JPS6349194B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a moving target detection radar device that detects a moving target by removing fixed clutter such as terrain, meteorological clutter such as rain clouds, and interfering clutter such as chaff.

As is well known, in order to extract only the moving target signal from the radar received signal, which is a reflected wave from the target, a moving target detection radar device decomposes the received signal into frequency components and detects the moving target from among them. are being developed in various ways. In such a conventional moving target detection radar device, for example, a plurality of Doppler filters are installed in parallel, and the Doppler signal amplitude obtained by background noise (clutter, receiver noise) for each scan (one rotation of the antenna) is A threshold value for the output signal amplitude of each of the Doppler filters is determined from the average estimated value, and a filter output signal exceeding the threshold value is detected as a moving target signal. However, in order to obtain the estimated background noise average value for each scan, a large-capacity storage device that is equivalent to the reflected signal for one scan is required, and an estimation error is required when estimating the average value for each scan. There is a possibility that incorrect information may be output due to Furthermore, automatic gain control or so-called area STC (a function to prevent receiver saturation by adjusting receiver sensitivity in particular for the relevant region) is generally applied in advance to large-amplitude clutter regions; Differences in levels occur near the boundaries of adjustment, which has been an obstacle in obtaining accurate average estimates.

This invention was made based on the above circumstances, and its purpose is to extract those with large amplitudes from among the Doppler frequency components sequentially obtained from radar reception signals, and to extract these components in the azimuth and distance directions. It is an object of the present invention to provide a moving target detection radar device that can detect moving targets more accurately with a simple configuration by identifying the state in which they are arranged.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. The transmitter 1 generates a radar transmission repetition pulse signal and sequentially derives it.
The output signal of the coherent oscillator (COHO) 11 is supplied together with the output signal of the highly stabilized oscillator (STALO) 2 to a mixer 12, and the transmission frequency signal obtained here is supplied to a modulation amplifier 13 equipped with, for example, a klystron. . The radar transmission repetitive pulse signal obtained by this modulation amplifier 13 is
For example, it is radiated into the search space from the antenna 4 via a transmitter/receiver switch 3 such as a diplexer.

This radiated pulse signal is reflected by the fixed target and the moving target, and after this reflected wave is also received by the antenna 4, it is supplied to the frequency converter 51 of the receiver 5 via the transmitter/receiver switch 3. Ru.
This frequency converter 51 includes the highly stabilized oscillator 2.
The received signal is frequency-converted to an intermediate frequency and amplified by this signal. The output signal of this frequency converter 51 is branched and supplied to first and second phase detectors 52 and 53, respectively, which output Doppler frequency components of the moving target. These first and second phase detectors 52 and 53 perform subsequent signal processing using complex vector operations. A signal is supplied via a 90° phase shifter 54, and a second phase detector 53 is directly supplied with the output signal of the coherent oscillator 11. Therefore, the first and second phase detectors 52 and 53 each output Doppler frequency components converted into so-called orthogonal videos (I, Q components) having a phase difference of 90 degrees. The reflected signal from the target whose phase has been detected in this manner is supplied to an analog-digital (A-D) converter 6.
In other words, the orthogonal video is supplied to the first and second A-D converters 61 and 62, respectively, and in the A-D converters 61 and 62, the phase detection output signal is output at every arbitrary sampling time. It is sampled and its amplitude information is converted into digital bits. This transform output is then supplied to the Fourier transform section 7.

This Fourier transform section 7 is configured as shown in FIG. 2, for example, and includes the first and second AD converters 6.
The digital output signals No. 1 and 62 are first supplied to a plurality of shift register circuits 71 having a shift time length corresponding to the radar transmission pulse repetition period. Digital detection signals in each azimuth direction for the same distance cells are derived from each output terminal of these shift register circuits 71 and supplied to the Fourier transformer 72. This Fourier transformer 72
is composed of, for example, eight parallel Doppler filters, and these Doppler filters are arranged to have pass frequency bands (filter banks) of F ₀ , ..., F ₇ in order from the low frequency side, and each The filters are sequentially numbered 0, . . . , 7.

