A wide-beam pulsed radar sea multipath signal estimation method

Abstract

The application discloses a wide-beam pulse radar offshore multipath signal estimation method, which comprises the following steps: step 1, effective distance calculation; step 2, route design; step 3, signal receiving; step 4, antenna directional diagram factor correction; and step 5, multipath signal estimation. The method disclosed by the application is suitable for a coastal radar, and can improve the target detection precision of the radar.

Description

Technical Field

[0001] This invention belongs to the field of radar, and specifically relates to a method for estimating multipath signals at sea using a wide-beam pulse radar. Background Technology

[0002] Maritime radar typically operates at small skidding angles or low elevation angles. When detecting, tracking, and identifying small, slow-moving targets on the sea surface, it is often affected by multipath signals, especially for wide-beam radars. This is because when the radar beam is wide, both the target's direct wave and the signal reflected from the sea surface are located within the main lobe of the beam. Furthermore, the characteristics of operating at small skidding angles or low elevation angles mean that the sea surface can sometimes be considered a smooth mirror, making the energy of multipath signals reflected from the sea surface non-negligible. Therefore, to improve the detection capability of maritime radar, it is necessary to estimate multipath signals.

[0003] However, accurately estimating multipath signals against a sea surface background is no easy task. While theoretical models of multipath propagation can provide predictions, they still fall short of practical applications. There are three main problems: first, the constantly changing sea surface makes the multipath propagation paths unstable, affecting the stability of the reflected signals; second, wave motion causes ship movement, affecting the attitude of the multipath signal receiving antenna; and third, measurements taken from a ship at a fixed location are insufficient to estimate the amplitude of the multipath signal, and maintaining ship stability at sea is also difficult. Therefore, relying solely on theoretical models is insufficient for accurate multipath signal estimation, and new methods are needed. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for estimating multipath signals at sea using a wide-beam pulse radar, which can be used to solve the multipath problem faced by sea clutter observation radars installed on the top of islands when performing target detection.

[0005] The present invention adopts the following technical solution:

[0006] An improved method for estimating multipath signals at sea using a wide-beam pulse radar includes the following steps:

[0007] Step 1, Calculate the effective distance:

[0008] According to radar transmission power P t Radar antenna gain G t Radar wavelength λ, radar system loss L R Dynamic range of electromagnetic signal receiver [S] EMRmin ,S EMRmax Electromagnetic signal receiver antenna gain G EMR Cable loss L EMR Calculate the theoretical range [R] used to receive radar signals.Thmin ,R Thmax ]:

[0009]

[0010]

[0011] Step 2, Route Design:

[0012] Based on the radar pulse width τ, the speed of light c, and the radar altitude H R Under terrain constraints, the maximum observable elevation angle θ0 of the radar, the radar depression angle α0, and the radar antenna pattern factor G R The electromagnetic signal receiver can measure a distance R. Based on the distance range calculated in step 1, design the sea route AB in the direction of the radar beam azimuth center. The actual distance range [R] corresponding to the two ends of the route. ACmin ,R ACmax ]for:

[0013]

[0014]

[0015] Solving equation 4 using the least squares method yields the maximum measurable distance R of the electromagnetic signal receiver. max Thus, R is obtained. ACmax :

[0016] R ACmax =min{R Thmax ,R max} (5)

[0017] Step 3, Signal Reception:

[0018] Based on radar latitude and longitude (LatR, LonR), radar altitude H R Azimuth angle φ0, actual distance range [R] ACmin ,R ACmax The latitude and longitude of the endpoint AB of the route are calculated using the Vincenty forward equation. Then, the ship is guided by GPS to move at a constant speed along the designed route, and the power data P of the multipath signal as a function of time t is obtained. MP (t), and at the same time, the real-time attitude of the ship A(α,β,γ,t) is recorded by the attitude instrument, where α is the pitch angle, β is the roll angle, and γ is the yaw angle;

[0019] Step 4, Antenna pattern factor correction:

[0020] According to radar altitude H R Electromagnetic signal receiver antenna height H EMRGiven the ship's latitude and longitude (LatS(t), LonS(t)) and the radar's latitude and longitude (LatR, LonR), the angle between the ship and the radar antenna beam center is calculated using Vincenty's inverse kinematics formula, expressed as elevation and azimuth angles. Based on the attitude sensor data A(α,β,γ,t) and Equation 6 below, calculate the angle between the radar and the center of the electromagnetic signal receiver antenna beam, expressed as the elevation and azimuth angles. The multipath signal power P after antenna pattern factor correction is obtained. MPAC ;

[0021]

[0022]

[0023] in, This refers to the antenna pattern factor of an electromagnetic signal receiver. This refers to the radar antenna pattern factor.

