title: Adding phase noise in signal
body: <p>I want to implement phase noise in matlab. Can anyone tell me why i can not see spreadning of my spectrum in frequency domain. Please help me out.In code, first I have plotted simple signal in frequency domain and after i have defined two noise components, one is syncronous and second is accumulating noise components and added into the signal.</p>
  
  <pre><code>fs = 200;
  ts = 1/fs;
  t = 0:ts:10000-ts;
  fc = 50;
  S = cos(2*pi*fc*t);                    %%% equation 7.1 noisless
  L = length(S);
  nfft = L*100;
  res = fft(S,nfft)/nfft; % resize into nfft nr of element % normalize the amplitude
  f = fs/2*linspace(0,1,nfft/2+1);
  res = res(1:nfft/2+1);
  figure, plot(f,abs(res));
  
  sigma = 0.2;
  phi_sync =  sigma * randn(1,length(t));   %%%% random variable with gaussian distributed
  phi_acc = sigma * randn(1,length(t));   %%%% random variable with gaussian distributed
  % h = 0;
  
  for i=1:length(S)
      h = phi_sync + phi_acc(i);
  end
  
  S1 = cos(2*pi*fc*t + h);
  
  L = length(S1);
  nfft = L*100;
  res = fft(S1,nfft)/nfft; % resize into nfft nr of element % normalize the amplitude
  f = fs/2*linspace(0,1,nfft/2+1);
  res = res(1:nfft/2+1);
  figure, plot(f,abs(res))
  return
  </code></pre>