JP2933053B2 - Radar equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device, and more particularly, to a radar device that detects and tracks a target moving at a high speed over a long distance.

[0001]

2. Description of the Related Art Conventionally, when searching for a target appearing from a horizontal direction at an extremely long distance such as an orbital missile at a high speed,
A fence search as shown in FIGS. 9A and 9B is used. That is, only along the ground surface (horizontal plane) direction, the beam width θ
A method of increasing the search data rate by scanning the beam scanning angle θ with the beam _B and reducing the loss of opportunity for target detection is adopted.

Next, a conventional radar device will be described with reference to FIGS. 10 and 11. FIG.

FIG. 10 is a block diagram showing a configuration of a conventional radar apparatus. A transmitter 1 generates a transmission pulse signal at a transmission repetition period determined from a search distance. The transmission pulse signal is supplied to the antenna 3 by the transmission / reception switch 2. The antenna 3 uses a phased array type antenna, and is composed of a power combiner / distributor 31, a plurality of phase shifters 32, and radiating elements 32 provided corresponding to each phase shifter 32. This is done by controlling the phase of the detector 32. The control signal for beam scanning is generated by the beam scanning controller 4 based on the data of the beam scanning program 5 corresponding to the above-described fence search.

The signal received by the antenna 3 is transmitted to the duplexer 2
, And is subjected to amplification and detection reception processing, and output to the multi-hit integrator 11. The multi-hit integrator 11 performs an integration process on the received signal supplied from the receiver 6 by performing a correlation process on a plurality of hits, and, for targets located at the same distance, the amplitude of the target is N (where N is the number of hits). ) Magnify twice. Here, the hit indicates that the transmission pulse hits the target, and the hit number indicates the number of transmission pulses hitting the target in one scan (beam scanning).

[0005] For uncorrelated noise, the accumulation of the amplitude becomes N times the root, and the signal-to-noise ratio (S / N) is increased N times for one hit. Threshold detector 1
2 sets a threshold level for detecting a target based on a desired target detection probability Pd and a false alarm probability Pfa, and detects a received signal having the threshold level or more as a target. The track establishment processor 10a establishes a track of a target based on data over a plurality of scans of the detected target signal.

A method for setting the threshold level in the threshold detector 12 will be described with reference to FIG.

Referring to FIG. 11, the amplitude probability densities of noise and signal + noise are plotted on the same plane.
By lowering the threshold level, the target detection probability Pd can be increased. On the other hand, the false alarm probability Pfa for detecting noise as an erroneous target is also increased at the same time. Normally, the threshold level is set to a value that satisfies both the detection probability Pd and the false alarm probability Pfa required for the radar.

Next, search (1) in a conventional radar device
(Scanning time), that is, the search data rate will be described.

In a conventional radar apparatus for performing a fence search, a search data rate Dt is represented by the following equation. Dt = [(beam scanning angle θ) / (beam width θ _B × S
F)] × (transmission repetition time PRT) × (hit number n) Here, SF indicates a stack factor, that is, a beam overlap coefficient.

[0010] For example, in the radar system for searching a target emerging from approximately 2000Km front, a target speed of about 10 Mach, the beam width theta _B about 1 degree, the stack factor 0.8, required beam scan angle (theta ) Is 45 degrees, the number of hits (n) is 8 hits, and the transmission repetition period (PRT) is about 14 ms, the time required for the target 2000 km ahead to travel a distance equivalent to the beam width is about 10 s. On the other hand, the search data rate is calculated as follows using the above formula, and Dt = [45 degrees / (1 degree × 0.8)] × 14 ms × 8 hits = 6.3 s.

Therefore, in the conventional radar device, as shown in FIG. 2A, the target detected in the first scan has already moved out of the beam in the second scan, and the opportunity for detection is lost. Will be. Usually, to establish a track, two consecutive scans or three
Two detections are required during scanning, and the number of data needs to be at least three or more. Therefore, in the above-mentioned conventional radar apparatus, it is necessary to reduce the search data rate to about 2.5 s in order to satisfy the condition.

