JPS61280586A - System for detecting target - Google Patents

Abstract

PURPOSE:To display a plurality of targets while separately discriminating the same regardless of the intensity of a receiving level, by judging that the targets were detected when there was an increase mode satisfying a definite condition in a receiving signal level and judging that the targets were not detected when there was the decrease mode of the definite condition. CONSTITUTION:An amplitude comparing means 17 performs amplitude comparison with respect to the coincidence, increase or decrease between the previous signal level and the next signal level on the basis of the receiving signal row from targets present at the same distance. When a signal showing that receiving signal exceeded a reference level arrived from a level judging means 16, (a) each of receiving signals continuing in the receiving signals corresponding to M-times of past pulse transmissions are set as one set and, when no level is present in one set or sets showing monotonous increase are present in the number of m-sets or more, a target detection means outputs a signal showing target detection to an output terminal 20. When sets showing the monotonous decrease of the receiving signal level are present in one set having (b) receiving signals continuing in the receiving signals corresponding to N-times of past pulse transmission in the number of n-sets or more, said means 18 outputs no target detection signal.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a pulse radar device that searches a space by emitting high-frequency pulse signals into space and receiving reflected signals from the target object. The present invention relates to a target detection method for automatically detecting reflected signals from a target.

(Prior art) In conventional pulse radar equipment, as a means of target detection,
A technique called sliding window is used. That is, a predetermined reference level determined from a predetermined detection rate of a predetermined target and a misidentification rate of an unnecessary signal as a target is set for n received signals corresponding to n consecutive transmitted pulses, and the reference level is set. Measure the number k of signals exceeding k
If is greater than or equal to the reference value, it is determined that the goals are the same.'(
The value of k represents the size of the target and is called the target run length).

However, in the above method, when two targets are located adjacent to each other in the azimuth direction at the same distance and with an interval equivalent to the azimuth resolution, the received signal pattern in the azimuth direction is pattern 2 in FIG.
7 and 28, and if the received signal level is strong, the level of the minimum point between the received signal patterns 27 and 28 will be higher than the reference level 29, so it will be detected as a single target. There are drawbacks. If the reference level is raised to the point shown by the one-dot chain line 30 in an attempt to eliminate this drawback, a problem arises in that it becomes impossible to detect weak target signals that do not reach the reference level 30, and the target detection rate decreases. .

As mentioned above, when a plurality of targets exist adjacently at the same distance with an azimuth interval equivalent to the azimuth resolution, it is an object of the present invention to The aim is to provide a target detection method that can identify a target as a target.

(Means for Solving the Problems) The method of the present invention is configured as follows to achieve the above object.

In a pulse radar device that transmits a high-frequency pulse signal into space while scanning an antenna direction and receives a reflected signal from a target object, when a received signal of interest exists at a distance and direction of interest that exceeds a predetermined reference level, A set includes a (<M) consecutive received signals of the direction for each transmitted pulse at the same distance corresponding to the past M consecutive transmissions of high-frequency pulse signals including the received signal of interest. , Compare the amplitude of each received signal in one set, and if there are m or more sets in which the received signal level does not change or increases monotonically, a target is detected at the time of reception of the received signal of interest. On the other hand, among the received signals in the direction of each transmitted pulse at the same distance corresponding to the past N consecutive transmissions of high-frequency pulse signals including the received signal of interest, consecutive b (<N)
If there are n or more sets in which the received signal level monotonically decreases, the target is detected at the time of reception of the received signal of interest. This is a target detection method that assumes that there was no such thing.

(Function) Hereinafter, the function of the method of the present invention will be explained based on the drawings. FIG. 1 is an explanatory diagram of the operation of the method of the present invention. The vertical axis shows the reception level, and the horizontal axis shows the azimuth angle. This is a diagram showing the reception signal level of the reflected signal received from the target object by transmitting high-frequency pulses while gradually shifting the direction of the radiation beam and irradiating the target object.The envelope connecting each reception level is the antenna beam after all. It will show a pattern. 1
is a predetermined reference level, points 2-12 are from a single target,
Now, −
For example, M=4, a=2, m=2, N=3, b=2,
The case where n=2 will be explained. When focusing on the received signal 5 that exceeded the reference level 1, the past 4 including the received signal 5 (M=
4) The consecutive received signals are from 2 to 5. The combinations of received signals 2 (a = 2>) are 3 sets of received signals 2 and 3, 3 and 4, and 4 and 5. All of these combinations are monotonous. Since the number of monotonically increasing combinations satisfies the condition of 2 (m=2) or more, it is assumed that target detection occurred when receiving signal 5 was received.Hereinafter, in the same manner up to receiving signal 8,
Since the conditions M=4, a=2, and m=2 are satisfied, it is assumed that a target has been detected in all cases.

