Question 52 on communication from GATE (Graduate Aptitude Test in Engineering) 2012 Electronics and Communication Engineering paper.
Q2. The power spectral density of a real process for positive frequencies is shown below. The values of and , respectively are
From the Weiner-Kinchin theorem, the auto-correlation function and power spectral density are Fourier Transform pairs, i.e.
Expressing in terms of , where
When the delay , the above equations simplifies to
Applying this to the problem at hand,
Further, since the power spectral density does not have any dc component, the mean of the signal
Based on the above, the right choice is (B)
 GATE Examination Question Papers [Previous Years] from Indian Institute of Technology, Madras http://gate.iitm.ac.in/gateqps/2012/ec.pdf