# How Can I Add noise to a Frequency Domain Input Signal?

I am new with Matlab and doing some work on Amplifier and Bipolar Shappers Amplifiers. Adding Noise to a Time Domain Signal is quite easy and I have done it multiple time as:

T=10/wu;
N=100;
time=1:1:N;
time=T*time/N;
noisevec =0.55e-3*sqrt(0.707)*randn(size(time));
y22t=y2t+noisevec;


But Now I want to add a particular bandwidth Limited Noise to INPUT SIGNAL in S-DOMAIN which is :

x1s=(exp(-s*to1))*1/s-(exp(-s*to2))*(1/s);


Can somebody help me with it? It may a simple or dumb question, sorry for that, BUT i just dont know how to add noise to a signal in S domain I tried to take Laplace of "noisevec =0.55e-3*sqrt(0.707)*randn(size(time));" but that does not help.

• so, you say you want to add noise in frequency domain. So why don't you do just exactly that? It's not really clear what the question here is. – Marcus Müller Apr 17 at 15:27
• The simple is that I am supposed to add a noise to S-domain Signal and I am helpless. – Syed Adeel Ali Shah Apr 17 at 15:43
• I literally don't understand the problem. You know how to add things. – Marcus Müller Apr 17 at 15:48
• Yea I know how to add BUT GENERATING the noise. As we use RAND function in matlab to add a Noise vector but I cant that to a S domain Signal, right? So i want to generate a NOISE that can be added to S-Domain Input signal which is given as: x1s=(exp(-sto1))*1/s-(exp(-sto2))*(1/s); – Syed Adeel Ali Shah Apr 17 at 16:08
• so you say "but that does not help": How can that not help? That's literally what you'd need to do. – Marcus Müller Apr 17 at 16:12