CN102305930A - Method for inhibiting precipitation clutter in radar echo - Google Patents

Abstract

The invention discloses a method for suppressing rain and snow clutter in radar echoes. Firstly, the radar echo image is input and the radar echo image is pattern matched according to the rain and snow noise distribution formula to identify the distribution areas of different signals; The distribution characteristics of clutter in different signal areas, the suspected target is marked with dyeing points; then the filter is used to separate the suspected rain and snow clutter signals, and the separated suspected rain and snow clutter signals are identified by rain and snow clutter , the hidden small target in the rain and snow clutter is separated by secondary scanning, and the non-rain and snow clutter small target is sent back to the radar echo image where the target signal is located, and the identified rain and snow clutter is filtered out; Finally, the target signal in the processed radar echo image is properly enhanced and input to the display system. The invention can effectively remove the clutter from the radar echo image under bad weather such as rain and snow, and has strong practicability.

Description

A Method of Suppressing Rain and Snow Clutter in Radar Echo

technical field

The invention relates to a clutter suppression method, in particular to a method for suppressing rain and snow clutter in radar echoes.

Background technique

The basic principle of radar is relatively simple, it works by radiating electromagnetic energy and detecting the echoes reflected by reflectors (targets). The characteristics of the echo signal provide information about the target. The distance to the target is obtained by measuring the time it takes for the radiant energy to travel to the target and back. The bearing of the target is identified by measuring the angle of arrival of the echo signal from a directional antenna (antenna with a narrow beam).

In the process of radar microwave transmission and reception, due to the rain and snow generated by natural reasons, there will be clutter in the process of radar microwave transmission and reception, especially the echo image. Due to the existence of rain and snow clutter, it is difficult for professionals Analyzing radar echo images caused some confusion. Traditional navigation radars mostly use analog circuit filters to reduce signal clutter noise. However, it is difficult to distinguish small targets from clutter with such a processing method. According to the actual test, in the environment with great influence of rain and snow, the traditional filter will filter out the short-distance small target and clutter together. Such treatment greatly affects the crew's judgment on surrounding targets and increases the risk of navigation.

Contents of the invention

The object of the present invention is to provide a method for suppressing rain and snow clutter in radar echoes with strong applicability and good effect against the defects of the prior art.

The purpose of the present invention is solved by the following technical solutions:

A method for suppressing rain and snow clutter in radar echoes, the steps of the method are as follows:

(1) Scan the radar echo to obtain the radar echo image;

(2) On the basis of the radar echo image, the radar echo image is pattern-matched according to the rain and snow noise distribution formula, and the distribution area of different signals is identified;

(3) According to the clutter distribution characteristics of different signal areas, the suspected targets are marked with colored points;

(4) Use filters to separate suspected rain and snow clutter signals;

(5) Carry out rain and snow clutter recognition on the separated suspected rain and snow clutter signals, and perform a second scan on the hidden small targets in the rain and snow clutter, and further separate the non-rain clutter in the rain and snow clutter according to the scanning information. Small snow clutter targets and non-rain and snow clutter small targets are returned to the radar echo image where the target signal is located, and the identified rain and snow clutter are filtered out;

(6) Appropriately enhance the target signal in the processed radar echo image and input it into the display system.

The rain and snow noise distribution formula in the step (2) is:

Among them, P is the echo intensity value; σ _N is the echo intensity parameter of this circle; σ _N-1 is the echo intensity parameter of the upper circle; M is the distance between the scanning point and the center point of the scanning image; λ is the wavelength.

The rain and snow noise distribution formula in the step (2) is:

Among them, f(x) is the rain and snow intensity value; μ=0; σ=1.8; x represents the distance between the scanning point and the center of the radar.

The signal distribution area in the step (2) is a rectangular distribution area, a circular distribution area and a polygonal distribution area.

The clutter distribution characteristic in the step (3) means that the short-distance clutter approximates a normal distribution, and the long-distance clutter approximates a Rayleigh distribution.

The identification method of rain and snow clutter in the step (5) is as follows: firstly judge the area where the rain and snow clutter is concentrated through the clutter distribution curve; then find the target point with the strongest reflection in the area, Weaken the surrounding targets to find out the small targets in the clutter; finally, confirm the small targets through the frame correlation accumulation judgment.

Compared with the prior art, the present invention has the following advantages:

The present invention analyzes the form of rain and snow and its echo attenuation characteristics, and uses advanced algorithms in data mining to perform pattern matching on radar echo images, and then discretely processes echoes that meet the characteristics of rain and snow, thereby gradually weakening the The rain and snow echo can achieve the purpose of rain and snow clutter suppression; and because the target echo has a long duration and dense distribution, it can be identified by the algorithm and effectively strengthen small targets.

The present invention can effectively remove clutter from echo images in severe weather such as heavy rain or heavy snow, has strong applicability, and can provide effective radar image processing for professional researchers in ocean research, ship navigation and other related fields .

