JPS60122381A - Moving target detector - Google Patents

Abstract

PURPOSE:To separate accurately a ground clutter and a moving target by processing a received video signal by the Doppler filter group of a pulse Doppler radar mounted on an aircraft, and using its mean output, etc. as an amplitude comparison threshold value. CONSTITUTION:A digital video receive signal which is separated, range by range, by a range gate is stored in an input memory 6 while separated into line spectra by a Doppler filter group with narrow band width. Then, the output of the (M)th filter for the moving target is processed by the 1st amplitude comparing circuit 8a which has a threshold value K1VH by multiplying the mean value VH of outputs of the (M-3)th-(M-1)th filters by a constant and the 2nd amplitude comparing circuit 8b which has a threshold value VL by averaging outputs of the (M+1)th-(M+3)th filters. Then, a gate circuit 10 through which the output passed through the (M)th filter after an AND gate 9 is passed is controlled according to an input high level output which exceeds the threshold values of the circuits 8a and 8b, and the ground clutter and moving target are separated accurately because no fixed threshold value is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in the removal of unnecessary reflections (hereinafter referred to as clutter) from ground, fire, etc. in an airborne radar.

[Prior art]

A conventional device of this type is shown in FIG.

In the figure, (for each range bin of the ljr/'i leg, there is a range gate circuit that performs a sound gate, an A/D converter that converts the output of the +21 Vi range gate into digital mvc, and (31 is the Po number of a certain range bin). km P
I (Doppler filter group that collects DPRF and separates them according to the difference in Doppler frequency, f41: Doppler filter group (3
) is a detection circuit that compares and detects the output of

Next, the operation shown in FIG. 1 will be explained. For pulse radar reception, the radar reception wave from the device passes through a phase detector and is divided into range bins by range gate tllK, and A/'
The signal is converted into a digital quantity by a D converter +21K, and this signal is sent to a group of Doppler filters where it is separated into m Doppler filters with a narrow bandwidth into Elimination line spectra. Also, this Doppler filter group! 31 K Eri S/N ratio does not improve. (41
is a detection circuit for comparing and detecting the output of the Doppler filter group (3) at a certain threshold, and if it is larger than the threshold, it is detected as being close to the target.

The conventional moving target detection system shown in Figure 2 often exceeds a fixed threshold when the clutter distribution is greater than OHz, and the clutter and the moving target 1! ! There was a drawback that i could not be separated.

If the fixed threshold is raised, clutter will be prevented from exceeding the threshold, but in this case, even small moving targets will not exceed the threshold and will become undetectable.

[Summary of the invention]

The present invention is designed to obviate the drawbacks of the above-mentioned prior art, and instead of providing a fixed threshold,
It is possible to accurately separate ground clutter from moving targets by focusing on fluctuations in the output levels of each filter in the Doppler filter group and setting the average level of these outputs or a level proportional to this as a new threshold. The objective is to provide a moving target device that can

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Third
In the figure, fil, +21, and +31 are the same as conventional moving target detection circuits, and are range gate circuits, respectively.

These are an A/D converter, a group of Doppler filters, and (51 is a mutual amplitude comparison circuit for separately detecting ground clutter and a moving target.

FIG. 4 shows a mutual amplitude comparison [four-way (51 one-groove formation example).

In the figure, (6) is a memory that stores the @ signal from the Doppler filter, and (7) is a circuit that generates signals for precise control to send signals of the filter outputs to be compared with each other to the total comparison circuit. (8a) and (8b) are the first. Second amplitude comparison circuit (9I is the first and second amplitude comparison circuit (8a)
, (8b) outputs are both °゛H°H° level, but matching circuit is used to obtain a matching circuit, (10) is analog output (
A predetermined gate circuit that applies a gate with the output of (9), (11
) is a predetermined detection filter 4 that stores the filter number of the HFC filter output when a moving target is detected. No. memory.

Next, the operation will be explained.

