Question

Which of the following condition should the unit sample response of a FIR filter satisfy to have a linear phase?

(a) h(M-1-n) n=0,1,2…M-1

(b) ±h(M-1-n) n=0,1,2…M-1

(c) -h(M-1-n) n=0,1,2…M-1

(d) None of the mentioned

I have been asked this question at a job interview.

My question is taken from Design of FIR Filters topic in portion Digital Filters Design of Digital Signal Processing

Answer 1

Correct option is (b) ±h(M-1-n) n=0,1,2…M-1

The best explanation: An FIR filter has an linear phase if its unit sample response satisfies the condition

h(n)= ±h(M-1-n) n=0,1,2…M-1.