JPH02195285A - Suppressing device for clutter - Google Patents

Abstract

PURPOSE:To increase the stability of a filter by providing an arithmetic unit computing a clutter Doppler frequency in a radar-received signal and a memory having stored a lattice filter coefficient and an average gain thereof. CONSTITUTION:First a clutter mapping mode is set so that a coefficient selector 5 may select a cutoff frequency band width directly by an operation of an operator. The operator sets manually an optimum cutoff frequency band width for each clutter at each position. Next, this optimum cutoff frequency band width is set manually. After a spectral shape (the cutoff frequency band width) is set in a clutter map, a selector 8 selects an output of the clutter map and a clutter map set value is outputted for each clutter. Next, an average gain of a filter shape is calculated and stored in memories 4a, 4b and 4c beforehand, together with a coefficient, and a gain controller 6 conducts gain regulation by using said average gain.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing device for suppressing clutter contained in radar received signals.

[Conventional technology]

Conventionally, as a signal processing device for suppressing clutter contained in a radar reception signal, for example, the IEKE International Conference on Acoustic Signal Processing (IEEE Inter-nationa)
l Conference on Acousies
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and Signal Processing) 1
986 Edition Proceedings Lecture No. 55.22 H, Watan
“Trade-off study of adaptive filtering algorithms used in adaptive moving target designation devices” by Abe et al.
rade 0ffStudies on Adapti
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sed For Adaptive Moving T
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FIG. 5 is a block diagram of a clutter suppression device using a conventional lattice filter. In fig.

(1aX1b) (1c) is I PRT (Pu1se
RepetitionTime = pulse repetition time)
A method for delaying input data by (15
m) (13b) (15c) are lattice filter coefficient calculation units that adaptively calculate the coefficients of a lattice filter that has a gain valley at the clutter center frequency according to the input signal; (2a) (2b) (2c) 4 with a suppressing lattice filter. FIG. 6 is a block diagram of the lattice filter.

The conventional clutter suppression device is configured as described above, and attempts to suppress shiclutter by estimating the power spectrum of clutter contained in the received radar signal and automatically configuring the inverse filter. . The operations of the conventional device can be expressed numerically as shown in equations (1) to (4).

f: (k) = f knee' (k) - A: (k) g name shi (k) (11X: conjugate complex fn (k) ” gn (k) = The symbols in the above formula for the radar received signal after A/D conversion correspond to the same symbols in FIG.

Since the conventional clutter suppression device operates according to equations (1) to (4), for example, as shown in FIG.
For clutter with a small spectrum spread, use a filter with a narrow cutoff bandwidth at a cutoff center frequency f1, and as shown in Figure 8, for clutter with a large spectrum spread at a center frequency f2, use a filter with a cutoff center frequency f2. Adaptively form a wide bandwidth filter.

[Problem to be solved by the invention]

The conventional clutter suppression device as described above attempts to respond faithfully to the clutter power spectrum in the input signal. However, the spectral shape of clutter, which is a reflected wave from natural phenomena, has slight variations when looking at each sample data. There was a problem in that it was not possible to form a filter.

Furthermore, the low stability of the filter characteristics also had a negative effect on the detection of the target signal.

The present invention was made to solve these problems, and it is an object of the present invention to form a stable filter while retaining the advantage of the conventional device that clutter can be suppressed regardless of the Doppler center frequency of the clutter. It is an object.

[Means to solve the problem]

The clutter suppression device according to the present invention includes an arithmetic unit that calculates the Doppler center frequency of clutter, and uses the output of this arithmetic unit as an input address. A lattice filter and a mesori that stores the coefficients of the lattice filter, a clutter map that stores the clutter position and spectrum spread bt, are provided.

[Effect]

In the present invention, patterned filter shapes are stored in a memory in advance, and a cutoff center frequency corresponding to the clutter Doppler center frequency calculated from input data is selected from the filter shapes. Further, the cutoff frequency bandwidth is selected from the memory corresponding to the spread of the clutter spectrum stored in the clutter map.

