of the SLC systems B11, B12,..., B1m of the auxiliary CH are added by the adder B2, and subtracted from the main CH signal by the subtractor B3, thereby forming nulls corresponding to the number of disturbances. Can do. FIG. 4 shows the case of the multi-loop MSN method (see Non-Patent Document 3), but the Gram Schmidt method (see Patent Document 1) and the direct solution method (see Non-Patent Document 4) that are cascade-connected, etc. It goes without saying that this method is acceptable.

(Second Embodiment)
FIG. 5 is a block diagram showing a configuration of a radar apparatus according to the second embodiment of the present invention. 5, the same parts as those in FIG. 1 are denoted by the same reference numerals, and different parts will be described here.

  As is clear from comparison of FIG. 5 with FIG. 1, in this embodiment, MTI processing is not performed, and clutter is suppressed for the main CH signal of the main antenna 11 and the retained CH signal of the auxiliary antenna 21. The DFT is performed by the DFT circuits 13 and 23 using the coefficients to suppress the clutter sufficiently, and then the SLC operation is performed using the same filter bank signal for the main CH and the auxiliary CH in the SLC circuits 30 to 3M-1. To implement.

  That is, the clutter component of the input signal of the main CH and auxiliary CH is suppressed by DFT having low sensitivity in the clutter direction on the frequency axis, and the SLC operation is performed after the interference signal component is dominant, so the interference component is also suppressed. be able to.

  This is to suppress the clutter sufficiently by making the side lobe shape of the filter bank of the DFT processing have a null with respect to the clutter instead of the post-MTI DFT processing of the first embodiment.

  Generally, it is formulated when the amplitude level is constrained (the main lobe on the frequency axis is a constant value and the clutter range is null). First, the constraint condition is as follows.

The recurrence formula of the complex weight of the DFT when the constraint condition is added using this becomes the following formula.

  DFT is performed using this weight.

The following processing is the same as in the first embodiment.

(Third embodiment)
Next, a radar apparatus according to a third embodiment of the present invention will be described.

  In this embodiment, in order to further suppress the clutter included in the auxiliary CH in the configuration of the first embodiment, the level of the clutter direction of the antenna pattern of the auxiliary CH is lowered, and the MTI and SLC of the signal are reduced. Each process is performed. As described above, in the auxiliary antenna 21, the clutter component of the input signal of the auxiliary CH is suppressed on the spatial axis by the antenna pattern of the auxiliary CH, and then the MTI and SLC processing of the first embodiment is performed. As a result, the clutter component of the auxiliary CH can be further reduced, and the influence of the clutter during the SLC operation can be further reduced. For this reason, both clutter and interference components can be suppressed.

  As described above, in order to sufficiently suppress clutter, a method for reducing the level of clutter in the antenna pattern of the auxiliary antenna will be described in detail below.

  The constraint condition in this case is a constraint on the angle axis and can be expressed by the following equation.

The recurrence formula of the complex weight when the constraint condition is added using this is as follows.

Using this weight, an auxiliary beam is formed by the following equation.

The process of the first embodiment may be performed using this auxiliary beam and the same main beam Xb as in the first embodiment.

(Fourth embodiment)
Next, a radar apparatus according to a fourth embodiment of the present invention will be described.

  In this embodiment, in order to further suppress the clutter included in the auxiliary CH in the configuration of the second embodiment, the level in the clutter direction of the antenna pattern of the auxiliary CH is reduced, and the second means is applied to the signal. Is to implement. As described above, in the auxiliary antenna 21, the clutter component of the input signal of the auxiliary CH is suppressed on the spatial axis by the antenna pattern of the auxiliary CH, and then the DFT and SLC processing of the second embodiment is performed. As a result, the clutter component of the auxiliary CH can be further reduced, and the influence of the clutter during the SLC operation can be further reduced. For this reason, both clutter and interference components can be suppressed.

(Modification)
In the third and fourth embodiments, the pattern of the auxiliary antenna is formulated by a general formula with a constraint condition, but it goes without saying that it can be applied even when there is no constraint condition. Of course, the auxiliary antenna includes a method of suppressing clutter by a simple method using a difference beam of two elements.

  Further, the present invention is not limited to the above-described embodiments as they are, 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.

1 is a block diagram showing a configuration of an SLC-mounted radar device according to a first embodiment of the present invention. FIG. 4 is a timing waveform diagram for explaining a processing operation of the radar apparatus shown in FIG. 1. FIG. 3 is a schematic waveform diagram for supplementarily explaining the processing content of FIG. 2. FIG. 3 is a block diagram showing a system configuration when there are a plurality of auxiliary CHs in the first embodiment. The block diagram which shows the structure of the radar apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Main antenna, 21 ... Auxiliary antenna, 12, 22 ... MTI, 13, 23 ... DFT circuit, 30-3M-1 ... SLC processing circuit, A1 ... Delay circuit, A2, A3 ... Amplifier, A4 ... Adder, A5 , A6... Multiplier, A7.

Claims (4)

MTI processing means for removing clutter from the main channel signal output from the main antenna and the auxiliary antenna signal output from the auxiliary antenna by MTI (Moving Target Indicator) processing,
Filter bank processing for suppressing clutter by a plurality of filter banks by DFT (Discrete Fourier Transform) processing or FFT (Fast Fourier Transform) processing for each of the main channel signal and auxiliary channel signal after the MTI processing Means,
SLC processing means for suppressing interference signals by applying SLC (Sidelobe Cancellation) processing of the main channel signal and auxiliary channel signal based on a set of processing results for each filter bank. Radar device. Each of the main channel signal output from the main antenna and the auxiliary antenna signal output from the auxiliary antenna is processed by a plurality of filter banks by DFT (Discrete Fourier Transform) processing or FFT (Fast Fourier Transform) processing. Filter bank processing means for suppressing clutter;
SLC processing means for suppressing interference signals by performing SLC (Sidelobe Cancellation) processing of the main channel signal and auxiliary channel signal in a set of processing results for each filter bank;
A radar apparatus characterized in that the filter bank processing means gives a null to the clutter of the side lobe shape of the filter bank.   2. The radar apparatus according to claim 1, further comprising: lowering a level of an antenna pattern in a clutter direction of the auxiliary channel signal and subjecting the signal to MTI and SLC processing.   2. The radar apparatus according to claim 1, further comprising: reducing a level of an antenna pattern in a clutter direction with respect to the auxiliary channel signal, and subjecting the signal to DFT and SLC processing.

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