JPS5944591B2 - STC method of pulse search radar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an STC system for pulse search radars.
ntrol) method is used.

In other words, since the reflected waves from a short distance are very strong, the receiver becomes saturated and cannot make detailed comparisons of the strengths and weaknesses of the reflected waves, resulting in poor resolution.

To prevent this, the STC method is used in which the receiver gain is lowered for reflected waves at short distances, and the gain is increased as the distance goes farther.

Conventionally, there have been the following STC methods.

(1) Distance function type STC method As shown in Figure 1a, this method applies STC that varies in depth in the distance direction over a distance R1 from the origin of the radar, and the normally used waveform is shown in Figure 1. As shown in the figure, the section very close to the origin is a constant temperature STC, and then up to R1 is a function curve of the square or fourth power of the distance.
This is a change in the shallow direction.

(2) Area-specified STC method As shown in Figure 2d, in this method STC is applied by manually specifying the width and depth of an area where fixed clutter exists, and at a certain azimuth θ. If we look at the STC waveform for this case, it becomes as shown in Figure 2.

As is generally known, the method (1) above is based on PP
This is an STC used in radars that visually check the indication by I, and is intended to prevent oversaturation of the received input amplitude of the target, and to make the amplitude constant in the distance direction, making it easier for the human eye to identify the target. It is something to do.

This method is inconvenient in a radar equipped with an automatic detection and tracking device that attempts to detect and track a target without the aid of human eyes because it causes unnecessary signal attenuation.

In addition, the method (2) above is an improvement on this point, and it specifies an area only in the area where the crank exists.
By applying TC, attenuation of the target signal in areas without clutter is avoided, and this STC is suitable when the antenna pattern usually has a C08eC square characteristic and the amplitude of the target signal with respect to distance is constant.

This STC is normally used within the MTI area.

In this method, it is necessary to adjust the STC depth for each area according to the clutter intensity to make it suitable for MTI processing, but in normal cases, the intensity of each scattered clutter area is measured, The operation of specifying and applying an STC of a corresponding depth over a necessary width is quite complicated in practice.

Therefore, actual operations are often performed based on intuition, and the STC is not always appropriate, which tends to deteriorate target detection characteristics in the clutter region.

In order to eliminate the above-mentioned drawbacks, this invention provides an STC system for a pulse search radar that automatically measures the position and intensity of clutter in each pre-divided area, and automatically applies an STC at a required depth. It provides a method.

An embodiment of the present invention will be described below with reference to FIGS. 3 to 8.

FIG. 3 shows the configuration of the present invention, and the portions indicated by solid lines in the figure are included in the present invention.

1 is a radar antenna, 2 is a front-end receiver, and it is assumed that the radar human signal has not reached the saturation level at this output point.

3 is a logarithmic amplifier having a sufficient dynamic range for the input signal.

At this output point, the received signal is detected and becomes a video signal.

4 is a video quantization circuit having one or more threshold discrimination circuits generally called slicers, and outputs only videos exceeding a certain threshold as signals (this threshold is hereinafter referred to as a quantization level). .

Reference numeral 5 denotes a range quantization circuit, which quantizes the signal in each minute section ΔR in the range direction.

ΔR corresponds to the distance resolution of the radar.

6 is a quantized video counting circuit that counts the number of quantized videos within a certain sub-area obtained by subdividing the radar coverage area.

Reference numeral 7 denotes an area control circuit for creating the above-mentioned subdivided small areas, and one example of such subdivision is shown in FIG.

8 is a memory circuit, which stores information for each sub-area during scanning.

A reference value comparison circuit 9 compares the output signal from the memory circuit 8 for each small area with a preset reference value, and outputs a control value depending on the magnitude of the value.

Among the control values, 10 is an output line for slicer selection control, and 11 is an output line for STC depth control.

Reference numeral 12 denotes a control conversion circuit that decodes the output of the reference value comparison circuit and converts it into a predetermined control value, that is, a selection signal of the STC depth.

13 is an STC depth control circuit, which is a control conversion circuit 1;
The gain of the variable gain receiver 14 is controlled in stages by the output from the variable gain receiver 14.

