sigma=2;    %銳利分布參數sigma
t=1e-3;     %雜波時間長度
fs=1e6;     %采樣率
ts=1/fs;
t1=0.05e-3:1/fs:0.2e-3-1/fs;
n=length(t1);
rand('state',0);
u=rand(1,n);
rayleigh_noise=sqrt(2*log2(1./u))*sigma;     %產生瑞利雜波

N=t/ts;
s_pc_1=[zeros(1,100),1,zeros(1,N-101)];     %點目標回波
noise=rand(1,N);
rayleigh_clutter=[zeros(1,50),rayleigh_noise,zeros(1,N-200)];   %產生疊加了瑞利雜波，熱噪聲的點目標回波
s_pc=s_pc_1+0.1*rayleigh_clutter+0.1*noise;
figure,plot((0:ts:t-ts),s_pc),xlabel('t(單位：s)'),title('疊加了瑞利分布雜波，熱噪聲的目標回波');

cfar_result=zeros(1,N);
cfar_result(1,1)=s_pc(1,1);
for i=2:N
    cfar_result(i)=s_pc(1,i)/mean(s_pc(1,1:i));
end
figure,plot((0:ts:t-ts),cfar_result),xlabel('t(單位：s)'),title('采用慢門限恒虛警處理結果');

cfar_result=zeros(1,N);
cfar_result(1,1)=s_pc(1,1)/(sqrt(2)/pi*mean(s_pc(1,2:17)));
for i=2:16
    noise_mean=sqrt(2)/pi*(mean(s_pc(1,1:i-1))+mean(s_pc(1,i+1:i+16)))/2;
    cfar_result(1,i)=s_pc(1,i)/noise_mean;
end
for i=17:N-17
    noise_mean=sqrt(2)/pi*max(mean(s_pc(1,i-16:i-1)),mean(s_pc(1,i+1:i+16)));
    cfar_result(1,i)=s_pc(1,i)/noise_mean;
end
for i=N-16:N-1
    noise_mean=sqrt(2)/pi*(mean(s_pc(1,i-16:i-1))+mean(s_pc(1,i+1:N)))/2;
    cfar_result(1,i)=s_pc(1,i)/noise_mean;
end

cfar_result(1,N)=s_pc(1,N)/(sqrt(2)/pi*mean(s_pc(1,N-16:N-1)));
figure,plot((0:ts:t-ts),cfar_result),xlabel('t(單位：s)'),title('采用快門限恒虛警處理結果');