Question

For providing a Roll-off greater than 60dB/decade/pole, filters with which characteristics are useful?

(a) Butterworth

(b) Chebyshev

(c) Bessel

(d) Butterworth & Bessel

The question was asked in an international level competition.

This question is from Advanced Problems on Filters topic in division Filters and Attenuators of Network Theory

Answer 1

Correct option is (b) Chebyshev

To explain: Roll off is a term commonly refers to the steepness of the transmission function with respect to the frequency. For a Chebyshev filter, the Roll-off value greater than 60. This characteristic feature is useful when a rapid roll-off is required because it provides a Roll-off rate more than 60. On the other hand, both Butterworth and Bessel have the Roll-off rate less than or equal to 60 dB/decade/pole.