JPS61189476A - Radar equipment - Google Patents

Abstract

PURPOSE:To obtain an equipment with a low error precaution rate by constituting detectors with two detectors of a frequency axis and a distance axis and preventing from detecting clutter as a target in error. CONSTITUTION:The radar equipment is provided with the detector I(DA.M.P). Then, the outputs of filters FM.P are inputted to the detector II(DB.M.P) detecting the filter outputs before and behind with FM.P as a center in the same distance (RM in the figure) with the frequency I. Further, the filter outputs before and behind on the distance axis with FM.P as a center with the same frequency (FP in the figure) are inputted to the detector II(DB.M.P) detecting on the distance axis. Then, the existence of a target is decided with both the detectors and the result is inputted to an AND circuit 4 and the AND circuit 4 outputs a signal to have the target only in case both are inputted. Hereby, the clutter is not detected as the target in error and the system with the low error precaution rate can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to Ce1lAve in pulsed Doppler radar.
r ag i ng CFAR (Coha tant
-Falae-Alarm-Rate) reception.

[Conventional technology]

FIG. 6 shows a general video processing part of a pulsed Doppler radar having a range gate group and a pulsed Doppler filter group.

In the figure, (1) divides the input video into minutes m for each distance.
(2) is a group of clutter (unwanted reflected waves from the ground or sea surface, etc.); (3) is a detector group that detects the presence or absence of a signal at the output of each filter.

Incidentally, as shown in the figure, range gates are prepared from tortoise, tortoise, and tortoise, respectively, for range gate group (1) Harenzi genus, RM, and so on. The Doppler filter group (2) has a frequency F1 divided by a predetermined frequency width for each range...
A pass filter that can detect each Doppler frequency corresponding to Fq is prepared.

Detector group (5) ri is prepared in correspondence with each filter of the Doppler filter group (2) so as to be able to detect the output of the filter.

Next, the detector group (5), which is a part of the present invention, will be explained.

FIG. 5 shows the clutter and target output status of each Doppler filter on the distance or frequency (Doppler frequency) axis.

Although the Doppler filter removes the clutter to a relatively low frequency, it is still output as residual clutter, as shown in the figure.

In addition, the remaining amount varies depending on the distance or frequency, and in order to detect the target at each detector in the detector group (5) (DMp in (5)), a constant detection level cannot be achieved, as shown in the figure. It is necessary to change the detection level for each distance or frequency.

As means having the above-mentioned changing detection level, there is a structure shown in FIG. 3 or FIG. 4. This is riCell
This is called Averaging CFAR.

FIG. 3 shows a method on the frequency axis, and FIG. 4 shows a method on the time axis. Incidentally, as a similar example to Fig. 4, r Introdu
ction To Rodar System, M
errill I.

5kolnik, Magraw Hill Inter
national book company p393
There is FiglO-11J.

First, FIG. 3 will be explained. The example in Figure 3 is filter F.
This is a detector for the output of M-p. Same on the frequency axis
Use each filter output in the range gate.

As shown in the figure, first, in the average circuit (6), FM, p
Average the lower multiple filter outputs.

(The figure shows an example of three ri.) Similarly, for FM, the higher filter outputs are compared in an averaging circuit (8), and the larger one is taken out.

This output is multiplied by a constant in multiplier I (9).

This determines the detection level. This constant is determined by the false alarm rate of the device.

The output of the FM, , is compared with the detection level described above at the detection circuit r (10), and only if it is larger, a target presence signal is output.

With such a function, the detection shown in FIG. 5 is executed.

FIG. 4 shows the number of distance axes, and the filter output having the same frequency for each range gate is input to the averaging circuit. The subsequent operation is the same as that shown in FIG.

[Problem that the invention seeks to solve]

In the conventional pulsed Doppler radar, only one of the detectors shown in FIG. 3 or FIG. 4 was used as the detector in the detector group (5).

For this reason, it is necessary to set the detection level relatively high so as not to mistakenly detect the clutter as a target, resulting in a problem that the performance of detecting inside the clutter deteriorates.

This invention was made to solve the above-mentioned problems, and it is possible to suppress the false alarm "4" in which clutter is mistakenly regarded as a target (or to lower the detection level without changing the false alarm rate). The purpose is to obtain a pulsed Doppler radar (which measures the same internal sensitivity).

