JPH0547076B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a three-dimensional radar device using a pencil beam scanning method, which detects interference signals and solar radio waves and performs processing to extract position data for interference signals and solar radio waves. The present invention relates to a signal processing device.

(Prior Art) In general, a radar received signal includes unnecessary received signals in addition to the target signal, so these unnecessary received signals may make it impossible to detect the target signal or cause signals other than the target signal to be detected. There may be cases where the received signal is mistakenly detected.

In particular, when strong electromagnetic waves within the radar reception band (hereinafter referred to as jamming signals) are artificially mixed in from the outside, it becomes difficult to detect targets in the direction of arrival of the jamming signals, and it becomes difficult to automatically track targets. When processing is performed by a computer, a large number of interference signals are erroneously detected, so that automatic target tracking processing may become impossible even in areas other than the direction in which the interference signals arrive.

In addition to means for suppressing the interference signal from the received signal, a radar apparatus that is likely to receive interference signals has means for detecting the presence or absence of an interference signal and accurately detecting the position data of the interference source.

A representative example of a means for extracting position data of a disturbance source in a three-dimensional radar device having an aerial beam scanned in the azimuth and elevation directions of the search space is disclosed in Japanese Patent Application No.
59-50423, the structure is roughly as shown in FIG. The representative example shown in Figure 2 is 1
In the case of a radar device in which a main beam is scanned, a logarithmic amplifier 22A that inputs the radar reception signal 201 from the reception signal input terminal 21A and outputs a logarithmic video 202, and a logarithmic amplifier 22A that outputs a logarithmic video 202,
The A/D converter 23A that performs D conversion and the receiving system
An STC amplitude correction circuit 24A for correcting the received signal strength attenuated by STC (Sensitivity Time Control); a clutter area setting circuit 26 for generating a clutter area gate 204 indicating that the ground clutter area is present; A clutter removal circuit 25A receives the clutter area gate 204 and inhibits the output video 203 of the STC amplitude correction circuit 24A while the clutter area gate is applied.
The output 205 of the clutter removal circuit 25A is compared with a preset threshold value corresponding to the receiver noise level, and the output 205 of the clutter removal circuit 25A is
Of the outputs 205 of , receiver noise is removed by outputting only the signals that exceed this threshold, and the number of data per radar sweep that exceeds the threshold is counted and a sample signal 206 is output. The receiver noise removal circuit 27 and the output 207 of this receiver noise removal circuit 27 are integrated for one radar sweep, and the integrated value is obtained by subtracting the time corresponding to the clutter area and the area containing only receiver noise in one radar sweep. An average amplitude extraction circuit 28 extracts and outputs the average interference signal amplitude value by dividing by time, and outputs the average amplitude value 208 which is the output of this average amplitude extraction circuit 28 after being delayed for one radar sweep. Sweep memory 29, a sweep memory 30 that outputs the output after further delaying the output of the sweep memory 29 by one sweep, and output signals of the average amplitude extraction circuit 28, sweep memories 29, and 30 after delaying them for one elevation scan. Elevation angle scan memories 31, 33 and 35 to be output,
Elevation angle scan memories 32, 34 and 3 output signals after further delaying the output signals of elevation angle scan memories 31, 33 and 35 by one elevation angle scan.
6, average amplitude extraction circuit 28, and sweep memory 2
9, 30, each output signal of the elevation scan memory 31 to 36, and the azimuth signal 40 are received, and the MAX
Extract the amplitude, SUB−AZ amplitude, and SUB−EL amplitude,
The MAX/SUB extraction circuit 37 outputs together with the azimuth signal, and a reference signal is received from the input terminal 41 which is set in advance to determine the sensitivity of interference signal detection, and the maximum value of the average amplitude exceeds this reference signal. In this case, the calculation circuit 38 calculates the azimuth, elevation angle, and run length of the interference signal source from the output of the MAX/SUB extraction circuit 37 and outputs the calculated values from the output terminal 39.

On the other hand, in a radar device, it is necessary to set its azimuth angle data and elevation angle data to absolutely correct values, and calibration for this purpose is generally performed using solar radio waves. In other words, since the absolute values of the sun's azimuth and elevation angle at a given time at a given place can be determined in advance, the radar output data can be corrected by matching the radar output data at the solar radio wave arrival direction or elevation angle. It can be done.

As one means of this calibration, the above-mentioned means for extracting the position data of the interference source is used.

