JPH07159523A - Radar signal processor - Google Patents

Abstract

PURPOSE:To enhance the detection rate of target signals with a limited number of filters by preparing two kinds of filters in a fixed clutter area, a moving clutter area and a clearing area, and providing the filters with slow-wave characteristics with different center frequencies. CONSTITUTION:No.1 and No.2 circuits 23, 24 having the same arrangement from a changeover switch 5 to a maximum value selector 16 are arranged parallel to each other. A filter factor controller 3a. provides two different kinds of filter factors so that the four filters 8 to 11 of each of the circuits 23, 25 have slow-wave characteristics with center frequencies deviating from one another. Therefore, the slow wave characteristics compensate for one another in a fixed clutter area, a moving clutter area and a clearing area, and the amplitude difference between video inputs captured can be reduced between the corresponding filters. Therefore, target signals can be detected at a high detection rate by selecting using a maximum value selector the greater of the outputs of a maximum value detector 16 for both circuits 23, 24 at every range bin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar signal processing apparatus used in a radar apparatus for mechanically rotating a radar antenna to scan a radar coverage area, and more particularly to a target signal detection method.

[0002]

As is well known, in a radar signal processing device, a canceller is used to cancel a fixed clutter signal from an input video signal, and a plurality of filters are used to remove a target signal and a fixed clutter signal from the input video signal. The remaining and moving clutter signals are separated according to the Doppler frequency to extract the target signal. For example, a radar signal processing device including four filters is configured as shown in FIG.

In FIG. 4, this radar signal processing device basically comprises an MTI map generator 1, an automatic clutter map generator 2, a filter coefficient controller 3b, a changeover switch 5, and an eraser 6. Switch 7 and 4 of 8-11
The number of filters, four clutter suppressors 12 to 15, and the maximum value selector 16 are provided.

The MTI map generator 1 generates an MTI map showing a manually set fixed clutter region distribution state in the fixed clutter region. Automatic clutter map generator 2
Automatically detects the distribution of moving clutter areas from an input video signal and generates a clutter map.

The filter coefficient controller 3b receives the MTI map output from the MTI map generator 1 and the clutter map output from the automatic clutter map generator 2, and receives the fixed clutter region, the moving clutter region, and the clear region. And output them to the four filters 8 to 11 through the signal line 22 and form the area designation signal for distinguishing the "fixed clutter area" from the "other area". It is output as a changeover control signal to the changeover switch 5 via the signal line 4.

The change-over switch 5 receives the video signal input via the signal line 18 from the one change-over output end via the signal line 19 when the area designation signal indicates the "fixed clutter area". To the output terminal side of the eraser 6 via the signal line 20 that bypasses the eraser 6 when the "other area" is indicated.

At the output terminal of the eraser 6, three filters 8 to 10 are directly connected in parallel, and the remaining one filter 11 is connected via a switch 7. Switch 7
Is opened and closed in conjunction with the changeover switch 5, and is opened when the area designation signal indicates "fixed clutter area",
It is closed to indicate "other areas". That is, since the eraser 6 is also a filter, the switch 7 is configured so that there are always the same number of filters (4 in the example of FIG. 4) in the “fixed clutter area” and the “other area”. Is there.

In the "fixed clutter region", the input video signal is input from the signal line 19 to the eliminator 6, the fixed clutter signal contained therein is erased, and is input to the three filters 8 to 10 in parallel. Contains the remaining clutter signal.

In the "other region", switch 7 is closed so that the input video signal is input in parallel to the four filters from signal line 20 to 8-11, which includes the moving clutter signal. Be done.

In the four filters 8 to 11, the filtering characteristics for the fixed clutter area, the moving clutter area, and the clear area (area where no clutter exists) are obtained according to the filter coefficient input through the signal line 22. Each is formed (FIG. 5), the fixed clutter signal remains from the input video signal, and the moving clutter signal and the target signal are separated according to the Doppler frequency. In FIG. 5, f _r
Is the transmission repetition frequency.

