How to add Guassian Noise to non sinusoidal signal

Question

Jayant chouragade 2020-5-10

0
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https://ww2.mathworks.cn/matlabcentral/answers/524377-how-to-add-guassian-noise-to-non-sinusoidal-signal

回答： Ameer Hamza 2020-5-10

采纳的回答： Ameer Hamza

在 MATLAB Online 中打开

Hi,

Given a SNR value in dB I want to add noise to my below narrow pulsed signal .

Fs=200e6;

Fs=200e6;
t=t=0:1/Fs:255/Fs;
Fc=50e6;
tau1=400e-9;
tau2=80e-9;
Req_SNR=10; % in dB
Sn= sin(2*pi*Fc*t).*exp(-4*pi*(((t-tau1)/tau2).^2));

I am following below steps to add noise to signal.

Pow_Sn=sum(St.^2);  % compute signal power
rn=randn(1, size(t)); 
rn_power=sum(rn.^2);
Noise_amp=sqrt(Pow_Sn./((10^(Req_SNR/10)))); % 
Noise=rn.*Noise_amp; 
Sn_Noise=Sn+Noise;
SNR_measured=snr(Sn_Noise,Noise); % to test.

My questions are as followings:

Is Signal power computation correct.
Is noise generation method correct.
Why SNR_measured do not equal to Req_SNR.

Note: randn outout are not in range of -3.25 to 3.02

.

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Answer 1

Ameer Hamza 2020-5-10

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/524377-how-to-add-guassian-noise-to-non-sinusoidal-signal#answer_431574

在 MATLAB Online 中打开

You are confusing the energy and power of the signal. Calculate the value power of signal like this

Pow_Sn=sum(Sn.^2)/numel(Sn);

Try the following code

Fs=200e6;
t=0:1/Fs:255/Fs;
Fc=50e6;
tau1=400e-9;
tau2=80e-9;
Req_SNR=10; % in dB
Sn= sin(2*pi*Fc*t).*exp(-4*pi*(((t-tau1)/tau2).^2));
Pow_Sn=sum(Sn.^2)/numel(Sn);  % compute signal power
rn=randn(1, numel(t)); 
rn_power=sum(rn.^2);
Noise_amp=sqrt(Pow_Sn./((10^(Req_SNR/10)))); % 
Noise=rn.*Noise_amp; 
Sn_Noise=Sn+Noise;
SNR_measured=snr(Sn,Noise); % to test.