Since solar radio waves are a type of noise signal, it can be assumed that very weak noise interference is mixed in from the outside. Calibration is made to match the azimuth and elevation values.

(Problem to be solved by the invention) However, solar radio waves are usually weaker than interference signals, and the reception level fluctuates as the elevation angle changes, so after being quantized by the A/D converter 23A, noise There may be cases where position data cannot be extracted stably because it is difficult to distinguish between

Furthermore, since the input level corresponding to one quantization level in the A/D converter 23A is determined by a logarithmic video having a logarithmic characteristic that does not saturate even when receiving a high dynamic range interference signal, it is extracted for solar radio waves. The accuracy of the acquired position data also does not improve beyond the position accuracy with respect to the interfering signal. This situation will be explained using FIG. 3.

301 in Figure 3 is the logarithmic amplifier 22A and A/D
The combined input/output characteristics of the converter 23A are schematically shown. The horizontal axis 302 represents the input level of the logarithmic amplifier expressed in logarithms, and the vertical axis 303 represents the quantized output of the A/D converter 23A. Reference numeral 304 indicates an input level range in consideration of interference signals, and the logarithmic amplifier 22A performs logarithmic detection on the input within the input level range 304 without saturation. 305 shows the average input level of receiver noise, and 307 shows its average value at the A/D converter output.

In other words, an unsaturated A/D converter output 310 is obtained for the input level 309.

Now, input level range 304 is A decibel, A/
If the number of pits of the D converter 23A is m, the input level corresponding to one quantization level of the A/D converter 23A is A/2 ^m (decibel/quantization level).

On the other hand, when the average reception level of solar radio waves reaches the level shown in 306, the A/D converter output becomes 308, and in this case, even though there is a difference between it and the average input level of receiver noise 305. This indicates that they are processed at the same level after A/D conversion. This phenomenon always accompanies A/D conversion, but the wider the input level range 304 is compared to the difference between the reception level of solar radio waves and the receiver noise level, the more the A/D conversion output receives solar radio waves. This makes it more likely that machine noise cannot be distinguished.

In addition, in Fig. 2, position data such as interference signals is calculated based on the maximum value of the average amplitude value of each radar beam and the next largest average amplitude value of the radar beams adjacent to the maximum value. However, the accuracy of this average amplitude value is also limited to A/2 ^m .

In this way, the interference source position data extraction means in conventional radar signal processing equipment extracts interference signals with a high dynamic range, so solar radio waves that are weaker than actual interference signals are used as interference signals. The disadvantage is that it is difficult to detect stably.

An object of the present invention is to solve the above-mentioned problems of the prior art by using a signal obtained by converting a normal video into a LOG, so that the difference between the solar radio wave reception level and the receiver noise level can be calculated in the process of processing. It is an object of the present invention to provide a radar signal processing device that can stably extract position data of solar radio waves by increasing .

(Means for Solving the Problems) The present invention has the following means configuration to achieve the above object. That is, the radar signal processing device of the present invention modulates the amplitude of received signals including interference signals and solar radio waves (hereinafter referred to as interference signals, etc.) received by an antenna pencil beam scanned in the azimuth and elevation directions of the search space. amplitude detection means for detecting and outputting a normal video; logarithmic detection means for logarithmically amplifying and detecting the received signal and outputting a first logarithmic video; logarithmically converting the normal video and outputting a second logarithmic video; a logarithmic conversion means that outputs the first logarithmic video and the second logarithmic video as input, selects the first logarithmic video during normal operation of the radar, and calibrates the position data from the radar using solar radio waves; video selection means for selecting and outputting the first logarithmic video or the second logarithmic video according to an external control signal for selecting the second logarithmic video when the video is to be performed; clutter areas removed from the output of the video selection means; clutter removal means for extracting interference signals etc. that do not include clutter; average amplitude extraction means for extracting an average signal intensity for each scanning beam from among the plurality of interference signals etc. extracted by the clutter removal means; Among the average signal intensities obtained for each scanning beam unit, the first average signal intensity (hereinafter referred to as MAX amplitude) in the first scanning beam that has the maximum intensity in the quadratic plane of azimuth and elevation angle, and the Among the second and third average signal intensities of the scanning beams adjacent to the first scanning beam in the azimuth direction, the one with the strongest intensity (hereinafter referred to as SUB-AZ amplitude) and the one adjacent to the first scanning beam in the elevation direction The strongest of the fourth and fifth average signals of the matching scanning beams (hereinafter referred to as
MAX− to extract SUB−EL amplitude)
SUB amplitude extraction means; the MAX amplitude, SUB−
A radar signal processing device comprising: calculation means for calculating the arrival direction and arrival elevation angle of a disturbance signal, etc. from the AZ amplitude, the SUB-EL amplitude, and the azimuth data and elevation angle data of a scanning beam giving these. be.

