JP2010085283A - Radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar system stably acquiring altitude information of a target, even in the environment where an influence of a multipath, etc. always changes. <P>SOLUTION: A plurality of receiving beams as angle measuring beams are simultaneously formed with respect to an elevation direction, altitude information of a target is calculated by using data in an effective angle measuring range from among angle measurement data with respect to the target acquired respectively by the receiving beams, and altitude information with respect to the same target is received from a secondary radar, to compare the information with this calculation result. When the standard deviation of the differences between both values exceeds a predetermined threshold value set beforehand, control is made so as to change the orientations of the plurality of receiving beams. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radar apparatus, and more particularly to a radar apparatus that stably acquires altitude information of a target by reducing the influence of a radar reflected wave due to multipath or the like.

  Conventionally, a radar device that acquires target altitude information scans a received beam in the elevation angle direction or forms a reception multi-beam in the elevation angle direction, and the angle information of the elevation angle direction from the radar reflected wave with these beams. And obtain altitude information based on this. Radar reflected waves from low elevation targets are often affected by so-called multipath. In other words, in addition to the direct reflected wave from the target, for example, a signal that is reflected on the sea surface or the ground surface and propagates through another route is mixed and received, so an error occurs when obtaining angle measurement values as angle information Will result. In particular, it is easily affected when the target altitude is low or the distance is long. In addition, the influence is not fixed, and changes greatly in a short time depending on the weather conditions on the propagation path and the prediction thereof is often difficult.

Examples have been disclosed that can cope with such multipath effects on target altitude information (see, for example, Patent Document 1). In the example disclosed in Patent Document 1, a plurality of reception beams having different directivity elevation angles with respect to a target azimuth are simultaneously formed, and approximate position information of a target target including altitude information is calculated from these reception beams. The angle measurement processing is performed using the angle measurement method selected based on the result, and the altitude information is acquired. In addition, techniques such as lowering the side lobe of the received beam and statistically processing results using a plurality of different transmission frequencies have been proposed.
JP 2001-272464 A (6th page, FIG. 3)

  When the target angle information is acquired, if it is affected by multipath, it is known that the measurement result varies randomly around the true value. It is also sensitive to slight changes in the directivity angle of the received beam. For this reason, when receiving target angle information by forming multi-beams for reception in the elevation direction, for example, the effect of multipath is reduced by averaging the measurement results for each beam. Can be considered.

  However, the effect of multipath is not necessarily fixed, and changes with difficulty relative to the target and changes with observation time. Then, the influence appears irregularly in each observation result with multi-beams, so that the dispersion of each measurement result becomes large, which causes the accuracy of angle information to deteriorate.

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a radar apparatus that stably acquires target altitude information while the influence of multipath and the like constantly changes.

In order to achieve the above object, a radar apparatus according to the present invention includes a plurality of antenna elements, an aerial part that receives a reflected wave of a radar transmission pulse, and a range in which an angle can be measured with respect to the same target. A multi-beam forming means for simultaneously forming a plurality of reception beams having different beam directing directions and receiving a reception signal from the antenna portion with each reception beam, and a beam output from the multi-beam forming means Angle measurement means for acquiring angle measurement data for the target detected every time, height measurement means for calculating altitude information of the target from angle measurement data of the target acquired for each beam output, and the target by a secondary radar The altitude information is received and compared with the target altitude information from the height measuring means, and in the multi-beam forming means according to the comparison result. Characterized in that a beam control means for controlling the orientation of the number of receive beams.

  According to the present invention, it is possible to obtain a radar apparatus that can stably acquire target altitude information even in an environment where the influence of multipath or the like constantly changes.

  Hereinafter, the best mode for carrying out a radar apparatus according to the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing the configuration of an embodiment of a radar apparatus according to the present invention. As illustrated in FIG. 1, the radar apparatus includes an aerial unit 11, a multibeam forming unit 12, a target detection unit 13, an angle measurement processing unit 14, an angle measurement data determination unit 15, an angle measurement and height conversion unit 16, and The beam control unit 17 is configured. The antenna unit 11 includes a plurality of antenna elements (not shown) arranged in a predetermined shape, and receives a reflected wave of a radar transmission pulse. The multi-beam forming unit 12 forms a plurality of reception beams with different directivity directions using a technique such as DBF (Digital Beam Forming) based on control from the beam control unit 17 to be described later, and receives from the antenna unit 11 A beam output is obtained by receiving a signal with the plurality of reception beams. The plurality of formed beams have different beam directing directions within a range in which the angle can be measured with respect to the same target, and an example thereof is modeled and shown in FIG. In the example shown in FIG. 2, four receiving beams 1 to 4 having slightly different directing directions are formed. Each received beam can be angled with respect to the same target, and further, a part of the overlapping range of the angled range of each received beam can be measured by these four received beams. The range. Further, in this embodiment, each beam pattern to be formed can be formed as either an amplitude comparison angle measurement or a monopulse angle measurement beam pattern in correspondence with the angle measurement method in the subsequent stage.

