JP2003028953A - Radar apparatus and control method for operation of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely discriminate a stationary in-flight helicopter from other moving targets, and to enhance its concealment properties. SOLUTION: The radar apparatus comprises a first target processor 1, equipped with M pieces of Doppler filters 4 and a second target processor 2 equipped with N pieces of Doppler filters 5 (where M<N). The first and second target processors comprise target discrimination circuit 6, 7, which can detect and process a target by using a plurality of threshold, when a target signal is decided. When the target is searched, the minimum number of hits required for its search is transmitted by the processor 1, and the target is detected. When the detected target is discriminated, the number of hits, which are more than those in the search is transmitted by the processor 2, the number of Doppler filters is increased, a Doppler resolution is increased, and the target is Doppler-discriminated. The radar apparatus comprises a target detection circuit, which comprises two kinds of threshold values for detecting the target, the target is detected by the large threshold, and a signal whose reception level is lowered, due to the fluctuation in the reflected signal, due to the rotation of the rotor of the stationary in flight stop helicopter is detected by the small threshold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device and an operation control method thereof, and more particularly, to distinguishing a helicopter for hovering from another moving target object when the target object is identified by utilizing the Doppler frequency of a received signal. The present invention relates to a radar device suitable for performing the operation and a method of controlling the operation thereof.

[0002]

2. Description of the Related Art In order to detect a target signal from reflected signals of a radar, it is necessary to suppress clutter, which is an unnecessary signal, in advance. An example of the radar device having the clutter suppression function is disclosed in the specification of Japanese Utility Model Laid-Open No. 63-90181, and FIG. 10 shows a functional block diagram thereof. In FIG. 10, 100 is a pulse Doppler filter, 200 is a constant false alarm reception processing circuit (CFAR),
300 is a frequency axis logical sum circuit, 400 is a zero Doppler detection circuit, 500 is a gate circuit, 600 is a reference value, 700
Is a comparator.

In the figure, a pulse Doppler filter 1
The output of 00 becomes a plurality of Doppler filter groups as shown in FIG. The CFAR circuit 200 performs target detection for each filter, and in the frequency axis logic circuit 300, the filter No. is set in the frequency axis direction for each distance. A logical sum is performed except for 0 to obtain a single distance direction detection signal. Therefore, although the output of the frequency-axis OR circuit 300 is obtained by removing the clutter, the pulse Doppler filter 100
The remaining clutter that exceeds the ability to suppress
0) is not removed as shown in FIGS. 11 (b) to 11 (c).

On the other hand, the output of the pulse Doppler filter 100 is compared with a reference value 600 in a comparator 700, and a signal exceeding the reference value is output as a detection signal. The detection output of the comparator 700 indicates which filter output of the pulse Doppler filter 100 in the zero Doppler detection circuit 400, the No. To detect. If the filter is No. When is 0, the Doppler spectrum is near 0 Hz and can be regarded as clutter. Also, due to strong clutter, No. Even if detected by a filter other than 0, No. If it is detected by the filter of 0 at the same time, it can be judged as clutter and removed.

Further, for example, when the spectrum of the reflected wave from the hovering helicopter stopped in the air is spread uniformly by the rotor blades, all the filter Nos. Since it is detected from, it can be recognized as a helicopter. From the above result, the zero Doppler detection circuit 400 generates the inhibition control signal to the gate circuit 500. The above operation is summarized in FIG.

The above operation will be described in more detail. Figure 11
(A) is the pulse Doppler filter 100 in FIG.
11A, the output of the CFAR circuit 200 is shown in FIG. 11B, the output of the frequency axis OR circuit 300 is shown in FIG.
(D) is the output of the zero Doppler detection circuit 400, FIG.
(E) shows the output of the gate circuit 500.

In FIG. 11B, the filter No. 0
If the clutter 70 is present in the zero doppler detection circuit 4
00 generates the inhibition control signal 1000 shown in FIG. 11 (d). When the gate circuit 500 receives the inhibition control signal 1000, the gate circuit 500 outputs the frequency axis logical sum circuit 300 to the output of FIG.
As shown in (c), even if the remaining clutter 60 is output as a detection signal, it is removed as shown in FIG. 11 (e) and only another moving target signal 80 such as an airplane is detected. To do.

Next, since the spectrum of the reflected wave from the helicopter stopped in the air is spread by the rotor,
It is detected by all the filters as shown by the signal 90 in FIG. When detected by all the filters, the zero Doppler detection circuit 400 determines the filter No. Even if 0 is detected, the inhibition control signal is not generated. Therefore, the helicopter is finally output as the target signal.

