JP2611654B2 - Radar signal processor - 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, and more particularly to a radar signal processing device employing a group stagger system.

[0002]

2. Description of the Related Art Conventionally, a signal processing device in a radar apparatus extracts only a target signal from an input video signal composed of various reflected signals. For this extraction, a canceller is used to suppress a fixed clutter signal, which is a first unnecessary signal due to reflection of a fixed object such as a building or the ground, from the input video signal. Further, a moving clutter signal due to reflection of a moving object such as a cloud or rain, which is a second unnecessary signal, is suppressed.

[0003] Each unnecessary signal is separated and suppressed according to the Doppler frequency using a filter, and as a result, only a target signal which is not suppressed is extracted. FIG. 4 shows an example of a circuit configuration of a radar signal processing device provided with four filters for this suppression.

In FIG. 4, an MTI (Moving Target In)
dicator / moving target indicating device) The map generator 1 displays the fixed clutter area MT in the fixed clutter area.
An I-map is generated, and the automatic clutter map generator 2 automatically detects the distribution state of the moving clutter area from the input video signal and generates an automatic clutter map in the moving clutter area. The filter coefficient controller 3b receives the MTI map output from the MTI map generator 1 and the automatic clutter map output from the automatic clutter map generator 2, and inputs the MCI map for the fixed clutter area, the moving clutter area, and the clear area. The filter coefficients are output to four filters 8, 9, 10, 11 via a signal line 18. Further, it outputs to the changeover switch 5 via the signal line 19 as a changeover control signal indicating whether the area is the fixed clutter area or the other area.

The changeover switch 5 inputs a video signal input via the signal line 17 to the erasure unit 6 via the signal line 20 in the case of a fixed clutter area, based on a switching control signal input from the signal line 19, In other areas, the signal is output to the output terminal side of the eraser 6 via the signal line 21.

[0006] To the output terminal of the erasure unit 6, three filters 8, 9, and 10 are connected, and one filter 11 is connected via a switch 7. Switch 7
It opens and closes in conjunction with the changeover switch 5 via the control line 22, and opens in a fixed clutter area and closes in an exceptional area. That is, the erasure unit 6 is also a filter, and the switch 7 always has the same number (four in the example of FIG. 4) of filters in the fixed clutter region and the other region.

[0007] In the fixed clutter region, the input video signal is input to the canceller 6 via the signal line 20, the fixed clutter signal contained therein is suppressed, and input to the three filters 8, 9 and 10.

In other areas, the signals are input to four filters 8, 9, 10, and 11 via a signal line 21. The filters 8, 9, 10, and 11 form filter characteristics for the fixed clutter region, the moving clutter region and the clear region shown in FIG. 5 according to the filter coefficient input via the signal line 18, and form the filter characteristics from the input video signal. The fixed clutter signal remains, and the moving clutter signal and the target signal are separated according to the Doppler frequency. The four clutter suppressors 12, 13, 14, 15 are provided with filters 8, 9, 1,
A clutter signal of an output video signal corresponding to each connection of 0 and 11 is suppressed. The maximum value selector 16 compares the video signals output from each of the four clutter suppressors 12, 13, 14, and 15, selects the maximum value, combines the maximum values, and outputs the resultant as an output video signal.

[0009]

However, in this conventional radar signal processing device, the number of filters is limited in relation to the number of hits of the radar device. Even if the target signal can be separated from the video signal in which the signal exists in accordance with the Doppler frequency, as shown in FIG. 6, the maximum power level of the filter (A) and the power level (B) at the intersection of the two adjacent filters are obtained. There is a problem that the detection rate of the target signal is reduced due to the power level difference (C).

An object of the present invention is to provide a radar signal processing apparatus capable of effectively utilizing a filter whose number is limited in relation to the number of hits and improving the target detection rate.

[0011]

In order to achieve the above object, a radar signal processing apparatus according to the present invention comprises: an MTI map generating means for setting an MTI map in a fixed clutter area;
Automatic clutter map generation means for setting an automatic clutter map in a moving clutter area from an input video signal, and a synchronizer for outputting a trigger pulse for a staggered period, the sampling interval of which is determined at least based on a target Doppler characteristic and the number of hits , An MTI map, an automatic clutter map, and a trigger pulse, and a filter coefficient control means for outputting a predetermined filter coefficient different for each trigger pulse, and a filter based on a predetermined filter coefficient output from the filter coefficient control means. A plurality of filters whose characteristics are set; a plurality of clutter suppressors for performing clutter suppression processing on each output of the plurality of filters; and a maximum for selecting a maximum value among the outputs of the plurality of clutter suppressors. Value selecting means, and the maximum value selecting means has a trigger parameter. Scan the output signal of a different predetermined filter for each, and selects the output signal becomes maximum, it is characterized by combining the output to the radar signal.

[0012]

Therefore, according to the radar signal processing apparatus of the present invention, the filter coefficient control means controls the M of the fixed clutter region.
A TI map, an automatic clutter map of a moving clutter region of an input video signal, and a trigger pulse for a staggered cycle are input, and a filter of a filter is determined based on a predetermined filter coefficient different for each trigger pulse output from the filter coefficient control means. The filter characteristics are set. For example, FIG.
As shown in (A) and (B), the center frequency of the plurality of filter characteristics in one stagger cycle is set to the intersection of the plurality of filter characteristics in the other stagger cycle. It goes without saying that FIG. 2 shows the best case. In this manner, the decrease in detection sensitivity in one stagger cycle can be compensated for in another stagger cycle, and the difference in detection sensitivity can be reduced. Therefore, by selecting a large signal in each stagger cycle, high detection can be achieved. The target signal can be obtained at a rate.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a radar signal processing apparatus according to the present invention. 1 to 3
FIG. 1 shows an embodiment of the radar signal processing apparatus according to the present invention. FIG. 1 is a block diagram of a circuit configuration showing an embodiment, FIG. 2 is a principle invention diagram of a target signal detection system of the present invention, (A) is a filter characteristic diagram of one stagger cycle, and (B) is another stagger cycle. It is a filter characteristic figure of a period.
FIG. 3 is an example of trigger pulse sampling for explaining the operation of the synchronizer included in the radar signal processing device according to the embodiment. FIG. 3A shows a frame trigger, FIG. 3C shows a staggered radar trigger, and FIG. This is a trigger pulse that is switched every stagger cycle.

The radar signal processing apparatus of this embodiment separates an input signal into a target signal and a clutter signal according to the Doppler frequency, and changes the characteristics of the filter at regular intervals.

A radar signal processing device having this function is an MT signal corresponding to a fixed clutter region of an input video signal.
An MTI map generator 1 for generating an I map, an automatic clutter map generator 2 for automatically detecting a moving clutter area from an input video signal and generating an automatic clutter map,
A filter coefficient controller 3a for outputting a filter coefficient, a synchronizer 4 for outputting a trigger pulse for changing a filter coefficient, a changeover switch 5 and a switch 7 for switching a signal line, an erasure unit 6 for eliminating fixed clutter by MTI processing, Filters 8, 9, 10, 1
1. Clutter suppressors 12, 13, 14, 15 for suppressing clutter signals in an input video signal, and selecting and synthesizing the largest signal among the video signals output from these clutter suppressors as an output video signal And a maximum value detector 16 to be output.

The MTI map generator 1 generates an MTI map in the fixed clutter area and outputs the generated MTI map to the filter coefficient controller 3a. Further, the automatic clutter map generator 2 automatically detects a moving clutter area from the input video signal, generates an automatic clutter map, and outputs it to the filter coefficient controller 3a.

The filter coefficient controller 3a identifies a fixed clutter area or another area from the MTI map output from the MTI map generator 1 and the automatic clutter map output from the automatic clutter map generator 2. The control circuit unit outputs the switching signal based on the identification to the changeover switch 5 via the signal line 19. The filter coefficient controller 3a further receives a trigger pulse output from the synchronizer 4 as an input signal, and filters each of a predetermined fixed clutter area, a moving clutter area, and a clear area filter which are different for each sampling of the trigger pulse. Output the coefficient.

FIG. 3 shows an example of sampling of trigger pulses output from the synchronizer 4 and having different pulse intervals.
This is shown in FIG. As described above, the filter characteristics of the filters 8 to 11 are switched and changed based on the sampling of the trigger pulse. The sampling interval of the trigger pulse output from the synchronizer 4 is arbitrary, and the sampling speed is determined based on the Doppler characteristics of the target, the number of hits, and the like.

The filter coefficient controller 3a outputs different filter coefficients to a signal line 18 based on a trigger pulse input from the synchronizer 4. Each filter 8 ~
Reference numeral 11 changes the filter characteristic by the filter coefficient output from the filter coefficient controller 3a, and the changed filter characteristic is held until a new filter coefficient is input.

FIG. 2A shows an example of the characteristics of the filters 8 to 11.
This is shown in (B). Each of the filter characteristics shown in FIGS. 2A and 2B has four filters 8 to 11.
And the four curves 28a, 29
a, 30a, 31a and 28b, 29b, 30b, 3
1b is a filter characteristic of each of the filters 8 to 11.
The two types of filter characteristics (A) and (B) are characteristics set based on a trigger pulse output from the synchronizer 4 and a filter coefficient output from the filter coefficient controller 3a. The two types of filter characteristics (A) and (B) of the present embodiment are set such that peaks / valleys of the characteristics of the output voltage level G with respect to the Doppler frequency f complement each other.

The changeover switches 5 and 7 are switches for changing the processing system based on the type of the clutter area during the processing of the input video signal. In this embodiment,
The switching is changed depending on whether the signal being processed is in the fixed clutter area.

If the information output from the filter coefficient controller 3a via the signal line 19 is in a fixed clutter area, the changeover switch 5 connects the signal lines 17 and 20 to delete the input video. It leads to the vessel 6. The erasure unit 6 eliminates fixed clutter of the input video signal guided to the signal line 20 by the changeover switch 5 by MTI processing. The video signal output from the erasure unit 6 is input to filters 8, 9, and 10.

The switch 7 is connected to the changeover switch 5 and the changeover control line 22. If the information output from the filter coefficient controller 3a via the signal line 19 is in the fixed clutter area, the switch 7 is opened. The video signal output from the eraser 6 is not sent to the filter 11. If the information output from the filter coefficient controller 3a via the signal line 19 is an area other than the fixed clutter area, the changeover switch 5 connects the signal line 17 and the signal line 21 to each other, and Are the filters 8, 9,
It is sent to 10,11.

The filters 8, 9, 10, and 11 receive the filter coefficients controlled by the filter coefficient controller 3a via the signal line 18, and each of the filters for the fixed clutter area, the moving clutter area and the clear area. The filter characteristic is formed, and the target signal, the residual of the fixed clutter signal and the moving clutter signal are frequency-separated from the video signal output from the canceller 6 or the video signal transmitted via the signal line 21.

The clutter suppressors 12 to 15 are circuit units for suppressing clutter signals. The clutter suppressor 12 is a circuit unit that suppresses the clutter signal of the video signal output from the filter 8 and outputs the signal to the maximum selector 16. The other clutter suppressors 13, 14, and 15 are also circuit components similar to the clutter suppressor 12, and suppress the moving clutter signals of the video signals output from the filters 9, 10, 11 and each have a maximum value selector. 16 is output.

The maximum value selector 16 compares the video signals output from the four clutter suppressors 12, 13, 14, and 15, selects a signal having the maximum value, and selects the selected video signal. This is a circuit unit for combining and outputting an output video signal.

Although the above embodiment is a preferred embodiment of the present invention, the present invention is not limited to this embodiment, and various modifications can be made without departing from the gist of the present invention. For example, the type of the filter characteristic to be switched is
The present invention is not limited to the two types in the embodiment, but may be three or more types.

[0028]

As described above, according to the present invention, in the fixed clutter area, the moving clutter area, and the clear area, two types of filters having different characteristics are prepared. Varying the type of filter characteristics over time. With this configuration, using a limited number of filters in relation to the number of hits,
There is an effect that the detection rate of the target signal can be further improved.

[Brief description of the drawings]

FIG. 1 is a circuit configuration block diagram illustrating an embodiment of a radar signal processing device of the present invention.

FIGS. 2A and 2B are diagrams illustrating examples of filter characteristics of the radar signal processing device illustrated in FIG. 1; FIGS.

3A and 3B are diagrams showing an example of a trigger pulse output by a synchronizer included in the radar signal processing device of FIG. 1, wherein FIG. 3A shows a frame trigger, FIG. 3B shows a trigger pulse switched every stagger cycle, and FIG. Is a staggered radar trigger.

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

5A and 5B are diagrams illustrating examples of characteristics of a plurality of filters in a conventional radar signal processing device, wherein FIG. 5A is a filter characteristic diagram in a fixed clutter region, FIG. (c) is a filter characteristic diagram of the clear region.

FIG. 6 is a diagram illustrating an example of a filter characteristic of the radar signal processing device of FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 MTI map generator 2 Automatic clutter map generator 3a Filter coefficient controller 4 Synchronizer 5 Changeover switch 6 Eraser 7 Switch 8, 9, 10, 11 Filter 12, 13, 14, 15 Clutter suppressor 16 Maximum value detector

Claims (2)

(57) [Claims] 1. An MTI map generating means for setting an MTI map in a fixed clutter area, an automatic clutter map generating means for setting an automatic clutter map in a moving clutter area from an input video signal, at least a target Doppler characteristic and a hit count. A synchronizer that outputs a trigger pulse for a staggered cycle, based on which a sampling interval is determined, and the MTI map, the automatic clutter map, and the trigger pulse are input, and a predetermined filter coefficient different for each trigger pulse is input. Filter coefficient control means for outputting, a plurality of filters whose filter characteristics are set based on the predetermined filter coefficient output from the filter coefficient control means, and performing a clutter suppression process on each output of the plurality of filters A plurality of clutter suppressors; Maximum value selecting means for selecting the maximum value among the outputs of several clutter suppressors, wherein the maximum value selecting means inputs an output signal of a predetermined filter different for each trigger pulse, and A radar signal processing apparatus for selecting the output signal and synthesizing a radar signal to be output. 2. The radar according to claim 1, wherein the different predetermined filter coefficients are set such that peaks / valleys of filter characteristics of the filter set by the filter coefficients complement each other. Signal processing device.