JP2011163968A - Radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar device for keeping and continuing stable tracking without being affected by a directly under clutter, a main lobe clutter, and a side lobe clutter. <P>SOLUTION: The radar device includes a signal processor 3 having a directly under clutter evaluation processing 321 for selecting a pulse repetition period (PRI) of a transmission signal where the generating region of the directly under clutter is not close to the detection position of a target signal in the range direction, a main lobe clutter evaluation processing 323 for selecting a pulse repetition period of a transmission signal where the generating region of the main lobe clutter is not close to the detection position of the target signal in the Doppler frequency direction, and a side lobe clutter evaluation processing 325 for selecting a pulse repetition period of a transmission signal where the generating region of the side lobe clutter is not close to the detection position of the target signal in the range direction and the Doppler frequency direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radar device mounted on a moving body such as an aircraft that can eliminate the influence of ground clutter (hereinafter referred to as clutter) that becomes an obstacle in target tracking processing.

  In the target tracking process in the pulse Doppler radar device, the presence of clutter hinders stable tracking of the target, leading to occurrence of erroneous tracking and deterioration of tracking accuracy. In order to solve such a problem, many signal processings that improve the S / C (Signal to Clutter) ratio by removing clutter and suppressing clutter have been proposed (for example, see Non-Patent Document 1). .

  A radar device that selects a pulse repetition interval (PRI) so that the detection position of the clutter region and the target signal does not compete has also been proposed (for example, see Patent Document 1). Is a direct under clutter and main lobe clutter, and side lobe clutter is not considered.

JP 2007-256135 A

Matsuo Sekine "Radar signal processing technology", edited by the Institute of Electronics, Information and Communication Engineers, April 10, 1993, 2nd edition, Chapter 6

  As an example, FIG. 8 shows a situation of clutter generated in an aircraft-mounted radar apparatus. The clutter generated by the antenna main lobe irradiating the ground surface is referred to as main lobe clutter, and the clutter generated by the antenna side lobe is referred to as side lobe clutter. Among the side lobes and clutters, the clutter from directly below the radar-equipped aircraft is defined as the direct clutter.

  The generation distribution of clutter observed by the radar apparatus is determined by the distance between the corresponding ground surface and the mounted aircraft, the speed of the own aircraft, and the beam direction, and shows the generation distribution of the range Doppler frequency as shown in FIG. Conventionally, even if clutter that affects target tracking is suppressed and the signal strength of the clutter is reduced, the clutter may be spread or in environments where the signal strength of the clutter is strong. There may be an unerased residue.

  FIG. 10 is a diagram showing a situation in which the clutter disappears when a clutter suppression filter in the Doppler frequency direction is applied. Under such circumstances, various remaining clutters may affect the target signal tracking process.

  The present invention has been made to solve the above-described problems, and by changing the PRI in the transmission PRI in which the range of the target signal and the Doppler frequency include folding in the distance direction and the frequency direction. Using the characteristic of the apparent range and Doppler frequency changing in the radar device, the optimum PRI is selected and tracking is performed so that the target signal and each clutter generation region are separated from each other.

  FIG. 11 shows a schematic diagram of a situation in which when the PRI is changed between PRI1 and PRI2, the target signal range and the Doppler frequency are equal, but the apparent detection position changes. The PRI selection algorithm in this radar system predicts the clutter generation area and target signal detection position from the attitude information of the platform on which the radar system is mounted, the beam pointing direction, and the previously observed target signal parameters. By controlling the pulse repetition period of the transmission wave transmitted from the radar device, the tracking processing of the target signal is maintained without being affected by the direct clutter, main lobe clutter, and side lobe clutter. It will be possible to continue.

  A radar apparatus according to the present invention includes a direct clutter evaluation process that selects a pulse repetition period of a transmission signal in which a detection area of a direct clutter and a detection position of a target signal are not close in the range direction, a main lobe / clutter generation area, The main lobe / clutter evaluation process that selects the pulse repetition period of the transmission signal where the target signal detection position is not close in the Doppler frequency direction, and the side lobe / clutter generation area and the target signal detection position are in the range direction and Doppler frequency. And a signal processing unit including a sidelobe / clutter evaluation process for selecting a pulse repetition period of transmission signals that are not close in direction.