In order to shorten the search data rate, it is conceivable to increase the beam width, shorten the transmission repetition period, reduce the number of hits, etc. However, the increase in the beam width is accompanied by a decrease in the antenna gain and the radar detection distance. Will be reduced. Further, since the transmission repetition period is a parameter limited by a desired detection distance, it is difficult to shorten it. Also, the reduction in the number of hits is difficult to achieve because the integration gain by multi-hit integration is reduced.

[0013]

The conventional radar device cannot detect a target moving at a very long distance at high speed with high accuracy. Further, as a technique for detecting this target with high accuracy, it is conceivable to significantly reduce the search data rate. However, it is difficult to easily realize the reduction of the search data rate by the conventional technology. .

[0014]

In order to solve the above-mentioned problems, a radar apparatus according to the present invention obtains a moving target from a moving target for each of a plurality of beam scans repeatedly executed according to a preset search data rate. Receiving means for receiving the received radio wave, extracting means for extracting a detection signal indicating a target and noise using a preset threshold value from a reception signal obtained for each beam scanning, and detecting the detection signal obtained for each beam scanning. Generating means for generating scan data by superimposing signals, and detecting means for extracting a line segment included in the scan data and detecting an object indicated by the detection signal correlated with the line segment as a movement target Search with
It has a processing system .

[0015] The radar apparatus of the present invention can be added to a search processing system.
The beam travels according to the preset tracking data rate.
Receiving means for receiving a radio wave obtained for each inspection,
The received signal obtained by the stage is received through the switch and
Multi-hit integration processing means to perform
Signal from the target using the desired threshold
And a tracking processing system having an output unit. These search offices
The science and tracking systems are phased using a common electronic scanning method.
An array antenna is used .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a radar apparatus according to the present invention will be described in detail with reference to the drawings.

The radar apparatus according to the present embodiment greatly reduces the number of hits required from the detection capability of the conventional radar apparatus, performs beam scanning at high speed, and determines a target from the obtained reception signal. At the time of detection, the detection threshold is greatly reduced, and target detection is performed with a desired detection probability Pd.
At this time, the false alarm probability Pfa also increases,
Focusing on the linearity of the target track, data of a plurality of scans are superimposed, and line segment detection processing is performed by correlation processing with line segments. This makes it possible to suppress noise uncorrelated with the line segment and detect the target, and to perform target detection that sufficiently satisfies the false alarm probability required for the radar device.

FIG. 1 is a block diagram showing the configuration of the radar apparatus according to the present embodiment. The transmitter 1 generates a transmission pulse signal at a transmission repetition period determined by a search distance. The transmission pulse signal is supplied to the antenna 3 by the transmission / reception switch 2. The antenna 3 employs, for example, a phased array type antenna, includes a power combiner / distributor, a phase shifter (φ), and a radiating element, and controls a phase shifter (φ) to perform desired beam scanning. Do. The beam scanning controller 4 and the beam scanning program 5 generate control signals for the phase shifter (φ) of the antenna 3 to perform beam scanning. The beam scanning program 5 is programmed to greatly reduce the number of transmission hits per beam and perform beam scanning in a desired beam scanning range at a high speed compared to the conventional radar apparatus.

FIGS. 2A and 2B show the concept of beam scanning in the conventional radar apparatus and the radar apparatus of the present embodiment in a comparative manner. Referring to FIG. 2A, the beam scanning of the present embodiment has a search data rate of about 0.8 second, which is 1/8 of that of the conventional beam scanning. Detection data of 10 scans or more is obtained.

As described above, in the radar apparatus according to the embodiment of the present invention, the search data rate in the conventional fence search is about 12 s, but the search data rate is set to about 2 s or less to achieve high speed. Beam scanning is realized. Here, in order to reduce the search data rate to about 2 s or less, the number of hits, that is, the number of transmission pulses hitting the target in one scan is set to about one.

