JPS6097284A - Clutter suppressing apparatus - Google Patents

Abstract

PURPOSE:To dispense with adjustment for aligning an amplitude level or timing, by simultaneously realizing the delay function possessed by a bypass circuit along with LOG/CFAR function by partially making use of a circuit for constituting LOG/CFAR. CONSTITUTION:A clutter suppressing circuit 5 consists of a logarithmic converter 321, a delay device 322 with a tap, a sum total operator 323, an 1/N operator 324, a subtractor 325, an anti-logarithmic converter 326 and a video change-over device 327. The video change-over device 327 has function for changing over the average value subtracting output of the subtractor 325 and the tap N/2 output of the delay devices 322 with the tap. When the video change- over device 327 is changed over to a B-side, LOG/CFAR output video is obtained at the output terminal of the anti-logarithmic converter 326. When the video change-over device 327 is changed over to an A-side. The output video of the logarithmic converter 321 is delayed by the delay device 322 with the tap before subjected to direct anti-logarithmic conversion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a clutter suppression device used in a surveillance and control radar device for monitoring aircraft, ships, etc.

In general, in surveillance and control radar equipment, in addition to reflected signals from targets such as aircraft and ships, ground clutter, which is a reflected signal from fixed objects on the ground (indicating the ground surface, buildings, mountains, etc.), and reflected signals from the sea surface are used. weather clutter, which is a signal reflected from rain clouds, etc.
Unwanted signals are received. For this reason, various clutter suppression means are used to remove these unnecessary signals and detect and display only the signals reflected from the target. As a clutter suppressing means for the above-mentioned g-clutter and weather clutter, a suppressing means generally called LOG/CFAR is often used.

However, it is known that when this clutter suppressing means is used when there is no target clutter, the signal strength of the target is weakened due to the characteristics of this means, and the target detection performance is degraded. For this reason, a system that passes through the LOG/CFAR and a system that bypasses the LOG/CFAR are usually used, and are switched depending on the occurrence of clutter.

An example of a clutter suppression device using conventional LO()/CIi'AR as a suppression means will be described with reference to FIG.

FIG. 1 shows a conventional clutter suppression device 3 and an antenna 1.
A transmitting/receiving device 2 and a video display device 4 are also shown.

The radar reception signal is supplied to the transmitting/receiving device 2 through the antenna l, and is converted into a video signal. This video signal is supplied to the clutter suppression device 3 and input to the linear video delay device 31 and LOG/CFAR 32. LOG/CF
The AR32 will be explained with reference to FIGS. 2 and 3. The input video signal shown in Figure 3(a) is logarithmic.
The log video is converted by the converter 321 into the log video shown in FIG. 3(b) and then supplied to the tapped delay unit 322. The tapped delay device 322 is a delay circuit capable of outputting N delay signals having equal delay time differences between adjacent taps from a tap l having a minimum delay time output to a tap Nt having a maximum delay time output. These N outputs are sent to the summation calculator 323, and the summation of the outputs from tap 1 to Nt is calculated. This sum is l
1/N of the total sum, that is, the third
The average value of the N delayed outputs shown in Figure <c> is calculated. This additive average value and the delayed output of tap N/2 are sent to the subtracter 325, and the additive average value including the clutter component is subtracted from the tap N/2 output, resulting in rack suppression as shown in FIG. 3(d). The average value subtracted output is obtained.

This output is still a video signal having a logarithmic amplitude characteristic, and is converted into a video signal having a linear characteristic shown in FIG. 3(e') by an antilog converter 326 in the next stage.
This is the output of OG/CFA 32.

Now, returning to FIG. 1 again to continue the explanation of the conventional clutter suppression device 3, the 2.gamma. video delay device 31 is LO
The output of the G/CFAR32 is connected to the tapped delay device 3 as described above.
22 causes a processing time delay, so this bypass circuit has a delay function for time correction so that there is no time lag between the two video signals when switching is performed. The conventional clutter suppression device 3 includes a linear video delay device 31 and a LOG/
The two outputs of the CFAR 32 are switched by a video switch 33 according to the occurrence of clutter and output to the video display device 4.

