title: Phase difference between two signals?
body: <p>I'm working on this embedded project where I have to resonate the transducer by calculating the phase difference between its Voltage and Current waveform and making it zero by changing its frequency. Where I(current) &amp; V(Voltage) are the same frequency signals at any instant but not the fixed frequency signals approx.(47Khz - 52kHz). All I have to do is to calculate phase difference between these two signals. Which method will be most effective.</p>
  
  <p>FFT of Two signals and then phase difference between the specific components
  Or cross-correlation of two signals?
  Or another if any ? Which method will give me most accurate result ? and with what resolution? Does sampling rate affects phase difference's resolution (minimum phase difference which can be sensed) ?
  I'm new to Digital signal processing, in case of any mistake, correct me.</p>
  
  <p>ADDITIONAL DETAILS:-</p>
  
  <ul>
  <li><p>Noise In my system can be white/Gaussian Noise(Not significant) &amp; Harmonics of Fundamental (Which might be significant one in resonant mismatch case).</p></li>
  <li><p>Yes 4046 can be a good alternative with switching regulators. I'm working with (NCO/DDS) where I can scale/ reshape sinusoidal on ongoing basis.</p></li>
  <li><p>Implementation of Analog filter will be very complex as I will require higher order filter with high roll-off rate for harmonic removal , so I'm choosing DSP based filter and its easy to work with MATLAB DSP Processors.</p></li>
  <li><p>What sampling rate would you suggest for a ~50 KHz (47Khz-52KHz) system for achieving result in FFT or Goertzel with phase resolution of preferably  =&lt;0.1 degrees or less and frequency steps will vary from as small as  ~1 to 2Hz . to 50 Hz-200Hz.</p></li>
  <li><p>My frequency is variable 45KHz - 55Khz ... But will be known to my system... Knowing phase error for the last fed frequency is more desirable. After FFT AND DIGITAL FILTERING , IFFT can be performed for more noise free samples which can be used for further processing. So i guess FFT do both the tasks ... </p></li>
  </ul>
  
  <p>But I'm wondering about the Phase difference accuracy cause thats the crucial part. </p>