JPH09133762A - Target detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow even the accurate measurement of target length by preventing a single target from being erroneously detected as a plurality of targets. SOLUTION: A reflected signal from a target is received with a transmitter 1, a circulator 2, an aerial line 3 and a receiver 4 respectively forming a high distance resolution radar and, then, processed with a target detector 5. The received signal after A/D conversion is made into a binary signal with a threshold detector 5-2. The binary signal sometimes represents a plurality of line segments, depending on the shape or the like of a target and, therefore, is processed with a line segment extractor 5-3, for example, for half conversion or the like, so as to make detection signals on a linear line continuous to each other, thereby forming a continuous signal. Then, the distance and length of the target are identified and displayed with the continuous signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar target detection device, and more particularly to a target detection device for a radar having a high range resolution.

[0002]

2. Description of the Related Art A conventional target detecting means in a radar sets a certain threshold to the amplitude of a received signal obtained from the radar, and if the threshold is exceeded, it is assumed that the target is detected in any case. The threshold detection method is used. FIG. 4 shows an example of the configuration of this system, and FIG. 5 shows a plot of the amplitude probability density function for noise only and the amplitude probability density function for signal + noise on the same plane (Matsuo Sekine, “Radar Signal Processing Technology "
April 10, 1993 (2nd edition) P. 28).

In FIG. 4, the transmitter 1 generates a transmission signal. The circulator 2 sends the output signal of the transmitter 1 to the antenna and sends the signal received by the antenna to the receiver 4. In the receiver 4, low noise amplification and detection are performed, and the received video signal is output to the target detection device 5. The target detection device 5 detects the target by the threshold detection method described above.

The threshold detection method will be additionally described with reference to FIG. In this method, if the threshold is set low, noise alone will exceed this, and erroneous determination will be made. Whether or not the noise exceeds the threshold is probabilistic, and this probability is called false alarm probability P _fa and is shown by hatching in FIG. On the other hand, whether or not the reflected signal from the target mixed in the noise exceeds the threshold is also probabilistically indicated, and this is called the detection probability P _d . In radar target detection, the detection threshold is set to a value that satisfies the required detection probability P _d and false alarm probability P _fa .

Here, in a radar having a high range resolution, a received signal can be obtained in the decomposition unit. For this reason, the received signal from one target will obtain a signal whose amplitude has changed according to the structure that constitutes the target. This situation is shown in FIG. Therefore, when this signal is detected at a certain threshold value, it is not detected where a sufficient SNR (signal-to-noise ratio) cannot be obtained, so the result of target detection is detected and displayed as a plurality of small targets. This state is shown in FIG. One of the applications of the high range resolution radar is to know the size of the target by measuring the length of the target, but in the conventional threshold detection method, the wrong judgment is made as described above. It is possible that it will end up.

[0006]

The problem of the above-mentioned conventional technique is that the SN is sufficiently high, especially in a high range resolution radar.
If R is not taken, one target is detected as a plurality of targets.

The reason for this is that since the received signal from one target is received in units of resolved distance, its amplitude changes within one target due to the difference in the reflection cross section of the structure. Therefore, the threshold is not detected in a portion where a sufficient SNR cannot be obtained.

An object of the present invention is to improve the detection characteristic of a target, and to improve the above-mentioned problems.

[0009]

A target detecting apparatus of the present invention is a target detecting apparatus using a radar for detecting a target having a length equal to or greater than a distance resolution, and converts a received signal into binary image data by threshold detection. The target is detected by performing a process and performing a line segment extraction process on the binary image data.

Further, the radar is a high range resolution radar, and the line segment extraction processing is performed by Hough transform.

In the received signal obtained from the high range resolution radar, since the received signals from one target are scattered on the straight line in the distance direction, the line segment extraction process in the target detection process using the above means. Will work effectively. As a result, the desired SNR cannot be ensured, and it can be detected as one continuous target even from the received signal in which a missing portion exists.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows the configuration of the present invention. For the transmitter 1, circulator 2, antenna 3 and receiver 4,
This is as described in the above-mentioned conventional technique. Here, in order to obtain a high range resolution radar, either of the following two measures is taken. First, the pulse width of the output transmission signal of the transmitter 1 is extremely short. As a result, distance resolution equivalent to the pulse width can be obtained. Secondly, in the receiver 4, high pulse compression is performed to compress the pulse width of the received signal to an extremely short pulse width to obtain a distance resolution equivalent to the main pulse width.

The high-distance resolution received signal is input from the receiver 4 to the target detection device 5. In the present device, the input reception signal is converted into digital data by the A / D converter 5-1. The threshold detector 5-2 detects the threshold and converts it into binary image data.
This is subjected to line segment extraction processing by the line segment extractor 5-3, and the result of the display and distance measurement of the target obtained in the target detection processing and the determination of the target length are output.

FIG. 2 shows the state of signals corresponding to the above series of processing flows. In the figure, in the threshold detection processing result ((b) in the figure), what is missing in one target is detected as one continuous target by the line segment extraction processing result ((c) in the figure). The display is shown.

Next, the line segment extraction processing will be described. In this embodiment, Hough transform is used for line segment extraction. The Hough transform is one of methods for detecting a figure (for example, a straight line, a circle, an ellipse, a parabola, etc.) that can be expressed by parameters from an image. H in Figure 3
We have shown one concept of the ough transform. As a property of the Hough transform, points on the straight line of the formula y = ax + b on the (x, y) plane are obtained as intersection lines on the (a, b) plane (Hough plane).

By utilizing this property, it is possible to extract continuous line segments from discrete sample data on the same straight line.

Specifically, after mapping all the sample data on the (x, y) plane on the (a, b) plane,
If a point where many straight lines gather on the (a, b) plane is detected, a corresponding straight line in the image plane can be obtained. The line segment is determined by the upper and lower limits of the sample data on the straight line.

Therefore, even when the target is facing diagonally,
It is easily understood that the line segment can be extracted by the Hough transform by having the azimuth resolution to such an extent that the linearity can be obtained. This state is shown in parallel in FIG. 2 as the process of making the detection pixels continuous.

[0020]

According to the target detecting apparatus of the present invention, one target can be determined as one target in a high range resolution radar even under the condition that a sufficient SNR cannot be obtained. Also,
The target length can be accurately determined. This is because the received signal from one target obtained from the high range resolution radar can be treated as discrete data on the same line segment in the length direction. This is because it can be determined as a linear straight line.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a processing result corresponding to the processing flow of FIG.

FIG. 3 is a conceptual diagram of Hough transform used for line segment extraction processing.

FIG. 4 is a configuration diagram showing a conventional target detection device.

5 is a conceptual diagram of a threshold detection method used in FIG.

[Explanation of symbols]

 1 Transmitter 2 Circulator 3 Antenna 4 Receiver 5 Target detection device 5-1 A / D converter 5-2 Threshold detector 5-3 Line segment extractor 5-4 Target detector

Claims (2)

[Claims] 1. A target detection device using a radar for detecting a target having a length equal to or greater than a distance resolution, the received signal being converted into binary image data by threshold detection, and the binary image data having a line segment. A target detection device characterized by detecting a target by performing extraction processing. 2. The target detecting apparatus, wherein the radar is a high range resolution radar, and the line segment extracting process is performed by Hough transform.