KR102146841B1 - Method of correcting azimuth angle for GMTI targets using difference channel in Monopulse radar - Google Patents

Abstract

A method for correcting an azimuth error of a GMTI target using a sum/difference channel in a monopulse radar according to the present invention comprises: a null point searching step of searching for a null point in a clutter spectrum to perform azimuth error correction; Comparing a maximum value and a null value for determining whether a difference between a peak value and a null value in each left/right region in the difference channel clutter spectrum is equal to or greater than a predetermined value; And a burst selection step of selecting a corresponding burst when the difference between the maximum value and the null value is greater than or equal to a threshold value (Thr_dB), there is an advantage that a separate hardware change is not required in the GMTI system, and implementation is simple in software.

Description

Method of correcting azimuth angle for GMTI targets using difference channel in Monopulse radar}

The present invention relates to a method for correcting an azimuth error of a GMTI target. More specifically, it relates to a method for correcting azimuth error of a GMTI target using a sum/difference channel in a monopulse radar.

A ground-moving target radar is a system that aims to detect a moving target on the ground, and the accuracy of the target's position corresponding to the result is important.

In order to reduce the orientation error of the antenna for image radar (SAR) and ground moving target radar mounted on an aircraft, a gimbal is installed as an antenna and a set. When installing an antenna/gimbal set on an aircraft, use an'EGI alignment fixture'. Align the coordinate system between the EGI and the antenna/gimbal set. EGI (Embedded GNSS/INS) is a sensor for aircraft attitude and navigation information, and because it receives information on the position, speed, and attitude of the aircraft and calculates the antenna orientation angle, it performs orientation control, so the alignment of the antenna/gimbal set and the EGI coordinate system is It is important.

Nevertheless, processing data acquired by image radar and ground moving target radar due to orientation accuracy of antenna/gimbal set itself, box misalignment error between EGI gyro sensor and housing, posture error during initial alignment of EGI, mechanical tolerance of EGI alignment fixture, etc. Azimuth errors may occur in the results.

In order to correct the azimuth error, there is a method of improving the orientation accuracy of the antenna/gimbal set or improving the performance of the EGI to increase its own accuracy, and a method of accurately estimating the generated error and electronically fine-steering the antenna. This method has a problem in that it may cause another error in the final result when the orientation error cannot be accurately measured due to unexpected influences such as mechanical deformation of an antenna and a radome.

Therefore, we propose a method of estimating and correcting the azimuth angle error from the received signal itself to correct the azimuth angle error that has occurred and obtain a meaningful result from the GMTI (Ground Moving Target Indicator).

Accordingly, an object of the present invention is to provide a method for correcting an azimuth error of a GMTI target using a sum/difference channel in a monopulse radar.

It is also an object of the present invention to provide a method of estimating and correcting an azimuth angle error from a received signal itself to correct the azimuth error generated and to provide a method for correcting an azimuth error of a GMTI target.

In the monopulse radar according to the present invention for solving the above problems, the azimuth error correction method of a GMTI target using a sum/difference channel is a null point search for a null point of a clutter spectrum to perform azimuth error correction. Point search step; Comparing a maximum value and a null value for determining whether a difference between a peak value and a null value in each left/right region in the difference channel clutter spectrum is equal to or greater than a predetermined value; And a burst selection step of selecting a corresponding burst when the difference between the maximum value and the null value is greater than or equal to a threshold value (Thr_dB), there is an advantage that a separate hardware change is not required in the GMTI system, and implementation is simple in software.

In an embodiment, prior to the null point search step, an absolute sum calculation step of calculating an absolute sum of spectral signals of the corresponding burst for the entire range of cells of the corresponding burst may be further included. .

In one embodiment, before the step of comparing the maximum value and the null value, a maximum value comparison step of comparing whether a difference between the maximum value Dmax1 and Dmax2, which is a peak value of each of the left and right regions, is a second threshold (Thr_Dmax) is further included. I can. At this time, if the difference between the Dmax1 and Dmax2 is less than the second threshold (Thr_Dmax), the burst is increased, and the null point search step, the maximum value and null value comparison step, and the burst selection step may be repeated for the increased burst. have.

