Phase Response

Definition. The phase response $\Theta(\omega)$ of an LTI filter is defined as the phase (or angle) of the frequency response $H(e^{j\omega T})$:

$$\zbox {\Theta(\omega) \isdefs \angle H(e^{j\omega T})}$$

The phase response is often referred to as the ``phase'' of the filter. For real filters (filters with real coefficients), the filter phase can be defined unambiguously as the phase of its frequency response.

The real-valued phase response $\Theta(\omega)$ gives the phase shift in radians that each input component sinusoid will undergo.