Question

What is the maximum value of fp with which good designs are obtained for M odd?

(a) 0.25

(b) 0.45

(c) 0.5

(d) 0.75

The question was asked in an interview.

This is a very interesting question from Design of FIR Differentiators in section Digital Filters Design of Digital Signal Processing

Answer 1

The correct answer is (b) 0.45

For explanation I would say: Designs based on M odd are particularly poor if the bandwidth exceeds 0.45. The problem is basically the zero in the frequency response at ω=π(f=1/2). When fp < 0.45, good designs are obtained for M odd.