JP4594680B2 - Height measuring radar device and its angle measurement processing method - Google Patents

Description

  The present invention relates to a height measurement radar apparatus that measures a target from angle measurement values in an elevation angle direction and an angle measurement processing method thereof.

  In conventional height measurement radar equipment, a method is generally adopted in which a target is detected with a plurality of beams set continuously in the elevation angle direction, and the angle measurement value of the beam with the highest received intensity is used for target height measurement. ing. Further, as a countermeasure against multipath, an amplitude comparison angle measurement method in which the directivity center of the received beam is shifted upward (off-bore) is used. This method detects the low-altitude flight target near the sea surface from the received beam formed off-bore, thereby reducing the influence of the reflected wave from the sea surface when calculating the target height.

  However, in the height-measuring radar device using the amplitude comparison angle measurement method, even for an off-bore received beam, the received intensity of the lower beam is partially affected by the reflected wave component from the sea surface due to restrictions such as the beam width. May become large, and an erroneous height measurement value may be calculated. Therefore, conventionally, as a technique for reducing this influence, a multi-beam that forms a plurality of reception beams having different directivity elevation angles in an area that is susceptible to multipath in the sea surface direction, and performs angle measurement processing on each of the reception beams. A scheme has been proposed. In addition, a method of reducing variations in height measurement accuracy due to the influence of multipaths by averaging the results of angle measurement by each beam is also considered.

  However, in the conventional multi-beam handling method as described above, an area susceptible to multi-path is predicted by appropriate judgment, and a plurality of multi-beams are inadvertently formed at an appropriate angle and direction. The increase in hardware scale due to the function is a problem.

An example of the conventional radar apparatus is disclosed in Patent Document 1 as a multipath countermeasure. In the multipath countermeasure example of this document, when a target is detected from a received signal, an off boresight angle is obtained, and a target position is specified and displayed based on an azimuth angle and an elevation angle obtained from the target detection result and the off boresight angle. In addition, the target velocity component is detected using the target detection result, and the indirect wave (multipath) component of the reflection component from the target is suppressed by performing filtering using the speed detection result and the target detection result. The elevation angle is recalculated and selectively switched for display. However, this example is applied to a target acquisition / tracking radar apparatus, and is of a different type from the radar apparatus of the present invention that requires high-precision height measurement.
Japanese Patent Application Laid-Open No. 2002-071795

  As described above, in the conventional height measuring radar apparatus, when the multi-beam method is adopted in order to reduce the influence of the multipath, an increase in hardware scale due to the function is a problem.

  The present invention solves the above-described problems, and provides a height measurement radar apparatus and an angle measurement processing method thereof capable of reducing an increase in hardware scale due to the function while reducing deterioration in height measurement accuracy due to multipath. For the purpose.

  In order to solve the above problem, a height measuring radar apparatus according to the present invention includes a transmission / reception unit that receives reflected waves of a transmission pulse transmitted into a coverage area by an antenna apparatus using a plurality of reception beams having different elevation angles, and Target detection means for extracting a target component from each of the received beams to identify a received beam from which the maximum amplitude can be obtained, and outputting the distance and elevation angle of the target reflected signal contained in the received beam as target distance information and a rough measured angle value, respectively A plurality of reception beams that are shifted in different directions based on the rough measured angle values for angle measurement using a storage unit that stores the reception signals of the antenna apparatus, and a received signal stored in the storage unit Angle measuring beam forming means for reshaping and measuring and averaging the target elevation angle with each of the plurality of angle measuring beams, and based on the target detection position of the target detecting means Characterized by comprising a measuring angle / measuring height calculation means obtains a high measuring Te.

  In particular, the antenna apparatus is an array antenna formed by arranging a plurality of antenna elements in an array, and the storage means stores element signals of the plurality of antenna elements.

  That is, in the height measurement radar apparatus having the above configuration, when a target is detected from any of a plurality of received beams, the distance information and the rough measured angle value of the detected target are obtained from the received signal of the target detection beam, and the rough measured angle value is obtained. Is shifted by a predetermined elevation angle to determine the pointing direction, and a signal corresponding to the target distance is read out from the received signal stored in advance to form a plurality of angle measuring beams. Based on the result of rough angle measurement using the target detection position and detection beam, a plurality of receive beams with different directional elevation angles are formed again, and angle measurement processing is performed. Reduce variation in accuracy. At this time, since the received signal is once stored and a necessary beam is re-formed at this time, a new transmission / reception is not required to form a plurality of beams again. Further, since beam reshaping only needs to be performed at a target distance, hardware for beam forming is minimal.

