Question

Which of the following is defined as the range of frequencies over which the signal has a non zero power spectral density?

(a) Null to null bandwidth

(b) Half power bandwidth

(c) 3 dB bandwidth

(d) Absolute bandwidth

I had been asked this question in semester exam.

This intriguing question comes from Digital Modulation in portion Modulation Techniques for Mobile Radio of Wireless/Mobile

Answer 1

Right answer is (d) Absolute bandwidth

To explain I would say: The absolute bandwidth is defined as the range of frequencies over which the signal has a non-zero power spectral density. For symbols represented as rectangular baseband pulses, the PSD profile extends over an infinite range of frequencies, and has an absolute bandwidth of infinity.