JP2008157679A - Radar signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar signal processor capable of restraining a clutter and a disturbance, and capable of holding a main probe to obtain high restraint performance. <P>SOLUTION: This radar signal processor is provided with a beam composing circuit 2 for beam-composing signals output from a main antenna 11, a Fourier transformation circuit 3 for Fourier-transforming an output from the beam composing circuit 2 to generate a main channel signal, a restraint auxiliary beam forming circuit 6 for subtracting a signal with an amplitude and a phase of a signal output from the Fourier transformation circuit matched to an amplitude and a phase of an auxiliary channel, from an auxiliary channel signal output from an auxiliary antenna 12, an adaptive processing circuit 4 for conducting adaptive processing by a tapped delay line, using a signal output from the restraint auxiliary beam forming circuit, and a canceling circuit 5 for restraining an unnecessary wave included in the main channel signal by subtracting an adaptive-processed signal from the main channel signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radar signal processing apparatus that performs signal processing in a radar apparatus, and more particularly to a technique for suppressing clutter and interference in space-time (on a frequency-angle axis).

  FIG. 9 is a diagram showing a configuration of a STAP (Space Time Adaptive Processing) processor applied to a conventional radar apparatus. This STAP processor receives input signals X1 to XN (N is a positive integer) sent from an antenna element (not shown) or a sub-array in which a plurality of antenna elements are arranged, as a TDL (Taped Delay Line). ) Is delayed by PRI (Pulse Repetition Interval), and a two-dimensional STAP process is performed on the signal output from each tap of the TDL under the control of the adaptive processing unit 20.

  Details of the TDL type adaptive array and STAP processing are described in Non-Patent Document 4 and Non-Patent Document 5, respectively.

  As a technique related to such a radar signal processing apparatus, Patent Document 1 discloses an adaptive antenna apparatus that is used in a radar apparatus, a wireless communication apparatus, or the like and automatically suppresses an unnecessary signal input to the antenna. ing.

This adaptive antenna apparatus is based on a DBF that performs beam forming after an antenna element signal is converted into a digital signal by an A / D converter, and each antenna element signal converted into a digital signal is given a predetermined weight by a complex weight. And main beam forming means for forming a main beam signal based on the pipeline processing of the first arithmetic cell array for performing addition synthesis of these weighted signals, and a part of the antenna element signal converted into a digital signal or A second arithmetic cell array that performs standardization of the amplitude value with respect to the extracted signal from which all are extracted, and unnecessary wave components included in each extracted signal with the normalized signal and its own cell output as reference signals Each of the third arithmetic cell arrays that perform correlation removal step by step in accordance with the corresponding reference signal. Based on the ipline processing, a preprocessor means for sequentially disposing unnecessary wave components included in the main beam signal from a component having a large amplitude value as a signal having a constant amplitude value, and a component signal decomposed and arranged by the preprocessor means, Based on the pipeline processing of the fourth arithmetic cell array, in which unnecessary wave components included in the formed main beam signal are sequentially correlated in accordance with each corresponding reference signal, using each cell output as a reference signal. And adaptive beam forming means for obtaining an adaptive beam signal.
Japanese Patent Laid-Open No. 02-039705 Nobuyoshi Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publishing (1999) pp. 35-37, 98-99 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. 40-49 Nobuyoshi Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publishing (1999) pp. 17-21 Richard Klemm, “SPACE-TIME ADAPTIVE PROCESSING”, IEE RADAR, SONAR, NAVIGATION AND AVIONICS 9, pp. 110-118 (1998)

  In the conventional radar signal processing apparatus described above, when two-dimensional STAP processing is performed using an input signal transmitted from an antenna element or a sub-array, the main lobe of the main channel (hereinafter abbreviated as “main CH”). May collapse.

  In order to maintain the main lobe during adaptive processing, there is also known a method of attaching a constraint condition (see Non-Patent Document 1). However, when the degree of freedom in the antenna elevation direction and azimuth direction is small, the main lobe is known. There is a problem that lobes are easily disturbed, and that a calculation operation load increases because a constraint operation is required.

  The present invention has been made in order to solve the above-described problems, and it is an object of the present invention to provide a radar signal processing device that can suppress clutter and interference, and can maintain a main lobe and obtain high suppression performance. There is to do.

