JP3006815B2 - Radar signal processing equipment - Google Patents

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 device used in a radar device for scanning a radar coverage area by mechanically rotating a radar antenna, and more particularly to a method for detecting a target signal.

[0002]

2. Description of the Related Art As is well known, in a radar signal processing apparatus, a fixed clutter signal is eliminated from an input video signal using an erasure device, and an input is made using a plurality of filters configured as a filter bank. Representative from video signal, such as target signal and fixed clutter signal remaining undisturbed and rain clouds
The moving clutter signal as a weather clutter is separated according to the Doppler frequency to extract the target signal.
For example, a radar signal processing device with four filters
It is configured as shown in FIG.

In FIG. 4, the radar signal processing apparatus basically includes an MTI map generator 1 for setting a fixed clutter area, an automatic clutter map generator 2 for automatically setting a moving clutter area, and a filter bank. filter
The fixed clutter area, the moving clutter area and the
Filter coefficient controller 3b for sequentially controlling for a clear area that does not include a clutter , a changeover switch 5, and a fixed clutter.
And erasing device 6 that pressure, the switch 7, the filter bank structure
And four moving filters,
And the target signal is transmitted as it is 12-
15 clutter suppressors and a maximum value selector 16 are provided.

[0004] The MTI map generator 1 generates an MTI map indicating the distribution state of a manually set fixed clutter area corresponding to the fixed clutter area. The automatic clutter map generator 2 automatically detects a distribution state of a moving clutter area from an input video signal and generates a moving clutter map.

The filter coefficient controller 3b receives the MTI map output from the MTI map generator 1 and the moving clutter map output from the automatic clutter map generator 2, and receives a fixed clutter area, a moving clutter area, and a clear area. Filter coefficients are sequentially formed and output to four filters 8 to 11 via a signal line 22.
These filters are for fixed clutter area and moving clutter
In addition to forming the filtering characteristics for the area and the clear area, an area designating signal for distinguishing between the "fixed clutter area" and the "other area" is formed and transmitted via the signal line 4. And outputs it to the changeover switch 5 as a changeover control signal.

The changeover switch 5 receives the video signal input through the signal line 18 from the eraser 6 via the signal line 19 from one of the switching output terminals when the area designation signal indicates "fixed clutter area". When the "other area" is indicated, the signal is sent from the other switching output terminal to the output terminal side of the erasure unit 6 via the signal line 20 bypassing the erasure unit 6.

[0007] At the output terminal of the erasure unit 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
Opens and closes in conjunction with the changeover switch 5, and opens when the area designation signal indicates "fixed clutter area";
Close to indicate "other areas". That is, since the canceller 6 is also a filter, the switch 7 is set so that the same number (four in the example of FIG. 4) of filters always exist in the “fixed clutter area” and the “other area”. It is.

In the "fixed clutter area", an input video signal is input to the canceller 6 from the signal line 19, and the fixed clutter signal contained therein is erased, as shown in FIG.
Filter coefficients controlled for fixed clutter region 8
The signals are input in parallel to three filters 10 to 10, which include the remaining signal of the fixed clutter. After this,
The filters 8 to 10 are moving clutter areas shown in FIG.
A filter section is sequentially used for the clear area shown in FIG.
The number is controlled.

In the "other area", since the switch 7 is closed, the input video signal is inputted in parallel to the four filters 8 to 11 from the signal line 20, which includes the moving clutter signal. It is.

In the case of “other area” , 4 of 8 to 11
In the number of filters, the filter coefficients are sequentially controlled in accordance with the filter coefficients input via the signal line 22 so that the filtering characteristics for the fixed clutter area, for the moving clutter area, and for the clear area (area where no clutter exists) are respectively obtained. The fixed clutter signal remains in the input video signal, and the moving clutter signal and the target signal are separated according to the Doppler frequency. In FIG. 5,
_fr is the transmission repetition frequency. FIG. 5 (a),
In the filtering characteristics of each filter shown in (b) and (c)
Each center frequency is transmitted repeatedly from zero Doppler (0)
_Are set to be different from each other within the frequency range ( _fr ).
In the fixed clutter region shown in FIG.
In (b) and (c) of Fig. 5, each is set so that it is divided into four equal parts.
Is determined. However, this setting is generally used for operational purposes, etc.
Can be arbitrarily set together with the filtering characteristics including the bandwidth.
You.

