Question

As the value of M _________ the bandwidth efficiency ________

(a) Increases, same.

(b) Increases, decreases

(c) Increases, increases

(d) Decreases, same

This question was posed to me during an interview for a job.

The origin of the question is Combined Linear and Constant Envelope Modulation Techniques in portion Modulation Techniques for Mobile Radio of Wireless/Mobile

Answer 1

Correct answer is (c) Increases, increases

To explain: The first null bandwidth of M-ary PSK signals decrease as M increases while Rb is held constant. Therefore, as the value of M increases, the bandwidth efficiency also increases.