# Deriving Phase response from Group Delay

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#### nightmaresc

##### Newbie level 3
Hi,
Assume I have a constant group delay of 1 second for all frequencies then I can determine the phase response to be: phase(f)=C - 2*pi* $\int$tau df where tau is the delay of 1 second. How do I determine the constant C which is the phase response at zero frequency?

#### SunnySkyguy

Your assumption is invalid at DC as there is no phase. There are limits for your given formula.

Realistically, C is negligble as f approaches DC and represents a unknown phase at any known frequency and group delay.

nightmaresc

### nightmaresc

Points: 2

#### nightmaresc

##### Newbie level 3
Thank you for the insight.

Is there any other way to determine phase response given group delay?

Another question I have is that for a filter that gives non linear phase response phase delay and group delay are generally different while for linear phase response group delay and phase delay are equal to each other. Which one is used to derive non linear phase response? Group delay or Phase delay?

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