Here, each output signal of the Fourier transform unit 7 is outputted sequentially in parallel for each range cell in the distance direction, and among each output information (azimuth region) of the shift register 71 introduced into the Fourier transformer 72, the center The azimuth direction is taken as the azimuth information of the output signal of the Fourier transformer 72. For convenience of explanation, the output of the Fourier transformer 72 is shown as a model in FIG. That is, in FIG. 3, the X-axis direction is the distance direction, and the Y-axis direction is the amplitude level, and the filter banks F ₀ to F ₇ are shown at each point in the Z-axis direction. In addition,
Although the amplitude levels are shown in analog form for ease of understanding, they are actually digital signals, of course.

Next, each output signal of each of the above-mentioned Doppler filters is supplied to a detector 8 that performs envelope detection. This detector 8 is composed of eight envelope detectors 80,..., 87 corresponding to each of the filter banks, and converts the output signal of each of the Doppler filters into √ ² +
Convert to the amplitude value of ^Q2 . Each output signal of this wave detector 8 is supplied to a detection circuit 9, and a signal with a relatively large amplitude, for example, the one with the maximum amplitude is detected.

FIG. 4 shows the configuration of this detection circuit, in which each output signal of the detector 8 is transmitted to each register 91 of a data register group 91 provided correspondingly.
It is temporarily stored in 0,...,917. By the way, the data stored in each of these registers 910,...,917 is in the format shown in FIG. 5. For example, in an 11-bit signal, the first 3 bits are the corresponding filter number, and the following 8 bits are is the amplitude value data. The output signal of the data register group 91 is inputted to one input terminal of the corresponding gate circuit 920, . . . , 927 of the gate circuit group 92, and further inputted to the comparison circuit group 93. This comparison circuit group 93 is a first stage comparison circuit 93
1,..., 934, second stage comparison circuit 935, 936
and a third stage comparison circuit 937, and each of these comparison circuits outputs amplitude value data of a signal having a large amplitude level among input signals and its corresponding filter number.

Incidentally, each of the comparison circuits 931, . . . , 937 is composed of a comparator A and a selection circuit B, as shown in FIG. 6, for example. That is,
Comparator A detects the signal with the larger amplitude of the two input signals, and its detection output signal is supplied to selection circuit B. This selection circuit B is supplied with the two input signals and the filter number outputting the signals, and the output signal of the comparator A determines the filter number and amplitude value of the larger one of the two input signals. Data is output. However, such a comparator A
and each comparison circuit 93 configured by selection circuit B.
1, . . . , 937, the first maximum value data and its filter number are stored in the first register 94, and at least the filter number is stored in the second register 95. Next, the second
The filter number stored in the register 95 is supplied to each other input terminal of the gate circuit group 92, and the gate circuit 920,..., 9 corresponding to the filter number is supplied to the other input terminal of the gate circuit group 92.
27 is turned off to prevent the first maximum value data from being input to the comparison circuit group 93. As a result, in the next step, the second maximum amplitude value of the signals stored in the data register group 91 is detected, and the second maximum amplitude value data and its filter number are stored in the third register 96. Ru.

Next, the signal data with large amplitudes selected as the first amplitude maximum value and the second amplitude maximum value detected by the detection circuit 9 are outputted in the order of distance cells and supplied to the correlation processing section 10. The correlation processing unit 10 is composed of an azimuth correlation processor 110 and a distance correlation processor 120.

First, the azimuthal correlation processor 110 will be explained. The specific configuration of this azimuth direction correlation processor 110 is shown in FIG. Add and count the number of pieces, compare this with the standard value,
Processing is performed to detect the target by removing clutter that spreads in the azimuth direction.