  In order to solve the above-mentioned problems, the invention described in claim 1 is directed to a beam combining circuit for beam combining signals output from a main antenna having a plurality of antenna elements or subarrays, and Fourier transforming the output of the beam combining circuit. The amplitude of the signal output from the Fourier transform circuit from the Fourier transform circuit that generates the main channel signal and the auxiliary channel signal output from the auxiliary antenna that shares a part or all of the plurality of antenna elements or subarrays A constrained auxiliary beam forming circuit that subtracts a signal whose phase is matched to the amplitude and phase of the auxiliary channel signal, and an adaptive process that performs adaptive processing using a tapped delay line using a signal output from the constrained auxiliary beam forming circuit The main channel signal sent from the processing circuit and Fourier transform circuit , Characterized by comprising a cancel processing circuit for suppressing unnecessary waves included in a main channel signal by subtracting signal adaptive processing has been performed by the adaptive processing circuit.

  According to a second aspect of the present invention, in the first aspect of the present invention, the constrained auxiliary beamforming circuit selects the main channel signal when the auxiliary channel signal that reduces the response level to the main lobe in space-time is selected. Auxiliary channel signal near the phase center is selected.

  The invention according to claim 3 is a beam combining circuit for beam combining signals output from a main antenna having a plurality of antenna elements or sub-arrays, and a main channel signal is generated by Fourier transforming the output of the beam combining circuit. And the amplitude and phase of the signal output from the Fourier transform circuit from the auxiliary channel signal output from the auxiliary antenna formed by sharing a part or all of a plurality of antenna elements or subarrays. The constrained auxiliary beamforming circuit that subtracts the signal in accordance with the amplitude and phase of the signal, and the adaptive weight of the signal output from the constrained auxiliary beamforming circuit are calculated using the recursive method. Adaptive processing with a tapped delay line by limiting the amplitude value An adaptive processing circuit that performs the processing, and a cancellation processing circuit that suppresses unnecessary waves included in the main channel signal by subtracting the signal that has been subjected to the adaptive processing by the adaptive processing circuit from the main channel signal sent from the Fourier transform circuit. It is provided with.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the adaptive processing circuit performs adaptive processing using a tapped delay line using a signal output from the constrained auxiliary beam forming circuit. In this case, when the adaptive weight of the signal is calculated, a limit is applied to the amplitude value of the adaptive weight using a recursive method.

  According to the present invention, it is possible to provide a radar signal processing device that can suppress both clutter and disturbance, can maintain the shape of the main lobe, and can be relatively reduced in circuit scale and computation scale. it can.

  In more detail, according to the first aspect of the present invention, the main channel signal is not changed from the main lobe shape, and the main channel signal can be suppressed from the auxiliary channel signal so that unnecessary waves from the side lobe direction can be suppressed. Since the adaptive processing is performed using a signal obtained by subtracting the amplitude and phase of the channel signal after matching with the auxiliary channel signal, that is, using the auxiliary channel signal having a low response to the main lobe, the main lobe can be easily held.

  According to the second aspect of the present invention, the auxiliary channel signal in the vicinity of the phase center of the main channel signal is selected as the auxiliary channel signal selection method for reducing the response level to the main lobe in time and space. This difference can be reduced, and by forming an auxiliary channel with an expanded range for reducing the response level to the main lobe, the main lobe can be easily held.

  According to the third aspect of the present invention, when calculating the adaptive weight of the auxiliary channel signal, a limit is applied to the amplitude value of the adaptive weight that changes sequentially using a recursive technique (for example, MSN, RLS, etc.). Therefore, the change of the weight value can be suppressed and the main lobe can be held.

  According to the invention described in claim 4, since the invention described in claim 1 or claim 2 is combined with the invention described in claim 3, the above-described claims 1 to 3 are provided. Compared to the described invention, the main lobe can be further retained.

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

  FIG. 1 is a block diagram showing the configuration of the radar signal processing apparatus according to the first embodiment of the present invention. In this radar signal processing device, signals transmitted and received by a plurality of antenna elements constituting the main antenna 11 are beam-synthesized by the beam synthesis circuit 2.

Instead of the plurality of antenna elements, a plurality of subarrays (the subarray is configured by arranging a plurality of antenna elements) can also be used. The signal synthesized by the beam synthesis circuit 2 is Fourier transformed by the Fourier transform circuit 3 to form a beam in space-time. Beam formation in space-time can be expressed as:

here,
X: Input signal (N × M, N: number of auxiliary antennas, M: number of taps)
X = [X1,..., XN, M] ^t
S: Space-time steering vector

        The above is the case of a linear array.