The radar receiver is the radar video direct number from the machine is the range gate (
+l, A/D converter (2), Doppler filter group (3
), and is input to the mutual amplitude comparison circuit (51).The mutual amplitude comparison circuit (up to the input of 51 is the same as the conventional moving target detection device.One embodiment of the mutual amplitude comparison circuit (51) is This is shown in Fig. 5, and this is shown in Fig. Assume that there is a moving target at .At this time, take the average of the outputs of the three Doppler filters M-3, M-2, and M-1, and calculate the average value VB or 1 times this average value, KIVH. The first amplitude comparison M (8a) with K as the threshold, the # dynamic target signal level Vs
Compare with. Then, as a result of comparison V) l>VB or KIV, ) If V99, (8a) I) Output is “L”
”, VB < vS or KIVH < VB fz If the output of (8a) is "IH" 1.Similarly, M+1.
M+2. Take the average output of the three Doppler filters M+3, and calculate this average value VI, or twice this average value,
K2VL k The second amplitude comparator circuit (
8b), it is compared with the signal level v8 of the moving target. And the result of this comparison is VL > VB and 1d K2VL
> VB fx et al. (8b) output tri “'L”
y VL<vB or n KzVj<Vs ft The output of the rubber (8b) is II H11. Above (8a
) and (8b) are sent to the matching circuit (9), and it is determined that there is a target to be transferred only when both [11H "1", (9)
The output of (10) is sent to the gate circuit (10), and the output code (analog value) of the M-th Doppler filter is output from +IO+ only when the output of (9) is °°H"°. (7) is The various digital circuits are control circuits that create a predetermined clock to control the output of the number, input, and control signals for reading. (111 is a memory that stores the filter number on which the calculation is being performed.

In the above explanation, if the average of the three filters M-3, M-2, and M-1 is expected to have a larger spread of clutter than the moving target, ll''t3f should be increased. .Also, set the threshold to KIVH, K2VL (!
:If you want to lower the false alarm rate, you can increase Kl a little, and if you want to increase the detection probability even if the false alarm rate gets worse, you can decrease 1.

The above theory #J explained the Mth filter, but
M-n,...--M-1, M+1.・・・・・・
. . . The M+n filter outputs are compared in the same way, and all moving targets are detected.

〔Effect of the invention〕

As mentioned above, if we improve this invention, what will the detection level be? Instead of setting a constant setting, all moving targets can be detected by comparing the amplitudes of the outputs of each filter in the Doppler filter group, so even in aircraft pulsed Doppler radars with large output level fluctuations, accuracy can be improved. Detection can be performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional Doppler radar moving target detection device, and Fig. 2 is a block diagram of an aircraft ground clutter and moving target using Doppler radar. It is a diagram showing the relationship between spectra and thresholds. circuit, +61 is the input memo IJ, 171 is the control circuit, (8a) and (8b) are the first and second amplitude comparison circuits, (9) is the matching circuit (AND
gate), tlQl is a gate circuit, (Illll-1
t filter number memory. The same reference numerals in each figure indicate the same parts or 7t indicate corresponding parts. Agent Masuo Oiwa Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Continued from page 1 Inventor Yoshiki Mori 1) Tsukaguchi Honmachi, Nai City 0 Inventor Hiroshi Ishii Tsukaguchi Honmachi, Amagasaki City 8-1-1 inside the factory Mitsubishi Electric Corporation Tsushinki 8-1-1
No. Mitsubishi Electric Co., Ltd. Telecommunication Equipment Commissioner of the Patent Office 1. Indication of the case: Japanese Patent Application No. 58-280940 2. Title of the invention: Moving target detection device 3. To the representative Hitoshi Katayama of the person making the amendment: 6. 'Smoking. , 8 ;:: Arithmetic 1] 1 (3) Figure 5 of the drawings will be corrected as shown in the attached sheet. 7. List of attached documents (1) 1 document indicating the scope of claims after correction (2)
Drawing 1 Tools Above Claims In an aircraft moving target detection device used in an aircraft pulsed Doppler radar, a line having a width that detects ground clutter and reflected waves from a moving target is detected from a video signal received by a radar receiving device. A group of Doppler filters that are separated into spectra, an M-th filter of the Doppler filter group, and n average outputs of M-1, M-2, . . . M -n, or a predetermined ratio thereof Proportional level and M
+1, M+2,...M A moving target characterized by comprising a mutual amplitude comparison circuit that uses n average outputs up to 10n or a level proportional to this at a predetermined ratio as a threshold. Detection device.

Claims (1)

[Claims] In aircraft moving target detection equipment used in aircraft pulsed Doppler radar, T-video is received by the radar receiver and separates ground clutter and reflected waves from moving targets into line spectra with widths. A Doppler filter group, the Mth filter of the Doppler filter group, and M-1, M-2°......n up to M-n.
M+1, M+21...M+n ``The average output of n units at J or the level proportional to hVc at a predetermined rate as the threshold. A moving target detection device characterized by comprising a mutual amplitude comparison circuit for use.