JPS62165174A - Radar device - Google Patents

Abstract

PURPOSE:To improve the visibility and direction accuracy of a moving target by interpolating a blip split and removal of a target signal for a signal after constant wrong alarm rate processing and filter selection of every Doppler frequency. CONSTITUTION:A reflected radio wave from the target is received by an antenna 3 and passed through a circulator 2, a receiver 2, etc., and a canceler 6 remove a fixed signal component. Then, only signal components in a pass-band frequency range are separated and extracted by Doppler filters 7A-7N and supplied to a filter selector 9 after moving clutter components are suppressed by constant wrong alarm rate processors 8A-8N. The selector 9 selects the signal with the largest amplitude among output signals of the processors 8A-8N in processing units in each distance direction and inputs the selected signal to an amplitude interpolator 10 as an output signal 101. Then, the signal 101 is compared at the same distance in each of three directions and only when the center direction signal level is smaller than the preceding and following direction signal levels, the center signal level is substituted with the mean signal level of the preceding and following signal levels to interpolate the blip split, etc., of the target signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radar device, and particularly to a radar device for identifying and detecting moving targets.

[Conventional technology]

Conventionally, radar for moving targets uses a moving target display canceler (hereinafter referred to as a canceller) to remove fixed clutter, and a signal between the moving clutter and the moving target using the difference in Doppler frequency after processing by the canceller. a constant false alarm rate processor (hereinafter referred to as a CFAR processor) to suppress the separated moving clutter; and a multiple Doppler filter to combine the Doppler filter output signals after the CFAR processing. It has a filter selector.

However, in this case, even if a reflected signal is obtained from the same moving target while changing the azimuth for each transmission, if the Doppler frequency of the received signal from the moving target matches an integral multiple of the transmitter return frequency (in this case Blind speed (the relative speed between a radar device and a moving target) is removed by canceller processing, so for example, among received signals corresponding to adjacent transmitted signals, a received signal in a certain direction may overlap received signals on both sides. It bothers me that it's so small in comparison.

In such a case, when the reflected signals are viewed through a PPI scope, the grip may crack so that the reflected signals from the same moving target appear as if they were reflected signals from two distant targets. Moreover, such a phenomenon may occur with respect to reflection from the edge of a moving target from which a reflected signal is obtained, and in this case, cracking of the prep occurs, leading to deterioration of azimuth accuracy. Hereinafter, the structure and operation of a conventional radar for detecting a moving target will be explained with reference to FIG. 6.

As shown in FIG. 6, an example of a conventional configuration of a radar for detecting a moving target includes a transmitter 21 and a circulator 22.
, an antenna 23, a receiver 24, an AD converter 25,
Canceller 26, Doppler filters 27A to 27N,
CFAR processors 28A to 28N and filter selector 2
9 and a display 32. The transmission pulses output from the transmitter 21, which transmits a predetermined number of pulses for each period for a plurality of preset periods, are as follows:
The radio waves are inputted to the antenna 23 via the circulator 22 and emitted as short pulse-like radio waves, and the radio waves reflected from the target and returned are received by the antenna 23 again and input to the receiver 24 via the circulator 22. .

The receiver 24 mixes the transmission frequency components, detects a frequency component that is different from the transmission frequency, and then transmits it to the AD converter 25, where it is converted into a digital signal. The digital signal is subjected to cancellation processing in the canceller 26 for each combination of two or three consecutive signals in the azimuth direction at the same distance to remove fixed signal components, and then passed through the Doppler filter 27A.
~27N.

The Doppler filters 27A to 27N separate and extract only the signal components within a predesigned passband frequency band, respectively, and pass them to the next stage CFAR processors 28A to 28.
At N, the energy component that constantly exists in both distance and direction is suppressed. After suppressing the moving clutter components in this way, the CFAR processor processing power is inputted to the filter selector 29, and the maximum amplitude signal is selected from among the CFAR processor processing power signals for each processing unit in each distance direction. is output as a filter selector output signal 201, and this signal is input to the display 32 and displayed.