  According to the radar apparatus according to the present invention, the target signal is estimated by predicting the clutter generation region and the detection position of the target signal, and controlling the pulse repetition period of the transmission wave transmitted from the radar apparatus so that the two do not compete with each other. Thus, stable tracking can be maintained and continued without being affected by the direct lower clutter, main lobe clutter, and side lobe clutter.

It is a figure which shows the structure of the radar apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the signal processor of the radar apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the side lobe clutter generation | occurrence | production location considered with the radar apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows each clutter distribution detected after signal processing of the radar apparatus which concerns on Embodiment 1 of this invention, and each evaluation process. It is a flowchart which shows operation | movement of the signal processor of the radar apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the side lobe clutter level evaluation process of the radar apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the signal processor of the radar apparatus concerning Embodiment 3 of this invention. It is a figure which shows the condition of the clutter which generate | occur | produces in an aircraft mounting radar apparatus. It is a figure which shows the generation | occurrence | production area | region of the clutter observed with a radar apparatus in the condition of FIG. It is a figure which shows the clutter disappearance remaining condition at the time of applying the clutter suppression filter to a frequency direction. It is a figure for demonstrating an apparent range doppler frequency.

  A preferred embodiment of a radar apparatus according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
A radar apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a diagram showing a configuration of a radar apparatus according to Embodiment 1 of the present invention. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  In FIG. 1, a radar apparatus 1 according to Embodiment 1 of the present invention includes a signal processor 3 that determines a pulse repetition period (PRI) from onboard platform information and target tracking information provided from an inertial navigation apparatus 2 on the onboard platform. And an excitation receiver 4 for generating a set PRI transmission signal and converting the received signal from an analog signal to a digital signal, and an antenna 5 for transmitting and receiving the signal.

  Next, the operation of the radar apparatus according to the first embodiment will be described with reference to the drawings.

  FIG. 2 is a flowchart showing the operation of the signal processor of the radar apparatus according to Embodiment 1 of the present invention.

  In the signal processor 3, the PRI selection processing unit 32 performs the PRI selection processing from the PRI database 31 that stores the PRI usable as the radar device 1, and the PRI determination unit 33 determines the optimal PRI, and receives the excitation. Set to vessel 4.

  First, in the direct clutter evaluation processing 321, the direct clutter uses characteristics that occur densely in a range corresponding to the altitude information of the radar-mounted platform, and (3) the target range of (1) altitude and target tracking information of the mounted platform information. Thus, as shown in FIG. 4B, it is determined for each PRI whether the direct clutter and the target signal are close to each other in the range direction. An evaluation formula is shown in Formula (1).

  If both are close, that is, if the distance in the range direction between the region where the direct clutter is generated and the target signal detection position is less than a predetermined threshold, the PRI is not selected and the PRI selection process is performed. Returning to the beginning, another PRI is extracted from the PRI database 31 and the same processing is performed. If the two are not close to each other, that is, if the distance in the range direction between the generation area of the direct clutter and the detection position of the target signal is equal to or larger than a predetermined threshold value, the process proceeds to the next main lobe / clutter evaluation process 323. .

  Next, in the main lobe / clutter evaluation processing 323, the main lobe / clutter is characterized by being densely generated at the Doppler frequency corresponding to the LOS (Line Of Sight) direction component of the speed of the radar-mounted platform. (2) From the (4) target speed and (5) target direction (radar beam pointing direction) of the speed and target tracking information, as shown in FIG. 4 (c), the main lobe clutter and the target signal are in the Doppler frequency direction. Is determined for each PRI. Formula (2) shows the evaluation formula.