  The target detection unit 13 detects a target from each of a plurality of beam outputs from the multi-beam forming unit 12 and sends the result to the angle measurement processing unit 14. The angle measurement processing unit 14 performs angle measurement processing on a target detected for each of a plurality of beam outputs, and acquires angle measurement data for each received beam. In the present embodiment, the angle measurement processing method is acquired by applying either the amplitude comparison method or the monopulse method. The angle measurement data determination unit 15 determines whether or not the angle measurement data for each reception beam is within the preset effective angle measurement range, rejects the angle measurement data outside the range, Are sent to the angle measurement and conversion unit 16 in the subsequent stage. The effective angle measurement range at the time of the above determination is set in advance corresponding to the formed reception beam. An example of the setting will be described with reference to FIG.

  In FIG. 2, the four received beams 1 to 4 that are formed are slightly angled to each other as angle measuring beams that can cover about 2 °. For example, the received beam 1 is −0.5 ° to 1 .5 °, receive beam 2 is directed from −0.3 ° to 1.7 °, receive beam 3 is directed from 0.0 ° to 2.0 °, and receive beam 4 is directed from 0.4 ° to 2.4 °. It shall be. In addition, for each of these received beams, as an effective angle measurement range, for example, the received beam 1 is −0.3 ° to 1.0 °, and the received beam 2 is −0.2 ° to 1. °. It is assumed that a range of 2 °, a reception beam 3 of 0.0 ° to 1.2 °, and a reception beam 4 of 0.6 ° to 2.0 ° are set in advance. In such a case, for example, 0.6 ° to 1.0 °, which is an overlapping portion of the angle measurement ranges of these four reception beams, is an effective angle measurement by these four reception beams 1 to 4. Set as a range.

  The angle measurement and measurement conversion unit 16 receives angle measurement data determined to be in the effective angle measurement range from the angle measurement data determination unit 15 and converts each into angle measurement data based on, for example, target distance information. Averaging processing is performed on the converted height measurement data, and the result is output as target altitude information. The beam control unit 17 controls a plurality of reception beams formed by the multi-beam forming unit 12. In addition, the altitude information of the target from the angle measurement conversion unit 16 is compared with the altitude information acquired by the secondary radar for the same target, the standard deviation of the difference is calculated, and the calculation result is predetermined. If the threshold value is exceeded, it is assumed that the influence of the multipath has changed, and control is performed so that the directivity directions of a plurality of reception beams formed by the multibeam forming unit 12 are changed. In the present embodiment, the directivity direction of any one of the plurality of reception beams to be formed is changed to either the upper or lower direction. It is also possible to change two or more at the same time.

  Next, the operation of the radar apparatus of the present embodiment configured as described above will be described with reference to the flowcharts of FIGS. 1 and 2 and FIGS. 3 and 4. FIG. 3 is a flowchart for explaining the operation of the radar apparatus according to the present invention illustrated in FIG.

  First, when the radar apparatus starts operation, the reflected wave of the radar transmission pulse is received by each antenna element of the antenna unit 11 and transmitted to the multi-beam forming unit 12 (ST301). In the multi-beam forming unit 12, a plurality of reception beams having different directivity elevation angles are formed using a technique such as DBF based on the control from the beam control unit 17, and the reception signal from the antenna unit 11 is received by these reception beams. As a result of reception, the reception result is obtained for each reception beam. The acquired beam output for each received beam is sent to the target detector 13 (ST302). Next, the target detection unit 13 performs target detection processing on each beam output from the multi-beam forming unit 12. Then, when a target is detected, for example, with the same target as the distance information, the angle measurement processing unit 14 performs angle measurement processing for each beam output and acquires the angle measurement data. To do. As an angle measurement method in the angle measurement processing unit 14, either an amplitude comparison method or a monopulse angle measurement method can be applied, and a reception beam as an angle measurement beam formed by the multi-beam forming unit 12 can also be used. A shape corresponding to the angle measurement method is formed (ST303).

  Next, the angle measurement data determination unit 15 determines whether each angle measurement data acquired by the angle measurement processing unit 14 is within a preset effective angle measurement range. As described above, the effective angle measurement range corresponds to an overlapping portion of the effective angle measurement ranges for each of the plurality of reception beams. By this determination, the angle measurement data based on the received beam that is assumed to be affected by multipath or the like is rejected, and angle measurement data that is assumed to be less affected is extracted. The extracted target angle measurement data is sent to the angle measurement and conversion unit 16 (ST304). Then, the angle measurement and height conversion unit 16 converts each of the target angle measurement data into height measurement data. In the conversion, since the angle measurement data corresponds to the angle information in the target elevation angle direction, the angle measurement data can be calculated by, for example, an arithmetic process using the distance information to the target and the like. Further, the angle measurement and height conversion unit 16 converts the respective angle measurement data into height measurement data, calculates the average of these, and sets the target target altitude information. The calculated altitude information is output to the subsequent stage and is also transmitted to the beam control unit 17 (ST305).