The filter selector output signal 201 is obtained by signal processing each received signal reflected from the corresponding direction for each signal, so even continuous signals obtained from the same moving target may not be received due to blind speed. Differences in signal levels can result in: 1. Even when gripping the same moving object, the middle of the prep may fall off or the end of the prep may break off.

rδ'F= Ell≠YotsuboIfrafusenrokumonshuozan1 The problem with the conventional technology that the present invention aims to solve is that, as mentioned above, the grip may be cracked or scraped as shown in the display. Unfortunately, it causes deterioration in the visibility and azimuth accuracy of moving targets such as aircraft.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a radar device that solves the above-mentioned drawbacks.

[Means for solving problems]

The radar device of the present invention includes a moving eye surface body display canceller;
A constant false alarm rate processor for each of the plurality of Doppler filters, and a CF
It is equipped with a filter selector that selectively combines the output signals of each Doppler filter channel after AR constant false alarm processing, and performs group staggered transmission that transmits a predetermined number of pulses for each period for a plurality of preset transmission periods. In the moving target display radar device, among the output signals from the filter selector, the signal level in the direction of interest among the signals continuous in the direction of the same distance is unique as a function of the signal levels of the adjacent two sides. When the amplitude is smaller than a predetermined value determined by the amplitude interpolation means, the output of the amplitude interpolation means is the same as that of the amplitude interpolation means, which outputs the relevant direction at the distance with a value uniquely determined as a function of the signal levels on both sides. and an integrating means that performs smoothing integration processing for azimuths within a predetermined range of distances.

〔Example〕

Next, the present invention will be described in detail with reference to drawings showing embodiments of the present invention.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIGS. 2(a) and (b) are block diagrams showing the configuration of an amplitude interpolator of the embodiment of the present invention, and FIG. The figure is a block diagram showing the structure of the smoothing integrator in the structure of one embodiment of the present invention, FIG. 4 is a chart showing the relative position between the distance direction and the interpolation direction of the present invention, and FIG. It is a chart showing an example of waveforms of an amplitude interpolator and a smoothing integrator in the configuration of one embodiment.

First, an outline of an embodiment of the present invention will be explained with reference to FIGS. 4 and 5. In Fig. 4, short pulse radio waves are sequentially emitted from the radar antenna in the distance directions 01 to θI to θM, reflected radio waves from targets and clutter in each direction are received, and from this signal, a canceller is first used. Remove fixed clutter components. Next, Doppler frequency signals proportional to the relative speeds of the target and moving clutter to the radar are separated and extracted through multiple Doppler filters, and the moving clutter components are suppressed by a CFAR processor, after which the output signal from each Doppler filter channel is extracted. Among them, the signal with the largest received energy is output from the filter selector as a filter selector output signal.

In this case, since the transmission repetition frequency differs for each of the multiple transmission pulses set in advance, the output signal level of the filter selector may differ depending on the azimuth direction even for the same moving object due to the effect of blind speed as a result of canceller processing. be.

Therefore, among the filter selector output signals obtained for each of the sequentially obtained distance directions θ1 to θ■ to θM, only the signals reflected from the circumference in the azimuth directions R1 to RH to RN centered on the radar 71 are sequentially collected. Arrange in time. Therefore, the relationship between the signal reflected from a point at which the distance to the radar 71 is constant and the direction (input/output as a signal corresponding to time) can be obtained. An example of this is the filter selector output signal level shown in the diagram of FIG. If such a signal is displayed on a display device, cracking of the prep may occur, and there is a risk of misidentification of the prep when monitoring the display. Therefore, the average of the reflected signal intensities in the directions on both sides of level 81 is formed at a position corresponding to level 81, thereby interpolating the prep break. At this time, when interpolating prep cracking, if the reflected signal strength is smaller than a certain threshold, that is, if it is buried in noise, the above processing is not performed, and the clutter remains or the noise signal is removed. This avoids the danger of stressing the grip.

