A method for eliminating left and right ambiguity of shipborne ground wave radar targets

Abstract

This invention discloses a method for eliminating left-right ambiguity in shipborne ground wave radar targets, relating to the field of target direction finding using shipborne ground wave radar. The basic steps are: acquiring frequency domain data, attitude data, and point detection results from the shipborne ground wave radar; determining the heading adjustment direction and angle of the shipborne platform based on the key area of ​​interest; identifying the same target associated with the target before and after the heading adjustment; distinguishing between forward and reverse targets based on the difference in azimuth angle of the same target and the difference in the platform's heading angle; and correcting the target point data in the forward and reverse target identification results. This invention fully considers the impact of shipborne platform maneuvering on target direction finding, and based on the characteristic that changes in platform heading affect target azimuth angle estimation, utilizes the relationship between the difference in heading angle and the difference in azimuth angle at different heading times of the shipborne platform to distinguish between forward and reverse targets, thus eliminating the left-right ambiguity of the target.

Description

Technical Field

[0001] This invention relates to the field of target direction finding using shipborne ground wave radar, and more particularly to a method for eliminating left and right ambiguity in shipborne ground wave radar targets. Background Technology

[0002] High-frequency ground-wave radar utilizes the characteristics of vertically polarized electromagnetic waves in the 3–30 MHz frequency band that diffract and propagate along the sea surface, enabling large-scale, over-the-horizon continuous tracking and detection of maritime targets. Compared to shore-based ground-wave radar, shipborne ground-wave radar can fully leverage the mobility and flexibility of its platform, freeing it from shore-based limitations and expanding its detection area, thus increasing its application range. Unlike shore-based ground-wave radar, which typically only receives sea surface echoes from one side of the antenna array, shipborne ground-wave radar, located on the open sea, allows its receiving antenna array to receive not only the desired right-hand side detection area (assuming the antenna array is mounted on the starboard side of the ship) but also the opposite side target signals from the port side. For shipborne ground-wave radar, targets in the desired right-hand side area are called "forward targets," while targets in the port side area are called "reverse targets." Because the steering vector of a left-side reverse target signal arriving at the receiving antenna is automatically identified by the radar as the steering vector of a signal from the desired detection area, the azimuth angle measured by the radar for this signal falls within the desired detection area. This causes confusion between forward and reverse targets, making it impossible to distinguish between them, resulting in left-right target ambiguity. This affects the target detection results and subsequent tracking performance. Therefore, to improve the target detection performance of shipborne ground wave radar, it is necessary to develop methods to eliminate left-right target ambiguity.

[0003] Currently, research on target detection using ground-wave radar rarely addresses the issue of eliminating left-right ambiguity. For example, shore-based radars, similar to shipborne radars, can receive target signals from both sides of the array, making it difficult for shore-based ground-wave radars alone to solve this problem. While there has been some research on shipborne ground-wave radar target detection in recent years, most focuses on target detection methods. Shipborne ground-wave radar target azimuth estimation typically treats targets as right-hand forward targets, without considering the issue of eliminating left-right ambiguity. Furthermore, no research on methods for analyzing and eliminating left-right ambiguity in shipborne ground-wave radar targets has been found. This invention, combining the characteristics of shipborne ground-wave radar and leveraging the advantage of the shipborne platform's ability to change its navigation state, proposes a method for eliminating left-right ambiguity in ship targets suitable for shipborne ground-wave radar, utilizing target detection results from different bow orientations, thereby improving target detection performance. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] The purpose of this invention is to provide a method for distinguishing between ship targets located on the left and right sides of a shipborne ground wave radar platform by using the target direction finding results before and after the bow change of the shipborne ground wave radar platform, so as to improve the target detection performance.

[0006] (II) Technical Solution

[0007] This invention includes the following steps:

[0008] (1) Set heading 1 as Get The shipborne ground wave radar frequency domain data, attitude data, and spot detection results at any given time.

