addnoise.m

能在一些信号处理中用到的

function xn = addnoise(sig_out,SNR_dB)
% 加噪函数


    snr = 10^(SNR_dB/10);  
    sigma = sqrt(0.5/snr); 
    noise = sigma*randn(length(sig_out),1); %sigma 是信号的标准方差，噪声的长度自己设定
    xn=sig_out+noise;
    
% [a,b]=size(x);
% A = 1;
% SNR=10^(SNR/10);
% power=10*log10(A^2/(2*SNR));%calculate SNR in dB for WGN function
% noise=wgn(a,b,power);%calculate noise at specified SNR
% xn = x + noise; %add noise to I with FSK/PSK phase shift