The four clutter suppressors 12 to 15 are 8
, A clutter signal of a video signal output by the corresponding one of the four filters
Suppress the remaining of the fixed clutter signal and target
The signal is output as it is. The maximum value selector 16 compares the magnitude relation between the outputs of the four clutter suppressors for each range bin, and selects and outputs the output video signal of the clutter suppressor having the maximum value as a target signal.

[0012]

As described above, in a radar signal processing apparatus, a target signal, a residual of a fixed clutter signal and a moving clutter signal are separated from an input video signal by using a plurality of filters in accordance with a Doppler frequency. The signal is extracted, but the detection sensitivity of the target signal depends on the filtering characteristics of the filter, gives a maximum value at the center frequency, and temporarily decreases toward the intersection of the filtering characteristics of the two adjacent filters.

That is, the radar signal processing apparatus to which the present invention is applied is a radar signal processing apparatus used in a radar apparatus which scans a radar coverage area by mechanically rotating a radar antenna. Is limited by the relationship with the number of hits of the radar device, the center frequencies of the filtering characteristics of the two adjacent filters are spaced apart to some extent.

Therefore, even if the target signal can be separated in accordance with the Doppler frequency from the video signal in which the target signal, the fixed clutter signal remains and the moving clutter signal exists, for example, as shown in FIG. The power level difference (C) between the maximum power level at the peak point (A) and the power level (A) at the intersection of the filtering characteristics of the filters on both sides affects the detection rate of the target signal. When the size is large, there is a problem that the detection rate of the target signal decreases.

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

[0016]

In order to achieve the above object, a radar signal processing apparatus according to the present invention has the following configuration. That is, the radar signal processing device of the present invention uses a radar.
Fixed clutter area set for the input video signal to be obtained
MTI map that expresses the area and expresses the moving clutter area
Filter banks based on automatic clutter maps
Control the clutter and output the target signal.
In Da signal processing apparatus, fixed from the input video signal
An eraser for eliminating clutter; said input video signal
Luo target signal, the rest and movement clutter signal disappears fixed clutter signal and a plurality of filters for separating according to Doppler frequency is the center frequency in the filtering characteristics
Doppler upper limit corresponding to zero Doppler and transmission repetition frequency
Are set differently from each other and are predetermined for the fixed clutter area, the moving clutter area, and the clear area.
A plurality of filters and which is controlled by the sequence; the double
Moving and fixed clutter including the output of several filters
Output signal and suppress target
A plurality of clutter suppressors corresponding to the plurality of filters
When; 2 circuit is provided a circuit including a; plurality of filters for the corresponding region in the two circuits, the center frequency respectively are set shifted from each other; together, the greater the output of the two circuits as a target signal A selection circuit;

[0017]

Next, the operation of the radar signal processing apparatus of the present invention having the above-mentioned structure will be described. In the radar signal processing apparatus of the present invention, two circuits including a plurality of filters for separating the target signal, the remaining unremoved fixed clutter signal and the moving clutter signal from the input video signal in accordance with the Doppler frequency are provided. In the moving clutter area and the clear area, two types of filters are prepared, and the respective filters have different filtering characteristics with different center frequencies.

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 of the filtering characteristics of a plurality of filters in the other circuit. It is to be. It goes without saying that FIG. 1 shows the best case.