Xout (θb, b): θb, beam output of bank b θb: beam directing direction b: frequency bank number (b = 1 to B)
λ: wavelength dn: position vector of phase center of subarray n (n = 1 to N)
t: transposition The Fourier transform circuit 3 can be configured to perform DFT (Discrete Fourier Transformation) or FFT (Fast Fourier Transform). The B filter bank signals Xinm_1 to Xinm_B decomposed by the Fourier transform circuit 3 are sent to the cancel processing circuit 5 as main CH signals and also sent to the constrained auxiliary beam forming circuit 6.

  Some or all of the plurality of antenna elements or subarrays constituting the main antenna 11 are shared as the auxiliary antenna 12. An auxiliary channel (hereinafter abbreviated as “auxiliary CH”) signal obtained by the auxiliary antenna 12 is sent to the constrained auxiliary beam forming circuit 6.

  The constrained auxiliary beam forming circuit 6 generates a constrained auxiliary beam based on the auxiliary CH signal from the auxiliary antenna 12 and the main CH signal from the Fourier transform circuit 3 and sends the constrained auxiliary beam to the adaptive processing circuit 4. FIG. 3 is a diagram conceptually showing the processing performed by the constrained auxiliary beam forming circuit 6, and FIG. 4 is a diagram for explaining the processing. FIG. 4A shows the amplitude of the auxiliary CH signal on the space-time axis, that is, on the axis of angle (space) and frequency (time) by angle data and frequency data. FIG. 4B shows the amplitude of the main CH signal on the space-time axis, that is, on the three axes of angle (space), frequency (time), and amplitude, as angle data and frequency data. Although not shown, the phase is the same as the amplitude.

  That is, the constrained auxiliary beam forming circuit 6 performs a predetermined calculation W on the main CH signal sent from the Fourier transform circuit 3 as shown in FIG. Is matched with the amplitude and phase of the auxiliary CH signal transmitted from the auxiliary antenna 12 as shown in FIG. That is, the peak values of the angle data and frequency data of the main CH signal are matched with the peak values of the angle data and frequency data of the auxiliary CH signal. Then, by taking these differences by subtraction, a sharp null is formed in the main lobe direction on the spatiotemporal axis as shown in FIG. By performing adaptive processing using the signal output from the constrained auxiliary beam forming circuit 6 as a new auxiliary CH signal Xina, unnecessary waves can be suppressed while maintaining the main lobe shape.

The adaptive processing circuit 4 uses the auxiliary CH signal Xina sent from the constrained auxiliary beam forming circuit 6 to suppress unnecessary waves by adaptive processing using a tapped delay line (hereinafter abbreviated as “TDL”). . In the case of the direct solution (see Non-Patent Document 1), the optimum weight Wopt of adaptive processing performed in the adaptive processing circuit 4 is performed in the SMI (Sampled Matrix Inversion) algorithm calculation unit 41 according to the following equation.

here,
Rxx: Correlation matrix of auxiliary CH signal X
Rxx = Xa · Xat ^*
rxd: correlation vector between auxiliary CH signal Xa and beam output Xout
rxd = Xa · Xout ^*
Rxx ⁻¹ : Inverse matrix of Rxx *: Complex conjugate The optimal weight Wopt calculated in the SMI algorithm calculation unit 41 is set in the calculation cell A inside the adaptive processing circuit 4. As shown in FIG. 2 (a), the computation cell A performs a predetermined computation using the optimum weight Wopt set from the SMI algorithm computation unit 41 and the auxiliary CH signal Xina sent from the TDL tap. The calculation result is sent to the external adder 8 as a signal Yout. The adder 8 adds You of M operation cells A output from each of the N adaptive processing circuits 4 and sends the result Y to the cancel processing circuit 5 as a signal Z.

  In the cancel processing circuit 5, the arithmetic cell B as shown in FIG. 2B is sent from the adaptive processing circuit 4 from the signal Xinm (main CH signal; signals Xinm — 1 to Xinm_B) sent from the Fourier transform circuit 3. The incoming signal Z is subtracted and output as a signal Xout. Therefore, the cancel processing circuit 5 outputs signals Xout_1 to Xout_B for the banks bank1 to bankB in which unnecessary waves included in the main CH signal are suppressed.

  Note that the calculation method of the optimum weight is not limited to the direct solution method. For example, the MSN (Maximum Signal to Noise Ratio) method (see Non-Patent Document 2), the RLS (Recursive Least Square) method (see Non-Patent Document 3), or Gram Other methods such as the Schmitt method (see Patent Document 1) can also be used.