[0009] Get Time-domain frequency data x1 r,d (f) (displayed in range-Doppler plot form), the point data Point1 includes target azimuth, radial distance, radial velocity, longitude, etc., and the k-th point is represented as Point1(k); the attitude data of the shipborne platform P includes heading... Platform Longitude lon1 p (t), Platform latitude lat1 p (t), heading1 P (t) and radar principal axis angle rs1(t) (relative to true north, clockwise is positive, rs1(t) = heading1 P (t)-π / 2); where t represents time, r represents the ground wave radar range dimension, and r∈[1,r] max ], r max Let d be the number of cells in the distance dimension, and d represent the Doppler dimension of the ground wave radar, where d∈[1,d]. max ], d max is the number of cells in the Doppler dimension, and f represents the amplitude.

[0010] (2) Based on the key areas of concern, determine the direction and angle of bow adjustment for the shipborne platform. The platform bow direction is adjusted from... Adjust at a constant speed to heading 2, i.e. Synchronize frequency domain data, attitude data, and spot detection results, and acquire frequency domain data during the heading adjustment process x3. r,d (f).

[0011] Bow adjustment includes determining the direction and angle of adjustment. The bow direction adjustment is based on... The relationship between the average angle (relative to true north) of the area within the time period and the radar principal axis angle rs1(t) at that moment is used to determine whether the heading adjustment direction is clockwise or counterclockwise.

[0012] Bow adjustment direction

[0013] And bow The adjustment angle β is mainly based on the target azimuth detection accuracy α of the shipborne ground wave radar, and can be set to β = 1.5α to ensure that the heading adjustment is greater than the target azimuth detection accuracy.

[0014] Get Frequency domain data at time x2 r,d (f) Point2, the data point; heading in the attitude data. Platform Longitude lon2 p (t), Platform latitude lat2 p (t), heading2 P (t) and radar main axis angle rs2(t).

[0015] (3) Determination of the same target based on the correlation between the target before and after the heading adjustment.

[0016] The relationship between the area in the distance-Doppler image during the heading adjustment process and the target point results before and after the heading adjustment is used to determine whether the target before and after the heading adjustment is the same.

[0017] The surface region detection results are derived from frequency domain data x3 r,d (f), where the velocity and distance distribution ranges of a certain surface region Q are [V1,V2] and [R1,R2], respectively. When Point1(i) satisfies:

[0018]

[0019] And Point2(j) also satisfies:

[0020]

[0021] This indicates that both points are located within the surface region Q, therefore they are the same target. Where Point1(i).V and Point1(i).R are respectively... The radial velocity and radial distance of target Point1(i) in the point data at time step, and Point2(j).V and Point2(j).R are respectively... The radial velocity and radial distance of target Point2(j) in the point data at time step, where i and j are the i-th and j-th targets, respectively;

[0022] (4) Distinguish between forward and reverse targets based on the difference in azimuth angle of the same target and the difference in bow angle of the platform.

[0023] Based on the association results of each same target obtained in (3), through and The difference in heading angle at time t. The relationship between Point (k) and the azimuth difference ΔPoint.a is used to distinguish whether a target point (k) in the area of ​​focus is a positive target. z Or the reverse target Point f .

[0024]

[0025] Where k is the k-th target, This is the difference in heading angle. ΔPoint.a is the target azimuth difference, ΔPoint.a = Point1(i).a - Point2(j).a, where Point1(i).a is... The azimuth angle of target Point1(i) at time t, and Point2(j).a is The azimuth angle of the target Point2(j) at any given time;

[0026] (5) Correction of target point data based on forward and reverse target recognition results.

[0027] renew Point data at time step, where the positive target Point z The information remains unchanged; the reverse target is Point. f The azimuth Point.α is updated to (π-Point.a), the longitude Point.lon is updated to Point'.lon, and the latitude Point.lat is updated to Point'.lat. The correction principle is as follows:

[0028]

[0029]

[0030] Among them, Point.a, Point.lon, Point.lat, and Point.R are The azimuth, longitude, latitude, and radial distance of the target at any given time. ARC is the Earth's radius, measured in km.

