JPS60244879A - Cfar device - Google Patents

Abstract

PURPOSE:To suppress a clutter due to rain, snow, etc., by adding a peak detecting circuit to the conventional CFAR device of a radar receiver. CONSTITUTION:A radar video signal is inputted to a delay circuit 1 and also inputted to an integration circuit 2 through the peak detecting circuit. The peak detecting circuit 4 detects the peak of the clutter part generated owing to rain, snow, etc. The peak detecting circuit 4 is provided with a time constant adjusting circuit, which is adjusted to perform optimum suppression corresponding to the intensity of the clutter. The detected wavelength signal obtained by the peak detecting circuit 4 is integrated by a succeeding integration circuit 2. A subtracting circuit 3 subtracts the clutter component of the integration circuit 2 from the radar video signal delayed by the delay circuit 1. Consequently, the radar waveform having the clutter part suppressed appears at the output of the subtracting circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an 0FAR device, and particularly to an 0FAR device for a radar receiver that suppresses clutter caused by rain, snow, etc. in a radar device.

(Prior Art) The most important issue in radar video processing is how to suppress noise, ie, clutter, contained in reflected radar video signals.

In marine radars, when the waves get high, so-called g-clutter, which is a reflected signal from the surrounding sea surface, occurs, and when the weather is bad, so-called weather clutter, which is a signal reflected back from rain, snow, etc., also occurs. . It is necessary to suppress unnecessary signals from among these reflected signals containing clutter without damaging the target signal, but this method requires STO.
(8ensi-tivity Time 0ontro
l) Circuit, FTO (Fast TJmeOontro
l) Circuit m 0FAR (0 instant False
7V1arm3ate) equipment, etc. are used to deal with this problem.

(0″@cDQ[,4),.

The operation of the conventional 0FAR device against clutter such as rain and snow is explained below with reference to FIGS. 1 and 2.

The conventional 0FAR device has the configuration shown in FIG.
2 is a delay circuit, 2 is an integration circuit, and 3 is a subtraction circuit. Fifth
The radar video signal shown in FIG. 5(A) includes clutter (range 8 in FIG. 5(A)) reflected by rain, snow, etc. This radar video signal is distributed to a delay circuit 1 and an integration circuit 2. The integrator circuit 2 averages the input radar video signal and produces a smooth waveform as shown in FIG. 5(0) even though the part S of clutter caused by rain, snow, etc. is shown in FIG. 5(A). The output will be as follows. Delay circuit 1
The input radar video signal is delayed by Δt and the waveform shown in FIG. 5(B) is output. This delay time Δ
t is made to match the delay time of the integrating circuit 2 for the radar video signal. If the radar video signal 'k f(t) is now set, the output of the delay circuit 1 can be set as f(t-Δt), and the output of the integrating circuit 2 can be set as r(t-Δt).

Lf(t-Δt) output from the delay circuit 1 and 1(1-Δt) output from the integrating circuit 2 are not subtracted by the subtraction circuit 3. t-Δt
) is output from the subtraction circuit 3. The subtraction circuit 3
The waveform output from F(t-Δ1)=f(1-Δt)
-f(t-Δt) includes the clutter portion S due to rain, snow, etc. in the waveform of f(t-Δt), that is, the waveform output from the delay circuit 1, and on the other hand? (
1 - Δt), that is, the waveform output from the integrating circuit 2, the clutter caused by rain, snow, etc. has been averaged out, resulting in a smooth waveform, as shown in Figure 5 (D). A portion S of clutter caused by rain, snow, etc. remains, as if it were a bit cluttered. If the DC output component of the integrating circuit 2 is increased in order to remove the clutter caused by rain, snow, etc., that is, if the DC level is increased and then the difference is extracted, the signal of the original target object will also be removed.

Conventional 0FAR devices have the disadvantage that it is difficult to suppress weather clutter caused by rain, snow, etc., and cannot fully automatically distinguish targets in rain or snow. .

(Object of the invention) The present invention aims to solve the above-mentioned drawbacks,
The object of the present invention is to provide an OFAR device that can suppress weather clutter caused by rain, snow, etc. with a simple circuit configuration.

(Structure of the Invention) In order to achieve the above object, the 0FAR device of the present invention includes a peak detection circuit that peak-detects a radar video signal;
an integration circuit that integrates the entire detection output signal of the quench detection circuit; a delay circuit that delays the radar video signal by a predetermined time; and a direct current of the delayed radar video signal and the radar video signal obtained from the integration circuit. and a subtraction circuit for extracting the difference between the components, and using the subtraction circuit to integrate the nJj radar video signal delayed for a predetermined time by the delay circuit and the detection output signal of the peak detection circuit.
It is characterized by extracting the difference signal output from the DC component of the radar video signal and completely removing the clutter noise component contained in the radar video signal. An embodiment of the present invention will be fully described below with reference to the drawings.

