% GO-CFAR干扰目标背景下检测性能仿真-
clc;clear all;close all;
N=36;             %参考单元长度
n=N/2;            %半滑窗长度
M=1e4;             %蒙特卡洛仿真次数
SNR_dB=5:1:35;        %信噪比
SNR=10.^(SNR_dB./10);
Simul_len=length(SNR);  %仿真长度
T=0.8551;
Pd_GO1=0;
for i=1:length(SNR)
    count=0;
    for j=1:M
        %%%%%%%%%%%产生指数噪声%%%%%%%%%%%%%%%%%%%%%%%
        lambda=1;
        u=rand(1,N-1);
        exp_noise=log(u)*(-lambda);
        %%%%%%%%%%%%产生目标回波%%%%%%%%%%%%%%%%%%%
        lambda=SNR(i)+1;
        u=rand(1,2);
        exp_target=log(u(1))*(-lambda);
        exp_noise(N)=log(u(2))*(-lambda);
        cfar_k=exp_target/max(sum(exp_noise(1:N/2)),sum(exp_noise((N/2+1):N)));
        if (cfar_k>T)
            count=count+1;
        end
    end
    Pd_GO1(i)=count/M;
end
figure;
plot(SNR_dB,Pd_GO1,'b--','LineWidth',1.5);
hold on
Pd_GO2=0;
for i=1:length(SNR)
    count=0;
    for j=1:M
        %%%%%%%%%%%产生指数噪声%%%%%%%%%%%%%%%%%%%%%%%
        lambda=1;
        u=rand(1,N-2);
        exp_noise=log(u)*(-lambda);
        %%%%%%%%%%%%产生目标回波%%%%%%%%%%%%%%%%%%%
        lambda=SNR(i)+1;
        u=rand(1,3);
        exp_target=log(u(1))*(-lambda);
        exp_noise(N)=log(u(2))*(-lambda);
        exp_noise(N-1)=log(u(3))*(-lambda);
        cfar_k=exp_target/max(sum(exp_noise(1:N/2)),sum(exp_noise((N/2+1):N)));
        if (cfar_k>T)
            count=count+1;
        end
    end
    Pd_GO2(i)=count/M;
end
plot(SNR_dB,Pd_GO2,'r--*','LineWidth',1.5);
hold on
Pd_GO3=0;
for i=1:length(SNR)
    count=0;
    for j=1:M
        %%%%%%%%%%%产生指数噪声%%%%%%%%%%%%%%%%%%%%%%%
        lambda=1;
        u=rand(1,N-2);
        exp_noise=log(u)*(-lambda);
        %%%%%%%%%%%%产生目标回波%%%%%%%%%%%%%%%%%%%
        lambda=SNR(i)+1;
        u=rand(1,3);
        exp_target=log(u(1))*(-lambda);
        exp_noise(N)=log(u(2))*(-lambda);
        exp_noise(N-1)=log(u(3))*(-lambda);
        exp_noise=[exp_noise(1:n-1) exp_noise(N-1) exp_noise(n:N-1) exp_noise(N)];
        cfar_k=exp_target/max(sum(exp_noise(1:N/2)),sum(exp_noise((N/2+1):N)));
        if (cfar_k>T)
            count=count+1;
        end
    end
    Pd_GO3(i)=count/M;
end
plot(SNR_dB,Pd_GO3,'g-.','LineWidth',1.5);
xlabel('信噪比(dB)');ylabel('检测概率');
title('干扰目标情况下GO-CAFR检测概率N=36,Pf=1e-6');
legend('r=(0,1)','r=(0,2)','r=(1,1)');