JPS61202174A - Receiving sensitivity control circuit for radar - Google Patents

Abstract

PURPOSE:To perform an automatic control of attenuation level according to the angle of elevation of an antenna, by memorizing a radar received signal attenuation level at in respective zones subdivided in terms of distance and bearing into a memory circuit at each angle of elevation of the antenna. CONSTITUTION:When a memory 13 is accessed with distance and bearing addresses 34 and 35 to supply attenuation level 30 manually inputted while the antenna angle 35 of elevation is specified by an input circuit 10, a radar received signal attenuation level in respective cell zones subdivided in terms of distance and bearing at each antenna angle of elevation is written and memorized into the memory 13. The memory contents thereof are read from the memory 13 according to the antenna angle of elevation using the target bearing and distance from an azimuth address counter 15 and a range address counter 14 as address and outputted via a D/A converter 12 to control the receiving sensitivity. Thus, the automatic attenuation level control of the radar received signal is performed according to the antenna angle of elevation to impart a required attenuation level easily and positively for a higher target/clutter ratio thereby assuring a greater freedom for radar operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to a target/clutter ratio (T/C ratio: Tar
This invention relates to a receiver sensitivity control circuit for a radar having an improved 8TC function.

(Prior Art) In general, in radar equipment, the main challenge is clutter suppression technology to extract only aircraft signals from various reflected signals, and a typical technology for this purpose is a moving target indication ( There is a technology (hereinafter referred to as MTI). However, it is difficult to detect targets superimposed on strong ground clutter from a short distance using this MTI technology alone.
The T/C ratio is improved by increasing the antenna gain at high elevation angles and by providing a constant amount of attenuation to the increased target received power due to this increased gain.

This function that provides a certain amount of attenuation is called 8TC,
In order to make the most effective use of this 8TC function, radar information must be divided into range (distance) and azimuth (direction) as a means of changing the STC attenuation according to the target received power strength and clutter received power strength and distribution. For each area, we set up several areas (areas) divided into 8TCs, which are inversely proportional to the 4th power, 2nd power, etc. of the distance. An optimal 8TC is given.

However, the target received power intensity and the clutter received power intensity change depending on the installation altitude of the antenna and the antenna elevation angle (the antenna beam angle). Although the antenna installation altitude is determined by the installation location of the antenna itself (land, buildings, etc.) and can easily change, it is considered that the antenna elevation angle can be easily changed automatically or manually.

but.

No consideration is given to automatically setting the 8TC in response to this antenna elevation angle.

FIG. 2(a) is an example of a vertical cover diagram of the radar.

In the figure, vertical coverage area 1 is the coverage area at a certain antenna elevation angle.

The other vertical coverage area 2 is a coverage area when the elevation angle is higher than the vertical coverage area IK. Note that the constant altitude 3 is a curved line due to the curvature of the earth. The target received power strength at a constant altitude of 3 in this radar device with a coverage area of 1°2 is:
As shown in FIG. 2(1)l, the target received power is 4 for the coverage area 1 and the target received power 5 is for the coverage area 2.

As an example of the optimal STC total settings for these target received power, the 8TC setting shown in Figure 2(c) provides a constant target received power strength even if the distance from the radar device to the target changes. Become. In the figure, 8'
rC attenuation amount 6 is for target received power 4, 8
The TC attenuation amount 7 is for the target received power 5. As can be seen from these STC attenuations of 6.7, the optimum S'l'C setting changes due to changes in the antenna elevation angle, and 8T
C? In order to set it optimally, it is necessary to set the 8TC attenuation in accordance with each antenna elevation angle, which poses a problem that limits the ability to freely change the antenna elevation angle during radar operation. .

(Object of the Invention) The object of the present invention is to solve such problems, and when attenuating a received signal using 8TC, the range direction and the azimuth direction are changed in steps or according to a certain function in response to the antenna elevation angle. Accordingly, it is an object of the present invention to provide a radar reception sensitivity control circuit that expands the degree of freedom in radar operation.

(Structure of the Invention) The radar reception sensitivity control circuit of the present invention is a memory circuit that subdivides radar reception information into distance and direction and stores received signal attenuation amount data for each section determined by these subdivisions. a switch circuit that switches between reading and reading data into the memory circuit; a data input circuit that reads attenuation data into the memory circuit; The attenuation amount readout circuit controls the readout radar reception sensitivity in correspondence with the azimuth and the antenna elevation angle.

(Saving example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

In the figure, 10 is a data input circuit that sets the amount of attenuation in accordance with the distance (range), azimuth, and antenna elevation angle, 11.14 is a latch circuit, 12 is a D/A converter, 13 is memory, and 15 16 is an azimuth address counter that reads out the azimuth using the azimuth reference signal (AR, P) and the incremental pulse signal (ACP) from input terminals 21.22, and 16 is O from input terminal 23.24.
Range azimuth counters 81 to S4 that read the range according to the range trigger and the clock are switches that switch between inputting and reading data to the memory 13.