The result is a signal that does not cause grip cracking on the display, such as the amplitude interpolator output signal level. This signal is further smoothed to make the display generally easier to see, as seen in the integrator output signal level. Furthermore, the maximum values of the filter selector output signal, amplitude interpolator output signal, and smoothed integral output signal in FIG.
Although there is a delay due to calculation time as shown in 83, it can be dealt with by correcting the angle signal. In this manner, the grip on the display is prevented from cracking or missing.

Next, an embodiment of the present invention will be described, focusing on its configuration and operation. As shown in FIG. 1, this embodiment includes a transmitter 1, a circulator 2, an antenna 3, a receiver 4, and an AD converter 5.
, canceller 6, Doppler filters 7A to 7N, and C
FAR processor processing-8A to 8N filter selector 9, amplitude interpolator 1o, smoothing integrator 11, display 12
It is equipped with

The transmission pulses output from the transmitter 1, which transmits a predetermined number of pulses for each period for a plurality of preset periods, are input to the antenna 3 via the circulator 2 and are transmitted as short pulse-shaped radio waves. The radiated radio waves reflected from the target and returned are received again by the antenna 3, passed through the circulator 2, and input into the receiver 4. receiver 4
Then, the transmission wave number components are mixed up, and after detecting the frequency component that is different from the transmission frequency, it is sent to the AD converter 5, where it is converted into a digital signal. The digital signal is sent to the canceller 6 in two or three consecutive directions at the same distance.
After canceller processing is performed for each combination of signals and fixed signal components are removed, the signals are supplied to Doppler filters 78 to 7N.

The Doppler filters 5A to 7N separate and extract only the signal components within the pre-designed bass band frequency bands, and the Doppler filters 5A to 7N separate and extract only the signal components within the pre-designed bass band frequency bands, and then process them in the next stage CFAR processor -8A to 8K.
>, the energy component that constantly exists in the distance direction is suppressed. After suppressing the moving clutter components in this way, the processing power of the CFAR processor is reduced to the filter selector 9.
K, each CFAR for each processing unit in each distance direction
Outputting the maximum amplitude signal from among the processor output signals as the filter selector output signal 101 is similar to the conventional technique.

The filter selector output signal 101 for each orientation is sequentially input to the amplitude interpolator 10, which compares the filter selector output signals for each of the three orientations corresponding to consecutive orientations and at the same distance. Only when the signal level corresponding to the central direction among three consecutive directions is smaller than the signal level corresponding to the directions before and after it, the signal level corresponding to the center direction is changed to the signal level corresponding to the directions before and after it. The amplitude interpolator output signal 102 replaced by the average signal level becomes a signal as shown in Fig. 5.

This amplitude interpolator output signal 102 is input to a smoothing integrator 11, which generates a waveform that is convenient for displaying the smoothed display without causing any splitting, i.e., a smoothing integrator as shown in FIG. The signal becomes an output signal 103 and is displayed on the display 11.

Here, details of the amplitude interpolator 10 and the smoothing integrator 11 will be explained. FIG. 2(a) is a block diagram showing the configuration of the first embodiment of the amplitude interpolator, in which the amplitude interpolator is connected to the memory 41.
- 42, an adder 43, a multiplier 44, a comparator 47, and a selector 48. The filter selector output signal 101 corresponding to the received signal for each transmission is stored in the memories 41 and 4.
2 and read out sequentially in synchronization with the output timing of the filter selector output signal 101.
・42 is controlled. Furthermore, the multiplier 44 is controlled by the multiplicate signal 105 and is set to 1/2, which is a kind of coefficient setting value that outputs 1/2 of the input signal level. Therefore, the filter selector output signal 101 and the memory output signals 111 and 112 are reflected signals from points corresponding to three consecutive azimuths and equidistant from the radar. Therefore, the comparator 47 has a certain azimuth signal level (memory output signal 11
1) and the average value of the signal levels in the directions before and after it (multiplier output signal 113), and if the memory output signal 111 is larger than the multiplier output signal 113, the former is output, and if it is smaller, the latter is output. The final control signal 114 is output to the selector 48. In addition, the selector 48 also selects the control signal 1.
14, either the memory output signal 111 or the multiplier output signal 113 is output as the amplitude interpolator output signal 102.