Description of drawings

Accompanying drawing 1 is unprocessed radar echo image;

Accompanying drawing 2 is the radar echo image after processing;

Accompanying drawing 3 is the image after the small target enhancement in radar echo image;

Accompanying drawing 4 is the distribution curve schematic diagram of clutter;

Accompanying drawing 5 is the schematic flow chart of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

或者

，对雷达回波图像进行模式匹配，识别出矩形、圆形和多边形信号的分布区域；接着根据不同信号区域的近距离杂波近似于正态分布、远距离杂波近似于瑞利分布的分布特性，对疑似目标使用染色点的方式标记；第四步使用过滤器对疑似雨雪杂波信号进行分离；第五步对分离出的疑似雨雪杂波信号进行雨雪杂波识别：先通过杂波分布曲线判断出雨雪杂波集中出现区域，接着在区域中找出反射最强的目标点并通过对强目标点周围目标的弱化，找出杂波中的小目标，然后通过帧相关累积判断，确认并分离小目标，并将小目标传回到目标信号所在的雷达回波图像中，同时将识别出的雨雪杂波滤除；最后将处理后的雷达回波图像中的目标信号适当增强后输入到显示系统中。 As shown in Figure 1-5: a method for suppressing rain and snow clutter in radar echoes, the steps of the method are as follows: first scan the radar echoes to obtain radar echo images; then on the basis of the radar echo images, according to Rain and snow noise distribution formula:

or

, pattern matching is performed on the radar echo image, and the distribution areas of rectangular, circular, and polygonal signals are identified; then, according to the distribution of close-range clutter in different signal areas, which approximates a normal distribution, and long-distance clutter approximates a Rayleigh distribution characteristics, use dyeing points to mark the suspected targets; the fourth step uses the filter to separate the suspected rain and snow clutter signals; the fifth step performs rain and snow clutter identification on the separated suspected rain and snow clutter signals: The clutter distribution curve judges the area where the rain and snow clutter is concentrated, and then finds the target point with the strongest reflection in the area, and finds the small target in the clutter by weakening the targets around the strong target point, and then through frame correlation Accumulate judgment, confirm and separate the small target, and send the small target back to the radar echo image where the target signal is located, and at the same time filter out the identified rain and snow clutter; finally, the target in the processed radar echo image The signal is properly enhanced and input to the display system.

When the present invention is in use, accompanying drawing 1 and accompanying drawing 2 are radar echo images before and after processing, wherein the white part is the radar echo, by comparing the white part in accompanying drawing 1 and accompanying drawing 2, it can be seen that in accompanying drawing 2 The white part is greatly enhanced, that is, part of the clutter in the radar echo is eliminated; at the same time, by comparing the data in Figure 1 and Figure 2, it can be seen that the rain and snow clutter in the radar echo signal is reduced from 235 to 2. From the above analysis, it can be seen that the present invention analyzes the form of rain and snow and its echo attenuation characteristics, and uses advanced algorithms in data mining to carry out pattern matching on radar echo images, and then discretize the echoes that meet the characteristics of rain and snow. processing, so as to weaken the rain and snow echo and achieve the purpose of rain and snow clutter suppression; and because the target echo lasts for a long time and is densely distributed, it can be identified by the algorithm and effectively strengthen the small target. The strengthened small target such as Shown in white area in Figure 3.

Claims (6)

1. a method for suppressing rain and snow clutter in radar echoes is characterized in that described method steps are as follows: (1) Scan the radar echo to obtain the radar echo image; (2) On the basis of the radar echo image, the radar echo image is pattern-matched according to the rain and snow noise distribution formula, and the distribution area of different signals is identified; (3) According to the distribution characteristics of clutter in different signal areas, the suspected targets are marked with colored points; (4) Use filters to separate suspected rain and snow clutter signals; (5) Carry out rain and snow clutter recognition on the separated suspected rain and snow clutter signals, and perform a second scan on the hidden small targets in the rain and snow clutter, and further separate the non-rain clutter in the rain and snow clutter according to the scanning information. Small snow clutter targets and non-rain and snow clutter small targets are returned to the radar echo image where the target signal is located, and the identified rain and snow clutter are filtered out; (6) Appropriately enhance the target signal in the processed radar echo image and input it into the display system. 2. The method for suppressing rain and snow clutter in radar echoes according to claim 1, characterized in that the distribution formula of rain and snow noise in the step (2) is:                                                                   

  Among them, P is the echo intensity value; σ _N is the echo intensity parameter of this circle; σ _N-1 is the echo intensity parameter of the upper circle; M is the distance between the scanning point and the center point of the scanning image; λ is the wavelength. 3. The method for suppressing rain and snow clutter in radar echo according to claim 1, characterized in that the distribution formula of rain and snow noise in the step (2) is:                        

Among them, f(x) is the rain and snow intensity value; μ=0; σ=1.8; x represents the distance between the scanning point and the center of the radar. 4. The method for suppressing rain and snow clutter in radar echo according to claim 1, characterized in that the signal distribution area in the step (2) is a rectangular distribution area, a circular distribution area and a polygonal distribution area. 5. The method for suppressing rain and snow clutter in radar echoes according to claim 1, characterized in that the clutter distribution characteristics in the step (3) refer to: close-range clutter is approximately normal distribution, and Distant clutter approximates a Rayleigh distribution. 6. The method for suppressing rain and snow clutter in radar echoes according to claim 1, characterized in that the identification method of rain and snow clutter in the step (5) is: firstly judge the rain and snow clutter through the clutter distribution curve The area where the clutter is concentrated; then find the target point with the strongest reflection in the area, and find the small target in the clutter by weakening the targets around the strong target point; finally, confirm the small target through the frame correlation accumulation judgment.

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