  If both are close, that is, if the distance in the Doppler frequency direction between the main lobe / clutter generation region and the target signal detection position is less than a predetermined threshold, the PRI is not selected and the PRI is not selected. Returning to the beginning of the selection process, another PRI is extracted from the PRI database 31 and a direct clutter evaluation process 321 is performed. If the two are not close to each other, that is, if the distance in the Doppler frequency direction between the main lobe / clutter generation region and the target signal detection position is greater than or equal to a predetermined threshold, the next sidelobe / clutter evaluation processing 325 is performed. Migrate to

  Next, in the sidelobe / clutter evaluation processing 325, (1) altitude, (2) speed, target tracking information (3) target range, (4) target speed, (5) target direction of the installed platform information As shown in FIG. 4D, it is determined whether the sidelobe clutter and the target signal are close to each other in the range direction and the Doppler frequency direction. Regarding the sidelobe / clutter evaluation processing 325, as shown in FIG. 9, since the generation region of the sidelobe / clutter is wide, whether the region where the level of sidelobe / clutter is generated is close to the target signal. Judge whether or not. The region where the side lobe / clutter is strongly generated corresponds to the outer edge portion of the side lobe / clutter region shown in FIG. 3, and can be expressed by Expression (3). Formula (4) shows the evaluation formula.

  When the two are close to each other, that is, when the distance in the Doppler frequency direction between the region where the sidelobe / clutter generation level is high and the target signal detection position is less than a predetermined threshold, the PRI is not selected. Returning to the beginning of the PRI selection process, another PRI is extracted from the PRI database 31 and the direct clutter evaluation process 321 is performed. When the two are not close to each other, that is, when the distance in the Doppler frequency direction between the generation region where the sidelobe / clutter is strong and the detection position of the target signal is equal to or greater than a predetermined threshold, the next PRI determination unit 33 And the PRI is determined as the optimum PRI.

  FIG. 4A shows the clutter distribution after signal processing in the radar apparatus, and FIGS. 4B to 4D show the state of each evaluation process.

Embodiment 2. FIG.
A radar apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 5 is a flowchart showing the operation of the signal processor of the radar apparatus according to Embodiment 2 of the present invention. The configuration of the radar apparatus according to Embodiment 2 of the present invention is the same as that of Embodiment 1 described above.

  In the second embodiment, the side lobe / clutter level evaluation processing 324 is inserted in the preprocessing of the side lobe / clutter evaluation processing 325 in the first embodiment. This is because the side lobe / clutter strength is weakened as the range is farther from the direct clutter at the location where the side lobe / clutter is strongly generated as shown in FIG. Is a process in which a priority is added to.

  The side lobe / clutter level evaluation processing 324 is shown in FIG. As in the first embodiment, the PRI is extracted through the direct clutter evaluation process 321 and the main lobe / clutter evaluation process 323, and then the target signal range and the direct clutter range are set for each PRI. The priority is added in the order in which they are far away. In FIG. 6, the shades of the side lobes and clutters correspond to the strength (large and small) of the side lobe and clutter levels. Also, priority is added in inverse proportion to the level of the sidelobe / clutter level. In other words, the lower the sidelobe clutter level, the higher the priority. In the sidelobe / clutter evaluation processing 325, whether or not the Doppler frequency of the target signal and the Doppler frequency of the sidelobe / clutter are close to each other in the high-priority PRI order added in the sidelobe / clutter level evaluation processing 324. Judgment is made.

  In the first embodiment, a plurality of PRIs are finally extracted, but in this second embodiment, the PRI that can detect the target signal at a position farthest from the sidelobe clutter is uniquely determined. Is possible.

Embodiment 3 FIG.
A radar apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 7 is a flowchart showing the operation of the signal processor of the radar apparatus according to Embodiment 3 of the present invention. The configuration of the radar apparatus according to Embodiment 3 of the present invention is the same as that of Embodiment 1 above.

  In the third embodiment, the direct clutter evaluation processing 321, main lobe / clutter evaluation processing 323, and side lobe / clutter level evaluation processing 324 in the second embodiment are replaced with table processing for the purpose of reducing processing load. It is processing.