[0031] (III) Beneficial Effects

[0032] The advantages of this invention are as follows:

[0033] This invention provides a method for eliminating left-right ambiguity of targets using shipborne ground wave radar. This method utilizes real-time acquired radar spot data, frequency domain data, and attitude information. First, it associates targets based on different headings in the platform's attitude information. Then, it estimates the azimuth angles of successfully associated targets in different headings. Finally, based on the relationship between the heading angle difference of the shipborne platform in different headings and the target azimuth angle difference, it determines the forward and reverse targets, thus eliminating the left-right ambiguity of the targets. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the basic process of the present invention.

[0035] Figure 2 A schematic diagram illustrating the association of targets in different headings.

[0036] Figure 3 To distinguish between forward and reverse targets based on the difference in heading angle and azimuth angle. Detailed Implementation

[0037] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings:

[0038] Reference Figure 1 The specific implementation steps of the present invention are as follows:

[0039] (1) Set heading 1 as Get The shipborne ground wave radar frequency domain data, attitude data, and spot detection results at any given time.

[0040] Get Shipborne high-frequency ground wave radar target trace data Point1 and frequency domain channel data x1 at any given time r,d (f) (shown as a range-Doppler graph) and attitude data of the shipborne platform P, where This represents the frequency domain data at the current moment, where r represents the ground wave radar range dimension, r∈[1,r]. max ], r max Let d be the number of cells in the distance dimension, and d represent the Doppler dimension of the ground wave radar, where d∈[1,d]. max ], d max f is the number of cells in the Doppler dimension. i,j This represents the amplitude value of the i-th distance cell and the j-th Doppler cell, (.). H Indicates transpose;

[0041] Point data Point1 includes information such as target azimuth, radial distance, radial velocity, longitude, etc., and the k-th point is represented as Point1(k); the attitude data of platform P includes heading... Platform Longitude lon1 p (t), Platform latitude lat1 p (t), heading1 P (t) and radar principal axis angle rs1(t) (relative to true north, clockwise is positive, rs1(t) = heading1 P (t)-π / 2), where t represents time;

[0042] (2) Based on the key areas of concern, determine the direction and angle of bow adjustment for the shipborne platform. The platform bow direction is adjusted from... Adjust to a constant speed Synchronize frequency domain data, attitude data, and spot detection results, and acquire frequency domain data during the heading adjustment process x3. r,d (f).

[0043] Bow direction adjustment: based on the key focus area. Given the range of angles (relative to true north) in the radar coordinate system at a given time, calculate the average azimuth angle Ave of the Area in the radar coordinate system. Then, use the relationship between the average azimuth angle Ave and the radar principal axis angle rs1(t) at that time to determine the heading. The direction of the adjustment is such that the target TARS within the area of ​​focus after the heading adjustment is closer to the radar's main axis. Specifically, the area of ​​focus is... The angle range in the radar coordinate system at any given time is [A n A m ], the distance range is [R n ,R m ];

[0044]

[0045] Bow adjustment direction

[0046] Bow angle adjustment: Bow The adjustment angle β is mainly based on the detection accuracy α of the shipborne radar, and can be set to β = 1.5α. This ensures that the target tar within the key area of ​​interest is within the radar's detection range, while also ensuring that the bow direction... The angle of change β will not be too large. Bow The specific adjustment process is as follows: at the bow... The vehicle maintains a constant velocity in linear motion. After a period of time, the heading angle is slowly adjusted. Once the adjustment angle β reaches 1.5α, the heading adjustment is stopped, and the heading angle is then maintained at this point. Uniform linear motion;

[0047] Get Frequency domain data at time x2 r,d (f) Point data Poit2; heading data in attitude data Platform Longitude lon2 p (t), Platform latitude lat2 p (t), heading2 P (t) and radar main axis angle rs2(t).