The four clutter suppressors 12 to 15 are 8
The clutter signal of the video signal output by the corresponding one of the four filters of 11 to 11 is suppressed. Maximum value selector 16
Compares the magnitude relationship between the outputs of the four clutter suppressors for each range bin, and selectively outputs the output video signal of the clutter suppressor showing the maximum value as the target signal.

[0012]

As described above, in the radar signal processing device, the target signal, the remaining unfixed clutter signal and the moving clutter signal are separated from the input video signal according to the Doppler frequency by using a plurality of filters. The signal is extracted, but the detection sensitivity of the target signal depends on the filter characteristic of the filter, and gives a maximum value at the center frequency, and temporarily decreases toward the intersection of the filter characteristics of both adjacent filters.

That is, the radar signal processing device to which the present invention is applied is a radar signal processing device used in a radar device for mechanically rotating a radar antenna to scan a radar coverage area. Since the number of the filters of (1) is limited by the relationship with the number of hits of the radar device, the center frequencies of the filtering characteristics of the filters adjacent to each other are spaced apart to some extent.

Therefore, even if the target signal can be separated according to the Doppler frequency from the video signal in which the target signal, the remaining unfixed clutter signal, and the moving clutter signal exist, for example, as shown in FIG. The power level difference (c) between the maximum power level at the peak point of (a) and the power level at the intersection of the filtering characteristics of the filters on both sides (b) affects the detection rate of the target signal. When the size becomes large, there is a problem that the detection rate of the target signal is lowered.

An object of the present invention is to provide a radar signal processing device capable of improving the detection rate of a target signal with a limited number of filters.

[0016]

In order to achieve the above object, the radar signal processing device of the present invention has the following configuration. That is, the radar signal processing apparatus according to the present invention is a plurality of filters for separating the target signal, the remaining unfixed clutter signal and the moving clutter signal from the input video signal according to the Doppler frequency, and the filtering characteristics thereof are fixed clutter. A plurality of filters controlled respectively for the region, the moving clutter region, and the clear region; a plurality of clutter suppressors for performing clutter suppression processing on the outputs of the plurality of filters; and outputs of the plurality of clutter suppressors A maximum value selector that selects the maximum value of the two, and two circuits are provided; and the center frequencies of the plurality of filters in one circuit and the plurality of filters in the other circuit are set to be different from each other. And the larger one of the outputs of the maximum value selectors in each circuit is selected as the target signal. It is characterized in that provided; road.

[0017]

Next, the operation of the radar signal processing apparatus of the present invention constructed as described above will be described. In the radar signal processing device of the present invention, two circuits including a plurality of filters for separating the target signal, the remaining unfixed clutter signal and the moving clutter signal from the input video signal according to the Doppler frequency are provided, that is, the fixed clutter region. , Two types of filters are prepared in the moving clutter region and the clear region, and the filtering characteristics of the filters are different from each other in the center frequency.

For example, as shown in FIGS. 1 (a) and 1 (b), the center frequency of each filtering characteristic of a plurality of filters in one circuit is the intersection point of the filtering characteristics of a plurality of filters in the other circuit. So that It goes without saying that FIG. 1 shows the best case.

In this way, the decrease in detection sensitivity in one circuit can be compensated for in the other circuit, and the difference in amplitude can be reduced, so that the larger one of the maximum values selected in each circuit is the target signal. When selected as, the target signal can be obtained with a high detection rate.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a radar signal processing device according to an embodiment of the present invention. In the present invention, in the one shown in FIG.
No. 1 circuit 2 from the changeover switch 5 to the maximum value selector 16
No. 2 circuit 24 having the same configuration is arranged in parallel, and some function is added to the filter coefficient controller 3a so that the area designating signal is given from the signal line 4 to both circuits in common. Is different in both circuits and is given to the No. 2 circuit 24 through the signal line 25. A maximum value selector 17 that selects one output of the maximum value selector 16 in both circuits is provided as an output circuit. Less than,
The part relating to the present invention will be mainly described.

