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1、-Matlab高频雷达海洋回波谱的模拟仿真-第 6 页%-一、二阶海杂波谱仿真图-%-线性调频连续波发射信号仿真-%clc;clear all;close all;%-初始参数设置-%T = 0.25; % 脉冲宽度(即脉冲重复周期)TT =64; % 相干积累时间N = TT/T; % 相干积累时间内的脉冲数% Fs = B*2; % 采样频率saNum = 5; % 每个周期的采样点数Ts = T/saNum; % 采样间隔sig_ran = 60; % 目标所在的距离单元Fs = 10e2; %-发射信号仿真-%tt = Ts:Ts:T;t = 0:1/(Fs):TT;%-海杂波信号仿真
2、-%-第一种-% 一阶海杂波f0 = 18e6; % 雷达载频g = 9.8; % 重力加速度c = 3e8;lambda = c/f0; % 电磁波波长alfa = 8.1e-3;beita = 0.74;U = 25; % 待变参数，海面上处的风速kc = g/U2 ; %截止波束theta = 180; % 雷达波束方向到海浪波列前进方向的转角fi = 0; % 雷达波束方向的方位角% theta+fi %表示海浪波列前进方向的方位角fw= 90; %海面风向的方位角k0 = 2*pi/lambda;fd1 = 0.1012 * (f0/1e6)0.5; % 一阶Bragg峰的多普勒频率
3、,存在洋流时偏移fd2 = -fd1;S1 = 0.005*(-2*k0)-4*exp(-0.74*(kc/(2*k0)2);% 两个Bragg峰的幅度不同(随海面风向的方向角)S2 = 0.005*(-2*k0)-4*exp(-0.74*(kc/(2*k0)2);% 两个Bragg峰的幅度不同(随海面风向的方向角)G1_1 = 4/(3*pi)*(cos(180-fw)*pi/180/2)4;G2_1 = 4/(3*pi)*(cos(0-fw)*pi/180/2)4;Bragg1_1 = 26*k04*pi*S1*G1_1*exp(2*pi*1i*fd1.*t).*exp(-(t).2./(
4、22)*0.4)./(2*pi)0.5*0.4); % 正轴一阶Bragg峰Bragg1_2 = 26*k04*pi*S2*G2_1*exp(2*pi*1i*fd2.*t).*exp(-(t).2./(22)*0.4)./(2*pi)0.5*0.4); % 负轴一阶Bragg峰% Noise= 1.2358e-004*randn(1,length(t);%29也行freq = linspace(-Fs/2,Fs/2,length(t);B_1 = fftshift(abs(fft(Bragg1_1+Bragg1_2);% B_11 = B_1/max(B_1);% B_11 = 20*log1
5、0(B_11);% figure(1);% plot(freq,B_11); %一阶bragg峰% xlim(-2 2);% 二阶海杂波f4 = linspace(-1.1*fd1,-2*fd1,20);f3 = linspace(-0.9*fd1,-0.1*fd1,80);f1 = linspace(0.1*fd1,0.9*fd1,80);f2 = linspace(1.1*fd1,2*fd1,20);delta_k = k0/40;delta = 0.011 - i*(0.0121);for n = 1:79 k_n = n*delta_k; for i = 1:length(f1) %m
6、=-1,m=1% if k_n-2*k0 k_p k_n+2*k0 theta = linspace(0,180,181); k_p = (2*pi*f1(i)+(g*k_n)0.5)2/g;% theta_1 = acos(k_p2-k_n2-4*k02)/4*k_n*k0); theta_2 = asin(k_n*sin(k_n*sin(theta.*pi/180)./k_p)-pi; kafang1 = -i*0.5*(k_n+k_p-k_n*k_p*(2*pi*f1(i)2+(2*pi*fd1)2)/(k_n*k_p)0.5/(2*pi*f1(i)2-(2*pi*fd1)2); kaf
7、ang2 = 0.5*(k_n*k0*-cos(theta.*pi/180).*(k_p*k0*-cos(theta_2.*pi/180)./k03/delta); kafang = (abs(kafang1+kafang2).2*26*k04*pi*n*(delta_k2); S1 = 0.005*(-k_n).-4*exp(-0.74*(kc/(-k_n)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) S2 = 0.005*(k_p).-4*exp(-0.74*(kc/(k_p)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) G1 = 4/(3*pi)*(cos(t
8、heta-fw).*pi/180/2).4; G2 = 4/(3*pi)*(cos(theta_2-fw).*pi/180/2).4; X(i) = trapz(kafang.*G1.*G2.*S1.*S2,theta.*pi/180); theta = linspace(-180,0,181); k_p = (2*pi*f1(i)+(g*k_n)0.5)2/g;% theta_1 = acos(k_p2-k_n2-4*k02)/4*k_n*k0); theta_2 = asin(k_n*sin(k_n*sin(theta.*pi/180)./k_p)+pi; kafang1 = -i*0.5
9、*(k_n+k_p-k_n*k_p*(2*pi*f1(i)2+(2*pi*fd1)2)/(k_n*k_p)0.5/(2*pi*f1(i)2-(2*pi*fd1)2); kafang2 = 0.5*(k_n*k0*-cos(theta.*pi/180).*(k_p*k0*-cos(theta_2.*pi/180)./k03/delta); kafang = (abs(kafang1+kafang2).2*26*k04*pi*n*(delta_k2); S1 = 0.005*(-k_n).-4*exp(-0.74*(kc/(-k_n)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) S2