  According to the radar signal processing apparatus according to the first embodiment of the present invention described above, the auxiliary channel can be suppressed so that the main lobe shape of the main CH signal is not changed and unnecessary waves from the side lobe direction in space-time can be suppressed. The main lobe is retained because adaptive processing is performed using the signal obtained by subtracting the amplitude and phase of the main CH signal from the CH signal after matching the auxiliary CH signal, that is, using the auxiliary CH signal having a low response to the main lobe. It becomes easy to do.

  The applicant of the present application is a technique for reducing the response level of the auxiliary CH signal to the main lobe in the previously filed “radar signal processing device” (Japanese Patent Application No. 2006-300240, filed on Nov. 6, 2006). However, this technique subtracts the main CH signal on the space (angle) axis from the auxiliary CH signals or from the auxiliary CH, and in the direction of the null formed on the space (angle) axis. When an unnecessary wave is input from the side lobe region of the frequency axis, the unnecessary wave cannot be suppressed.

  On the other hand, in the radar signal processing road according to the first embodiment, a null is formed in the auxiliary CH on the spatio-temporal axis (both the angle axis and the frequency axis). Therefore, as shown in FIG. Unnecessary waves from all side lobe regions other than the main lobe direction can be suppressed.

  The radar signal processing apparatus according to the second embodiment of the present invention selects an auxiliary CH having a phase center close to the phase center of the main CH when the auxiliary CH is selected in the radar signal processing apparatus according to the first embodiment. It is a thing. The configuration of the radar signal processing device according to the second embodiment is the same as the configuration of the radar signal processing device according to the first embodiment.

  Next, the operation of the radar signal processing apparatus according to the second embodiment will be described with reference to FIGS. FIG. 5 shows a case where the phase center of the auxiliary CH is away from the phase center of the main CH. The inclination of the phase pattern of the auxiliary CH is large, and the phase is also included when subtracting the main CH signal from the auxiliary CH signal. Therefore, it is difficult to form a null of the auxiliary CH over the entire main lobe because the phases are aligned and subtracted only in a certain angular direction.

  On the other hand, FIG. 6 shows a case where the phase center of the auxiliary CH is close to the phase center of the main CH, and the auxiliary CH in which the inclination of the phase pattern is small and null is formed in a wide range of the main lobe can be formed. By using the auxiliary CH and applying the adaptive processing of the first embodiment, the main lobe can be easily held.

  According to the radar signal processing apparatus according to the second embodiment of the present invention described above, the auxiliary CH signal in the vicinity of the phase center of the main CH signal is selected as a method for selecting the auxiliary CH signal that reduces the response level to the main lobe in space and time. Therefore, the difference in the phase pattern can be reduced, and by forming the auxiliary CH with an expanded range for reducing the response level to the main lobe, the main lobe can be easily held.

  The radar signal processing apparatus according to the third embodiment of the present invention uses a recursive technique (MSN, RLS, etc.) to further limit the weight amplitude value when calculating the adaptive CH adaptive weight, The disturbance of the main lobe is suppressed.

  FIG. 7 is a block diagram showing the configuration of the radar signal processing apparatus according to Embodiment 3 of the present invention. This radar signal processing apparatus is configured by changing the adaptive processing circuit 4 of the radar signal processing apparatus according to the first embodiment to an MSN adaptive processing circuit 7. In the MSN adaptive processing circuit 7, the SMI algorithm calculation unit 41 is removed from the adaptive processing circuit 4 according to the first embodiment, and a calculation cell C is provided instead of the calculation cell A. A signal Xout sent from the cancel processing circuit 5 is input to the arithmetic cell C.

  FIG. 8 is a diagram showing a detailed configuration of the arithmetic cell C. As shown in FIG. This calculation cell C performs a predetermined calculation based on the signal Xout sent from the cancel processing circuit 5 and the auxiliary CH signal Xina sent from the TDL tap, thereby weighting the amplitude value with a limit. W is calculated, and the result obtained by multiplying the weight W by the signal Xina is sent to the external adder 8 as a signal Yout. Details of the arithmetic cell C are described in Patent Document 1.

The amplitude limit value for limiting the amplitude value of the adaptive weight may be selected so as not to affect the main lobe during adaptive processing. The weight calculation formula is shown below.

here,
W (i): Wait (i = 0 to ITER)
Xout: Main CH output (Xout_1 to Xout_B)
Xina: Auxiliary CH input (m = 1 to M, n = 1 to N)
g: constant a: constant Xinm: main CH input (Xinm_1 to Xinm_B)
*: Complex conjugate According to the radar signal processing apparatus according to the third embodiment of the present invention described above, the adaptive weight of the auxiliary CH signal is calculated sequentially using a recursive technique (for example, MSN, RLS, etc.). Since the limit is applied to the amplitude value of the changing adaptive weight, the change of the weight value can be suppressed and the main lobe can be held.