(Example) Next, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of a radar signal processing device according to the invention. In this embodiment, the radar reception signal 101 from input terminal 1 is input,
A logarithmic amplifier 2 that outputs a logarithmic video 102, an A/D converter 3 that A/D converts the logarithmic video 102, and an amplitude detector 4 that also receives the radar reception signal 101 and outputs a normal video 103.
, an A/D converter 5 which A/D converts this normal video 103 having the same number of bits as the A/D converter 3, and an A/D converter 5 which performs logarithmic conversion on the A/D converted normal video and outputs a second logarithmic video. LOG converter 6
, the outputs of the A/D converter 3 and the LOG converter 6 are input, and the 2
The video selector 7 outputs one of the two inputs, and the STC (Sensitivity Time
a clutter area setting circuit 9 that generates a clutter area gate 106 indicating that the ground clutter area is present;
In response to this clutter area gate 106, while this clutter area gate 106 is on, the STC is
A clutter removal circuit 10 for inhibiting the output video 105 of the amplitude correction circuit 8 and the clutter removal circuit 1
a receiver noise removal circuit 11 that removes receiver noise from an output 107 of 0 and outputs a video signal 108 from which the receiver noise has been removed and a sample signal 109 for calculating an average amplitude value;
The average jamming signal amplitude value can be calculated by integrating the output 108 of 1 for one radar sweep and dividing the integrated value by the time obtained by subtracting the time corresponding to the clutter region and receiver noise only region in one radar sweep. Average amplitude extraction circuit 12 that extracts and outputs
, a sweep memory 13 that outputs the output of the average amplitude extraction circuit 12 after delaying it for one radar sweep, and a sweep memory 14 that outputs the output of the sweep memory 13 after delaying it for one more sweep.
, average amplitude extraction circuit 12, sweep memory 1
3. Elevation scan memory 15, which outputs the output signal of No. 14 after delaying it for one elevation scan.
7 and 19, and an elevation scan memory 1 which outputs the output signals of elevation scan memories 15, 17, and 19 after further delaying them by one elevation scan.
6, 18 and 20, and average amplitude extraction circuit 1
2. Receive the output signals of the sweep memories 13 and 14, the elevation scan memories 15 to 20, and the azimuth signal 24, and receive the MAX amplitude, SUB-AZ amplitude,
A MAX/SUB extraction circuit 21 that extracts the SUB-EL amplitude and outputs it together with the azimuth signal receives a reference signal from an input terminal 25 that is set externally to determine the sensitivity of interference signal detection, If the value exceeds the level of this reference signal
It is configured to include an arithmetic circuit 22 that calculates the azimuth, elevation angle, and run length of the interference signal source from the output of the MAX/SUB extraction circuit 21 and outputs it from the output terminal 23.

Among the above configurations, sweep memory 13, sweep memory 1
4. Elevation scan memory 15 to 20 and
The MAX/SUB extraction circuit 21 constitutes MAX/SUB amplitude extraction means.

In this embodiment, during normal operation of the radar, A/
When the output of the D converter 3 is used to calibrate position data from the radar using solar radio waves, a control signal 104 is applied from the outside so that the output of the LOG converter 6 is selected as the output of the video selector 7.

If the output of A/D converter 3 is selected, the second
The configuration is exactly the same as the prior art configuration example shown in the figure.

If LOG converter 6 is selected, A/
This is equivalent to increasing the number of bits of the D converter and making the steps of quantization finer, and as shown below, the drawbacks of the prior art described using FIG. 3 can be eliminated.

In FIG. 4, 401 schematically shows the input/output characteristics of the amplitude detector 4, A/D converter 5, and LOG converter 6, and the horizontal axis represents the input level of the amplitude detector in logarithm. The vertical axis represents the output of the LOG converter 6. The output of the LOG converter 6 is a digital quantity in units of steps on the vertical axis. 404 indicates the input level of the amplitude detector corresponding to the normal video level range. When the LOG converter 6 is selected, a non-saturated signal can be obtained as the output of the video selector 7 only in this range, and the output of the LOG converter 6 for radar reception signals exceeding the range 404 is saturated and all have the same value. becomes. Input level example 409
The LOG converter output 410 for illustrating this example. However, for the received signal in the input level range 404, as shown in the input/output characteristic 401, quantization is performed in finer increments than in the input/output characteristic 301 of FIG. 6, the output will be more faithful.

