JP2584523B2 - Radar equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus, and more particularly, to detection of a target by a constant false alarm rate (CFAR) in the radar apparatus.

[Conventional technology]

The second conventional radar device that performs detection using two-dimensional CFAR
Shown in the figure. FIG. 2 shows 439 of JP-A-61-189476.
It is a device similar to FIG. 1 posted on the page. In the figure, 1 is an A / D converter, 2 is a Doppler filter, 3 is a video integrator 4, and 4 is a CFAR detector.

 Next, the operation will be described.

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 outputs a signal corresponding to a Doppler frequency. The signal output from the Doppler filter 2 is improved in S / N by the video integrator 3 and CFAR
It is sent to the detector 4. Here, the function of the CFAR detector 4 will be described with reference to FIG. A description will be given by taking the cells of the range gate R _i and the Doppler filter F _j as an example. First, the neighborhood average value of the corresponding cell in the range direction and the filter direction is obtained. Here, when calculating the neighborhood average value, R which is the cell next to the corresponding cell
_{i + 1} , R _i-1 (range direction) and F _{j + 1} , F _j-1 (filter direction)
Is not included in the calculation, the reason is that the neighboring cell is not detected as a target when the CFAR process is performed by including the neighboring cell in the average because there is no large difference in the level of the corresponding cell and the neighboring cell due to the effect of the target signal This is because a case may occur. The average value in the range direction is obtained by averaging the signal levels at _Ri-2 , _Ri-3 , ..., _{Rin and} the signal levels at _{Ri + 2} , _{Ri + 3} , ..., _{Ri + n} . Then, the average of both is calculated (processing 20 to 22).
Then multiplied by a constant to the average value (process 23) compares the signal value of the value and the corresponding cell R _i (processing 24), and "with hit detection" when towards the level of a corresponding cell is greater . Next, in the same manner, a neighborhood average value of the corresponding cell in the Doppler frequency direction is obtained. _{That, F j-2, F j} -3, ..., mean and F _{j + 2} of the signal level in _{F jm, F j + 3,} ..., determine the average signal level in F _{j + m,} further average of the two (Processes 30 to 32). Then, the obtained average value is multiplied by a constant (process 33), and the obtained value is compared with the signal value of the corresponding cell _Fj (process 34). . The AND of the hit detection in the above two directions (range direction and Doppler filter direction) is performed (process 40), and the detected hit is output from the CFAR detector 4 only when both of them have hit detection.

This concludes the description of the CFAR function. By the way, considering the case where the level value becomes as shown in FIG. 4, for example, the following problem occurs which cannot be dealt with only by the above CFAR function. In FIG. Looking at the CFAR processing in the cells surrounded by, the neighborhood average value in the range direction is 15 and the neighborhood average value in the filter direction is 16, so the average of both is 15.5. Assuming that the multiplication constant in the range direction and the filter direction is 1 for simplicity, 10 in the center cell is not detected as a target. However, In the CFAR processing in the cells surrounded by, the neighborhood average value in the range direction is 6 and the filter direction is also 6. Therefore, the average of both is 6. Thus, the center cell 8 is detected as a target despite a value lower than 10. Thus, depending on the intensity distribution of the neighboring cells, it is smaller than the neighboring cells (not the local maximum),
That is, a signal that is not the target may be detected as the target.

[Problems to be solved by the invention]

Since the conventional CFAR detector is configured as described above, there is a problem that a signal having a non-maximum value (meaning a value larger than any of eight cells adjacent to the corresponding cell) is detected as a target. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a radar apparatus that can prevent a signal having a non-maximum value from being detected as a target.

[Means for solving the problem]

The radar device according to the present invention provides, for a predetermined cell,
An average value of the signal levels of a plurality of cells adjacent in the range direction or the filter direction is obtained, and the average value is compared with the signal level of the predetermined cell, and the level of the predetermined cell is larger than the average value. In such a case, a CFAR (Constant False Alarm Rate:
(Constant false alarm rate) detector, when the CFAR detector detects the predetermined cell as a target, comparing the level of the predetermined cell and the level of each cell constituting the plurality of adjacent cells Only when the level of the predetermined cell is higher than any of the levels of the adjacent cells, the CFAR
A maximum value detector that makes the detection result by the detector valid.