First, when inputting all data to the data input circuit 10, the switches 81 to 84 are set to the data input side and the azimuth address signal 33. Specifies the range address signal 34 and antenna elevation angle signal 35, and outputs the memory control signal (CONT) 3.
Attenuation amount input data is set according to 2.

The attenuation input settings in this case are shown in Figure 3 (al and (b)
), as shown in Figure 4 (al and middle). That is, the STC attenuation deca data 30 radar information is subdivided into range and azimuth, and each cell determined by this subdivision is manually set by the data input circuit 10 and input into the memory 13. In this case, as shown in FIGS. 3(a) and 3(b), the divisions resulting from subdivision of range and azimuth are made up of cells, and the numbers in each cell indicate an example of attenuation data, and as shown in FIG. a), (
In b), this setting example is displayed three-dimensionally.

Next, when reading the attenuation amount data from the memory 13 in order to use the set attenuation amount data, first switch 81
~S4 is switched to the reading example (when used). The operation timing at this time is shown in the waveform diagrams of FIGS. 5(a) to 5(e).

In FIG. 1, attenuation amount data 30 input to the memory 13 are a zero range trigger (FIG. 5(a)) generated at the position of range 0, a clock signal, and an azimuth reference signal obtained from a specific rotational direction of the antenna. (ARP) and incremental pulse signal (ACP) at input terminals 23.
24, 22. Received from 21, range azimuth counter 1
5, an azimuth address counter 16, and an antenna elevation angle signal to designate an address and read out the memory contents. The output of this range address counter 16 is
For example, range 0 to maximum 200 as shown in Figure 5(b).
Reading is performed sequentially until the end. Further, the output of the azimuth address counter 15 is addressed, for example, as 10' and 10.1°, as shown in FIG. 5(c). The azimuth information obtained by the azimuth address counter 15 is latched by the latch circuit 14 for each 0 range trigger. The antenna elevation angle signal is addressed, for example, by 2°, as shown in FIG. 5(d). The attenuation amount data (FIG. 5(e)) of the memory contents is read based on each of these address information.

The read attenuation amount data signal 31 is latched by the latch circuit 11 and then outputted from the output terminal 20 as a drive signal for the 8TC circuit via the D/Afi converter 12.

(Effects of the Invention) As explained above, according to the present invention, it is possible to change the 8TC attenuation amount in accordance with the antenna elevation angle, and the 8TC setting is changed each time the antenna elevation angle is changed during radar operation. This eliminates the need to do everything manually,
Therefore, it has the effect of expanding the degree of freedom in radar operation.

[Brief Description of the Drawings] Figure 1 is a block diagram of an embodiment of the present invention, Figure 2 (a)
is an example of a radar vertical coverage map, Figure 2 (in Figure 2) is a target received power intensity diagram at a constant altitude of 3, Figure 2 (C) is an 8TC setting diagram to keep the target received power constant, Figure 3 (
Figures 4 (a) and 4 (b) show examples of STC attenuation input data according to this embodiment in azimuth. Characteristic diagrams shown two-dimensionally and three-dimensionally in correspondence to the range and the antenna elevation angle, and FIGS. 5(a) to 5(e) are waveform diagrams illustrating the operation of FIG. 1. In the figure 1.2...
・Vertical coverage area at a certain angle, 3... constant altitude, 4.
5...Target reception strength at constant altitude 3, 6,7...STC attenuation, 10...
Data input circuit, 11.14...Latch circuit,
12...D/A converter, 13...Memory, 15...Azimuth address counter, 16
...Range address counter, 20...
・STC circuit drive signal output terminal, 21...AC
P input terminal, 22...ARP input terminal, 23.
...0 range trigger input terminal, 24...
Clock input terminal, 25... Antenna elevation angle input terminal, 30... STC attenuation attenuation deca data 1.
...Read out STC attenuation data, 32...
...Memory control signal, 33...Azimuth at/s signal, 34...Range address signal,
35...Antenna elevation angle signal. -1shi; Somo2 21fu 17- (Reno

Claims (1)

[Claims] A memory circuit that subdivides radar reception information into each of distance and direction and stores received signal attenuation data for each section determined by these subdivisions, and a switch that switches between reading data into and reading out data from this memory circuit. a data input circuit for reading attenuation data into the memory circuit; and a data input circuit for reading attenuation data stored in the memory circuit in correspondence with the distance, azimuth, and antenna elevation angle of a radar reception signal to control radar reception sensitivity. A radar reception sensitivity control circuit including an attenuation amount readout circuit.