The clutter map stores the clutter spectrum spread and its position set by the operator during the clutter mapping mode. A lattice filter realizes the filter shape selected as described above and performs clutter suppression.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.
1aX1bX2aX2bX2c) is completely the same as the above conventional device. (3) is a clutter center frequency calculation unit which receives two successive radar reception signals as input. (4aX4bX4c) are memories storing coefficients having filter shapes having the same cutoff frequency bandwidth and different cutoff center frequencies. For example, in (4a), coefficients for realizing a patterned filter shape as shown in FIG. 3 are stored.

Focusing on a certain clutter center frequency (input address), a filter shape shown in FIG. 4 is stored in (4aX4bX4c). (5) is a coefficient selector that selects the cutoff frequency bandwidth based on the clutter map output or operator operation. (6) is a gain controller for final gain adjustment of this device.

(7) is a memory that stores the clutter position and its spectrum shape, and C8) is a selector that outputs the value set by the operator in the clutter mapping mode, and the value stored in the clutter map in other modes. .

FIG. 2 is a detailed block diagram of the clutter center frequency calculation section (3). In FIG. 2, (9) is a conjugate complex signal converter, a(I is a multiplier, and a is a moving adder.

A3 is a phase difference detection circuit for determining the phase tracking Doppler frequency of the input 1 channel and Q channel.

In the clutter suppression device configured as described above,
First, the clutter center frequency calculation section (3) is calculated using the following equation (5).
Find the clutter center frequency.

clutter center frequency Im(·): represents the imaginary part (Q channel).

Re(.): represents the real part (I channel).

Next, using the clutter center frequency as an input address, the memories (4a), (4b), and (4c) output coefficients having a filter shape that has been pre-multiplied. The coefficient selector (5) selects the coefficient according to the value set in the clutter map or the value set by the operator.

Select one of the above coefficients and apply a suppression filter with an arbitrary cutoff frequency bandwidth to the above lattice filter (2a) (
2b) (2c) is formed.

The spectral shape is stored in the clutter map using the following method. First, the clutter mapping mode is set so that the coefficient selector (5) directly selects the cutoff frequency bandwidth by the operator's operation.

The operator manually sets the optimal cutoff frequency bandwidth for each clutter at each location. Next, this optimal set value is stored in the clutter map (7). After the spectral shape (cutoff frequency bandwidth) is set in the clutter map, the selector (8) selects the output of the clutter map, and a clutter map setting value is output for each clutter.

Next, the average gain of the filter shape is calculated in advance and stored in the memory (4aX4bX4c) together with the coefficients, and the gain controller (6) adjusts the gain using this average gain.

〔Effect of the invention〕

The present invention is constructed in accordance with one or more of the above descriptions and has the advantages described below.

Since the cutoff center frequency is determined according to the input signal and the cutoff frequency bandwidth is determined by the clutter map, it is possible to improve the stability of the filter while retaining the advantage of conventional devices that clutter suppression is possible regardless of the clutter Doppler frequency. becomes.

Furthermore, since a circuit for calculating the average gain of the filter is not required, the H/W can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. Fig. 2 is a detailed block diagram of the center frequency calculation section in Fig. 1, Figs. 3 and 4 are diagrams showing the contents of the memory in Fig. 1, and Fig. 5 shows a conventional clutter suppression device. FIG. 6 is a detailed block diagram of the lattice filter section in FIG. 5, and FIGS. T and A are diagrams showing the operation of the conventional device. In the figure, (1a), (1b, and 1c) are delay memories of 1PRT, (2m), (2b, and 2c) are lattice filters, (3) is center frequency calculation unit, (4aX4bX4
c) is a memory for storing the filter shape, +51 is a coefficient selector, and (6) is a gain controller. (7) is a clutter map, and (8) is a cutoff frequency setting selector. a3 is the I channel and Q channel phase difference detection circuit. (13a) (13bX13c) are lattice filter coefficient calculation units. Note that in FIG. 1, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] An arithmetic unit that calculates the Kuratsuta Doppler frequency in the radar received signal, a memory that stores Latisse filter coefficients with multiple types of cutoff center frequencies and cutoff frequency bandwidths, and their average gains, a Kuratsuta map that stores the location and spectrum spread of Kuratsuta, What is claimed is: 1. A clutter suppressing device comprising: a lattice filter that forms a clutter suppression filter; and a gain controller that adjusts the gain of the output of the lattice filter.