JPH03245080A - Target tracking apparatus - Google Patents

Abstract

PURPOSE:To accurately detect a plurality of targets by making an averaging cell blank on the basis of an estimate position and an estimate error when the estimate position of the target corresponds to the averaging cell of a constant false alarm rate (CFAR). CONSTITUTION:A target tracking apparatus 6 calculates the estimate position and estimate error to the target A2 high in a level among two targets A1, A2. When the estimate position data corresponds to the averaging cells 211 (or 212, and so forth) of a CFAR circuit 20, five cells of the cells 211 are changed over to a blank state on the basis of the estimate position and the estimate error. By this constitution, since no output is taken out of five cells 5, the threshold level L1 to the other target A1 becomes low and the target A1 can be certainly detected without being affected by the target A2. At this time, since the detection probability of the target lowers generally when the number M of the cells 211 is smaller than a predetermined number, the outputs of the cells 211 are controlled so as to be supplied to an adder 151 by the number of the cells brought to the blank state in order to secure the number M and the lowering of detection probability is prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding a target tracking method in a radar device that passes signals obtained from a pulse radar through a CFAR circuit to maintain a constant false alarm probability and detect only targets with a low false detection probability, the present invention relates to a target tracking method for a radar device that detects only a target with a low false alarm probability. The purpose is to accurately detect any target when reflected waves from two or more targets exist simultaneously in the CFAR circuit, and the predicted position data of the target obtained by the target tracking device is the average of the CFΔR circuit. Based on the predicted position data and prediction error data, the corresponding cell in the averaging cells of the CFAR circuit is blanked, and the corresponding cell is added for threshold setting in the CFAR circuit. The configuration is such that it is controlled so that it is not used for operation.

(Industrial Application Field) The present invention aims to detect only targets with a low probability of false detection by passing signals obtained from a pulse radar through a CFAR circuit (hereinafter referred to as C-ΔR) to a constant false alarm probability. A tracking type pulse radar emits a pulse as shown in FIG. 4, for example, and determines the target position by receiving the reflected wave. Here, the radar signal from pulse radar 1 is MT l (Movina Taroet
Non-zero Doppler signals (echoes from targets moving vertically and echoes from the ground) are canceled by the lndicator) 2 and are echoes from targets moving in directions other than vertically. ``Ding (Fast Fourier
Transform) Doppler filter 3 performs a Noe transform and divides into frequencies Fo~N and extracts them.
4o to 4N are supplied to CF8. CFAR4o~4N
is provided with a threshold value and is used to detect a target from among many reflected waves from targets, mountains, clouds, rain, forests, etc., and is used in the target determination circuit 5 based on the detection results of each of CFAR4o to 4N. The target is determined, and the target tracking device 6 tracks the target. The target tracking device 6 is configured to be able to track a plurality of targets.

In this case, when the pulse radar 1 is emitting pulses in a certain direction, two or more target radars 1~ may exist and reflected waves may return from them at the same time. They will exist in the CFAR for one frequency at the same time. In such cases, it is necessary to accurately detect any target.

(Prior art) For example, if reflected waves from a cloud and a target are obtained as a radar signal as shown in FIG.
~4N, in order to detect only the target, a threshold value called a threshold is reset one after another according to the incoming reflected waves, and if the reflected wave level is above llfa, this is the target, and if it is below the threshold, this is the clutter. ,noise(
regarded as a nuisance signal other than the target). That is, C.F.A.
R is the false alarm probability (probability of doing the opposite of the above) P
This is for finding a threshold value with fa constant.

Figure 6 shows an example of a conventional CFAR (Cell Avera
ging C to ΔR) is shown. The figure shows CFAR in one frequency bank. As shown in the figure, the AR is roughly composed of a shift register section io, an a value setting section 11, and a comparator 12.The shift register section 10 has M averaging cells 13+, 132.
, test cell 14, averaging cell 1
A guard cell is provided between 31 and 132 and the test cell 14. Here, when radar signals as shown in FIG.
53, averaged by the averaging circuit 16, and multiplied by a fixed value determined by the false alarm probability Pfa by the multiplier 17 to obtain a threshold value. On the other hand, the output of the test cell 14 is supplied to the comparator 12, and its level is compared with the threshold value from the multiplier 17.

For example, for reflected waves that have a gentle level change in the direction of the distance R (R+, R2, . . . is the minimum unit of the distance 1111R, and is called a range bin) like a cloud, the output level of the test cell 14 at the range bin RTI and averaging cell 13+ after range don RTl#ilJ
, 132, the cloud level is less than the threshold level L' as shown in FIG.

On the other hand, for reflected waves that have a steep level change in the direction of distance 111R, such as a target, range bin Rm
The output level of the test cell 14 and the range bin Rm at
By comparing the threshold level L obtained from the average value of the output levels of the averaging cells 13132 before and after, the level of the target becomes equal to or higher than the threshold level 1, as shown in FIG. The results of the level comparisons in CF A R4o to 4N are supplied to the target determination circuit 5, and a reflected wave having a threshold level or higher is determined to be a target, and the target tracking device 6 tracks the target.

(Problem to be Solved by the Invention) By the way, as shown in FIG. 7, there is a target A2 with a large reflection area (with a steep and large level change in the direction of distance R) near the target A1, and these reflections If waves enter one CFAR at the same time, that is, if the wave reflected by target A1 exists in the averaging cell 131 and the wave reflected by target A1 exists in the test cell 14, the following problem will occur. arise. Due to the large reflected wave level of target A2 (larger than the reflected wave level of target t-A+), the threshold value obtained from the average value of averaging cell 13132 becomes a relatively large level, that is, due to the influence of target A2, the threshold level L1 becomes Therefore, even though the reflected wave from the target A1 is present in the test cell 14, 1 to the target is less than 1 on the threshold level, resulting in a problem that the target A1 cannot be detected accurately.