[0048] (3) Determination of the same target based on the target association before and after heading adjustment.

[0049] The relationship between the area in the distance-Doppler image during the heading adjustment process and the target point results before and after the heading adjustment is used to determine whether the target before and after the heading adjustment is the same.

[0050] To determine The target Point1(i) in the target point trace Point1 at time point and Whether the target Ponint2(j) in the target point trace Point2 at any given time belongs to the same target is mainly determined by whether the two points are located in the distance-Doppler surface region Q during the heading adjustment process.

[0051] Will The target Ponint1(i) at time 1 and The target Ponint2(j) at time step and the surface target detection results are displayed in the same coordinate system, where the surface region detection results are derived from frequency domain data x3. r,d (f) The velocity and distance distribution ranges of a certain surface region Q are [V1,V2] and [R1,R2], respectively. When Point1(i) satisfies:

[0052]

[0053] And Point2(j) also satisfies:

[0054]

[0055] This indicates that both points are located within the surface region Q, therefore they are a single target. Where Point1(i).V and Point1(i).R are respectively... The radial velocity and radial distance of target Point1(i) in the point data at time step, and Point2(j).V and Point2(j).R are respectively... The radial velocity and radial distance of target Point2(j) in the point data at time step, where i and j are the i-th and j-th targets, respectively;

[0056] (4) Distinguish between forward and reverse targets based on the difference in azimuth angle of the same target and the difference in bow angle of the platform.

[0057] Based on the association results of each same target obtained in (3), through and The difference in heading angle at time t. The relationship between Point (k) and the azimuth difference ΔPoint.a is used to distinguish whether a target point (k) in the area of ​​focus is a positive target. z Or the reverse target Point f .

[0058]

[0059] Where k is the k-th target, This is the difference in heading angle. ΔPoint.a is the target azimuth difference, ΔPoint.a = Point1(i).a - Point2(j).a, where Point1(i).a is... The azimuth angle of target Point1(i) at time t, and Point2(j).a is The azimuth angle of target Point2(j) at time moment.

[0060] (5) Correction of target point data based on forward and reverse target recognition results.

[0061] renew Point data at time step, where the positive target Point z The information remains unchanged; reverse target Point f The azimuth point Point.a is updated to (π-Point.a), the longitude Point.lon is updated to Point'.lon, and the latitude Point.lat is updated to Point'.lat. The correction principle is as follows:

[0062]

[0063]

[0064] Among them, Point.a, Point.lon, Point.lat, and Point.R are respectively The azimuth, longitude, latitude, and radial distance of the target at any given time. ARC is the Earth's radius, measured in km.

[0065] Select different key areas of interest and repeat steps (2), (3), (4), and (5) until the entire detection area is covered. This completes the differentiation between forward and reverse targets by the shipborne ground wave radar, eliminates the left-right ambiguity of the targets, and corrects the information of reverse targets in the point data, thereby improving the accuracy of the point data.

[0066] The innovation of this invention is reflected in the following aspects:

[0067] This invention fully considers the impact of changes in the maneuvering of the shipborne platform on target orientation, and based on the characteristic that changes in the platform's heading will affect the estimation of the target's azimuth angle, it utilizes the relationship between the difference in heading angle and the difference in azimuth angle at different times of the shipborne platform's heading to distinguish between forward and reverse targets, thus eliminating the left-right ambiguity of the target.

