The GATE Grind

GATE 2026 BM – Question 41

Signals and Systems · Digital Filters · 2 marks · Multiple choice

A moving-average filter obeys y[n]=(x[n]+2x[n−1]+x[n−2])/4. Which describes its transfer function?

  1. Two poles and two zeros
  2. Two poles and no zeros
  3. No poles and two zeros
  4. One pole and one zero

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (A) Two poles and two zeros

Explanation

Its z-transform is $H(z)=(1+2z^{-1}+z^{-2})/4=(z+1)^2/(4z^2)$. Thus it has a double zero at z=−1 and a double pole at z=0, counting multiplicity. Hence A; being FIR does not eliminate the origin poles when written as a rational function of z.

More Digital Filters questions

All Digital Filters questions →