[0009]

Generally, in a radar device, a certain number of hits are integrated to obtain the S / S of the target signal.
A technique for improving N is used. Here, since the number of filters of the Doppler filter is the same as the number of hits, if the number of hits is large, the number of filters will also increase. In the above-mentioned conventional technique, other moving targets such as a hovering helicopter and an airplane are identified by the difference in the spread of the frequency spectrum. However, if the number of hits is small and the number of filters is small, it is difficult to distinguish between multiple targets and helicopters. .
On the other hand, since the helicopter is determined when all the filters have signals, there is a possibility that if any one of the filters lacks a signal, the helicopter will not be determined if the number of filters is large.

For example, as shown in FIG. 13, the level reflected by the blade of the hovering helicopter, that is, the received signal level may fluctuate, and the target signal may not be received. Since the threshold value for determining the target is set so as to reduce the probability of erroneous detection, a low level signal may not be detected as the target. As described above, since the level of the reflected wave of the hovering helicopter varies, the reflected wave may be detected as a target at one time and may not be detected as a target at another time.

If a large number of hits are taken in order to increase the number of filters, the S / N will be improved, but the data rate will be slower and the other party will be more likely to be detected, which is disadvantageous in terms of confidentiality. There is.

An object of the present invention is to solve the above-mentioned problems of the prior art, to accurately identify a hovering helicopter and another moving target, and to improve confidentiality, and a radar control method thereof. Is to provide.

[0013]

According to the present invention, there is provided a radar device for identifying a target object by using the Doppler frequency of a received signal, wherein M (for dividing the Doppler frequency into filter groups is used. M is an integer greater than or equal to 2), and a first target discriminating circuit that processes the outputs of the pulse Doppler filters using a plurality of threshold values and performs target discrimination according to the processing result. One target processing means, N (N is an integer greater than M) pulse Doppler filters for dividing the Doppler frequency into filter groups, and the outputs of these pulse Doppler filters using a plurality of thresholds. Second target processing means having a second target identifying circuit for performing target processing according to the result of the processing and switching means for switching between the first and second target processing means. Radar device is obtained, which comprises a.

When searching for a target object, the first target processing means detects a target, and when the detected target object is identified, the second target processing means performs target identification. And Further, the threshold value of the first target identification circuit, a first threshold value, and a second threshold value that is smaller than the first threshold value is set, and the determination result by these first and second threshold values The target detection is performed according to the above.

Further, the threshold value of the second target identification circuit is
A third threshold value and a fourth threshold value smaller than the third threshold value are set, and the target identification is performed according to a determination result by the third and fourth threshold values. .
Further, the target detection is performed with the third threshold value, and the reception signal whose level is lowered due to the fluctuation of the reflection signal due to the rotation of the rotor of the hovering helicopter is detected with the fourth threshold value.

According to the present invention, M (M is an integer of 2 or more) pulse Doppler filters for dividing the Doppler frequency of the received signal into filter groups, and the outputs of these pulse Doppler filters are converted into a plurality of threshold values. Target processing means having a first target discriminating circuit which performs target discrimination according to the processing result and N pieces (N is M) for dividing the Doppler frequency into filter groups. A larger integer) pulse Doppler filters, and a second target discriminating circuit that processes the outputs of these pulse Doppler filters using a plurality of thresholds and performs target discrimination according to the processing result. And a step of performing detection of the target by the first target processing means at the time of searching for a target object.
When the detected target object is identified, a step of identifying the target by the second target processing means is included, thereby providing an operation control method.

That is, the present invention has a first target processing device having M Doppler filters in which the number of Doppler filters is M <N, and a second target processing device having N Doppler filters. However, each of the first and second target processing devices has a target identification circuit that can perform detection processing using a plurality of threshold values (threshold values) in target signal determination, and the first target processing when searching for a target object. The device sends the minimum number of hits required for detection to detect the target,
When identifying the detected target, the second target processor is used to transmit a larger number of hits than when searching and increase the number of Doppler filters to improve Doppler resolution and identify the target Doppler. Have the means to do.

