# Phase distortion

**Phase distortion**:

Distortion that occurs when (a) the phase-frequency characteristic is not linear over the frequency range of interest,

*i.e.* , the

phase shift introduced by a

circuit or device is not directly proportional to frequency, or (b) the zero-frequency intercept of the phase-frequency characteristic is not 0 or an integral multiple of 2π radians.

*Synonym* **phase-frequency distortion.**
Source: from Federal Standard 1037C and from MIL-STD-188