A reception signal obtained by such beam scanning is transmitted from the antenna 3 via the transmission / reception switch 2 to the receiver 6.
, And amplification and detection reception processing are performed. Receiver 6
The received signal supplied to the threshold detector 7 from
Realizes the detection probability Pd required for radar by extracting the received signal component larger than the detection threshold using the detection threshold set in advance to a lower value than the conventional one without performing the conventional multi-hit integration process I do. That is, the target is detected under the condition of low S / N (signal-to-noise ratio). In this case, many noises are detected as erroneous targets, and at this time, the false alarm probability Pfa required for the radar device is not satisfied. That is, the false alarm probability Pfa is about 10 ^-2 .

The detected signal is supplied to a line segment target detector 9 by superimposing data of a plurality of scans in a scan data generator 8. Here, FIGS. 3A, 3B and 3C show processing in the threshold detector 7 and detection signals thereof, and FIG. 4 shows data obtained by superimposing data of a plurality of scans obtained by the scan data generator 8. It is shown.

The line segment target detector 9 includes a Hough transformer 9a, an intersection line number measuring device 9b, and a target detector 9c, and detects a target from many noises by performing a correlation process with the line segment using Hough transform. Is what you do.

Here, a method of detecting a target by Hough transform will be described with reference to FIGS. 5A and 5B.

As shown in FIGS. 5A and 5B, as a property of the Hough transform, an arbitrary point on the (x, y) plane is expressed as follows.
On the (a, b) plane, which is a Hough plane, a point is represented as a straight line, and further, a point constituting the straight line on the (x, y) plane is a plurality of straight lines (hereinafter, referred to as a line) intersecting at one point on the Hough plane. This straight line is referred to as an intersection line). The Huff transformer 9a applies this property to the output of the scan data generator 8 shown in FIG. 4, so that the target data describing the wake on a straight line forms an intersection on the Hough plane, and the noise is Since there is no correlation with the line segment indicating the target data, data that does not form an intersection on the Hough plane is output. Intersection line measuring instrument 9
b, the number of intersection lines after the Hough transform is measured, and the target detector 9c calculates
Threshold detection for the number of intersections is performed, and data whose number of intersections is larger than a preset threshold is detected as a target. Here, the threshold is set to a value that satisfies the false alarm probability Pfa required by the radar. In the target detector 9c, the intersection line on the Hough plane detected as the target is extracted as a point on a straight line on the (x, y) plane as shown in FIG. Thus, in the target detection by the line segment target detector 9,
The false alarm probability Pfa can secure about 10 ^-6 .

The track establishment processor 10 includes a line segment target detector 9
Is established as the target track.

As described above, in the present embodiment, the desired detection probability cannot be obtained as it is because the amplitude level of the received signal is reduced by the high-speed beam scanning. The threshold level is set to a low value so that the detection probability becomes about 50% or more. When the threshold level is set to a low value in this manner, many noise components are detected. However, by applying a line segment extraction process using the property of the Hough transform, detection data containing much noise is detected. , Detection data on the same line segment is extracted as target data, and the line segment is established as a target track.

Since the Hough transform shows similar properties not only to a straight line but also to a line segment such as a circle or a parabola, the present embodiment has described the target detection on a straight line.
Target detection from wake data indicating another line segment is also possible.

The radar apparatus according to the present invention is not necessarily limited to the application of the phased array type antenna as in the above-described embodiment, and as shown in FIG. The antenna 31 may be used. In this case, the beam scanning controller 4
Then, a drive control signal for controlling the mechanical driver 32 for driving the antenna 31 is generated.

Further, in the radar device of the present embodiment, since the target detection system adopts a method of detecting a target with a low S / N, the accuracy of distance measurement and angle measurement is higher than that of a conventional radar device. Deteriorates. Therefore, as shown in FIG. 8, a target detection system including a multi-hit integrator 11 and a threshold detector 12 provided in a conventional radar device is added to the radar device of the present embodiment as a tracking beam processing system. This makes it possible to detect a target with the same measurement accuracy as that of a conventional radar device.

That is, the track establishment processor 1 of the search processing system
When the moving target is detected by 0, the received signal from the detected tracking target is processed by the tracking beam processing system via the processing system selector 15 so that the track tracking processor 1 is processed.
4 can maintain the measurement accuracy in the tracking processing.