[0024] Step 5, Multipath Signal Estimation:

[0025] According to radar altitude H R Electromagnetic signal receiver antenna height H EMR Given the ship's latitude and longitude (LatS(t), LonS(t)) and the radar's latitude and longitude (LatR, LonR), the distance R(t) from the electromagnetic signal receiver antenna to the radar is calculated using Vincenty's inverse kinematics formula. This distance is then combined with the Fresnel reflection coefficient Γ and the effective wave height h. s Given the radar wavelength λ, the multipath signal power P is theoretically estimated using Equation 8 below. MPTh (t), and establish the system of equations P based on the measured data. MPTh (t)=P MPAC (t), using the particle swarm optimization algorithm to optimize the parameters, the optimal prediction curve P of the multipath signal over time is estimated. opt (t);

[0026]

[0027] in, ψ is Γ e phase,

[0028]

[0029] in, Γ eC These are the optimized parameters.

[0030] The beneficial effects of this invention are:

[0031] The method disclosed in this invention is applicable to marine radars installed along the coast and can improve the target detection accuracy of the radar. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the method of the present invention;

[0033] Figure 2 It is a geometric diagram of the designed flight path;

[0034] Figure 3 It is the estimation result of the multipath signal. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] Example 1: This example discloses a method for estimating multipath signals at sea using a wide-beam pulse radar, such as... Figure 1 As shown, it includes the following steps:

[0037] Step 1, Calculate the effective distance:

[0038] According to radar transmission power P t Radar antenna gain G t Radar wavelength λ, radar system loss L R Dynamic range of electromagnetic signal receiver [S] EMRmin ,S EMRmax Electromagnetic signal receiver antenna gain G EMR Cable loss L EMR Calculate the theoretical range [R] used to receive radar signals. Thmin ,R Thmax ]:

[0039]

[0040]

[0041] Step 2, Route Design:

[0042] like Figure 2 As shown, based on the radar pulse width τ, the speed of light c, and the radar altitude H... R Under terrain constraints, the maximum observable elevation angle θ0 of the radar, the radar depression angle α0, and the radar antenna pattern factor G RThe electromagnetic signal receiver can measure a distance R. Combining this with the distance range calculated in step 1, the actual distance range applicable to multipath signal measurement is determined. A sea route AB is designed along the azimuth center direction of the radar beam. The actual distance ranges [R] corresponding to the two ends of the route are then determined. ACmin ,R ACmax ]for:

[0043]

[0044]

[0045] Solving equation 4 using the least squares method yields the maximum measurable distance R of the electromagnetic signal receiver. max Thus, R is obtained. ACmax :

[0046] R ACmax =min{R Thmax ,R max} (5)

[0047] Step 3, Signal Reception:

[0048] Based on radar latitude and longitude (LatR, LonR), radar altitude H R Azimuth angle φ0, actual distance range [R] ACmin ,R ACmax The latitude and longitude of the endpoint AB of the route are calculated using the Vincenty forward equation. GPS then guides the vessel to move at a constant speed along the designed route. The vessel is equipped with an electromagnetic signal receiving system to acquire the power data P of the radar multipath signal as a function of time t. MP (t), and at the same time, the real-time attitude of the ship A(α,β,γ,t) is recorded by the attitude instrument, where α is the pitch angle, β is the roll angle, and γ is the yaw angle;

[0049] Step 4, Antenna pattern factor correction:

[0050] According to radar altitude H R Electromagnetic signal receiver antenna height H EMR Given the ship's latitude and longitude (LatS(t), LonS(t)) and the radar's latitude and longitude (LatR, LonR), the angle between the ship and the radar antenna beam center is calculated using Vincenty's inverse kinematics formula, expressed as elevation and azimuth angles. Based on the attitude sensor data A(α,β,γ,t) and Equation 6 below, calculate the angle between the radar and the center of the electromagnetic signal receiver antenna beam, expressed as the elevation and azimuth angles. The multipath signal power P after antenna pattern factor correction is obtained. MPAC ;

[0051]

[0052]

[0053] in, This refers to the antenna pattern factor of an electromagnetic signal receiver. This refers to the radar antenna pattern factor.