The black circles drawn through dotted lines at the bottom of received signals 5 to 8 indicate that a target has been detected.9 When received signal 9 is received next, this received signal is set as the received signal of interest. The number of received signals for the past 3 (N=3) times, including the number of received signals, is the same 7 to the same. The combinations of 2 (b=2) received signals are 2 sets: received signals 7 and 8, and 8 and 9. And all these combinations are monotonically decreasing,
Since the condition that the number of monotonically decreasing combinations is 2 (n=2) or more is satisfied, it is assumed that no target is detected. Therefore, there is no black circle under the received signal 9. Therefore, when two targets are located adjacent to each other at the same distance with an azimuth interval equivalent to the azimuth resolution, the peak value of the received signal level is Two cases will be considered: one case where it is sufficiently larger than the reference level and one case where it slightly exceeds the reference level.

FIG. 2 is a diagram showing received signal sequences when two strong targets exist adjacent to each other in the azimuth direction at the same distance, and when two weak targets exist adjacent to each other in the azimuth direction. Similar to Figure 1, the vertical axis shows the received level, and the horizontal axis shows the azimuth. 13 is the reference level, 14 is the envelope of the stronger received signal level, and 15 is the envelope of the weaker received signal level. It is a line.

Now, like the example in Figure 1, M=4, a=2, m±2, N
=3, b=2, n=2, mark indicating target detection (
When the black circles) are illustrated, they look like column A. On the contrary,
When target detection is performed using a conventional sliding window method with a reference value of 2, marks (white circles) indicating target detection are shown in column B. That is, in the conventional sliding window detection method, target detection is performed continuously for the stronger received signal, so the target display is as if it were a continuous line, that is, received signals from one target. It is expressed as such. On the other hand, in the method of the present invention, target detection is missed three times near the minimum point of the envelope 14, as shown in column A. Therefore, the objects are displayed as two objects that are adjacent to each other at the same distance and in the same direction. In addition, for weaker received signals, the conventional sliding window detection method does not satisfy the condition of = 2 because the received signal exceeds the reference level only once for each target, so the target cannot be detected at all. Therefore, there is no mark indicating target detection in column B, whereas in target detection using the method of the present invention, if each setting condition in the case of Fig. 1 is applied, A is detected.
Target detection is performed twice for each target like a column, and between the two target detections, there are 4 times when no target is detected.
There are times. This lick target display indicates that there are two targets that are the same distance and adjacent in direction.

In this way, the target detection method of the present invention is not simply based on the number of received signals that exceed a reference level, but focuses on how the level of the received signal increases and decreases based on the antenna pattern, and satisfies certain conditions. increase! Since the detection method assumes that a target has been detected since Bal is present, and that there is no longer a target detected when there is a decrease in a certain condition, the azimuth interval of multiple adjacent targets is determined by the pulse. As long as the radar is separated by an angle equivalent to the azimuth resolution and the envelope of the continuously received signal level has a minimum point as shown in Figure 2, there will be no target detected, so the target will be separated into multiple targets. will be displayed.

(Example) Hereinafter, a configuration example of a means for implementing the method of the present invention will be described based on the drawings.

FIG. 3 is a block diagram showing an example of the configuration of means for implementing the method of the present invention. The received signal input from the input terminal 19 is applied to the level determining means 16 and the amplitude comparing means 17. The level determining means 16 determines whether the level of the received signal exceeds a predetermined reference level and sends a signal indicating the determination result to the target detecting means 18. The amplitude comparison means 17 compares the amplitudes of received signal sequences from targets at the same distance to determine whether the level of the next received signal is the same, increased, or decreased with respect to the level of the previous received signal. A signal indicating a certain state, a signal indicating an increase, or a signal indicating a decrease is sent to the target detection means 18. When a signal indicating that the reference level has been exceeded is received from the level determining means 16, the target detecting means 18 detects a number of continuous pulses in the received signals corresponding to the past M pulse transmissions including the received signal at that time. A signal indicating target detection is outputted to the output terminal 20 when there are m or more sets in which the received signal level does not change or shows a monotonous increase. On the other hand, when a signal indicating that the reference level has been exceeded arrives, a set of b consecutive received signals corresponding to the past N pulse transmissions including the received signal at that time is defined as one set. If there are n or more sets in which the received signal level monotonically decreases, no target detection signal is output.

