title: Add harmonic to a signal
body: <p>How can I add a harmonic of the input signal ?</p>
  
  <ul>
  <li>without  making frequency estimations ( frequency is provided )</li>
  <li>by making frequency estimations </li>
  </ul>
  
  <p>input  : vectorized form of signal
  output : same format as input</p>
  
  <p>NOTE : If you know answer, can you give me algorithm or link which will help me to solve this problem.</p>