With this arrangement, the lowering of the detection sensitivity in one circuit can be compensated for in the other circuit, and the difference in amplitude can be reduced. Therefore, the larger one of the maximum values selected in each circuit is used as the target signal. , A 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 one embodiment of the present invention. In the present invention, in the one shown in FIG.
No.1 circuit 2 from changeover switch 5 to maximum value selector 16
3, a similar configuration is provided in parallel as a No. 2 circuit 24, and a small function is added to the filter coefficient controller 3a. An area designation signal is commonly supplied from the signal line 4 to both circuits. Is different between the two circuits, and is applied to the No. 2 circuit 24 via the signal line 25. A maximum value selector 17 for selecting one output of the maximum value selector 16 in both circuits is provided as an output circuit. Less than,
The description will focus on the parts according to the present invention.

The filter coefficient controller 3a forms a filter coefficient and an area designation signal in the same manner as in the prior art, but in the present invention, the filter coefficient is equal to four filters of the No. 1 circuit 23 and N
o. The No. 1 circuit 23 and the four filters of the No. 1 circuit 23 are arranged so that the center frequencies of the filtering characteristics are shifted from each other.
No. 2 circuit 24 and two types are formed.

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, the fixed clutter region, the moving clutter The filtering characteristics in the region and the clear region are as shown in FIG. 3, and the intersection (valley) of the filtering characteristics of one of the adjacent circuits.
Corresponds to the maximum point (peak) of the filtering characteristic of the other circuit,
The output sensitivities complement each other, and the difference in the amplitude of the input video captured between the corresponding filters can be reduced.
Note that the setting of the center frequency of the filtering characteristics of the No. 1 circuit shown in FIG.
The setting is the same as in the case of FIG. 5 described above.

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

[0024]

As described above, in the radar signal processing device of the present invention, a target signal, a target signal,
Two circuits including a plurality of filters for separating the remaining of the fixed 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 area, the moving clutter area, and the clear area, Since each filter has different filtering characteristics with different center frequencies and the one with the larger output of both circuits is selected, the detection rate of the target signal can be reduced 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 the drawings]

FIG. 1 is a diagram for explaining the principle of a target signal detection system according to the present invention, in which FIG.
(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 one embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between 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 diagrams showing filtering characteristics of a plurality of filters in a conventional radar signal processing device, wherein FIG. 5A is a diagram showing filtering characteristics in a fixed clutter region, and FIG. 5B is a diagram showing filtering characteristics in a moving clutter region. ,
(C) is a filtering characteristic diagram of a clear region.

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

[Explanation of symbols]

 Reference Signs List 1 MTI map generator 2 Automatic clutter map generator 3a Filter coefficient controller 5 Changeover switch 6 Eliminator 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (2)

(57) [Claims] 1. An input video signal acquired by a radar.
MTI map representing a fixed clutter area to be set
An automatic clutter map representing the moving clutter area
Control the filter bank to suppress clutter
In a radar signal processor that outputs a get signal,
Canceller to erase fixed clutter from serial input video signal
And a plurality of filters for separating a target signal, a residual clutter signal, and a moving clutter signal from the input video signal according to a Doppler frequency, wherein a center frequency in a filtering characteristic thereof is zero Doppler and a transmission repetition frequency.
Shall be different from the Doppler upper limit corresponding to the wave number.
Set for fixed clutter area, for moving clutter area,
Respectively for the clear area and a plurality of filters which are controlled in a predetermined sequence; including the outputs of the plurality of filters
Suppress the disappearance of moving clutter and fixed clutter
For the plurality of filters that output the target signal.
2 circuit is provided a circuit including a; and a plurality of clutter suppressor that respond more filters for the corresponding region in the two circuits, the center frequency respectively are set shifted from each other; together, the outputs of the two circuits A circuit for selecting a larger one as a target signal. 2. A method according to claim 1, wherein a plurality of files in said two circuits are provided.
The filter is set so that the center frequency of each filtering characteristic of the plurality of filters in one circuit is the intersection of the filtering characteristics of the plurality of filters in the other circuit; 2. The radar signal processing device according to claim 1.