M=4, a= set in the explanation of the operation of the method of the present invention
2, m = 2, N = 3, b = 2, n = 2 are examples of settings 0 The method of the present invention provides excellent effects as described above in separating and identifying multiple targets; By also using the conventional sliding window target detection method, the relay device as a whole exhibits even more excellent effects as described below.

The target detection method of the present invention can effectively separate and identify multiple targets when they exist, but on the other hand, even if there is only one target, the received signal may be affected by fluctuations in the propagation state of radio waves, etc. Due to the resulting oscillation, if there is a minimum portion 26 where the received signal level decreases as shown in FIG. 4, it may be detected as two targets. Therefore, in order to avoid such problems, the 5th r5! 21 is a configuration for implementing the target detection method of the present invention, 22 is a configuration for detecting a target using the conventional sliding window method, and 23 is a configuration for detecting a received signal from the configuration 22 that exceeds a reference value. Determine whether the number of runs (run length) exceeds a predetermined set value, and if it does not exceed the set value, configure 22.
The determination means outputs the signal from the means configuration 21 as the target detection signal, and when the value exceeds the target detection signal, outputs the signal from the means configuration 21 as the target detection signal. If the above set value is set to correspond to the run length obtained in the case of a single target, when the run length is less than this set value, the signal from the configuration 22 will be output as the target detection signal. The target object is no longer output to the output terminal 25 as a plurality of target objects.

(Effects of the Invention) The target detection method of the present invention has the following advantages: When high-frequency pulse transmission is performed while changing the direction of the antenna as explained above,
Focusing on the fact that the level of the received signal due to reflection from the target changes according to the antenna pattern, the presence or absence of target detection is determined by setting conditions for that change, so it is possible to detect multiple targets. As long as the objects are spaced at angular intervals corresponding to the azimuth resolution of the radar device, it has the excellent effect of being able to separate and identify a plurality of objects and display them regardless of the strength of the overall level of the received signal train.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of the method of the present invention, FIG. 2 is a diagram showing a received signal sequence when two targets with strong reflection are adjacent and two targets with weak reflection are adjacent, and FIG. 3 is a diagram illustrating the method according to the present invention. A diagram showing a configuration example of a means for implementing the method, FIG. 4 is a diagram showing a received signal train from a single target having an extremely small portion, and FIG. Fig. 6 is a block diagram of the configuration when both of the window method methods are used together, and is a diagram showing the pattern and reference level of received signal levels from two adjacent targets in the azimuth direction.
・Reference level, 2 to 12... Received signal, 13
...Reference level, 14.15 ... Envelope of received signal level, 16 ... Level judgment means, 17 ... Amplitude comparison means, 18 ...・・・
...Target detection means, 19...Input terminal, 2
0... Output terminal, 21... Means configuration for implementing the method of the present invention, 22... Target detection means using a sliding window method, 23...
- Judgment means, 24... Input terminal, 25...
...output terminal, 26...minimum point, 27
．． 28... Received signal pattern, 29°30.
...Standard level agent Yoshi Yahata Hirokata A Preparation of the vertical angle invention method Diagram 1 Ftl Diagram 0 Akane Constituent block diagram of means for implementing the invention method No. 3

Claims (1)

[Claims] In a pulse radar device that transmits a high-frequency pulse signal into space while scanning an antenna direction and receives a reflected signal from a target object, when a received signal of interest exists at a distance and direction of interest that exceeds a predetermined reference level, A set includes a (<M) consecutive received signals of the direction for each transmitted pulse at the same distance corresponding to the past M consecutive transmissions of high-frequency pulse signals including the received signal of interest. , Compare the amplitude of each received signal in one set, and if there are m or more sets in which the received signal level does not change or increases monotonically, a target is detected at the time of reception of the received signal of interest. On the other hand, among the received signals in the direction of each transmitted pulse at the same distance corresponding to the past N consecutive transmissions of high-frequency pulse signals including the received signal of interest, consecutive b (<N)
If there are n or more sets in which the received signal level monotonically decreases, the target is detected at the time of reception of the received signal of interest. A target detection method characterized in that it is assumed that there was no target.