# linear phase and generalised linear phase filters

I know that for linear phase filters, all frequency components have equal delay times. That is, there is no distortion of signal due to the time delay of frequencies relative to one another.

However, for filters generalised linear phase, where the phase is of the form $$a\omega+b$$, and $$b$$ is not zero. Will the same be true for them? Thanks in advance!

• @hotpaw2: OK, so is there phase distortion? – freak_warrior Feb 13 '14 at 1:32
• @hotpaw2, that doesn't sound right. The phase response $\phi=a\omega + b$ produces a delay of $d\phi / d\omega = a$, so a is nonzero for non-trivial causal filters. On the other hand, $b$ introduces a global phaseshift which requires a complex filter unless $b=n \pi$ for natural $n$. That is unless you allow a discontinuity of $b$ at $\omega=0$, which would not be obvious from what the OP stated. – Jazzmaniac Feb 13 '14 at 15:17
• @Jazzmaniac: Can you provide an answer for my question above? Thanks! – freak_warrior Feb 13 '14 at 15:41