JPH03261884A - Radar apparatus - Google Patents

Abstract

PURPOSE:To prevent a value which is not a maximum value from being detected as the value of a target by adding maximum value detector for detecting the maximum value from within a cell adjacent to the one detected as the target in a CFAR detector to a radar apparatus. CONSTITUTION:A radar apparatus is provided with a maximum value detector 5 for comparing the levels of a cell detected as a target by a CFAR detector 4 and of eight cells adjacent to first-said cell. The detector 5 checks the levels of the cell detected as the target by the CFAR detector 4 and of the adjacent eight cells and, when one of the eight cells has the level higher than that of the cell detected as the target, the signals detected before as the signal of the target are invalidated. Thus, since the signal that is not originally of the target is not detected as that of the target, a wrong alarm rate can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radar device, and particularly to a radar device that has a constant false alarm rate (CF A R).
lseAlarm Rate).

[Conventional technology]

FIG. 2 shows a conventional radar device that performs two-dimensional CFAR detection. Figure 2 is published patent publication A 1894-1894.
This is a device similar to Figure 1 published on page 439 of No. 76. In the figure, 1 is an A/D converter, 2 is a Doppler filter, 3 is a video integrator, and 4 is a CFAR detector.

Next, the operation will be explained.

In Fig. 2, a video signal sent from a receiver is converted from an analog signal to a digital signal by an A/D converter 1 of a signal processor, and a Doppler filter 2 configured by FFT (fast Fourier transform) converts the video signal to a Doppler frequency. Outputs a signal corresponding to

The signal output from the Doppler filter 2 has its S/N ratio improved by a video integration circuit 3 and is sent to a CFAR detector 4. Here, the function of the CFAR detector 4 will be explained using FIG. 3. Assume that a cell that appears to contain a signal from the target exists at the position of the range gate R, and the Doppler filter F.

First, the neighborhood average values in the range direction and filter direction of the relevant cell are determined. Here, when calculating the neighborhood average value, R, .

(range direction) and Fj, 1. FJ-1 (filter direction)
The reason for this is that adjacent cells are affected by the target signal, so there is not much difference in level between the target cell and the adjacent cell, so if you include the adjacent cell in the average and perform CFAR processing, it will be detected as a target. This is because there may be cases where it is not done. The neighborhood average value in the range direction is Ri-1r R1-21・
...+RI−++ average signal level and Ri”!
＋Rib! + ... Find the average signal level at +R1+R, and then take the average of both (processing 2
0-22). Next, multiply this average value by a constant (process 23)
, compare that value with the signal value of the corresponding cell R1 and process 24
), if the level of the corresponding cell is higher, it is determined that "hit has been detected".

Next, in the same manner, the neighborhood average value in the Doppler frequency direction of the relevant cell is determined. That is, F j-2+ F j-3+
...Average signal level at F j−a and F j+
Z I F j+3 r... The average signal level at F j *a is determined, and the average of both is further taken (processes 30 to 32). Then, the obtained average value is multiplied by a constant (process 33), and the value is compared with the signal value of the corresponding cell F (process 34), and if the level of the corresponding cell is higher, it is determined that "a hit has been detected". The above two directions (range direction, Doppler filter direction) are ANDed (processing 40), and CF is performed only when there is a human detection in both directions.
A detected hit is output from the AR detector 4.

This concludes the explanation of the CFAR function. By the way, if we consider the case where the level arrangement is as shown in FIG. 4, for example, the following problems arise that cannot be dealt with only by the above-mentioned CFAR function. Looking at the CFAR processing in the cells surrounded by 0 in FIG. 4, the neighborhood average value in the range direction is 15, and the neighborhood average value in the filter direction is 18. If the multiplication constants in the range direction and the filter direction are assumed to be 1 for simplicity, the center cell 10 will not be detected as a target. However, in the CFAR processing for the cell surrounded by the mouth, the neighborhood average value in the range direction is 6, the filter direction is also 6, and the center cell 8 is detected as a target even though it has a value lower than 10. In this way, depending on the intensity distribution of neighboring cells,
A signal that is smaller than the neighboring cell (not a maximum value), that is, a signal that is not a target, may be detected as a target.