[Means for solving problems]

The pulsed Doppler radar according to the present invention detects the °C target on two detectors on the time axis and the frequency axis, and the °C target is detected on both detectors.
A target is determined only when a target is detected.

[For production]

In this invention, two detectors are provided, one on the time axis and one on the frequency axis, and it is determined whether there is a target or not based on whether the target is detected by both detectors. [Embodiments of the Invention] Hereinafter, this invention An example of this will be described with reference to the drawings. 1st
In the figure, (1) and +21 are the same as the conventional technology,
There are rangecate groups and Doppler filter groups. (3) is the frequency axis detector 1 provided for each Doppler filter.
(Dmu・x-y) and the detector on the time axis (DB・Engineering・
J). The detector ■ has the configuration shown in Figure 3, and the detector ■ has the configuration shown in Figure 4.If you take one set and write the connection with the AND circuit (4) in detail, it will be as shown in Figure 2). Become. Here, suffix A is detector 1, B
indicates detector ■. Also shown is a detector corresponding to the Doppler frequency J of the Engineering/J Keshinjige-1-1. (4)
is an AND circuit group that outputs a signal only when there are outputs from the above-mentioned detectors ① and ②.

The operation will be explained with reference to FIG. Figure 2 (A) is an explanatory diagram of the frequency-distance plane of the detection signal, and Figure 2 (B) is the corresponding detector I (DA, g), detector ■ (Dn-m-p), and AND circuit. As shown in Figure 2, which shows the connection relationship of
With respect to the output of the filter FM, p, °C is the detector I that detects the filter outputs before and after the center of the FM, p′t within the same distance (tri RM in the figure) on the frequency axis.
Input (D□0m-p).

The detector If (Dn, topp) that detects on the distance axis has the same frequency (Fp in the figure), and the 0 detector I and the detector that input the filter outputs before and after on the distance axis with 8, p as the center. The operation of device (2) has been explained in the prior art section and will therefore be omitted.

The presence or absence of the target is determined by the rain detector, and as a result, HAND
It is input to the circuit (4). The AND circuit (4) outputs a signal indicating that there is a target only when both people have the strength.

In addition, in the above embodiment, the detector 1 and the detector 2 detect the presence of the target.
Although the presence/absence of the target was determined, it is also possible to compare the detection levels obtained by the detector I and the detector (2), take out the larger one, and use this larger detection level to determine whether the target exists or not.

〔Effect of the invention〕

As described above, according to the present invention, since the detector is configured with two detectors on the frequency axis and the distance axis, there is an effect that a low false alarm rate can be obtained.

[Brief explanation of the drawing]

@Figure 1 is a diagram showing an embodiment of this invention, Figure 2 is an explanatory diagram of this invention, Figure 3 is a configuration diagram of a detector ■ for signals on the frequency axis, and Figure 4 is a diagram for signals on the distance axis. FIG. 5 is an explanatory diagram of the detection level, and FIG. 6 is a diagram showing the configuration of the conventional system. In the figure, (1)... range gate group, (2)...
・Doppler filter group, (3)...detector group, (DA-
x, z)...Detector I, (DB, Engineering 1.)...Detector II-(4)...AND circuit group. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] a range gate group consisting of a plurality of range gates that are equipped with gates that distinguish differences in distance to the reflection point by differences in arrival times of reflected signals, and extract reflected signals from the reflection point by distinguishing them by distance to the reflection point; A Doppler filter group consisting of a plurality of Doppler filters extracts the reflected signal from a reflection point by distinguishing its Doppler frequency in predetermined frequency units, and detects the presence or absence of a signal in a predetermined distance range from multiple distance ranges before and after the said distance range. A first detector that determines the presence or absence of a signal in a predetermined Doppler frequency range by comparing it with an average level of the signal, and a second detector that determines the presence or absence of a signal in a predetermined Doppler frequency range by comparing it with the average signal level of a plurality of Doppler frequency ranges before and after the Doppler frequency range. The apparatus comprises a detector and an OR circuit that performs a logical sum of the outputs of the first detector and the second detector, and detects the presence or absence of a reflected wave in a predetermined Doppler frequency range in a predetermined distance range. Characteristic radar equipment.