  On the other hand, the target altitude information sent from the elevation measurement and angle conversion unit 16 and the target altitude information from the secondary radar are sent to the beam control unit 17, and the beam control unit 17 The directivity directions of a plurality of reception beams formed by the multi-beam forming unit 12 are controlled according to the comparison result. In this embodiment, the standard deviation of the difference between the target altitude information from the altitude measurement angle conversion unit 16 and the altitude information from the secondary radar is calculated, and this value is compared with a predetermined threshold value. (ST306). When the threshold value is exceeded, it is determined that the target altitude information acquired by the height measurement and angle conversion unit 16 has a large variation and is unstable and is greatly affected by multipath, Control proceeds to directivity control of the received beam (Y in ST307).

  Since the influence of multipath or the like is sensitive to a slight change in the beam directivity angle, in this embodiment, the directivity direction of the received beam is controlled as follows. In other words, the directing direction of any one of the plurality of reception beams is slightly changed with respect to one control opportunity. As a specific example, in the case of FIG. 2 described above, at the first control opportunity, for example, the directional elevation angle of the reception beam 1 is changed upward by 0.05 °, and the effective angle measurement range remains unchanged. In the second control opportunity in which the operation step ST308 is executed again after the operation is continued, for example, the directional elevation angle of the received beam 2 is changed upward by 0.05 °, which is different from the first time. Further, at the next control opportunity, the operation is continued by controlling the directivity elevation angle of the received beam different from these. FIG. 4 is an example of a flowchart for explaining the flow of control opportunities with respect to the directing direction of the received beam repeated in this manner based on the flowchart of FIG. Further, it is possible to control not only one received beam but also a plurality of received beams at the same angle in the same direction and reset the effective angle measurement range (ST308). Thereafter, the above-described operation steps are continued until an operation end is instructed (ST309).

  As described above, in this embodiment, a plurality of reception beams as angle measurement beams are simultaneously formed in the elevation angle direction, and effective angle measurement is performed from the angle measurement data for the target acquired by each of these reception beams. The altitude information of the target is calculated using the range data, and the altitude information for the same target from the secondary radar is received and compared with the calculation result. Then, when the standard deviation of the difference between the two exceeds a predetermined threshold value set in advance, control is performed so as to change the directivity directions of a plurality of reception beams. This can reduce the effects of multipath on radar reflected waves that appear irregularly with the relative position of the target and the time course of observation, in an environment where the effects of multipath, etc. are constantly changing. Even the target altitude information can be acquired stably.

  Note that 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. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The block diagram which shows the structure of one Example of the radar apparatus which concerns on this invention. The conceptual diagram for demonstrating the some beam formed, and the effective angle measurement range by these beams. 2 is a flowchart for explaining the operation of the radar apparatus illustrated in FIG. 1. The flowchart for demonstrating the flow of the control opportunity of the directivity direction of a receiving beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Aerial part 12 Multi beam formation part 13 Target detection part 14 Angle measurement process part 15 Angle measurement data determination part 16 Angle measurement height conversion part 17 Beam control part

Claims (5)

An antenna unit for arranging a plurality of antenna elements and receiving a reflected wave of a radar transmission pulse;
A multi-receiver that simultaneously forms a plurality of received beams having different beam directing directions within a range in which the angle can be measured with respect to the same target, and obtains a beam output obtained by receiving the received signal from the antenna portion with each received beam. Beam forming means;
Angle measuring means for acquiring angle measurement data for the target detected for each beam output from the multi-beam forming means;
Height measuring means for calculating the target altitude information from the target angle measurement data acquired for each beam output;
Receiving the altitude information of the target from the secondary radar and comparing it with the altitude information of the target from the height measuring means, and controlling the directivity directions of the plurality of received beams in the multi-beam forming means according to the comparison result A radar apparatus comprising a beam control means.   The beam control unit calculates a standard deviation of a difference in altitude information from the height measuring unit with respect to the target altitude information by a secondary radar within a predetermined period, and the calculation result is a predetermined threshold value set in advance. When one of the plurality of received beams by the multi-beam forming means is exceeded, the directivity direction of any one of the plurality of received beams is changed within a range in which the angle can be continuously measured with respect to the target. The radar apparatus according to 1.   The beam control unit calculates a standard deviation of a difference in altitude information from the height measuring unit with respect to the target altitude information by a secondary radar within a predetermined period, and the calculation result is a predetermined threshold value set in advance. When two or more directing directions among a plurality of received beams by the multi-beam forming means are continuously changed with respect to the target, the same angle is changed in the same direction within a range in which any angle can be measured. The radar apparatus according to claim 1.   The height measuring means is a target angle measurement data acquired for each beam output received from the angle measurement means, and the angle measurement is within a predetermined angle measurement range corresponding to the received beam to be formed. 2. The data is extracted and the others are rejected, and the extracted angle measurement data is converted into target height measurement data, and the target altitude information is calculated based on an average processing result thereof. The radar apparatus according to any one of claims 3 to 3.   The angle measuring means acquires angle measurement data by an amplitude comparison method or a monopulse method, and the multi-beam forming means forms the reception beam corresponding to these methods. Item 5. The radar device according to any one of items 4 to 6.

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