In one embodiment, if the difference between Dmax1 and Dmax2 is less than the threshold value (Thr_Dmax) and the burst is a predetermined nth burst, the number of rescans is increased by 1, increasing from the initialized burst, and the null The point search step, the maximum value and null value comparison step, and the burst selection step may be repeated.

In an embodiment, if the number of rescans is N in advance and the burst is an nth burst, an azimuth offset calculation step of calculating an azimuth offset based on the selected burst may be performed.

In one embodiment, in the comparing of the maximum value and the null value, if the difference between the maximum value and the null value is less than or equal to the threshold (Thr_dB), increasing a burst and searching for the null point for the increased burst, the maximum value and The null value comparison step and the burst selection step may be repeated.

In one embodiment, in the step of comparing the maximum value and the null value, if the difference between the maximum value and the null value is greater than or equal to the threshold value (Thr_dB), the corresponding burst is selected, and the selection according to the difference between the maximum value and the null value The azimuth offset may be calculated in the azimuth offset calculation step by weighting averaged bursts.

According to at least one embodiment of the present invention, there is an advantage that a separate hardware change is not required in the GMTI system, and implementation is simple in software.

In addition, according to at least one embodiment of the present invention, as a method of using a received signal, even if a physical orientation error occurs in an antenna, the accuracy of a final result can be improved.

1 shows a flowchart for performing azimuth error correction according to the present invention.
2 shows a conceptual diagram of finding a null point of a clutter spectrum according to the present invention.
3 shows a difference channel clutter spectrum according to the present invention.
4 shows a conceptual diagram for finding the left/right maximum values in the clutter spectrum according to the present invention.
5 shows a conceptual diagram for comparing left/right maximum values in a clutter spectrum according to the present invention.
6 shows data of cases excluded by the algorithm of FIG. 1.
7 is an example of a clutter spectrum for calculating an azimuth offset amount.
8 is a result of before and after applying the azimuth offset correction algorithm proposed in the present invention.

The features and effects of the present invention described above will become more apparent through the following detailed description in connection with the accompanying drawings, and accordingly, those of ordinary skill in the technical field to which the present invention pertains can easily implement the technical idea of the present invention. I will be able to.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all changes, equivalents, or substitutes included in the spirit and scope of the present invention.

In describing each drawing, similar reference numerals are used for similar elements.

Terms such as first and second may be used to describe various elements, but the elements should not be limited by the terms. These terms are used only for the purpose of distinguishing one component from another component.

For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. The term and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Shouldn't.

The suffix modules, blocks, and parts for the components used in the following description are given or mixed in consideration of only the ease of writing the specification, and do not have meanings or roles that are distinguished from each other by themselves.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement them. In the following description of the embodiments of the present invention, when it is determined that a detailed description of a related known function or a known configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

Hereinafter, a method of correcting an azimuth error of a GMTI target using a sum/difference channel in a monopulse radar according to the present invention will be described.

The present invention intends to propose a method of estimating and correcting the azimuth error from the difference channel received signal itself for the purpose of correcting the azimuth error of the target from the result detected by GMTI.

The monopulse radar used in GMTI uses sum and difference patterns to determine the angle of the target. The sum channel forms the main beam around the boresight axis, which is the physical axis of the antenna, and the difference channel has the lowest gain in the boresight axis, and the highest point of the sum pattern and the lowest point of the difference pattern coincide in the antenna boresight axis. The Doppler Centroid of the received signal represents the Doppler frequency of the signal incident in the direction of the phase center of the antenna. At this point, the phase difference between channels becomes zero. Therefore, in the sum and difference clutter spectrum of the received signal, the clutter center frequency becomes 0 Hz. However, when the antenna/gimbal set or EGI is mounted, coordinate alignment is poor, or the center of the clutter spectrum is out of 0Hz due to its own accuracy limit. In this case, the azimuth error can be corrected by calculating the amount that the received difference channel signal deviates from 0 Hz.

However, if the data acquisition environment is complex, the azimuth error estimation may be incorrect. Accordingly, the present invention proposes a method of estimating an azimuth error under the best condition without using the received signal as it is, excluding a signal that interferes with the azimuth error estimation.