[0054] Step 5, Multipath Signal Estimation:

[0055] According to radar altitude H R Electromagnetic signal receiver antenna height H EMR Given the ship's latitude and longitude (LatS(t), LonS(t)) and the radar's latitude and longitude (LatR, LonR), the distance R(t) from the electromagnetic signal receiver antenna to the radar is calculated using Vincenty's inverse kinematics formula. This distance is then combined with the Fresnel reflection coefficient Γ and the effective wave height h. s Given the radar wavelength λ, the multipath signal power P is theoretically estimated using Equation 8 below. MPTh (t), and establish the system of equations P based on the measured data. MPTh (t)=P MPAC (t), using the particle swarm optimization algorithm to optimize the parameters, the optimal prediction curve P of the multipath signal over time is estimated. opt (t);

[0056]

[0057] in, ψ is Γ e phase,

[0058]

[0059] in, Γ eC These are the optimized parameters.

[0060] The estimation results of the multipath signal are as follows: Figure 3 As shown.

Claims

1. A method for estimating multipath signals at sea using a wide-beam pulse radar, characterized in that, Includes the following steps: Step 1, Calculate the effective distance: According to radar transmission power P t Radar antenna gain G t Radar wavelength λ, radar system loss L R Dynamic range of electromagnetic signal receiver [S] EMRmin ,S EMRmax Electromagnetic signal receiver antenna gain G EMR Cable loss L EMR Calculate the theoretical range [R] used to receive radar signals. Thmin ,R Thmax ]: Step 2, Route Design: Based on the radar pulse width τ, the speed of light c, and the radar altitude H R Under terrain constraints, the maximum observable elevation angle θ0 of the radar, the radar depression angle α0, and the radar antenna pattern factor G R The electromagnetic signal receiver can measure a distance R. Based on the distance range calculated in step 1, design the sea route AB in the direction of the radar beam azimuth center. The actual distance range [R] corresponding to the two ends of the route. ACmin ,R ACmax ]for: Solving equation 4 using the least squares method yields the maximum measurable distance R of the electromagnetic signal receiver. max Thus, R is obtained. ACmax : R ACmax =min{R Thmax ,R max } (5) Step 3, Signal Reception: Based on radar latitude and longitude (LatR, LonR), radar altitude H R Azimuth angle φ0, actual distance range [R] ACmin ,R ACmax The latitude and longitude of the endpoint AB of the route are calculated using the Vincenty forward equation. Then, the ship is guided by GPS to move at a constant speed along the designed route, and the power data P of the multipath signal as a function of time t is obtained. MP (t), and at the same time, the real-time attitude of the ship A(α,β,γ,t) is recorded by the attitude instrument, where α is the pitch angle, β is the roll angle, and γ is the yaw angle; Step 4, Antenna pattern factor correction: According to radar altitude H R Electromagnetic signal receiver antenna height H EMR Given the ship's latitude and longitude (LatS(t), LonS(t)) and the radar's latitude and longitude (LatR, LonR), the angle between the ship and the radar antenna beam center is calculated using Vincenty's inverse kinematics formula, expressed as elevation and azimuth angles. Based on the attitude sensor data A(α,β,γ,t) and Equation 6 below, calculate the angle between the radar and the center of the electromagnetic signal receiver antenna beam, expressed as the elevation and azimuth angles. The multipath signal power P after antenna pattern factor correction is obtained. MPAC ; in, This refers to the antenna pattern factor of an electromagnetic signal receiver. This refers to the radar antenna pattern factor. Step 5, Multipath Signal Estimation: According to radar altitude H R Electromagnetic signal receiver antenna height H EMR Given the ship's latitude and longitude (LatS(t), LonS(t)) and the radar's latitude and longitude (LatR, LonR), the distance R(t) from the electromagnetic signal receiver antenna to the radar is calculated using Vincenty's inverse kinematics formula. This distance is then combined with the Fresnel reflection coefficient Γ and the effective wave height h. s Given the radar wavelength λ, the multipath signal power P is theoretically estimated using Equation 8 below. MPTh (t), and establish the system of equations P based on the measured data. MPTh (t)=P MPAC (t), using the particle swarm optimization algorithm to optimize the parameters, the optimal prediction curve P of the multipath signal over time is estimated. opt (t); in, ψ is Γ e phase, in, Γ eC These are the optimized parameters.

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