Next, FIG. 2(b) is a block diagram showing the configuration of a second embodiment of the amplitude interpolator.・56 and
A selector 58 is provided. The comparator 55 compares the multiplier output signal 113 (the average value of the signal levels in directions before and after a certain direction) with the threshold value 106, and when the multiplier output signal 113 is smaller than the threshold value 1106, ,
A memory output signal 111 (level of a received signal in a certain detection direction) is output as an amplitude interpolator output signal 102. Further, when the multiplier output signal 113 is larger than the threshold value 106, the same operation as in the first embodiment is performed.

Next, details t/c of the smoothing integrator 8 will be explained.

FIG. 3 is a block diagram showing the configuration of an embodiment of the smoothing integrator, and the smoothing integrator includes memories 61, 64, 66, adders 63, 65, and multipliers 67, 68. . The amplitude interpolator output signal 102 for a predetermined azimuth range is stored in a memo IJ 61K, and the signal is read out at every same distance, and an adder 63, a memory 64, and an adder 6
5 and a memory 66, and is output as a smoothed integrator output signal 103. Simultaneously smoothing integrator signal 103
are added to adders 65 and 63 through multipliers 67 and 68, respectively.
, and the multipliers 67 and 68 add 1 to the multiplicand signal.
K.

is added to form an integrating circuit with feedback.

The memories 64 and 65 are used as a form of delay circuit to store the received signal read out from the memory 61, read it out continuously after a preset time, and output it to the next circuit. .K in the multiplicable signal is set in advance so as to approximate the directivity of the smoothing integrator output signal waveform shown in FIG. By the method described above, it is possible to display the grip without cracking or scraping.

〔Effect of the invention〕

As explained in detail above, the radar device of the present invention performs canceller processing, and interpolates cracks and scrapes in the prep of the target signal caused by blind speed with respect to signals that are CFAR-processed and filter-selected for each Doppler frequency. This has the effect of improving visibility on the display and azimuth accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIGS. 2(a) and (b) are block diagrams showing the configuration of an amplitude interpolator of the embodiment of the present invention, and FIG. The figure is a block diagram showing the structure of the smoothing integrator in the structure of one embodiment of the present invention, FIG. 4 is a chart showing the relative position between the distance direction and the interpolation direction of the present invention, and FIG. FIG. 6 is a diagram showing an example of waveforms of input and output signals of an amplitude interpolator and a smoothing integrator in the configuration of an embodiment, and FIG. 6 is a block diagram showing an example of a configuration according to a conventional technique. 1...Transmitter, 2...Circulator, 3...Antenna, 4...Receiver, 5...
...AD converter, 6...Canceller, 7
A~7N...Doppler filter, 88~8N...
...CFAR processor, 9...Filter selector, 10...Amplitude interpolator, 11...Smoothing integrator, 12...Display . ij supervisor DR ■ grass 2 υσ (5) broom 3 Figure No. 4 [! I Kaya 5 circles

Claims (1)

[Claims] A moving target object display canceller, a plurality of Doppler filters, a constant false alarm rate processor for each Doppler filter, and selectively combining the output signals of each Doppler filter channel after constant false alarm processing. In a moving target display radar device that performs group staggered transmission in which a predetermined number of pulses are transmitted in each period for a plurality of preset transmission periods, the moving target display radar device is equipped with a filter selector and performs group staggered transmission, in which a predetermined number of pulses are transmitted in each period for a plurality of preset transmission periods.About the output signal from the filter selector. , when the signal level in the direction of interest is smaller than the value uniquely determined as a function of the signal levels of the adjacent two neighbors among signals that are continuous in the same direction in the same distance, the signal level of the two neighbors is an amplitude interpolation means for outputting a value uniquely determined as a function in the direction in question at the distance; and an integration means for performing smoothing and integration processing on the output of the amplitude interpolation means for a predetermined range of direction in the same distance. A radar device equipped with