1 shows a flowchart for performing azimuth error correction according to the present invention. The algorithm shown in FIG. 1 proceeds in the following order.

① Finding the null point of the clutter spectrum

② Find the peak of each area in the clutter spectrum of the second channel

③ Comparison of the maximum value in ②

④ Compare the maximum and null values in ③

⑤ Calculate azimuth offset amount by averaging the selected burst

Meanwhile, each step illustrated in FIG. 1 will be described with reference to FIG. 1. The azimuth error correction method of a GMTI target according to the present invention includes an absolute sum calculation step (S110), a null point search step (S120), a maximum value comparison step (S125), a maximum value and a null value comparison step (S130), and a burst selection step (S140). ). In addition, the azimuth error correction method of the GMTI target further includes an azimuth offset calculation step (S150).

Meanwhile, in the absolute sum calculation step S110, an absolute sum of the spectral signals of the corresponding burst is calculated for the entire range of cells of the corresponding burst. In addition, in the null point search step S120, a null point search for a clutter spectrum is performed to perform azimuth error correction.

Meanwhile, in the maximum value comparison step S125, it is compared whether the difference between Dmax1 and Dmax2, which is the peak value of each left/right region, is a second threshold Thr_Dmax. At this time, if the difference between Dmax1 and Dmax2 is less than or equal to the second threshold Thr_Dmax, the burst is increased. Accordingly, the null point search step (S120), the maximum value and the null value comparison step (S130), and the burst selection step (S140) may be repeated for the increased burst.

On the other hand, if the difference between Dmax1 and Dmax2 is less than or equal to the threshold value (Thr_Dmax) and the burst is a predetermined nth burst, the number of rescans is increased by 1 and increased from the initialized burst, while searching for a null point (S120 ), comparing the maximum value and the null value (S130), and the burst selection step (S140) may be repeated.

Meanwhile, in the comparing of the maximum value and the null value (S130), it may be determined whether a difference between a peak value and a null value of each region of the left/right in the difference channel clutter spectrum is greater than or equal to a predetermined value. In addition, in the burst selection step S140, when the difference between the maximum value and the null value is greater than or equal to the threshold Thr_dB, a corresponding burst may be selected.

On the other hand, in the step of comparing the maximum value and the null value (S130), if the difference between the maximum value and the null value is less than or equal to the threshold value (Thr_dB), the burst is increased and a null point search step for the increased burst (S120), the maximum value and the null value are compared. Step (S130) and the burst selection step (S140) may be repeated.

Meanwhile, in the azimuth offset calculation step S150, the azimuth offset may be calculated based on the selected burst. In this regard, if the number of rescans is N in advance and the burst is an nth burst, an azimuth offset calculation step S150 of calculating an azimuth offset based on the selected burst may be performed. That is, since the operation for the burst has been completed, it is necessary to calculate the azimuth offset for other burst combinations.

Meanwhile, this may be performed by considering a weight according to signal quality for a burst selected in connection with the azimuth offset calculation. First, in the step of comparing the maximum value and the null value (S130), if the difference between the maximum value and the null value is greater than or equal to the threshold value Thr_dB, a corresponding burst is selected. Next, the azimuth offset may be calculated in the azimuth offset calculation step by weighted average of the bursts selected according to the difference between the maximum value and the null value. Therefore, when the difference between the maximum value and the null value is large, that is, when the signal quality is good, there is a high probability that the azimuth offset value estimated therefrom is similar to the actual offset value.

Meanwhile, in FIG. 2, a null point (Null_point) of the clutter spectrum is found. That is, FIG. 2 shows a conceptual diagram of finding a null point of a clutter spectrum according to the present invention.

In this regard, you need to specify a range to find nulls. The range can be set in consideration of the mechanical error or accuracy range. The range to find the null point is from -Thr_Guard to Thr_Guard.

3 shows a difference channel clutter spectrum according to the present invention. Specifically, it is to find the maximum value from the minimum range of the clutter spectrum to the Null_point and the maximum value from the Null_point to the maximum range in the difference channel. Based on the null_point, the maximum value up to the minimum area is defined as'Dmax1' and the maximum value up to the maximum area is defined as'Dmax2', and this value is found. The range for searching for the minimum and maximum points of the clutter spectrum can be calculated from the antenna beam pattern data.