  In each of the above-described evaluation processes in the first embodiment and the second embodiment, the calculation of the evaluation is performed for all the PRIs stored in the PRI database 31, but there are many PRIs stored in the PRI database 31. In this case, the processing load becomes high.

  In order to reduce the processing load described above, a direct clutter evaluation table 327, a main lobe / clutter evaluation table 328, and a side lobe / clutter level evaluation table 329 in which evaluation results are recorded in advance for each PRI using an input parameter as an argument are prepared. Then, the PRI is extracted by referring to it.

  The direct clutter evaluation table 327 obtains the relationship between PRI, (1) altitude of mounted platform information, and (3) target range of target tracking information in advance based on the formula (1). It is tabulated as “0” and “1” when it is not close.

  The main lobe / clutter evaluation table 328 obtains in advance the relationship between PRI, (2) speed of the installed platform information, (4) target speed of the target tracking information, and (5) target direction based on the equation (2). For example, it is tabulated as “0” when close and “1” when not close.

  The side lobe / clutter level evaluation table 329 is obtained in advance based on the second embodiment based on the second embodiment based on the priorities of PRI, (1) altitude of platform information, and (3) target range of target tracking information. For example, the table is set as “0” when close to each other and “1” when not close to each other.

  In the sidelobe / clutter evaluation processing 325, since there are many input parameters and the method of referring to the table cannot be adopted, the same processing as in the second embodiment is performed.

  DESCRIPTION OF SYMBOLS 1 Radar apparatus, 2 inertial navigation apparatus, 3 signal processor, 4 excitation receiver, 5 antenna, 31 PRI database, 32 PRI selection process part, 33 PRI determination part, 321 direct clutter evaluation process, 323 main lobe clutter evaluation process 324 Side lobe / clutter level evaluation processing, 325 Side lobe / clutter evaluation processing, 327 Directly under clutter evaluation table, 328 Main lobe / clutter evaluation table, 329 Side lobe / clutter level evaluation table.

Claims (3)

A direct clutter evaluation process for selecting a pulse repetition period of a transmission signal in which the generation area of the direct clutter and the detection position of the target signal are not close in the range direction;
A main lobe / clutter evaluation process for selecting a pulse repetition period of a transmission signal in which the generation region of the main lobe / clutter and the detection position of the target signal are not close in the Doppler frequency direction;
A signal processor including a sidelobe / clutter evaluation process for selecting a pulse repetition period of a transmission signal in which a side lobe / clutter generation region and a target signal detection position are not close in the range direction and the Doppler frequency direction is provided. A radar device characterized by the above. The signal processor is
A sidelobe / clutter level evaluation process for adding priority in the order in which the range of the detection position of the target signal and the range of the generation area of the direct clutter are far from each other for each pulse repetition period;
The sidelobe / clutter evaluation process is:
The pulse repetition period of the transmission signal in which the side lobe / clutter generation area and the target signal detection position are not close to each other in the Doppler frequency direction in the order of the high-priority pulse repetition period added by the side lobe / clutter level evaluation process. The radar apparatus according to claim 1, wherein the radar apparatus is selected. Select the pulse repetition period of the transmission signal with reference to the direct clutter evaluation table that shows whether the generation area of the direct clutter and the detection position of the target signal are not close in the range direction,
A signal processor that selects the pulse repetition period of the transmission signal by referring to the main lobe / clutter evaluation table that determines whether the main lobe / clutter generation region and the target signal detection position are not close in the Doppler frequency direction With
The signal processor is
For each pulse repetition period, refer to the sidelobe / clutter level evaluation table in which the priority order is added in the order in which the range of the detection position of the target signal and the range of the generation area of the direct clutter are distant. It includes a sidelobe / clutter evaluation process that selects the pulse repetition period of the transmission signal in which the side lobe / clutter generation region and the target signal detection position are not close to each other in the Doppler frequency direction in the order of the repetition period. Radar device.

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