  According to the present invention, it is possible to provide a height measurement radar apparatus and its angle measurement processing method capable of reducing the increase in hardware scale due to the function while reducing deterioration in height measurement accuracy due to multipath.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of a height measuring radar apparatus according to the present invention. In FIG. 1, the antenna device 11 is composed of, for example, an array antenna in which a plurality of antenna elements are arranged in an array and the power supply amplitude and phase of each element can be arbitrarily controlled. Then, a transmission beam (usually a second beam) having a predetermined beam width is formed in an arbitrary azimuth / elevation direction, a transmission pulse is transmitted, and the reflected wave is received.

  The reception signal of the antenna device 11 is sent to the detection beam forming circuit 12. The detection beam forming circuit 12 forms a multi-beam in the elevation angle direction for target detection and obtains a reception signal for each beam. The reception signal of each detection beam is input to the target detection circuit 13. The target detection circuit 13 detects a target element, that is, target distance (range) information and a rough angle measurement value for each received signal of each detection beam, and the detection result is sent to the angle measurement / height measurement calculation circuit 14. Sent. Further, the target distance information obtained by the target detection circuit 13 is supplied to the element signal memory 15, and the coarse angle measurement value is sent to the angle measurement beam forming circuit 16.

  On the other hand, the received signal obtained by each element of the antenna device 11 is supplied to the element signal memory 15. The element signal memory 15 stores each element signal in a certain range before and after the target distance information from the target detection circuit 13, and reads and outputs it in response to a request from the angle measurement beam forming circuit 16. The angle measuring beam forming circuit 16 is based on the rough measured angle value from the target detecting circuit 13, and the element signal memory in a direction in which the pointing center is shifted (off-bore) by a predetermined angle in the elevation direction from the detection beam. A multi-beam is formed using the element signal stored in 15, and a received signal is obtained for each beam. The received signal of each angle measurement beam is sent to the angle measurement / height measurement calculation circuit 14.

  The angle measurement / height measurement calculation circuit 14 measures the target elevation angle with the angle measurement beam formed by the angle measurement beam forming circuit 15 for each target element obtained by the target detection circuit 13, and the angle measurement result. The measured height value is converted from the distance between the target element and the obtained height measurement result is sent to the correlation tracking circuit 17, and the correlation tracking of the detection target is performed and displayed on the display 18.

  In the above configuration, the processing operation will be described below with reference to FIGS.

  Now, the antenna device 11 transmits a transmission pulse in a predetermined direction as a co-second beam as shown in FIG. 2A, and first to n-th detections having different elevation angles as shown in FIG. 2B. Assume that the reflected signals of the transmission pulses are received by the beams # 1 to #n, respectively.

  It is assumed that the target detection circuit 13 has obtained the amplitude component of the target signal from any of the detection beams # 1 to #n. At this time, the target detection circuit 13 obtains the distance information and the rough measurement angle value of the detection target from the beam reception signal from which the target is detected, and sends the distance information to the angle measurement / height measurement calculation circuit 14 and the distance information to the element signal memory. 15, the rough angle measurement value is sent to the angle measurement beam forming circuit 16.

  The angle measuring beam forming circuit 16 determines the directing direction by shifting the coarse angle value obtained by the target detection by a predetermined elevation angle, reads the element signal stored in accordance with the target distance from the element signal memory 15, A beam for angle measurement is formed. Here, paying attention to the fact that the variation in angle measurement (height measurement) accuracy due to multipath varies around the true value, a plurality of angle measurement beams shifted in different directions with respect to the coarse angle measurement value. Form.

  That is, a plurality of received beams having different directivity elevation angles are formed again on the detected target based on the target angle detection result and the approximate angle measurement result by the detection beam, and angle measurement processing is performed on each of the received beams. Then, by averaging the results obtained by measuring the angles of the respective beams by the angle measurement / height measurement calculation circuit 14, variations in height measurement accuracy due to the influence of multipath are reduced. At this time, the element signal stored in the element signal memory 15 is used for beam reforming.

