JPS58129375A - Clutter suppression apparatus - Google Patents

Abstract

PURPOSE:To enable automatic switching of a clutter suppression means by evaluating a clutter area while identifying fixed clutters and moving clutters. CONSTITUTION:A signal having a Doppler frequency zero or close to zero is extracted with a zero Doppler filter 10 and a fixed clutter is detected with a clutter detector A11 from the output signal thereof. A fixed clutter and a moving clutter are detected with a clutter detector B12 from a normal video. A video switch control 9 evaluates an area without clutter, an area of a fixed clutter and an area of a moving clutter on an output signal of a clutter detector A11 and a clutter detector B12 and generates a control signal to operate a video switch 7. Thus, a video is automatically outputted according to various clutters.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a moving clutter suppression device used in a pulse radar device for displaying moving targets.

Generally, in monitoring pulse radar equipment that displays moving targets such as aircraft, fixed objects on the ground (ground surface) are used.

Fixed clutter such as ground clutter, which is an unnecessary reflected signal from buildings, mountains, etc. (shown), and moving clutter, which is a reflected signal from moving objects such as rain clouds, are removed, and moving objects such as aircraft are detected. Various clutter removal or suppression means may be provided for display purposes. KoO
As a means of suppressing O fixed clutter such as ground clutter, a moving eye S indicator (
Hereinafter referred to as MTI is often used. MTI
Regarding this, please refer to Chapter 17 of the technical book "Ruder Handbook" published by McGraw-Hill Company in the United States in 1970.
For moving clutter signals such as rain clouds, moving clutter suppression means called clutter locking MTI is used. 19 for clutter-locking MTI
For details, refer to @Chapter 9 of the friend technical book "Ruder Design Principles" published by the same publisher in 1969.

Since these various clutter suppressing means have different suppressing effects depending on the type of clutter, it is necessary to select and use the suppressing means depending on the type and position of clutter. Conventionally, such selection has been carried out by a radar operator who determines and operates the position where each suppression means should be used while looking at the radar scope 1.

tit stores the device or time selected in advance.

A friend who automatically switches. FIG. 1 shows one implementation of the latter.

Referring to Figure 1, to explain the conventional method, the transmission radio waves sent out from the transmitter side 1 pass through the transmitter/receiver switch 2 and then reach the air 1.
It is radiated into the air from 13. The received radio waves reflected from the object and returned to the antenna 3 and transmission/reception switching [! It is sent to the receiver 4 after passing through 2￥r. Among the output video signals from the receiver 4, the amplitude detection video (hereinafter referred to as normal video) is sent as is to the video switch 7, and the other is the phase detection video 1-MTlTl cancellation and 5 clutter, which is the Q output video signal. My King MTI Erase 1ff) 3 of MT video and clutter locking MTl video obtained through St.
One of the two video signals is selected and sent to the radar scope 8 for display. The video switch 7 stores in advance the time when the switch Q operates.

Video switching control r# that controls the operation tW based on the stored information
9.

According to the above-mentioned conventional method, moving clutter such as reflected signals from rain clouds moves or disappears over time, so it is necessary to periodically change the time during which the SO operation is performed or to change the time when the SO operation is performed. It is necessary to take measures against force Q to expand the range of options for selecting materials.

In particular, in the case of the latter countermeasure, the clutter locking MTII will pass even in areas where there is no moving clutter, but the clutter locking MTI generally has a lower target detection rate on fixed clutter than the normal MTI. Often reduces performance.

In order to eliminate the troublesome operations such as changing the operating time of the video switching device and the deterioration of target detection performance in the conventional method, the present invention determines the clutter area and distinguishes between fixed clutter and moving clutter. The object of the present invention is to provide a device that can automatically switch the clutter suppressing means depending on the function.

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 2, which shows the configuration of the clutter suppression device according to the present invention, the implementation array of the present invention includes a zero Doppler filter 10, a clutter detector All
and clutter detection! Including 5812 and Kai.

One of the output videos from receiver 4, the phase detection video, is MTI-cancelled v! 5 and clutter locking MTI cancellation 186 and zero Doppler filter 10 at the same time.
sent to. The zero Doppler filter 10 has the function of passing only received signals having a Doppler station wave number t that is zero or close to zero, such as ground clutter, out of the received Irl1 signal.
t, and exhibits a frequency characteristic exactly opposite to that of MTI cancellation 1) 5, that is, FIG. 3 and FIG. Also Q, delay line 13 and subtraction r114
The delay line 1 is shown as follows:
3 is for delaying only the Ruder pulse repetition time, and the characteristics of the drug quencher are as shown in FIG. 3(b). -10,000% @4 Figure (a) shows one implementation of the zero Doppler filter lO, and the above-mentioned O delay line 13
It can be simply configured by adding tl15 and addition tl15, and FIG. 10(b) shows its characteristics.