4 shows a conceptual diagram for finding the left/right maximum values in the clutter spectrum according to the present invention. Specifically, FIG. 4 shows a step of comparing the maximum value in the left area and the maximum value in the right area based on the Null_point in the clutter spectrum, and using the corresponding data only when it is less than a certain value.

5 shows a conceptual diagram for comparing the left/right maximum values in the clutter spectrum according to the present invention. Specifically, FIG. 5 shows a step of comparing values of Dmax1 and Dmax2 and using the data only when the difference between the larger value and the Null_point value of the two is greater than or equal to a predetermined value.

When data satisfies the above conditions, calculate the amount of Null_point deviated from 0Hz with the data and use it for azimuth error correction.

6 corresponds to data of cases excluded by the algorithm of FIG. 1, and FIG. 7 is an example of a clutter spectrum for calculating an azimuth offset amount. 8 is a result of before and after applying the azimuth offset correction algorithm proposed in the present invention.

In the above, a method of correcting an azimuth error of a GMTI target using a sum/difference channel in a monopulse radar according to the present invention will be described.

According to at least one embodiment of the present invention, there is an advantage that a separate hardware change is not required in the GMTI system, and implementation is simple in software.

In addition, according to at least one embodiment of the present invention, as a method of using a received signal, even if a physical orientation error occurs in an antenna, the accuracy of a final result can be improved.

According to the software implementation, not only the procedures and functions described in the present specification, but also design and parameter optimization for each component may be implemented as a separate software module. The software code can be implemented as a software application written in an appropriate programming language. The software code may be stored in a memory and executed by a controller or a processor.

Claims (7)

In the azimuth error correction method of a GMTI target using a sum/difference channel in a monopulse radar,
A null point searching step of searching for a null point of a clutter spectrum to perform azimuth error correction;
Comparing a maximum value and a null value for determining whether a difference between a peak value and a null value in each left/right region in the difference channel clutter spectrum is equal to or greater than a predetermined value; And
A burst selection step of selecting a corresponding burst when the difference between the maximum value and the null value is greater than or equal to the threshold (Thr_dB),
Before the step of comparing the maximum and null values,
A maximum value comparison step of comparing whether a difference between Dmax1 and Dmax2, which is a peak value of each of the left and right regions, is a second threshold (Thr_Dmax),
If the difference between the Dmax1 and Dmax2 is less than or equal to a second threshold (Thr_Dmax), the burst is increased and the null point search step, the maximum value and null value comparison step, and the burst selection step are repeated for the increased burst,
If the difference between the Dmax1 and Dmax2 is less than or equal to a second threshold (Thr_Dmax) and the burst is a predetermined nth burst, the number of rescans is increased by 1 and increased from the initialized burst, while searching for the null point, Repeat the step of comparing the maximum and null values and the step of selecting the burst,
The azimuth offset calculation step of calculating the azimuth offset based on the selected burst is performed when the number of rescans is a predetermined N, and the burst is the nth burst, azimuth error correction of a GMTI target Way. The method of claim 1,
Before the null point search step,
Comprising an absolute sum calculation step of calculating an absolute sum of the spectral signals of the corresponding burst for the entire range of cells of the corresponding burst, GMTI target azimuth error correction method. delete delete delete The method of claim 1,
In the comparing the maximum value and the null value, if the difference between the maximum value and the null value is less than or equal to a threshold (Thr_dB), increasing a burst and searching for the null point for the increased burst, comparing the maximum and null values, and the A method for correcting an azimuth error of a GMTI target, characterized in that the burst selection step is repeated. The method of claim 1,
In the step of comparing the maximum value and the null value, if the difference between the maximum value and the null value is greater than or equal to a threshold value (Thr_dB), the corresponding burst is selected, and a weighted average of the selected burst according to the difference between the maximum value and the null value Comprising the azimuth offset in the azimuth offset calculation step, GMTI target azimuth error correction method.

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