Question

For providing a Roll-off greater than 20dB/decade/pole, filters with which characteristics are useful?

(a) Butterworth

(b) Chebyshev

(c) Bessel

(d) Butterworth & Bessel

This question was addressed to me in an interview for job.

My question comes from Ideal LPF, HPF, BPF and BSF Characteristics in section Signal Transmission Through Linear Systems of Signals and Systems

Answer 1

Correct answer is (b) Chebyshev

The best I can explain: Roll off is a term commonly refers to the steepness of the transmission function wrt to the frequency.

For a Chebyshev filter, the Roll-off value greater than 20. This characteristic feature is useful when a rapid roll-off is required because it provides a Roll-off rate is more than 20.

On the other hand, both Butterworth and Bessel have the Roll-off rate less than or equal to 20 dB/decade/pole.