(Embodiment of the invention) Figure 1 shows the configuration of an embodiment of the 0FAR device according to the present invention.
FIG. 2 shows the circuit configuration of one embodiment of the peak detection circuit, and FIG. 3 shows an explanatory diagram of the operating waveforms of FIG. 1.

In FIG. 1, a delay circuit 1, an integration circuit 2. Subtraction circuit 3
is the same as that used in the conventional 0FAR device shown in FIG. 4 as described above, and its operation is exactly the same except for the delay time Δt' of the delay circuit 1.

It's like that. In the 0FAR device of the present invention, the radar video signal is input to the delay circuit 1 and also to the peak detection circuit 4, and the detection output thereof is input to the integration circuit 2 at the next stage.

Then, the time corresponding to the delay n of the radar video signal due to double integration between the peak detection circuit 4 and the integration circuit 2, that is, the delay time, is changed to the delay time Δt of the delay circuit 1 shown in FIG. 5(R). Δt' corresponds to that.

The radar video signal in FIG. 3(A), which includes the clutter area 8 due to rain, snow, etc., is detected by the peak detection circuit 4, and the detection circuit shown in FIG. This results in a waveform with an increased level of DC component.

In this peak detection, by changing the time constant of the peak detection circuit 4, the DC level in the range of the clutter S caused by rain, snow, etc. can be changed.

FIG. 2 shows an embodiment of the peak detection circuit, which is composed of a transistor 5 constituting a high input impedance, a detection diode 6, a capacitor 7, an output resistor 8, and bias resistors 9 and 10. By changing the capacitance of the capacitor 7, its time constant is changed. Note that the peak detection circuit 4 may be constructed using an operational amplifier or the like instead of the transistor 5.

Peak detection circuit 4 detects the peak! ' Figure 3 (0
) is integrated by the next-stage integrating circuit 3, resulting in the waveform n1 shown in FIG. 3(D). In other words, the waveform has a raised level in the range corresponding to the clutter S due to rain, snow, etc. Then, as shown in FIG. 3 (D>), the DC component of the integrated reflected signal and the delay time Δ
Subtraction with the radar video signal delayed by t' is performed in the subtraction circuit 3, and the result is shown in FIG. 3(E). L6
! Only the clutter caused by rain, snow, etc. is suppressed n1
A waveform that does not damage other target signals is output.

As is clear from the above description, the 0FAR device of the present invention performs peak detection by the peak detection circuit 4.
By adjusting the peak hold time, it is possible to adjust the degree to which clutter caused by rain, snow, etc. is to be suppressed. For example, if no shark detection is applied at all, it will be the same as a conventional 0FAR device.

Further, the O, F&R device of the present invention can be put to practical use even if the delay circuit 1 is completely omitted as a simplified version, as long as the delay time Δt' is not extremely large.

(Effects of the Invention) As explained above, the present invention has a simple circuit configuration in which a peak detection circuit is added to a conventional 0FAR device, and a double integration method using the peak detection circuit and an integration circuit is used. , weather clutter can be suppressed, and targets in rain, snow, etc. can be fully automatically distinguished and detected to obtain the desired radar video signal. Furthermore, by changing the time constant of the peak detection circuit, the degree of suppression/removal of clutter can be adjusted in accordance with the intensity of the clutter, so it can also be used as a conventional F'TO circuit.

[Brief explanation of drawings]

FIG. 1 shows an example of the configuration of an OFA R device according to the present invention, FIG. 2 shows an example of the circuit configuration of an example of a peak detection circuit, and FIG.
The figure is the operating waveform diagram of Figure 1, and Figure 4 is the conventional OF&RFA.
FIG. 5 is an operational waveform diagram of FIG. 4. DESCRIPTION OF SYMBOLS 1...Delay circuit, 2...Integrator circuit, 3...Subtraction circuit, 4...Peak detection circuit, 5...Transistor,
6...Detection diode, 7...Capacitor, 8.
9.10...Resistance. Figure 1 Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] a peak detection circuit that peak-detects a radar video signal;
an integrating circuit that integrates the detection output signal of the peak detection circuit; a delay circuit that delays the radar video signal by a predetermined time; and a delay circuit that delays the radar video signal by a predetermined time; and a subtraction circuit for extracting the difference from the direct current component, and using the sound of the subtraction circuit to integrate the radar video signal delayed by the delay circuit for a predetermined time and the detection output signal of the peak detection circuit. A CFAR device characterized in that a clutter noise component contained in a radar video signal is removed by extracting a differential signal output from a direct current component of the radar video signal.