matlab awgn函数加入高斯白噪声

信噪比

信噪比，电子设备或者通信系统中有效信号和噪声的比值，英文名称叫做SNR或S/N（SIGNAL-NOISE RATIO)；

awgn描述

awgn函数可以将白色高斯噪声添加到信号中。

语法

y = awgn(x,snr) 
y = awgn(x,snr,sigpower) 
y = awgn(x,snr,'measured') 
y = awgn(x,snr,sigpower,state) 
y = awgn(x,snr,'measured',state) 
y = awgn(...,powertype) 

描述

• y = awgn(x,snr)将白高斯噪声添加到向量信号x中。标量snr指定了每一个采样点信号与噪声的比率，单位为dB。如果x是复数的，awgn将会添加复数噪声。这个语法假设x的能量是0dBW。
• y = awgn(x,snr,sigpower)和上面的语法相同，除了sigpower是x的能量，单位为dBW。
• y = awgn(x,snr,‘measured’)和y = awgn(x,snr)是相同的，除了agwn在添加噪声之前测量了x的能量。
• y = awgn(x,snr,sigpower,state)和y = awgn(x,snr,sigpower)是相同的，除了awgn首先重置了正态随机数产生器randn的状态为整数状态。
• y = awgn(x,snr,‘measured’,state)和y = awgn(x,snr,‘measured’)是相同的，除了awgn首先重置了正态随机数产生器randn的状态为整数状态。
• y = awgn(…,powertype)和前面的语法相同，除了字符串powertype指定了snr和sigpower的单位。powertype的选择有’db’ and ‘linear’，如果powertype是’db’，那么snr是按照dB为单位测量的，sigpower是按照dBW为单位测量的。如果powertype是线性的，snr是按照一个比率测量的，sigpower是以瓦特为单位测量的。Relationship Among SNR, Es/N0, and Eb/N0
  对于SNR和其他的噪声相对能量测量的关系，查看Describing the Noise Level of an AWGN Channel。

例子

%	Example 1: 
         % To specify the power of X to be 0 dBW and add noise to produce
         % an SNR of 10dB, use:
         X = sqrt(2)*sin(0:pi/8:6*pi);
         Y = awgn(X,10,0);
 
 %	Example 2: 
         % To specify the power of X to be 3 Watts and add noise to
         % produce a linear SNR of 4, use:
         X = sqrt(2)*sin(0:pi/8:6*pi);
         Y = awgn(X,4,3,'linear');
 
 %   Example 3: 
         % To cause awgn to measure the power of X and add noise to
         % produce a linear SNR of 4, use:
         X = sqrt(2)*sin(0:pi/8:6*pi);
         Y = awgn(X,4,'measured','linear');
 
 %   Example 4: 
         % To specify the power of X to be 0 dBW, add noise to produce
         % an SNR of 10dB, and utilize a local random stream, use:
         S = RandStream('mt19937ar','seed',5489);
         X = sqrt(2)*sin(0:pi/8:6*pi);
         Y = awgn(X,10,0,S);
 
%    Example 5: 
         % To specify the power of X to be 0 dBW, add noise to produce
         % an SNR of 10dB, and produce reproducible results, use:
         reset(RandStream.getGlobalStream)
         X = sqrt(2)*sin(0:pi/8:6*pi);
         Y = awgn(X,10,0,S);

matlab 程序 正弦+白噪声

f1=50;  	%  频率
fs=1000;  	%  采样频率
Ts=1/fs;  	%  采样间隔
N=200;    	%  采样点数
n=1:N;
y=sin(2*pi*f1*n*Ts);
snr=30;		%  信噪比
r=awgn(y,snr);
subplot(2,1,1);
plot(y,'black')
axis([-inf,inf,-2,2,])
title('原信号');
subplot(2,1,2);
%hold on
plot(r,'black')
axis([-inf,inf,-2,2,])
title('原信号+高斯噪声');

SNR=10

SNR=20

SNR=30

matlab 程序 锯齿波+噪声

t = 0:.1:20;
x = sawtooth(t); % Create sawtooth signal.
snr=10;

y = awgn(x,snr,'measured'); % Add white Gaussian noise.
subplot(1,3,1);
plot(t,x,t,y) % Plot both signals.
legend('Original signal','Signal with AWGN');
axis([-inf,inf,-1.5,1.5,])
title('SNR=10');

snr=20;
y = awgn(x,snr,'measured'); % Add white Gaussian noise.
subplot(1,3,2);
plot(t,x,t,y) % Plot both signals.
legend('Original signal','Signal with AWGN');
axis([-inf,inf,-1.5,1.5,])
title('SNR=20');

snr=30;
y = awgn(x,snr,'measured'); % Add white Gaussian noise.
subplot(1,3,3);
plot(t,x,t,y) % Plot both signals.
legend('Original signal','Signal with AWGN');
axis([-inf,inf,-1.5,1.5,])
title('SNR=30');

修改信噪比