FIR to linear-phase FIR

1. What is linear phase in FIR?
2. What are the conditions for a FIR filter to have a linear phase?
3. Are all FIR filters linear phase?
4. What are the 4 types of FIR?

What is linear phase in FIR?

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.

What are the conditions for a FIR filter to have a linear phase?

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.

Are all FIR filters linear phase?

No! FIR filters are NOT always linear phase. The acronym 'FIR" only tells you that the impulse response is finite in duration, nothing more and nothing less. So called "minimum phase" FIR filters are not linear phase.

What are the 4 types of FIR?

Special types of FIR filters are namely, Boxcar, Hilbert Transformer, Differentiator, Lth-Band and Raised-Cosine.