[0032]

As described above, the radar apparatus of the present invention performs beam scanning at a high speed by greatly reducing the number of hits required from the conventional radar detection ability. The received signal is subjected to threshold detection processing that greatly lowers the detection threshold, and the detected data is overlapped for multiple scans, and line segment detection processing using Hough transform is performed, which is required by radar. Detection probability and false alarm probability can be satisfied.

As a result, in the radar apparatus of the present invention, it is possible to perform beam scanning at a high speed, and it is possible to greatly improve a detection opportunity particularly in a search scene of a target moving at a very long distance at a high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment of a radar apparatus according to the present invention.

2A and 2B are diagrams showing beam scanning, FIG. 2A is a diagram showing beam scanning in a conventional radar device, and FIG. 2B is a diagram showing beam scanning in a radar device of the present embodiment.

FIG. 3 is a diagram showing low threshold detection data detected by the threshold detector in FIG. 1,
FIGS. 3A, 3B, and 3C show data detected in the first scan (beam scan), the second scan, and the third scan, respectively.

FIG. 4 is based on the data obtained according to FIG.
FIG. 4 is a diagram showing targets and noise on a radar plane output from a scan data generator in FIG.

FIG. 5 is a diagram for explaining the nature of the Hough transform, and FIG.
Shows that a plurality of detection points exist on the (x, y) plane, and FIG. 5B shows a Hough plane obtained by performing a Hough transform on each point on the (x, y) plane shown in FIG. 5A. It is a figure showing a plurality of upper straight lines.

FIG. 6 is a diagram illustrating data after a line segment extraction process output from the line segment target detector in FIG. 1;

FIG. 7 is a block diagram showing a configuration of another embodiment of the radar apparatus of the present invention.

FIG. 8 is a block diagram showing a configuration of still another embodiment of the radar apparatus of the present invention.

FIG. 9 is a diagram for explaining a fence search.

FIG. 10 is a block diagram illustrating a configuration of a conventional radar device.

11 is a diagram for explaining a method of setting a threshold level in the threshold detector in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitter 2 Transmission / reception switch 3 Phased array antenna 4 Beam scanning controller 5 Beam scanning program 6 Receiver 7 Threshold detector 8 Scan data generator 9 Segment target detector 9a Hough converter 9b Intersection number measuring instrument 9c Target Detector 10 Track establishment processor 11 Multi-hit integrator 12 Threshold detector 13 Measurement processor 14 Track tracking processor 15 Processing system selector

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-271615 (JP, A) JP-A-10-104347 (JP, A) JP-A-9-133762 (JP, A) JP-A-4- 161883 (JP, A) JP-A-4-55787 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/95

Claims (4)

(57) [Claims] 1. A receiving means for receiving a radio wave obtained from a moving target for each of a plurality of beam scans repeatedly executed in accordance with a preset search data rate; Extracting means for extracting a detection signal indicating a target and noise using a set threshold; generating means for generating scan data by superimposing the detection signals obtained for each of the beam scans; and A search processing system including a detection unit that extracts a line segment to be detected and detects an object indicated by the detection signal correlated with the line segment as a moving target, and a beam scanning corresponding to a preset tracking data rate. Receiving means for receiving the radio wave obtained from the receiving means, and multi-hit integration for receiving and integrating the received signal obtained by the receiving means via a switch. Radar apparatus characterized by comprising: a management unit, and a tracking processing system comprising detection means for detecting a signal from the target with a desired threshold from the integration processed signals. Wherein said search processing radar apparatus according to claim 1, wherein the tracking using the tracking process based respect detected target by system. 3. The search data rate is set to such an extent that one pulse hits the moving target in one beam scan, and the tracking data rate is a multiple pulse in one beam scan. 2. The radar apparatus according to claim 1 , wherein the radar apparatus is set to such an extent that it hits a target to be detected and tracked. 4. The search processing system and the tracking processing system share
The use of an electronic scanning type phased array antenna
The radar device according to claim 3, wherein: