低干信比:
无噪声环境下脉冲压缩
射频噪声干扰性能研究
调幅噪声干扰脉冲压缩
噪声调频干扰脉冲压缩
三种干扰叠加脉冲压缩
高干信比:
射频噪声干扰
调幅噪声干扰
调频噪声干扰
三种干扰叠加干扰
MATLAB代码
clc;
clear all;
close all;
%%
%雷达参数
c = 3e8;
A = 1;
tp = 10e-6; %脉宽
B = 3e7;
fc = 0;
R_t = [10.5e3 11e3 12e3 (12e3)+50 13e3 (13e3)+20];
k = B/tp; %带宽和脉宽%%%线性调频信号的调频斜率
fs = 5*B; %抽样频率
PRF = 2000; %脉冲重复频率
Tmax = 15*tp; %雷达观察的距离时间范围
t = 0:1/fs:Tmax+tp; %离散的时间采样
lamda = c/fs;
N = ceil((Tmax+tp)*fs);
%%
%目标参数
N_target = 4; %目标个数
RCS_t = 5*rand(1,N_target)+5; %随机生成目标的RCS,最大为10,最小为5
%%
%回波模拟
[noise_nor,noise_nor_sum] = gsfb_tm(0,1,N,N_target);
noise_Am = noise_Am_tm(A,N,N_target);
noise_Fm = noise_Fm_tm(2*A,100,N,N_target);
temp = 0;
for n_t = 1:N_target
de = 2*R_t(n_t)/c; %目标延时
st = RCS_t(n_t)*rectpuls(t-de-tp/2,tp).*exp(-1i*pi*k*(t-de-tp/2).^2); %目标回波
temp = temp+st; %多个目标回波的叠加
end
y0 = temp;
y1 = temp+5*noise_nor_sum;
y2 = temp+5*noise_Am;
y3 = temp+5*noise_Fm;
y4 = temp+5*noise_nor_sum+5*noise_Am+5*noise_Fm;
%%
%无噪声信号脉冲压缩
replica = A*rectpuls(t-tp/2,tp).*exp(-1i*pi*(B/tp).*(t-tp/2).^2); %基带线性调频信号
nfft = length(t);
rfft0 = fft(replica,nfft);
yfft0 = fft(y0,nfft);
out0 = abs(ifft((conj(rfft0) .* (yfft0))));
pow = sum(out0.^2)/Tmax; %中频功率
% pow = sum(out0.^2)/(length(out0)*Tmax); %中频功率
%%
%有噪声信号的脉冲压缩
yfft1 = fft(y1,nfft);
out1 = abs(ifft((conj(rfft0) .* (yfft1))));
noise_lv1 = out1-out0;
yfft2 = fft(y2,nfft);
out2 = abs(ifft((conj(rfft0) .* (yfft2))));
noise_lv2 = out2-out0;
yfft3 = fft(y3,nfft);
out3 = abs(ifft((conj(rfft0) .* (yfft3))));
noise_lv3 = out3-out0;
yfft4 = fft(y4,nfft);
out4 = abs(ifft((conj(rfft0) .* (yfft4))));
noise_lv4 = out4-out0;
%%
%对发现概率的影响
Pfa = log(1e-6);
ut = zeros(1,4);
ut(1) = sqrt(-2*var(noise_lv1)*Pfa);%匹配滤波后的门限电压
ut(2) = sqrt(-2*var(noise_lv2)*Pfa);%匹配滤波后的门限电压
ut(3) = sqrt(-2*var(noise_lv3)*Pfa);%匹配滤波后的门限电压
ut(4) = sqrt(-2*var(noise_lv4)*Pfa);%匹配滤波后的门限电压
Y = zeros(1,4);
Y(1) = sum(abs(fft(out1,N)).^2)/N;
Y(2) = sum(abs(fft(out2,N)).^2)/N;
Y(3) = sum(abs(fft(out3,N)).^2)/N;
Y(4) = sum(abs(fft(out4,N)).^2)/N;
W = zeros(1,4);
W(1) = sum(abs(fft(noise_nor_sum)).^2)/N;
W(2) = sum(abs(fft(noise_Am)).^2)/N;
W(3) = sum(abs(fft(noise_Fm)).^2)/N;
W(4) = sum(abs(fft(noise_nor_sum+noise_Am+noise_Fm)).^2)/N;
a = zeros(1,4);
Pd = a;
for i = 1:4
a(i) = 1e4*pow/W(i);
x = normrnd(0,1,[1 1000]);
y = normrnd(a(i),1,[1 1000]);
Pdr = sqrt(x.^2+y.^2);
Pd(i) = sum(Pdr>ut(i))/N;
end
%%
%压制系数
Ka = zeros(1,4);
for i = 1:4
Ka(i) = W(i)/Y(i);
end
%%
%画图
figure,
subplot(2,1,1);plot(t*c/2,y0);title('脉冲压缩前无噪声的信号');
subplot(2,1,2);plot(c/2*t,out0);title('脉冲压缩后的信号');
%脉冲压缩后能看到4根谱线是因为R_t = [10.5e3 11e3 12e3 (12e3)+5 13e3 (13e3)+2],
% 其中目标3与目标4、目标5与目标6距离过近,脉冲压缩后仍无法分辨
figure,
subplot(2,1,1);plot(t*c/2,y1);title('脉冲压缩前叠加高斯噪声的信号');
subplot(2,1,2);plot(c/2*t,out1);line([0,c/2*Tmax],[ut(1),ut(1)],'color','r','linewidth',2);
title('叠加高斯噪声、脉冲压缩后的信号');
figure,
subplot(2,1,1);plot(t*c/2,y2);title('脉冲压缩前叠加调幅噪声的信号');
subplot(2,1,2);plot(c/2*t,out2);line([0,c/2*Tmax],[ut(2),ut(2)],'color','r','linewidth',2);
title('叠加调幅噪声、脉冲压缩后的信号');
figure,
subplot(2,1,1);plot(t*c/2,y3);title('脉冲压缩前叠加调频噪声的信号');
subplot(2,1,2);plot(c/2*t,out3);line([0,c/2*Tmax],[ut(3),ut(3)],'color','r','linewidth',2);
title('叠加调频噪声、脉冲压缩后的信号');
figure,
subplot(2,1,1);plot(t*c/2,y4);title('脉冲压缩前叠加高斯、调幅、调频噪声的信号');
subplot(2,1,2);plot(c/2*t,out4);line([0,c/2*Tmax],[ut(4),ut(4)],'color','r','linewidth',2);
title('叠加高斯、调幅、调频噪声,脉冲压缩后的信号');
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