  As the weight limit method, for example, when the amplitude value of the adaptive weight exceeds the limit value, a method of fixing the limit value is used. Can be used.

  The radar signal processing apparatus according to the third embodiment has a radar signal according to the first or second embodiment in which the response level of the auxiliary CH signal to the main lobe is reduced so as not to change the shape of the main lobe of the main CH. It can also be configured in combination with a processing device. According to this configuration, the main lobe can be held further than the radar signal processing apparatus according to the first to third embodiments.

  The present invention is applicable to a radar apparatus that requires suppression of both clutter and disturbance.

It is a figure which shows the structure of the radar signal processing apparatus which concerns on Example 1 of this invention. It is a figure which shows the calculation cell used with the radar signal processing apparatus which concerns on Example 1 of this invention. It is a figure which shows notionally the process performed in the constrained auxiliary beam forming circuit in the radar signal processing apparatus according to Embodiment 1 of the present invention. It is a figure for demonstrating the process performed by the restraint auxiliary beam forming circuit in the radar signal processing apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating operation | movement of the radar signal processing apparatus which concerns on Example 2 of this invention. It is a figure for demonstrating operation | movement of the radar signal processing apparatus which concerns on Example 2 of this invention. It is a figure which shows the structure of the radar signal processing apparatus which concerns on Example 3 of this invention. It is a figure which shows the detailed structure of the calculation cell used with the radar signal processing apparatus which concerns on Example 3 of this invention. It is a figure for demonstrating the conventional radar signal processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Main antenna 12 Auxiliary antenna 2 Beam synthesis circuit 3 Fourier transform circuit 4 Adaptive processing circuit 41 SMI algorithm operation part 5 Cancel processing circuit 6 Constrained auxiliary beam forming circuit 7 MSN adaptive processing circuit 8 Adder

Claims (4)

A beam combining circuit that combines signals output from a main antenna having a plurality of antenna elements or sub-arrays;
A Fourier transform circuit for generating a main channel signal by Fourier transforming the output of the beam combining circuit;
From the auxiliary channel signal output from the auxiliary antenna formed by sharing a part or all of the plurality of antenna elements or subarrays, the amplitude and phase of the signal output from the Fourier transform circuit are set to the amplitude of the auxiliary channel signal and A constrained auxiliary beam forming circuit that subtracts a signal in accordance with the phase;
An adaptive processing circuit for performing adaptive processing by a tapped delay line using a signal output from the constrained auxiliary beam forming circuit;
A cancellation processing circuit that suppresses unnecessary waves included in the main channel signal by subtracting a signal that has been subjected to adaptive processing by the adaptive processing circuit from the main channel signal sent from the Fourier transform circuit;
A radar signal processing apparatus comprising:   The constrained auxiliary beam forming circuit selects an auxiliary channel signal in the vicinity of the phase center of the main channel signal when selecting an auxiliary channel signal that reduces a response level to the main lobe in space and time. Item 2. The radar signal processing device according to Item 1. A beam combining circuit that combines signals output from a main antenna having a plurality of antenna elements or sub-arrays;
A Fourier transform circuit for generating a main channel signal by Fourier transforming the output of the beam combining circuit;
From the auxiliary channel signal output from the auxiliary antenna formed by sharing a part or all of the plurality of antenna elements or subarrays, the amplitude and phase of the signal output from the Fourier transform circuit are set to the amplitude of the auxiliary channel signal and A constrained auxiliary beam forming circuit that subtracts a signal in accordance with the phase;
An adaptive processing circuit that performs adaptive processing using a tapped delay line by limiting the amplitude value of the adaptive weight using a recursive method when calculating the adaptive weight of the signal output from the constrained auxiliary beam forming circuit When,
A cancellation processing circuit that suppresses unnecessary waves included in the main channel signal by subtracting a signal that has been subjected to adaptive processing by the adaptive processing circuit from the main channel signal sent from the Fourier transform circuit;
A radar signal processing apparatus comprising:   The adaptive processing circuit uses a recursive method when calculating an adaptive weight of the signal when performing adaptive processing by a tapped delay line using the signal output from the constrained auxiliary beam forming circuit. 3. The radar signal processing apparatus according to claim 1, wherein a limit is applied to the amplitude value of the adaptive weight.

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