As a result, the solar radio wave reception signal and the receiver noise, which could not be distinguished as the output of the A/D converter 23 in the example of FIG. 3, are obtained as different levels in the output of the LOG converter 6.

That is, the average input level of receiver noise 405 in FIG. 4 indicates the average level of receiver noise corresponding to the average input level of receiver noise 305 in FIG. 3, and 407 indicates the output of the LOG converter 6 for this. ing. At this time, if the solar radio wave reception level is the average reception level 406 which is the same level as the example 306 of the average reception level of solar radio waves in FIG. Since it is smaller than that in FIG. 3, the output level of the LOG converter becomes as shown in 408, and it becomes possible to distinguish between receiver noise and solar radio waves, which were indistinguishable in the example of FIG.

Even if there is a difference between the average received level of solar radio waves and the average level of receiver noise at the A/D converter 3 output in Figure 1, the difference between the two at the LOG converter 6 output will be the difference between the A/D converter 3. Compared to this, the threshold value becomes larger and the threshold value control in the arithmetic circuit 22 of FIG. 1 becomes easier. That is, in FIG. 3, the average input level 311 of receiver noise and the average reception level 312 of solar radio waves are compared to
The outputs of A become A/D converter quantization output levels 313 and 314, respectively.

Most of the receiver noise is suppressed by the receiver noise removal circuit 27, but since the receiver noise is a noise signal, there are cases where it is not suppressed by the noise removal circuit stochastically. In order to suppress false detections and reliably extract solar radio wave position data, the level of the detection reference signal must be set to the A/D converter quantization output level 315 shown in FIG.

If the detection reference signal level is higher than level 315, solar radio waves are not detected, and the level 315 is higher than level 315.
If it is lower, false detection due to receiver noise will occur.

The smaller the difference between the average intensity of the receiver noise at the A/D converter output and the intensity of the solar radio wave reception signal, the smaller the allowable value for the reference signal setting that allows stable detection of the solar radio wave reception signal, and the smaller the reference signal setting. It becomes difficult to do so.

On the other hand, in FIG. 4, the output of the LOG converter 6 is Since the LOG converter output levels 413 and 414 are larger than the A/D converter quantized output levels 313 and 314 in FIG. 3, the reference signal at the input terminal 25 in FIG. Output level 415 to 4
16, and there is more leeway in the settings than in the case of FIG. 3, making it easier to stably detect solar radio waves.

Also, if the input level range 404 of the amplitude detector is B decibels (B<A) and the number of bits of the A/D converter is m bits, which is the same as in the case of FIG. The input level is B/2 ^m
(<A/2 ^m ), so equivalently the number of bits (increments on the vertical axis) is increased in Figure 3, and the accuracy of the average amplitude value becomes finer, resulting in an increase in the accuracy of the position data. I can do it.

In FIG. 1, the operations after the STC amplitude correction circuit 8 are the same as those of the prior art shown in FIG.