Again lol! Returning to Figure 2, the output of the zero Doppler filter 10 is sent to the clutter detection 11A11 to determine the fixed clutter area. It will be revealed. Since clutter generally exists with a planar spread t compared to targets such as aircraft, clutter detection rI gives the input signal a certain level ○ threshold hold that is larger than the radar receiver noise level,
It is simply constructed by a circuit that detects all signals exceeding t and a circuit that determines the planar spread of the signal. Clutter detection 16A11 generates a signal indicating fixed clutter, which signal is sent to video switching controller 9 at the next stage.

- 10,000, another output video of the receiver 4, the normal video, is sent to the clutter detector B12. Clutter detector B12 has the same function as clutter detector All. Normal video meeting dog 2 information [Motanai 9th clutter detection! The output of IB12 indicates both fixed and moving clutter areas and is sent to video switch N19.

The video switching controller 9 includes a clutter detector A11 and a clutter detector B1.
From the output signal of 2, a clutter-free area, a fixed clutter area, and a moving clutter area are determined, and the video switch 7
Generates a control signal for switching.

That is, to explain with reference to Figures 1wIJ5 and 6, Figure 5 is a diagram showing an example of a clutter area centered on the radar at point 0, and fixed clutter A and moving clutter Bt.
- Figure 6 (a) is a cross-sectional view between O-P, and Figure 9 (b)
) and (C) are clutter ejectors All and B1, respectively.
Similarly, (d) is a signal indicating moving clutter, which can be generated at the pWR rate by subtracting the signal (b) from the signal (e) at the video switching controller 9.

The video switching controller 9 is normal video t% when the signals (b) and (C) are at a low level; when the signal (b) is at a high level, the MT
When the video t- and (C) are at high level, a control signal a is generated so that the clutter locking MTI video t-video switch 'a7 is selected.

As explained above, the present invention includes a zero Doppler filter that extracts a signal with a Doppler frequency t close to zero, and a method for identifying clutter from the output signal. A circuit for detecting fixed clutter and moving clutter from normal video, and a means for switching between the normal video and the output video of various clutter suppression means based on these clutter detection signals, automatically respond to various types of clutter. This has the effect of outputting a video that is

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of a conventional clutter suppression device, and Fig. 2 is an example of a clutter suppression IT according to the present invention.
Implementation fIIt - A block diagram showing @3 and ¥R4 are diagrams showing one configuration sequence of the MTI canceler and zero Doppler filter and at that time. Fig. 5 is a top view showing the fU range of clutter [@6 The figure is a signal diagram showing 1tt1 of clutter, the output signal of each clutter detector, and the *@ signal of the video switching controller. l...Transmitter, 2...Transmission/reception switch, 3
...Antenna, 4...Receiver, 5...
...MTI eraser, 6...Clutter locking MTI eraser, f...Video switch, 8...
... Radar scope, 9 ... Video switching controller, 10 ... Zero Doppler filter, 11
······the law of nature? Ivy detector A112...Clutter detector B, 13...Delay line, 14
...Subtractor, 15...Addition wI. τ ￥″5 times% + Akimine S country 1 figure

Claims (1)

[Claims] Receiving means for outputting a video signal obtained by phase detection or synchronous detection of a radar reception signal, a hiteo polarization obtained by Ii width detection, and a phase detection or synchronous detection video signal. A means for suppressing fixed clutter and a means for suppressing moving clutter. Zero 12 is only the received signal t with a Doppler frequency t close to zero.
a filter means for extracting a signal indicating a fixed clutter area from the output of the filter hand RO; a clutter ejecting means for generating a signal indicating a fixed and moving clutter area from the amplitude detected video signal;
A clutter-free area, a fixed clutter area, and a moving clutter area are determined from the output signals of two clutter detection means, and the amplitude detection video inertia is automatically detected during the output video decoding of the fixed clutter suppression means and the moving clutter suppression means. means for generating a signal 0111IIlffi to switch to the video tvIJll! by means of a control signal; 1. A clutter suppressing device comprising: a switching means for controlling the clutter.