Further, there is provided a target detection circuit capable of detecting a threshold value for detecting a target with two kinds of threshold values TH1> TH2, and the threshold value TH
1 to detect the target object, and to detect a signal whose reception level has become low due to fluctuations in the reflected signal due to the rotation of the rotor of the hovering helicopter at the threshold value TH2.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, a pulse Doppler filter 4 for separating a received signal by a Doppler frequency, a CFAR (constant false alarm circuit) 6 for detecting a target from the signals separated for each filter, and each filter A target processing device 1 including a target identification circuit 8 for identifying a target based on the detection signal in step 1, and a target processing device 2 including a pulse Doppler filter 5, CFAR 7, and a target identification circuit 9 similarly to the target processing device 1. , A changeover switch 3 for selecting the target processing device 1 and the target processing device 2,
The target processing apparatus 1 and the target processing apparatus 2 are composed of a synthesis circuit 10 for synthesizing signals.

The target discriminating circuit 8 and the target discriminating circuit 9 include
Two threshold values (threshold values) for target detection judgment
Double threshold detection circuit 11 and 14 with
And an inter-filter correlation circuit 12, 1 for correlating the output signals detected at the two thresholds between the filters.
There is 5. Further, the target identifying circuit 8 has a filter number switching instruction circuit 13 for controlling the changeover switch 3 based on the information obtained by the inter-filter correlation circuit 12.

The difference between the target processing apparatus 1 and the target processing apparatus 2 is the number of filters of the Doppler filter, the Doppler filter 4 has a small number of filters of 0 to M for the search mode, and the Doppler filter 5 is for the identification mode. 0 to
It has a larger number of filters than the N search modes and has a relationship of M <N.

Next, the operation of the embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. The received signal reflected from the clutter or the target is input to the target processing device 1 in the search mode and to the target processing device 2 in the identification mode by switching the changeover switch 3. The received signal input to the target processing device 1 is filtered by the Doppler filter 4 to have Doppler frequencies of filters 0 to M. As an example, FIG. 2 shows the Doppler filter and the received signal when M = 2. The received signal is filtered by a Doppler filter according to frequency components, and CFAR6
In, each filter bank is divided into amplitude information in the distance direction.

Next, in the target identifying circuit 8, the signal is compared with the threshold value for detecting as a target, and the signal exceeding the threshold value is judged as the target signal. Normal,
The moving target is the high threshold value (TH1) shown in FIG.
However, in the case of a hovering helicopter, it is not detected in TH1 except for filter 0.

Therefore, the double threshold detection circuit 1
By using 1 and providing a low threshold value (TH2) in consideration of the fluctuation of the reflected signal level of the hovering helicopter, the lowered reflected signal level of the hovering helicopter can be detected. Figure 3 shows the threshold value TH
2 shows the results obtained as information on the filter and the distance. The signals detected by TH1 and TH2 are detected by the inter-filter correlation circuit 12 as shown in FIG.

By this operation, the filter N is set at TH2.
o. If the signal is detected by a filter other than 0, the target may be a helicopter. When it is necessary to identify whether the helicopter is a helicopter, an instruction signal for switching to the target processing device 2 is transmitted from the filter switching instructing circuit to the changeover switch 3 to switch to the target processing device 2. The received signal input to the target processing device 2 is filtered by the Doppler filter 5 into frequencies of filter 0 to filter N. As an example, FIG. 5 shows the Doppler filter and the received signal when N = 5.

Similar to the target processing apparatus 1, the received signal is filtered by the Doppler filter by the frequency component and divided into the amplitude information in the distance direction for each filter bank in the CFAR 7. Next, the target discriminating circuit 9 compares it with a threshold value for detecting it as a target, and judges that the signal exceeding the threshold value is the target signal. Also in the target processing device 2, the double threshold detection circuit 14 has threshold values TH3 and TH4,
It is possible to cope with the fluctuation of the reflected signal level of the hovering helicopter. FIG. 6 shows the results obtained as information on the filters and distances detected by TH4. Target processing device 2
, The resolution of the Doppler frequency is improved because the number of filters is increased.

The outputs of the threshold values TH3 and TH4 are identified by the inter-filter correlation circuit 15 as shown in FIG. The point different from the conventional technique as the criterion for target identification proposed in the present invention is that the conventional technique determines a helicopter by signal detection of all filters, but at the Doppler frequency where the helicopter has spread, as shown in FIG. The decision criterion is to consider the fact that a filter that is undetected due to noise is generated. FIG. 9 shows the received signal from the hovering helicopter that is not detected by all the filters as the information on the filter and the distance. Even in such a case, it is possible to identify the hovering helicopter.