That is, in FIG. 7, the filter number corresponding to the first maximum amplitude output from the detection circuit 9 is input to one input terminal of each filter number detection circuit constituting the filter number detection circuit 111. A different filter number is input to the other input terminal of each filter number detection circuit, and a match is made between this filter number and the filter number inputted above, and a "1" signal is output from the matched filter number detection circuit. is output, and "0" signals are output from the circuits in which there is no match in the order of the distance cells. This signal is branched, one is inputted to one input terminal of the corresponding adder circuit in the adder circuit group 112, and is added to the cumulative result of the above "1" signal for the same distance supplied from the buffer register 116. Then, the number of times the first amplitude reaches the maximum value within the azimuth range tested for each filter number is derived.

The other signal from the filter number detection circuit group 111 is composed of a shift register with a length corresponding to the product of the number of distance cells in the distance direction and the number of sweeps (number of windows) included in the azimuth width to be verified. The signal is supplied to a shift register group 113.

Each output of this shift register group 113 is supplied to each subtracter circuit of a subtracter circuit group 114 together with each corresponding output of the adder circuit group 112, and the output of the shift register group 113 is subtracted from the output of the adder circuit group 112. That is, the subtracting circuit group 114 subtracts the detection result of the oldest filter number detection circuit in this azimuth area from the cumulative result of the "1" signals within the azimuth width tested over the same distance. The results of this subtraction are respectively stored in the range memory group 115.
is supplied to each memory. Range memory group 115
is a shift register having a length equal to the number of distance cells in the distance direction, and the above-mentioned subtraction results are accumulated in the order of the distance cells. This range memory group 115
The outputs are respectively supplied to the other input terminals of the adder circuit 112 via the buffer register group 116, and are added to the output of the filter number detection circuit group 111 in the latest sweep to determine the direction tested at the same distance. The count value of the filter number where the first amplitude maximum value within the width exists is derived. Data processing is performed in order for each distance sampling time, and when one sweep is completed, processing is performed in the order of distance in the next sweep. Therefore, for the same distance, the addition content in the addition circuit 112 is updated sequentially every radar transmission pulse period (one sweep), and the azimuth width to be verified is moved in the azimuth direction by the angle between the sweeps every sweep. While letting
The number of times the first amplitude takes the maximum value within the azimuth width is derived for each filter number.

The input side of the first amplitude maximum value data has been explained above, but the input signal of the second amplitude maximum value data also has the same circuit configuration and circuit operation, so the drawing and its explanation are omitted in FIG. 7. .

The input number of first amplitude maximum values determined as described above is added to the input number of second amplitude maximum values for each filter number. That is, the output signal of the adder circuit group 112 is the output signal of the adder circuit group having the second maximum amplitude value, and the output signal of the adder circuit group 112 is the first amplitude signal for each filter number.
The signal is supplied to an adder circuit 117 that calculates the total number of inputs of the maximum value and the second maximum value. This is a means for removing clutter and reliably detecting the target when the target is present in the clutter. In addition, if there is fluctuation in the moving speed of the clutter, the amplitude value for each filter number may fluctuate, and even if the frequency of the clutter is the same, the amplitude is not always constant. It is a means to prevent and reliably detect targets.

That is, when the target signal amplitude is smaller than the clutter signal amplitude, focusing only on the first amplitude maximum value may result in failure to detect the target signal. In addition, if the amplitude changes due to fluctuations in the moving speed of the clutter, focusing only on the first maximum amplitude value will result in fewer times than it should be possible to take the maximum amplitude value, and the clutter will be determined as the target. There is a risk of it happening. Therefore, in order to remove clutter, detect the target reliably, and prevent false detection of the target, the number of inputs with the second maximum amplitude value is also counted, and the number of inputs with the first maximum amplitude value is added. .

The output signal of this adder circuit group 117 is supplied to a determination circuit group 1181. This judgment circuit group 1181
is for verifying how many pieces of information regarding moving targets are included in the azimuth to be verified, and a predetermined reference value is supplied from a detection standard setting device 1182 to each determination circuit. When the determination circuit group 1181 determines that it is a target, it supplies the filter number and amplitude value data to the OR circuit 119, and causes the OR circuit 119 to output the filter number and amplitude value data that are moving target information.

