Question

Which of the following filter transformation is not possible?

(a) High pass analog filter to low pass digital filter

(b) High pass analog filter to high pass digital filter

(c) Low pass analog filter to low pass digital filter

(d) None of the mentioned

This question was addressed to me in unit test.

My question is taken from IIR Filter Design by Approximation of Derivatives in section Digital Filters Design of Digital Signal Processing

Answer 1

The correct answer is (b) High pass analog filter to high pass digital filter

The best I can explain: We know that only low pass and band pass filters with low resonant frequencies in the digital can be designed. So, it is not possible to transform a high pass analog filter into a corresponding high pass digital filter.