Question

If M and N are the orders of numerator and denominator of rational system function respectively, then how many memory locations are required in direct form-II realization of that IIR filter?

(a) M+N+1

(b) M+N

(c) Min [M,N]

(d) Max [M,N]

This question was posed to me during a job interview.

My doubt stems from Structures for IIR Systems in division Discrete Time Systems Implementation of Digital Signal Processing

Answer 1

Right option is (d) Max [M,N]

For explanation I would say: From the direct form-II realization of the IIR filter, if M and N are the orders of numerator and denominator of rational system function respectively, then Max[M,N] memory locations are required.