The signals processed by the target processing device 1 and the target processing device 2 are used as information required by the synthesizing circuit 10,
It is output to a display (not shown).

[0029]

According to the present invention, there is an effect that the hovering helicopter and another target are accurately identified and the confidentiality is improved. The reason is that by providing a plurality of target processing devices each having a number of filters matching the number of hits and selecting and using them, the target object search is performed by selecting a small number of hits with high confidentiality, and the detected target object is identified. This is because it is possible to increase the switching resolution for processing with a large number of filters.
Further, since the target detection is performed with a plurality of threshold values, it is possible to deal with the fluctuation of the received signal level due to the rotation of the blade of the hovering helicopter.

[Brief description of drawings]

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

2 is a diagram showing a relationship between a received signal and a pulse Doppler filter of the first target processing apparatus 1 in FIG.

FIG. 3 is a diagram showing amplitude information of a filter pair distance in the first target processing device 1 of FIG.

4 is a diagram showing a detected filter No. in the first target processing apparatus 1 of FIG. FIG. 5 is a diagram showing a relationship between the signal type and the signal as a relationship between threshold values.

5 is a diagram showing a relationship between a received signal and a Doppler filter of the second target processing device 2 in FIG.

6 is a diagram showing amplitude information of a filter pair distance in the second target processing device 2 of FIG.

7 is a diagram showing a detected filter No. in the second target processing apparatus 2 of FIG. FIG. 5 is a diagram showing a relationship between the signal type and the signal as a relationship between threshold values.

FIG. 8 is a diagram showing a relationship between a received signal of a hovering helicopter and a Doppler filter.

FIG. 9 is a diagram showing amplitude information of a filter pair distance of a hovering helicopter.

FIG. 10 is a block diagram of a target identifying circuit according to a conventional technique.

FIG. 11 is a diagram for explaining the operation of the circuit of FIG.

12 is a filter N detected in the circuit of FIG.
o. It is a figure which shows the relationship between and the kind of signal.

FIG. 13 is a diagram for explaining level fluctuations of a hovering helicopter.

[Explanation of symbols]

1, 2 target processor 3 Changeover switch 4,5 pulse Doppler filter 6,7 CFAR 8, 9 Target discrimination circuit 10 Compositing circuit 11,14 Double threshold detection circuit 12, 15 Filter correlation circuit 13 Filter number switching instruction circuit

Claims (6)

[Claims] 1. A radar device for identifying a target object using a Doppler frequency of a received signal, wherein M (M is an integer of 2 or more) pulse Doppler for dividing the Doppler frequency into filter groups. First target processing means having a filter and outputs of these pulse Doppler filters, the target processing means using a plurality of threshold values, and a first target identification circuit for performing target identification according to the processing result; N pulse Doppler filters for dividing the frequency into filter groups (N is an integer larger than M) and the outputs of these pulse Doppler filters are processed using a plurality of thresholds, and the processing results are A radar characterized by including: second target processing means having a second target identification circuit for performing target identification; and switching means for switching between the first and second target processing means. apparatus. 2. A target is detected by the first target processing means when a target is searched, and a target is detected by the second target processing means when the detected target is identified. The radar device according to claim 1. 3. The first target discriminating circuit has a threshold value set to a first threshold value and a second threshold value smaller than the first threshold value. The first and second threshold values are set. The radar device according to claim 2, wherein the target detection is performed according to a determination result by the. 4. The threshold value of the second target discriminating circuit is set to a third threshold value and a fourth threshold value smaller than the third threshold value. These third and fourth threshold values are set. The radar apparatus according to claim 2 or 3, wherein the target identification is performed according to a determination result by the. 5. The target detection is performed with the third threshold value,
The radar device according to claim 4, wherein the received signal whose level is lowered by the fluctuation of the reflected signal due to the rotation of the rotor of the hovering helicopter is detected with the fourth threshold value. 6. The M (M is an integer of 2 or more) pulse Doppler filters for dividing the Doppler frequency of the input signal into filter groups, and the outputs of these pulse Doppler filters using a plurality of threshold values. First target processing means having a first target identification circuit for processing and performing target identification according to the processing result, and N (N is an integer greater than M for dividing the Doppler frequency into filter groups. ) Pulse Doppler filters and a second target processing means for processing the outputs of these pulse Doppler filters using a plurality of threshold values and performing target identification according to the processing result. And a step of detecting the target by the first target processing means at the time of searching for a target, and a step of detecting the target at the time of identifying the detected target. And a step of identifying the target by the second target processing means.