# average linear phase (group delay)- how can be calculated, given a signal samples at frequency F?

Average linear phase (group delay)- how can be calculated, given a signal samples at frequency F? The definition doesn't help since the frequency is constant:

$$-[signalPhase(n)-signalPhase(n-1)]/[frequency(n)-frequency(n-1)]$$

at n's point of data

(matlab function 'grpdelay' gave a result but how can it be calculated approximately?)

• You way want to change the index of the signalPhase() from to $n$ o $n-1$ and put a minus sign in front of this, but other than that, this should work (provided signalPhase is properly unwrapped) – Hilmar Jan 28 '19 at 21:32
• yes, a typo here I edited but it's not the issue. – student Jan 29 '19 at 3:31
• Then you should be fine. What's your problem ? – Hilmar Jan 30 '19 at 13:17

## 1 Answer

The group velocity or group delay is the derivative of the phase with respect to the frequency. Hence, if the frequency is constant, then the phase is constant with respect to the frequency, and group delay is 0.