An object of the present invention is to provide a target tracking method that can accurately detect any target when reflected waves from two or more targets are simultaneously present in the CFAR for a certain frequency.

(Means for Solving the Problem) FIG. 1 shows a diagram of the principle of the present invention. In the same figure, 30 is CFA
At R, the level of the radar signal is compared with successively set threshold levels to obtain a comparison result. 31 is a target determination circuit that determines the target based on the comparison result. 32 is a target tracking device that tracks a target. In the present invention, it is detected that the predicted position data of the target obtained by the target tracking device 32 corresponds to the averaging cell of the CFAR circuit 30, and the CFAR circuit 30 is activated based on the predicted position data and prediction error data. CF the corresponding cell in the averaging cells by leaving it blank.
$111 so that it is not used for the addition operation of the AR circuit 30! l
do.

[Operation] Out of targets A+ and A2, for example, target 2, which has a higher level, is being tracked by target tracking bag W132, and the predicted position and prediction error for target A2 are determined. This predicted position and prediction error are CFA
When corresponding to R30 averaging cell, predicted position and predicted S
Based on the error, the corresponding cell in the averaging cells is blanked. Nowadays, in addition to target 2, target A
+ simultaneously in the same CFAR and target A1
corresponds to the test cell, the threshold level for target A1 is lowered as described above, and target A1 can be reliably detected without being affected by target A2.

[Embodiment] FIG. 2 shows a configuration diagram of an embodiment of the present invention, in which the same components as in FIGS. 4 and 6 are given the same numbers. In Figure 2, 20 is the CFAR, which is roughly the averaging cell 21+
, 212 , a shift register section 22 . consisting of test cells 14 . II value setting section 11. It is composed of a comparator 12. In particular, the number of averaging cells 21+ and 212 is greater than M in the conventional example described above, and based on the predicted position and prediction error σ of the target 2 determined by the target tracking device 6, the corresponding cells are blanked. The configuration is such that it can be switched to

Here, the target A2 is being tracked by the target tracking device 6. Generally, the target tracking device 6 predicts the position data at the time t2 immediately after the current time t1 from the position data at the current time t1 and the position data at the immediately preceding time to, and tracks the target based on this prediction. Further, the pre-1s error σ defines the range within which the target is predicted to fall within a predetermined range from this predicted position. The target tracking device 6 tracks the target while determining the predicted position and prediction error.

In this way, the target tracking device 6 calculates the predicted position and prediction error for the target 82, so at time t2 when these are calculated, the target tracking device 6 calculates the predicted position and prediction error for the corresponding cell (this (5 cells of the averaging cell 21) are switched to a blank state. This switching is performed when the predicted position data is stored in the averaging cell 21.
(212) is detected and executed. As a result of this switching, at time t2, no output is taken out from the five blanked cells, so that the II value level L1 for target A+ becomes low as shown in FIG. ? It can be detected reliably without any influence. In this case, since the relevant cells are sequentially moved to the right, the blank state is also sequentially moved.

In this case, the target detection probability generally depends on the number M of averaging cells. If the number of averaging cells is smaller than a predetermined number M, the detection probability will decrease, so in order to secure the predetermined number M of averaging cells, the number of cells left blank (five in the above embodiment) is increased. The cell output of the averaging cell 21+ that had not been supplied to the adder 151 until then is sent to the adder 15.
1.

Incidentally, in the above embodiment, the predicted position of target A2 corresponds to the averaging cell 211, but one averaging cell 2
The same applies to the case corresponding to 12.

(Effects of the Invention) As explained above, according to the present invention, the predicted position of the target A2 determined by the target tracking device is
When dealing with the averaging cell of R, since the corresponding cell of the averaging cell is controlled to be in a blank state based on the predicted position and prediction error, there are two targets AΔ2 in one CFAR. If the other target A1 was present in the test cell, the threshold level for the other target A1 would be lower, and the target A1 would be lower.
1 can be reliably detected without the influence of 2 on the target.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle of the present invention, Figure 2 is a configuration diagram of an embodiment of the present invention, Figure 3 is a diagram explaining blanking operation in the present invention, Figure 4 is a diagram explaining a general target tracking method. Figure 5 is C
FIG. 6 is a diagram illustrating the general operation of the FAR, FIG. 6 is a configuration diagram of the CFAR used in the conventional system, and FIG. 7 is a diagram illustrating the operation in the conventional system. 17 is a multiplier, 20.304. tCFAR circuit, 21+ and 212 are averaging cells, and 22 is a shift register section.

Claims (1)

[Claims] The level of the radar signal is determined by CFAR (Constant F
The target determination circuit (31) determines the target based on the comparison result, and the target tracking device (32) determines the target based on the comparison result. In the method of tracking the target, it is detected that the predicted position data of the target obtained by the target tracking device (32) corresponds to the averaging cell of the CFAR circuit (30), and the predicted position data and Based on the prediction error data, a corresponding cell in the averaging cells of the CFAR circuit (30) is blanked and this corresponding cell is used in the CFAR circuit (30).
A target tracking method characterized in that the AR circuit (30) is controlled so as not to be used for an addition operation for setting a threshold value.