14 is a variable gain receiver that changes the depth of the STC.

Instead of the variable gain receiver 14, a normal receiver and a variable attenuator may be used in the preceding stage or between the stages.

15 is an output line to a subsequent MTI receiver, and 16 is a normal MTI receiver.

Next, the operation of the STC system according to the present invention configured as described above will be explained with reference to FIGS. 4 to 8.

The radar human input signal is branched at the front receiver 2, one of its outputs is supplied to a logarithmic amplifier 3, and the other output is supplied to a variable gain receiver 14.

The signal supplied to the logarithmic amplifier 3 is here amplified and detected with logarithmic characteristics to become a video signal.

This video signal is supplied to the video quantization circuit 4 at the next stage.

In this circuit, the quantization levels of n slicers (n≧1) are set at predetermined intervals with respect to the output voltage, as shown in FIG. 5, corresponding to the dynamic range of the logarithmic amplifier 3.

Which slicer is selected is determined by the control output from the reference value comparison circuit 9.

The set voltages of the slicers are set to v1, respectively, as shown in FIG.
v2...Vn, the corresponding input level of the logarithmic amplifier 3 is C1, C2...αndBm
It can be expressed as

Now, considering one quantization level vX of the video quantization circuit 4, videos exceeding this quantization level are supplied to the range quantization circuit 5, where they are subjected to range quantization.

This range quantized signal is supplied to a quantized video counting circuit 6, where the number of quantized videos included in sub-area A1, which will be described later, is counted.

The area control circuit 7 creates subdivided areas of the radar coverage area as shown in Fig. 4a.If we explain the subdivided subareas of the radar coverage area in more detail, Fig. 4 shows the area control circuit 7. As shown in , for example, the small area A1 is a quantization unit in the distance direction, that is, R1. R2・
. . . AZ, where Rn is a subdivision unit in the distance direction, and n quantization units in the AZ direction, that is, n minute angles Δθ are grouped together.

AZ2...AZn is the subdivision unit in the AZ direction.

Therefore, the adjacent sub-area, for example A2, is arranged as shown in FIG.

Now, let's temporarily set the first sweep of the radar to AZ.

Then, in this sweep, ranges R1, R2...
A memory address change signal is sent to the area control circuit 7 for each Rn.
is supplied to the memory circuit 8, so that the subarea A1 is selected in the range R4.

On the other hand, in the quantized video counting circuit 6, the number of quantized videos in the AZo sweep is in the range R1J R2...
...Reset by the output signal of the area control circuit 7 for each Rn.

Therefore, in AZo, the count value between R4 and R5 is stored in the memory corresponding to the small area hole ○.

A similar operation is performed by sweeping every minute angle Δθ, and A
During the n sweeps up to Z1, for example, in the example of FIG. 4, four quantized videos, indicated by *, are stored as the number of quantized videos in the subarea A, until the next scan.

When reaching AZl, the small area A2 is designated as a memory within the same range R4 to R5.

Furthermore, it is stored at a predetermined location in the memory circuit 8.

In some cases, the counting results for the same area can be averaged over several scans.

The reference value comparison circuit 9 compares a predetermined reference value with the output value from the memory circuit 8 for the /J area A1, and if the output value from the memory circuit 8 is greater than the reference value, it is quantized. A control signal for selecting a slicer with a high level, holding it if appropriate, and lowering it if the level is low is supplied to the video quantization circuit 4 through an output line 10 for slicer selection control.

The reference value comparison circuit 9 also sends its output to the memory circuit 8 so that it can be referenced for the next determination operation.

The video quantization circuit 4 performs a slicer selection operation in response to the output from the reference value comparison circuit 9, and continues this operation until a hold signal is finally received, at which point a steady state is reached.

The state of the quantization level in a steady state is shown in FIG. 6 in terms of the relationship between clutter and amplitude for a certain direction of the radar.

That is, by appropriately setting the reference value of the reference value comparison circuit 9, the quantization level is distributed along the smoothed envelope of the clutter amplitude as shown in FIG.

In other words, the slicer is determined according to the clutter intensity.

This determined slice level is therefore indicative of the clutter intensity in that area.