(Effects of the Invention) As explained above, the present invention utilizes a signal obtained by converting normal video into LOG when calibrating position data from radar using solar radio waves. The difference between the radio wave reception level and the receiver noise level is increased compared to the conventional case, and as a result, there is more leeway in setting the reference signal that determines the detection sensitivity, which has the effect of stably extracting solar radio wave position data. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a block diagram showing a configuration example of the conventional technology, FIG. 3 is an input/output characteristic diagram showing the radar reception signal level and A/D converter output in FIG. 2, and FIG. 4 is a diagram showing the radar reception signal level and A/D converter output in FIG. Received signal level and LOG
FIG. 3 is an input/output characteristic diagram showing a converter output. 1... Input terminal, 2... Logarithmic amplifier, 3...
A/D converter, 4...amplitude detector, 5...A/D
Converter, 6...LOG converter, 7...Video selector, 8...STC amplitude correction circuit, 9...Clutter area setting circuit, 10...Clutter removal circuit, 11
... Receiver noise removal circuit, 12 ... Average amplitude extraction circuit, 13, 14 ... Sweep memory, 15-2
0...Elevation angle scan memory, 21...MAX/
SUB extraction circuit, 21A...received signal input terminal,
22... Arithmetic circuit, 22A... Logarithmic amplifier, 23
...Output terminal, 23A...A/D converter, 24...
...Azimuth signal, 24A...STC amplitude correction circuit,
25...Input terminal, 25A...Clutter removal circuit, 26...Clutter area setting circuit, 27...Receiver noise removal circuit, 28...Average amplitude extraction circuit,
29, 30...Sweep memory, 31-36...
Elevation scan memory, 37...MAX/SUB extraction circuit, 38... Arithmetic circuit, 39... Output terminal, 4
0...Azimuth signal, 41...Input terminal, 101...
...Radar received signal, 102 ... Logarithmic video, 10
3...Normal video, 104...Control signal, 1
05... STC amplitude correction circuit output, 106... clutter area gate, 107... clutter removal circuit output, 108... video signal from which receiver noise has been removed, 109... sample signal, 201... radar received signal, 202... Logarithmic video, 203...
STC amplitude correction circuit output, 204...Clutter region gate, 205...Clutter removal circuit output, 2
06...Sample signal, 207...Receiver noise removal circuit output, 208...Average amplitude value, 301...
Input/output characteristics, 302... Logarithmic amplifier input level shown in logarithm, 303... A/D converter quantized output, 304... Input level range, 305... Average input level of receiver noise, 306... Sun Example of average reception level of radio waves, 307...A/D converter output for average input level 305 of receiver noise, 308...Average reception level of solar radio waves 306
A/D converter output for 309...Example of input level of interference signal, 310...A/D converter output for input level 309 of interference signal, 311...
...Average input level of receiver noise, 312...Average reception level of solar radio waves, 313...A/D converter quantization output for average input level 311 of receiver noise, 314...Average reception level of solar radio waves 312 A/D converter quantized output for, 31
5... Reference signal level for detection, 401... Input/output characteristics, 404... Input level range of amplitude detector corresponding to normal video level range, 405...
...Average input level of receiver noise, 406...Average reception level of solar radio waves at the same level as example 306 of average reception level of solar radio waves in Fig. 3, 407...
...for average input level 405 of receiver noise
LOG converter output, 408...LOG converter output level relative to the average reception level 406 of solar radio waves,
409...Example of input level of interference signal, 410...
LOG converter output for input level example 409,
411...Average input level of receiver noise, 41
2...Average reception level of solar radio waves, 413...Average input level of receiver noise 411
LOG converter output level, 414...LOG converter output level relative to the average received level 412 of solar radio waves.

Claims (1)

[Claims] 1. Jamming signals and solar radio waves received by an aerial pencil beam scanned in the azimuth and elevation directions of the search space (hereinafter referred to as jamming signals, etc.)
amplitude detection means for amplitude-detecting a received signal containing the signal and outputting a normal video; logarithmic detection means for similarly logarithmically amplifying and detecting the received signal and outputting a first logarithmic video; and logarithmically converting the normal video. , a logarithmic conversion means for outputting a second logarithmic video; the first logarithmic video and the second logarithmic video are input, the first logarithmic video is selected during normal operation of the radar, and the radar is converted by solar radio waves. When attempting to calibrate position data from
by an external control signal to select the logarithmic video of the first
a video selection means for selecting and outputting the logarithmic video or the second logarithm video; clutter removal means for removing a clutter area from the output of the video selection means and extracting a disturbance signal, etc. that does not include clutter; the clutter removal means an average amplitude extracting means for extracting an average signal intensity for each scanning beam unit from a plurality of interference signals etc. extracted by; The first one has the maximum intensity in the next plane.
The first average signal strength in the scanning beam of
MAX amplitude), and the second and third scanning beams adjacent to the first scanning beam in the azimuth direction.
Among the average signal strengths of
SUB-AZ amplitude), and the stronger one of the fourth and fifth average signals of the scanning beams adjacent in the elevation direction to the first scanning beam (hereinafter referred to as SUB-AZ amplitude).
MAX− to extract SUB−EL amplitude)
SUB amplitude extraction means; the MAX amplitude, SUB−
A radar signal processing device comprising: calculation means for calculating the arrival direction and arrival angle of an interfering signal, etc. from AZ amplitude, SUB-EL amplitude, and azimuth data and elevation angle data of a scanning beam that provides these.