Next, the azimuth direction correlation processor 1 shown in FIG.
10 will be supplementarily explained with reference to FIGS. 8 and 9.

Figure 8a is a part of the radar scan, azimuth angles θ ₁ to θ ₂
This figure shows the situation in the past, and shows the reflected Doppler frequency components obtained from clutter that is currently spreading over a wide area.
Assume that the Doppler frequency component reflected from the moving target existing in _the clutter is obtained as F _{5 (} corresponding to filter bank number F ₅ ). do.

Now, the output after Fourier transformation of the target reflected Doppler signal chained in the azimuth direction for a specific range cell is expressed for each filter number as shown _{in FIG .} represents the clutter reflection component, and _F5 represents the target reflection component. The signal shown in FIG. 8b is supplied to the detection circuit 9 and the azimuthal correlation processor 110 of the correlation processor 10 via the detector 8, as described above. In this azimuth direction correlation processor 110, the data is expressed as a series of filter numbers divided into azimuth cells, as shown in FIGS. 9a and 9c, for example. The examples in Figure 9 a and c are extracted from one sequence of azimuths at a certain distance,
Actually, such a sequence exists as many as the number of distance cells in the distance direction.

FIG. 9a shows a series of filter numbers that take the first maximum amplitude value, and FIG. 9c shows a series of filter numbers that take the second maximum amplitude value. Here, if the number of windows in the azimuth direction to be verified is, for example, 10, the number of filter numbers corresponding to the first maximum amplitude value is counted for each sweep as shown in FIG. 9b,
The number of filter numbers corresponding to the second maximum amplitude value is counted for each sweep as shown in FIG. 9d. Of course, within one sweep time, counting is sequentially performed on data arranged in the same manner as in FIGS. 9a and 9c for each distance sample time.

These counted values are then summed up for each filter number, and this total value is set to, for example, "5" or "6".
By comparing it with the reference value set in , F5 of filter number " ₅ " is determined to be a signal, and all others are rejected. In this way, the target signal is extracted from within the clutter that spreads in the azimuth direction.

Now, next, since the output of the OR circuit 119 of the azimuth direction correlation processor 110 is output in the order of the distance direction at each distance sample time, based on this output signal, the first By counting the number of times the amplitude reaches the maximum of 2 and comparing this counted value with a predetermined reference value, it is possible to remove clutter that spreads in the distance direction and extract the target signal.

FIG. 10 shows the configuration of this distance direction correlation processor 120. That is, the azimuthal correlation processor 1
The filter numbers, which are the output signals of the ten OR circuits 119, are sequentially supplied to one input terminal of each filter number detection circuit constituting the filter number detection circuit group 121 at each distance sample time. The output signal of the OR circuit 119 is signal information that is determined to be a target in the azimuth direction. In addition, different filter numbers are input to the other input terminal of each filter number detection circuit, and this filter number is matched with the input filter number. This coincidence output signal, for example a "1" signal, is input to each shift register 1221 of the counting circuit group 122. This shift register 1221 has a length corresponding to, for example, seven distance cells, and while shifting data in order at each distance sample time, "1" included in the seven distance cells is
The number of signals is counted by each adding circuit 1222. The count outputs are then input to the corresponding determination circuits of the determination circuit group 123, respectively. A reference signal indicating a reference range is supplied to each of the judgment circuits from the detection reference setter 124, and each addition circuit 12
If the count value at 22 is within the reference range, it is determined that the target is the target in the distance direction, and a determination output signal is supplied to the OR circuit 125. Distance correlation processor 1
20 is supplied with the output from the azimuth direction correlation processor 110 when the target is determined in the azimuth direction, so the OR circuit 125 outputs the output when the target is determined in both the azimuth direction and the distance direction. A target signal indicating the presence or absence of the target is output. Thus, from this OR circuit 125, a target signal from which clutter that spreads in the azimuth and distance directions has been removed is extracted.