On the other hand, another output signal of the reference value comparison circuit 9, which is applied to the output line 11, is an output signal for controlling the depth of the STC in accordance with the slicer selected as described above. is decoded by the control conversion circuit 12 to become an ST'C depth selection signal, which is then supplied to the control circuit 13.

The control circuit 13 is capable of outputting one or more gain attenuation values set at predetermined intervals according to the output signal from the control conversion circuit 12, and uses this output to attenuate the gain of the variable gain receiver 14. .

Here, the following relationship is established between the quantization level selected in the steady state by the video quantization circuit 4 and the gain attenuation value in the control circuit 13.

Now, if the quantization level is Vn, then from FIG. 5 the input level of the logarithmic amplifier is αn dBm.

The value obtained by converting this to the input level of the front receiver 2 is αn′
Then, as shown in Fig. 7, the required attenuation value, that is, ST
The C depth is a value necessary to attenuate αn to α□, that is, αAdB.

For those whose rutter strength does not exceed αL,
Set the attenuation value to zero.

When such an STC is applied, the output crack waveform of the variable gain receiver 14 has a maximum level near the saturation level of the receiver system composed of the front-stage receiver 2 and the variable gain receiver 14, as shown in FIG. suppressed by

As a result, oversaturated clutter can be avoided from being left in place during MTI processing.

In the above explanation, the operation of the automatic control system was treated as discontinuous control performed using multiple slicers in the video quantization circuit and multiple predetermined attenuation values in the control circuit. In principle, it is also possible to implement each slicer and one attenuation value whose values can be changed continuously.

As is clear from the above explanation, according to the STC method of the pulse search radar according to the present invention, the position and intensity of clutter are automatically measured in each pre-divided area, and the STC at the required depth is calculated. It can be applied automatically, which simplifies the operation of applying STC, and it can be done automatically without relying on intuition, so an appropriate STC can be obtained and excellent target detection characteristics in the clutter area can be obtained. It will be done.

In addition, the receiver includes a front-stage receiver included in the radar receiver,
The variable gain receiver, MT receiver, etc. all have known components.

[Brief explanation of drawings]

Figures 1 and 2 are characteristic diagrams based on the conventional STC method.
FIG. 3 is a block diagram showing an embodiment of the present invention, FIG. 4 is a diagram showing subdivided areas of the radar coverage area, FIG. 5 is a diagram showing quantization level settings, and FIG. 6 is a diagram showing clutter -A diagram showing the relationship between amplitude and quantization level, Figure 7 shows clutter-
FIG. 8 is a diagram showing the relationship between strength and STC depth, and FIG. 8 is a diagram showing the crack waveform after STC. In the figure, 3 is a logarithmic amplifier, 4 is a video quantization circuit, 5 is a range quantization circuit, 6 is a quantized video counting circuit, 7 is an area control circuit, 8 is a memory circuit, 9 is a reference value comparison circuit,
12 is a control exchange circuit, 13 is a control circuit, and 14 is a variable gain receiver.

Claims (1)

[Claims] In a pulse search radar using I STC, a logarithmic amplifier amplifies and detects an input signal to a receiver in front of the radar antenna with logarithmic characteristics and converts it into a video signal;
A video quantization circuit that outputs as a signal only the video that exceeds a certain threshold value of the converted video signal, a range quantization circuit that quantizes in the range direction, and an area control that subdivides the radar coverage area to create predetermined small areas. a quantization video counting circuit for counting the quantized signal corresponding to the predetermined area; a memory circuit for storing counting information for each sub-area during scanning; and an output from the memory circuit. a reference value comparison circuit that compares the value with a preset reference value for a small area and generates a signal that causes the video quantization circuit to select a predetermined value corresponding to clutter-noise within the predetermined area; A control conversion circuit and a control circuit for determining the depth of the STC within the predetermined area in accordance with a predetermined value of the video quantization circuit, and controlling the gain of the variable gain receiver and providing it to the receiver that performs MTI processing. Clutter intensity within a small area is automatically measured using the STC applying circuit of the variable gain receiver to automatically apply STC of a required depth corresponding to the input clutter level. Search radar S
TC method.