title: Frequency shift using FFT in Matlab
body: <p>I am working on implementing BFSK modulation and demodulation with frequency hopping and I need to test my results using Matlab. The output the I am getting from my BFSK program is an array of sine values corresponding to the carrier signal for different bits. These signals are passband signals centered at 2.51KHz with a band width of 4KHz around it. But to test the demodulation step, I need to convert the signal to baseband. So I need to center my output signal at 0Hz. </p>
  
  <p>I know that creating a complex signal of 2.51KHz and multiplying it in time-domain would do this job. But is there any method that I can use with <code>fft()</code> function in matlab to shift the center frequency of the signal and then take an <code>ifft()</code> of the signal to generate the baseband signal.</p>
  
  <p>Thanks,
  Anshu</p>