  Therefore, in the height measurement radar apparatus having the above configuration, a plurality of reception beams having different directivity elevation angles are formed for one target (referred to as beam space diversity), and the angle measurement processing results of the beams are averaged. Therefore, the influence of multipath can be reduced, and the element signals are once stored and the necessary beams are re-formed, so that new transmission / reception is required to form multiple beams again. In this way, the increase in hardware scale can be reduced.

  In the height measurement radar apparatus according to the present invention, a pair of the sum beam Σ as shown in FIG. 3 (b) with reference to the received beam from which the target is detected as shown in FIG. 3 (a). A mono-pulse angle measurement method that forms a difference beam Δ and obtains an angle measurement value from the level difference between them, or performs angle measurement processing by comparing amplitudes with a plurality of Σhigh and Σlow beams as shown in FIG. Any angle measurement method of amplitude comparison angle measurement in which an angle measurement value is obtained from a ratio of amplitude levels may be used. However, when the target exists at a low elevation angle, it can be said that an amplitude comparison angle measurement method that does not require a difference beam Δ having a beam spread on the lower side is advantageous.

  Note that the present invention does not limit the number of multi-beams. In addition, when a plurality of beams are formed by reading a received signal from the element signal memory 15, the beams do not necessarily have to be formed at the same time. It can be implemented.

  Further, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The block block diagram which shows one Embodiment of the height measurement radar apparatus which concerns on this invention. The figure which shows the beam formation pattern for demonstrating the processing operation of the height measurement radar apparatus by the structure of FIG. The conceptual diagram which shows the example of the angle measurement system applicable in embodiment of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Antenna apparatus, 12 ... Detection beam formation circuit, 13 ... Target detection circuit, 14 ... Angle measurement / height measurement calculation circuit, 15 ... Element signal memory, 16 ... Beam formation circuit for angle measurement, 17 ... Correlation tracking circuit, 18: Display.

Claims (4)

An array antenna in which a plurality of antenna elements are arranged in an array, and an antenna device that receives reflected waves of transmission pulses transmitted into a covered area by the plurality of antenna elements, respectively;
Target detection beam forming means for acquiring a signal for each reception beam by forming a plurality of reception beams for target detection in directions different from each other in the elevation angle from reception signals of each of the plurality of antenna elements;
A target component is extracted from the received signals of each of the plurality of received beams for target detection, a received beam from which a maximum amplitude is obtained is specified, distance information from the target reflected signal included in the received beam to the target is obtained, Target detection means for outputting the directional elevation angle of the received beam as a rough angle measurement value;
Storage means for storing received signals of each of the plurality of antenna elements;
Angle measurement using a reception signal of each antenna element stored in the storage means, and re-forming a plurality of reception beams shifted from the elevation angle indicated by the rough measurement angle value in the direction of low elevation angle and high elevation angle for angle measurement. Beam forming means,
A target elevation angle is measured and averaged by each of the plurality of reception beams for angle measurement , and a height measurement value is obtained based on the averaged angle measurement value and distance information to the target of the target detection means. A height-measuring radar apparatus comprising a high calculation means.   The height measuring radar apparatus according to claim 1, wherein the storage means extracts and stores a predetermined range based on distance information from the received signal to the target.   2. The height measuring radar device according to claim 1, wherein the angle measuring beam forming means is a monopulse angle measuring method or an amplitude comparison angle measuring method. By the plurality of antenna elements arranged in an array, each of the reflected waves of the transmission pulse transmitted into the covered area is received,
From the reception signals of each of the plurality of antenna elements, obtain a signal for each reception beam by forming a plurality of reception beams for target detection in directions different from each other in elevation angle;
Identifying a received beam from which a maximum amplitude can be obtained by extracting a target component from a received signal of each of the plurality of received beams for target detection;
Obtaining distance information from the target reflected signal included in the received beam from which the maximum amplitude is obtained to the target, and outputting the directional elevation angle of the received beam as a rough angle value,
Storing reception signals received by each of the plurality of antenna elements;
Using the stored reception signals of the respective antenna elements, a plurality of reception beams shifted from the elevation angle indicated by the coarse angle measurement value in the low elevation angle direction and the high elevation angle direction are re-formed for angle measurement,
Measure and average the target elevation angle with each of the plurality of receiving beams for angle measurement,
An angle measurement processing method for a height measurement radar apparatus, wherein a height measurement value is obtained based on the averaged angle measurement value and distance information to the target.

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