[Action]

The local maximum value detector according to the present invention compares the level of a cell once detected as a target in CFAR processing with the level of an adjacent cell, and if there is a cell having a higher level than the target cell, A signal indicating that detection has been performed is made invalid.

〔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 the conventional radar apparatus. Reference numeral 5 denotes a local maximum detector which compares the level of a cell detected as a target by the CFAR detector 4 with eight adjacent cells, and determines whether the hit is valid or invalid based on the result.

 Next, the operation will be described.

Here, the operation other than the operation of detecting the maximum value is the same as the operation described in the above-described conventional example, and therefore, only the operation different from the conventional technology will be described below. The maximum value detector 5 added according to the present embodiment checks the level of eight cells adjacent to the cell detected as a target by the CFAR detector 4, and if any of the cells detected as the target is If there is a higher level than that, the signal detected as the target before that is invalidated. Therefore, in the present embodiment, a signal that is not originally a target is not detected as a target, so that the false alarm rate can be reduced.

In the above embodiment, the two directions of the range direction and the filter direction are used.
Although the local maximum detector is added to the CFAR detector that performs the CFAR processing in the direction, the same effect can be obtained by adding the local maximum detector to the CFAR in only one direction.

Another embodiment of the present invention is shown in FIG. 5 and FIG. FIG. 5 shows an example of detection and determination in only one direction (in this case, the range direction), and FIG. 6 shows a level arrangement diagram that is effective even in a CFAR in only one direction. FIGS. 6 (a) and 6 (b) show the same group of cells, but FIG. 6 (a) shows a case where the center cell is 8 and the neighborhood average is 5.
At 5 it is detected as a target. However, in this case, the local maximum value detector compares the value of the center cell 8 with the value of the two adjacent cells, and there are 10 cells larger than 8, so that the 8 cells are regarded as having the target detection. Invalidate the signal.

In addition, when the center 10 is set at (b), the center cell 10 is not detected as a target with the neighborhood average 11. As described above, the maximum value detector works effectively even in one-way CFAR, and a value other than the maximum value is not detected as a target.

Also, in FIGS. 3 and 5, CFAR (called Cell Averaging CFAR) for multiplying the average of the neighboring average values on both sides by a constant has been described. of the present invention may be applied to the present invention.

In this case, 22, 32 in FIG. 3 and 22 in FIG.
However, the effect of the present invention is the same, except for the change from “large selection” to “large selection”.

〔The invention's effect〕

As described above, according to the present invention, after performing the CFAR detection, the configuration is such that the level check of the cell adjacent to the cell detected as the target is performed, so that a value that is not the maximum value is detected as the target. There is an effect that disappears.

[Brief description of the 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,
FIG. 4 is a diagram showing an example of a level arrangement that cannot be dealt with only by normal CFAR processing, and FIG. 5 is a CFAR that detects and determines in only one direction.
FIG. 6 is a block diagram of the detector, and FIG. 6 is a diagram showing an example in which, in the case of CFAR in only one direction, a target that is not a local maximum is detected as a target only by CFAR processing. 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. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] An average value of signal levels of a plurality of cells adjacent to a predetermined cell in a range direction or a filter direction is determined, and the average value is compared with the signal level of the predetermined cell. A constant false alarm rate (CFAR) detector for detecting the predetermined cell as a target when the level of the predetermined cell is higher than the average value; When a cell is detected as a target, the level of the predetermined cell is compared with the level of each cell constituting the plurality of adjacent cells, and the level of the predetermined cell is equal to the level of the plurality of adjacent cells. A radar apparatus comprising: a maximum value detector that makes the detection result of the CFAR detector valid only when the value is larger than any of the above.