10、 = 0.005*(k_p).-4*exp(-0.74*(kc/(k_p)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) G1 = 4/(3*pi)*(cos(theta-fw).*pi/180/2).4; G2 = 4/(3*pi)*(cos(theta_2-fw).*pi/180/2).4; Y(i) = trapz(kafang.*G1.*G2.*S1.*S2,theta.*pi/180); %m=1,m=-1 theta = linspace(0,180,181); k_p = (2*pi*f1(i)-(g*k_n)0.5)2/g;% theta_1 = acos(k_p2
11、-k_n2-4*k02)/4*k_n*k0); theta_2 = asin(k_n*sin(k_n*sin(theta.*pi/180)./k_p)-pi; kafang1 = -i*0.5*(k_n+k_p-k_n*k_p*(2*pi*f1(i)2+(2*pi*fd1)2)/(k_n*k_p)0.5/(2*pi*f1(i)2-(2*pi*fd1)2); kafang2 = 0.5*(k_n*k0*-cos(theta.*pi/180).*(k_p*k0*-cos(theta_2.*pi/180)./k03/delta); kafang = (abs(kafang1+kafang2).2*2
12、6*k04*pi*n*(delta_k2); S1 = 0.005*(k_n).-4*exp(-0.74*(kc/(k_n)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) S2 = 0.005*(-k_p).-4*exp(-0.74*(kc/(-k_p)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) G1 = 4/(3*pi)*(cos(theta-fw).*pi/180/2).4; G2 = 4/(3*pi)*(cos(theta_2-fw).*pi/180/2).4; A(i) = trapz(kafang.*G1.*G2.*S1.*S2,theta.*pi/180
13、); theta = linspace(-180,0,181); k_p = (2*pi*f1(i)-(g*k_n)0.5)2/g;% theta_1 = acos(k_p2-k_n2-4*k02)/4*k_n*k0); theta_2 = asin(k_n*sin(k_n*sin(theta.*pi/180)./k_p)+pi; kafang1 = -i*0.5*(k_n+k_p-k_n*k_p*(2*pi*f1(i)2+(2*pi*fd1)2)/(k_n*k_p)0.5/(2*pi*f1(i)2-(2*pi*fd1)2); kafang2 = 0.5*(k_n*k0*-cos(theta.
14、*pi/180).*(k_p*k0*-cos(theta_2.*pi/180)./k03/delta); kafang = (abs(kafang1+kafang2).2*26*k04*pi*n*(delta_k2); S1 = 0.005*(k_n).-4*exp(-0.74*(kc/(k_n)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) S2 = 0.005*(-k_p).-4*exp(-0.74*(kc/(-k_p)2);% 两个Bragg峰的幅度不同(随海面风向的方向角) G1 = 4/(3*pi)*(cos(theta-fw).*pi/180/2).4; G2 = 4/
15、(3*pi)*(cos(theta_2-fw).*pi/180/2).4; B(i) = trapz(kafang.*G1.*G2.*S1.*S2,theta.*pi/180); Bragg(i,:) = (X(i)+Y(i)+A(i)+B(i)*exp(2*pi*1i*f1(i)*t); end Bragg1(n,:) = sum(Bragg,1);%endendBB2 = sum(Bragg1,1)./10;B_2 = fftshift(abs(fft(BB2);% BB2 = B_2/max(B_2);% BB2 = 20*log10(BB2);% figure(3)% plot(fre
16、q,B_2);% xlim(-2 2);for n = 1:79 k_n = n*delta_k; for i = 1:length(f3) %m=1,m=-1% if k_n-2*k0 k_p k_n+2*k0 theta = linspace(0,180,181); k_p = (2*pi*f1(i)-(g*k_n)0.5)2/g;% theta_1 = acos(k_p2-k_n2-4*k02)/4*k_n*k0); theta_2 = asin(k_n*sin(k_n*sin(theta.*pi/180)./k_p)-pi; kafang1 = -i*0.5*(k_n+k_p-k_n*
17、k_p*(2*pi*f1(i)2+(2*pi*fd1)2)/(k_n*k_p)0.5/(2*pi*f1(i)2-(2*pi*fd1)2); kafang2 = 0.5*(k_n*k0*-cos(theta.*pi/180).*(k_p*k0*-cos(theta_2.*pi/180)./k03/delta); kafang = (abs(kafang1+kafang2).2*26*k04*pi*n*(delta_k2); S1 = 0.005*(k_n).-4*exp(-0.74*(kc/(k_n)2);% ) S2 = 0.005*(-k_p).-4*exp(-0.74*(kc/(-k_p)2);%) G1 = 4/(3*pi)*(cos(theta-fw).*pi/180/2).4; G2 = 4/(3*pi)*(cos(theta_2-fw).*pi/180/2).4; X(i) = trapz(kafang.*G1.*G2.*S1.*S2,theta.*pi/180); BBB = B_1+B_2 +B_3 ;BBB = BBB/max(BBB);BBB = 20*log10(BBB);plot(freq,BBB);xlabel(多普勒频率（Hz）);ylabel(归一化回波功率（dB）);xlim(-2 2);ylim(-80 0)