Arbitrary phase FIR filter design

1. What is the phase of FIR filter?
2. What is arbitrary frequency response?
3. Do FIR filters have phase shift?

What is the phase of FIR filter?

FIR filters are usually designed to be linear-phase (but they don't have to be.) 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.

What is arbitrary frequency response?

The term "arbitrary" in this context refers to the desired frequency response, and what it means is that the respective design method accepts any desired response.

Do FIR filters have phase shift?

The FIR filters have a phase response that traces out a straight line. Both of these FIR filters exhibit linear phase [1][2]. This means that those sinusoidal components are given a constant phase shift and that the phase shift is constant relative to each frequency.