Note that the reference value or reference range set by the detection reference setters 1182 and 124 is determined as follows. First, for each of the Kuratsuta and goals (based on actual flight tests),
A statistical total value distribution of the number of appearances of the total value for each filter number of the count values shown in FIGS. 9b and 9d (how many times each appears) is determined. Here, since the clutter spans a wider range than the target, the peak of the total value distribution for the clutter is located much larger than the peak of the total value distribution for the target. Therefore, the detection standard setter 1182 determines, for example, the total value that is the peak of the total value distribution on the target side as the reference value or a certain range on both sides of the peak as the reference range. Further, from the statistics of the number of appearances in the distance direction of the total value within this reference value or reference range, the reference value or reference range is determined by the detection standard setter 124 based on, for example, the peak value of the number of appearances. As a result, during actual measurement,
If the total value and the number of appearances each match the reference value or are within the reference range, it can be identified as a target.

By the way, such a distance direction correlation processor 12
0, since correlation processing is performed regarding the filter number, even if multiple targets have approximately the same distance from the radar to the target (slant distance), if they have different Doppler components, this will not be rejected.
This will be explained using FIGS. 11a and 11b.

That is, in FIG. 11a, the Doppler frequencies of target T ₁ and target T ₂ are respectively F ₅ and F ₆ ,
In a situation where each filter bank spans, for example, two distance cells and the slant distance is separated by, for example, two distance cells, the series of filter banks in the distance direction after the maximum amplitude value is detected is as shown in FIG. 11b. Therefore, since the filter banks are different from F ₅ and F ₆ , they are identified as two targets without being rejected as clutter that spreads in the distance direction.

The target detected as described above is displayed on a display 11 made of, for example, PPI.

Furthermore, in addition to the output signal from the distance correlation processor 120, the display 11 displays, for example, the first amplitude maximum value data of the azimuth correlation processor 110 and the detection circuit 9, as shown in FIG. It is also possible to supply and display the signals selectively or simultaneously via the switches a and b.

According to the moving target detection radar device having the above configuration,
After Fourier-transforming the reflected signal from a moving target existing in a clutter that spreads in the azimuth direction and distance direction, the first and second amplitude maximum values are determined based on the filter number of the Doppler filter obtained by this Fourier transformation. 1. Count the second maximum amplitude value for each filter number, compare the total of each count value with a predetermined reference value, extract a moving target from the clutter that spreads in the azimuth direction, and then extract the moving target from the clutter that spreads in the distance direction. Extracting moving targets. Therefore, this signal processing is performed on the filter number that indicates the maximum value regardless of the amplitude value of the received signal, so it is less affected by the area STC boundary area or the automatic gain adjustment of the receiver. , the ability to suppress clutter and extract signals is extremely accurate. In addition, such signal processing has the effect that even if a plurality of targets connected in the distance direction have different filter numbers, they will not be determined as clutter and the target can be detected.

Furthermore, for maximum value detection, it is not necessary to process all filter banks;
It is also possible to reduce the hardware configuration because it is sufficient to detect the maximum value of the degree.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, when counting the chain status of Doppler filter numbers, weighting is applied to each Doppler filter (for example, a large coefficient for F ₀ , a large coefficient for F ₁ ~ It is also possible to adjust the rejection ability of the clutter by adjusting F ₇ (a small coefficient).

Incidentally, it is also possible to newly add a color graphic display device to the moving target detection radar device of the present invention to the device configuration shown in FIG. FIG. 12 shows an embodiment of this color graphic display device, which displays radar reception signals in different colors according to their signal levels.

That is, the detection output signals of the detector 8 are sequentially stored in the buffer memory 200 for each sweep. Writing into buffer memory 200 is performed using a write signal output from determiner 201 and an address designation signal. That is, the determiner 201 is supplied with an angle signal from the angle signal generator 202 provided in the antenna 4, and the address designation signal corresponding to this angle signal is supplied to the determiner 201.
is output from. Therefore, the detection output is stored in the buffer memory 200 in a state corresponding to the rotation angle of the antenna 4.

