Howtosignalprocessing
- Why IIR filters cannot have linear phase?
- Is it possible to construct a digital IIR filter with linear phase?
- What are the conditions to be satisfied for linear phase FIR filters?
- Can linear phase IIR filters be stable?
Why IIR filters cannot have linear phase?
For an IIR filter to satisfy the linear phase condition, both the poles and zeros would need to have mirror images outside the unit circle of the z-plane. However, poles outside the unit circle ⇒ unstable. Therefore, a causal, stable IIR cannot have linear phase.
Is it possible to construct a digital IIR filter with linear phase?
Based upon this statement, it would seem that it's not possible to design an IIR to have linear phase. However, a discussed below, phase equalisation filters can be used to linearise the passband phase response.
What are the conditions to be satisfied for linear phase FIR filters?
A FIR filter is linear-phase if (and only if) its coefficients are symmetrical around the center coefficient, that is, the first coefficient is the same as the last; the second is the same as the next-to-last, etc.
Can linear phase IIR filters be stable?
you're right, IIR filters can have linear phase but they can't be causal a the same time. So, consequently, linear phase IIR filters are not realizable.