Claims

1. A method for eliminating left-right ambiguity of a target using shipborne ground wave radar, comprising the following steps: (1) Set heading 1 as Get Shipborne ground wave radar frequency domain data, attitude data, and spot detection results at any given time: Get Time-domain frequency data x1 r,d (f) The frequency domain data at this moment is displayed in the form of a range-Doppler map. The point data Point1 includes information such as the target azimuth, radial distance, radial velocity, longitude, etc., and the k-th point is represented as Point1(k); the attitude data of the shipborne platform P includes heading... Platform Longitude lon1 p (t), Platform latitude lat1 p (t), heading1 P (t) and radar principal axis angle rs1(t), where, heading1 P rs1(t) and rs1(t) are positive relative to due north, clockwise is positive, and rs1(t) = heading1 P (t)-π / 2, where t represents time, r represents the ground wave radar range dimension, and r∈[1,r] max ], r max Let d be the number of cells in the distance dimension, and d represent the Doppler dimension of the ground wave radar, where d∈[1,d]. max ], d max The number of cells represents the Doppler dimension, and f represents the amplitude. (2) Based on the key areas of concern, determine the direction and angle of bow adjustment for the shipborne platform. The platform bow direction is adjusted from... Adjust at a constant speed to heading 2, i.e. Synchronize frequency domain data, attitude data, and spot detection results, and acquire frequency domain data during the heading adjustment process x3. r,d (f): Bow adjustment includes determining the direction and angle of adjustment. The bow direction adjustment is based on... During the time period, focus on the relationship between the average angle Ave of each point in the Area relative to true north and the radar principal axis angle rs1(t) at that moment to determine whether the heading adjustment direction is clockwise or counterclockwise. Bow adjustment direction And bow The adjustment angle β is mainly based on the target azimuth detection accuracy α of the shipborne ground wave radar. β is set to 1.5α to ensure that the heading adjustment is greater than the target azimuth detection accuracy. Get Frequency domain data at time x2 r,d (f) Point2, the data point; heading in the attitude data. Platform Longitude lon2 p (t), Platform latitude lta2 p (t), heading2 P (t) and radar principal axis angle rs2(t); (3) Determination of the same target based on the correlation between the target before and after heading adjustment: The relationship between the area in the distance-Doppler image during the heading adjustment process and the target point results before and after the heading adjustment is used to determine whether the target before and after the heading adjustment is the same. The surface region detection results are derived from frequency domain data x3 r,d (f), where the velocity and distance distribution ranges of a certain surface region Q are [V1,V2] and [R1,R2], respectively, when Point1(i) satisfies: And Point2(j) also satisfies: This indicates that both points are located within the surface region Q, therefore they are the same target, where Point1(i).V and Point1(i).R are respectively... The radial velocity and radial distance of target Point1(i) in the point data at time step, and Point2(j).V and Point2(j).R are respectively... The radial velocity and radial distance of target Point2(j) in the point data at time step, where i and j are the i-th and j-th targets, respectively; (4) Distinguishing between forward and reverse targets based on the difference in azimuth angle of the same target and the difference in bow angle of the platform: Based on the association results of each same target obtained in (3), through and The difference in heading angle at time t. The relationship between Point (k) and the azimuth difference ΔPoint.a is used to distinguish whether a target point (k) in the area of ​​focus is a positive target. z Or the reverse target Point f , Where k is the k-th target, This is the difference in heading angle. ΔPoint.a is the target azimuth difference, ΔPoint.a = Point1(i).a - Point2(j).a, where Point1(i).a is... The azimuth angle of target Point1(i) at time t, and Point2(j).a is The azimuth angle of the target Point2(j) at any given time; (5) Correction of target point data based on forward and reverse target recognition results: renew Point data at time step, where the positive target Point z The information remains unchanged; the reverse target is Point. f The azimuth point Point.a is updated to (π-Point.a), the longitude Point.lon is updated to Point′.lon, and the latitude Point.lat is updated to Point′.lat. The correction principle is as follows: Among them, Point.a, Point.lon, Point.lat, and Point.R are The target's azimuth, longitude, latitude, and radial distance at any given time. p (t), lat p (t) is The time platform's longitude and latitude; ARC is the Earth's radius, measured in km.

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