Question

If the conversion technique is to be effective, then the LHP of s-plane should be mapped into _____________

(a) Outside of unit circle

(b) Unit circle

(c) Inside unit circle

(d) Does not matter

The question was asked during an online interview.

Question is taken from Design of IIR Filters from Analog Filters in chapter Digital Filters Design of Digital Signal Processing

Answer 1

The correct choice is (c) Inside unit circle

Explanation: If the conversion technique is to be effective, then the LHP of s-plane should be mapped into the inside of the unit circle in the z-plane. Thus a stable analog filter will be converted to a stable digital filter.