The filter coefficient controller 3a forms the filter coefficient and the area designating signal as in the conventional case, but in the present invention, the filter coefficient is the four filters of the No. 1 circuit 23 and N.
o.2 The circuit for the No. 1 circuit 23 is arranged so that the four filters of the circuit 24 are arranged so that the center frequencies of the filtering characteristics are shifted from each other.
Two types are formed, one for the No. 2 circuit 24.

If the filtering characteristics of the four filters of the No. 1 circuit 23 and the four filters of the No. 2 circuit 24 are set as shown in FIG. 1, for example, a fixed clutter area and a moving clutter are provided. The filtering characteristics in the area and the clear area are as shown in FIG. 3 and are complementary to each other, and the amplitude difference of the input video captured between the corresponding filters can be reduced.

Therefore, if the maximum value selector 17 selects the larger output of the maximum value detectors 16 in both circuits for each range bin, the target signal can be obtained with a high detection rate.

[0024]

As described above, in the radar signal processing device of the present invention, the target signal from the input video signal,
Two circuits including a plurality of filters for separating the remaining clutter signal and the moving clutter signal according to the Doppler frequency are provided, that is, two types of filters are prepared in the fixed clutter region, the moving clutter region, and the clear region, The filter characteristics of each circuit have different center frequencies, and the one with the larger output of both circuits is selected.Therefore, the detection rate of the target signal is detected by using a limited number of filters in relation to the number of hits. There is an effect that can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of a target signal detection method of the present invention, in which (a) is a filter characteristic diagram of a filter of one circuit,
(B) is a filter characteristic diagram of the filter of the other circuit.

FIG. 2 is a configuration block diagram of a radar signal processing device according to an embodiment of the present invention.

FIG. 3 is a relationship diagram of the filtering characteristics of the No. 1 circuit and the No. 2 circuit.

FIG. 4 is a configuration block diagram of a conventional radar signal processing device.

5A and 5B are filtering characteristic diagrams of a plurality of filters in a conventional radar signal processing device, FIG. 5A is a filtering characteristic diagram of a fixed clutter region, and FIG. 5B is a filtering characteristic diagram of a moving clutter region. ,
(C) is a filtering characteristic diagram of a clear area.

FIG. 6 is an explanatory diagram of a target signal detection operation by a plurality of filters in a conventional radar signal processing device.

[Explanation of symbols]

 1 MTI map generator 2 automatic clutter map generator 3a filter coefficient controller 5 selector switch 6 eraser 7 switch 8 filter 9 filter 10 filter 11 filter 12 clutter suppressor 13 clutter suppressor 14 clutter suppressor 15 clutter suppressor 16 maximum Value selector 17 Maximum value selector 23 No.1 circuit 24 No.2 circuit

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[Procedure amendment]

[Submission date] July 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

In order to achieve the above object, the radar signal processing device of the present invention has the following configuration. That is, the radar signal processing apparatus according to the present invention is a plurality of filters for separating the target signal, the remaining unfixed clutter signal and the moving clutter signal from the input video signal according to the Doppler frequency, and the filtering characteristics thereof are fixed clutter. Two circuits including a plurality of filters controlled respectively for the area, the moving clutter area, and the clear area ;
K; multiple filters for corresponding areas in the two circuits.
The center frequency is set so that the center frequencies are shifted from each other; and a circuit that selects a larger one of the outputs of the circuits as a target signal is provided.

Claims (1)

[Claims] 1. A plurality of filters for separating a target signal, an unerased fixed clutter signal, and a moving clutter signal from an input video signal according to a Doppler frequency, the filtering characteristics of which are for a fixed clutter region and a moving clutter region. A plurality of filters that are respectively controlled for a clear area and a clear region; a plurality of clutter suppressors that perform clutter suppression processing on the outputs of the plurality of filters; and a maximum value of the outputs of the plurality of clutter suppressors. A maximum value selector for selecting; and two circuits provided with; the plurality of filters in one circuit and the plurality of filters in the other circuit are set such that their center frequencies are shifted from each other; A circuit that selects a larger one of the outputs of the maximum value selector in the circuit as a target signal; Radar signal processing device.