The above-mentioned conventional clutter suppression device is expensive due to the linear video delay device 31, which is a noise circuit, and in order to switch with the output of the LOG/CFAR 32, the amplitude level and timing of the peer 141 of both outputs must be adjusted. This required some adjustments.

The present invention eliminates the above drawbacks by reusing a part of the circuit constituting the LOG/CFAR.
The present invention provides a clutter suppression device that can simultaneously have the delay function of an innoc circuit as well as the ARfi function.

The clutter suppression device of the present invention includes a means for amplitude-detecting a radar reception signal and outputting a log video signal obtained by performing log conversion, and a means for outputting a signal obtained by time-delaying the log video signal, and also for outputting a signal obtained by time-delaying the log video signal. a tapped delay means capable of outputting a delayed output; a means for calculating an average value of the plurality of delayed outputs; a means for outputting an average value subtraction result obtained by subtracting the average output from the delayed output; and the average value. The apparatus includes means for switching between the subtracted output and the delayed output, and means for outputting a video signal obtained by performing antilog conversion on the output of the switching means.

Next, an embodiment of the present invention will be described with reference to FIG.

The clutter suppression device 5 of the present invention includes a log converter 321, a tapped delay device 322, a summation arithmetic unit 323, a 1/N arithmetic unit 324, and a subtractor that constitute the LOG/CFAR 32 of the conventional clutter suppression device 3 described above. 325, an anti-log converter 326, and a video switch 327. The constituent circuits other than video switch 327 have the same functions as described above.

The video switch 327 has a function of switching between the average value subtraction output of the subtracter 325 and the tap N/2 output of the tapped delay unit 322. These two outputs are both video signals having logarithmic characteristics, and are converted by the anti-log converter 326 into a video signal having linear characteristics and output. That is, when the video switch 327 is switched to the B side, the above-mentioned LOG/C1''AR output video is transferred to the anti-log converter 32.
It is obtained at the output end of 6. On the other hand, when switched to the A side, the output log video of the log converter 321 is transferred to the tapped delay device 3.
After being delayed by 22, the average value is not subtracted and anti-log conversion is performed directly.
A bypassed and delayed video signal is obtained.

As explained above, the present invention utilizes some of the circuits that make up the LOG/CFAR, so that the original LOG/CFAR
Since it can have both the AR function and the delay function of the bypass circuit, it has the feature that the rutter suppression device can be easily configured without requiring the bypass circuit only and without the need for adjustment to match two amplitude levels or timings.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a monitoring and control radar device including a conventional clutter suppression device, Fig. 2 is a diagram showing the configuration of LOG/CFAR that constitutes the conventional clutter suppression device, and Fig. 3 is a block diagram showing the LOG/CFAR configuration. FIG. 2 is a signal waveform diagram showing input and output signals of each circuit configuring the /CFA box. FIG. 4 is a block diagram showing one embodiment of the present invention. 1... Antenna, 2... Transmitting/receiving device, 3
, 5..., clutter suppression device, 4...
Video display device, 31...Linear video delay device, 32...LOG/CF/R. 33. 327...Video switch, 321...
... Log converter, 322 ... Delay device with tap, 323 ... Summation calculator, 324 ...
・l/N calculator, 325...Subtractor, 326・
...Antilog converter. (C) しΩ Ura k) q brush [fji, power (j Binoe ``Jin v (IL; A': sashi) (, 3 two ka (C Noah > proa °゛ love 1 moxibustion)

Claims (1)

[Claims] A means for amplitude-detecting a radar reception signal, performing logarithmic conversion and outputting it as a log video signal, and outputting a signal obtained by time-delaying the log video signal, and also outputting a plurality of delayed outputs in the middle. a tapped delay means;
means for calculating an average value of the plurality of delayed outputs;
means for outputting an average value subtraction result obtained by subtracting the average output from the delayed output; means for switching between the average value subtraction output and the delayed output; and anti-log transformation of the output of the switching means. and means for outputting a video signal obtained by the clutter suppressing apparatus.