[Problem to be solved by the invention]

Conventional CFAR detectors are configured as described above, so even if there is a signal with a higher level than that cell around the cell targeted for CFAR processing, it is treated as if there is no signal, so the maximum value ( There is a problem in that a signal that is not (meaning a value larger than any of the eight cells adjacent to the cell in question) is detected as a target.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a radar device that can prevent a signal that is not a maximum value from being detected as a target.

[Means to solve the problem]

The radar device according to the second aspect of the present invention includes a maximum value detector that detects a maximum value from cells adjacent to the cell detected as a target by the CFAR detector.

[Effect]

The maximum value detector in this invention compares the level of a cell detected as a target in -degree CFAR processing with the level of an adjacent cell, and if there is a cell with a higher level than the target cell, This is designed to invalidate the signal indicating that a target has been detected.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, blocks indicated by 1 to 4 are the same as those of a conventional radar device. Reference numeral 5 denotes a maximum value detector that compares the levels of the cell detected as a target by the CFAR detector 4 and eight adjacent cells.

Next, the operation will be explained.

Here, the operations other than the local maximum value detection are the same as those described in the prior art example, so only the operations that are different from the prior art will be described below. The maximum value detector 5 added according to this embodiment checks the levels of eight cells adjacent to the cell detected as a target by the CFAR detector 4, and if there is a cell detected as a target among them. If there is a signal with a higher level than that, the previously detected target signal is invalidated. Therefore, in this embodiment, a signal that is not originally a target is not detected as a target, so that the false alarm rate can be lowered.

In addition, in the above embodiment, a local maximum value detector was added to the CFAR detector that performs CFAR processing in two directions, the range direction and the filter direction, but a local maximum value detector was added to the CFAR in only one direction. You can also get the same effect.

Another embodiment of the invention is shown in FIGS. 5 and 6.

FIG. 5 shows an example of detection/judgment in only one direction (in this case, the range direction), and FIG. 6 shows a level allocation diagram that is effective even with CFAR in only one direction. 6(a) and (1)) are a collection of the same cells, but in (a) the center cell is set to 8 and is detected as a target with a neighborhood average of 5.5. However, in this case, the maximum value detector compares the value of 8 in the center cell with the value of the two adjacent cells, and since there are 10 cells larger than 8, the cell of 8 is determined to have a target detected. Disable the signal.

In addition, when the center is 10 in b), the neighborhood average is 11, and the central cell IO is not detected as a target.

In this way, the local maximum value detector works effectively even for unidirectional CFAR, and a value other than the local maximum value is not detected as a target.

〔Effect of the invention〕

As described above, according to the present invention, after performing CFAR detection, a level check is performed on cells adjacent to a cell detected as a target, so that a value other than a local maximum value is detected as a target. It has the effect of eliminating things.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a signal processor of a radar device according to an embodiment of the present invention, FIG. 2 is a block diagram of a signal processor of a conventional radar device, FIG. 3 is a functional explanatory diagram of a CFAR detector, and FIG. Figure 4 is a diagram showing an example of level arrangement that cannot be handled by normal CFAR processing alone, Figure 5 is a block diagram of a CFAR single detector that detects and judges only in one direction, and Figure 6 shows how CFAR is handled in the case of CFAR in only one direction. FIG. 6 is a diagram illustrating an example of a radar arrangement in which a target that is not a local maximum value is detected by processing alone. 1 is an A/D converter, 2 is a Doppler filter, 3 is a video integrator, 4 is a CFAR detector, and 5 is a local maximum detector. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a radar device having a signal processor that performs constant false alarm rate detection processing for target detection, the signal processor may include an A/D converter that converts an analog video signal output by the receiver into a digital signal. , a Doppler filter, a video integrator that integrates the output of the Doppler filter to improve the S/N of the output signal, a CFAR detector that performs CFAR processing and outputs a detection hit, and a cell that is subjected to CFAR processing. and a maximum value detector that detects the maximum value of an adjacent cell.