Furthermore, the data stored in the buffer memory 200 is output in accordance with the area designation signal supplied to the determiner 201. That is, the determiner 201 matches the area designation signal with the angle signal from the angle signal generator 202, and in the matched state, a read signal and an address designation signal corresponding to the angle signal are supplied to the buffer memory 200. Thus, the detection output signal of the specified area is read from the buffer memory 200, and this signal is supplied to the signal strength-code converter 203. This signal strength -
The code converter 203 generates a color signal according to the signal strength of the detected output signal, and the output signal of the signal strength-code converter 203 is supplied to a color graphic display 204. The display 204 displays distance and filter banks as shown in FIG. 13, and the color-converted detection output signal is displayed for each filter bank and for each distance cell.

Note that FIG. 13 shows a case where the signal shown in FIG. 8b is displayed, and for example, clutter is shown in green and the signal is shown in red.

Furthermore, it is also possible to arrange the Doppler filter output amplitude values, which are the outputs of the Fourier transformer 72, in the order of magnitude at the distance and display them on a distance sweep axis.

Using a display device with this configuration eliminates the need for a level compressor, etc., making it possible to achieve a high dynamic range of the display, and since it is displayed in color, it is easier for the operator to visually see the target than a monochrome display. It has the advantage of facilitating detection.

As described in detail above, according to the present invention, it is possible to provide a moving target detection radar device which has an extremely highly accurate signal detection ability and can more accurately detect a target within a clutter, for example.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of a moving target detection radar device according to the present invention, FIG. 2 is a configuration diagram showing the Fourier transform section of FIG. 1, and FIG. 3 is a diagram of the Fourier transform section of FIG. 2. FIG. 4 is a configuration diagram showing the detection circuit of FIG. 1, FIG. 5 is a diagram showing the storage format of the data register in FIG. 4, and FIG. is a block diagram showing the comparison circuit in FIG. 4, FIG. 7 is a block diagram showing a part of the azimuthal correlation processor in FIG. 1, FIGS. 8 a, b, and 9 a, b, c, d is a diagram for explaining the signal processing of the azimuth direction correlation processor, FIG. 10 is a diagram showing the configuration of the distance direction correlation processor of FIG. 1, and FIGS.
b is a diagram for explaining the signal processing of the distance direction correlation processor, FIG. 12 is a schematic configuration diagram showing an example of a color graphic display device, and FIG.
FIG. 2 is a diagram showing an example of a display format of the display device shown in the figure. 1... Transmitter, 5... Receiver, 6... A-D converter,
7...Fourier transform unit, 8...Detector, 9...Detection circuit, 110...Azimuth direction correlation processor, 120...Distance direction correlation processor, 11...Display device.

Claims (1)

[Claims] 1. A transmitter that sequentially derives repeated radar transmission pulse signals and supplies them to the antenna via the transmission/reception switching device; and a transmitter that sequentially derives the radar transmission repetitive pulse signal and supplies it to the antenna via the transmission/reception switching device; A receiver that is introduced and detects after frequency conversion,
An analog-to-digital converter connected to the receiver and converting the amplitude information of the detected output signal into a digital signal; A Fourier transform section that performs Fourier transform on each of multiple signals connected sequentially in the direction of distance and in the azimuth direction, and outputs the output signals to different output terminals for each different frequency component; a detector that detects signals from each end; a detection circuit that is connected to the detector and detects first and second frequency components having the first and second largest amplitudes; said first and second connected in the same direction area and the same distance direction area.
a correlation processing unit that counts the total number of signals of frequency components for each frequency component and determines that the counted value matches a reference value or a signal of a frequency component that is within a reference setting range as a target signal; A moving target detection radar device comprising: a display device for displaying a signal determined to be a target signal by the section;