267. The Fourier transform of a conjugate symmetric function is always

A. imaginary

B. conjugate anti-symmetric

C. real

D. conjugate symmetric

268. The gain margin for the system with open-loop transfer function G(s)H(z) =and modulating signal frequency are 1 MHz and 2 kHz respectively. An appropriate value for the time constant of the envelope detector is

A. 500 usec

B. 20 usec

C. 0.2 usec

D. 1 usec

269. An AM signal and a narrow-band FM signal with identical carriers, modulating signals and modulation indices of 0.1 are added together. The resultant signal can be closely approximated by

A. broadband FM

B. SSB with carrier

C. DSB-SC

D. SSB without carrier

270. Consider the sequence x[n]=[-4?j5 1 + j2 41 The conjugate anti-symmetric part of the sequence is

A. [-4 ? j2.5 j2 4 ? j2.S]

B. [?j2.5 1 j2.5]

C. ?j5 j2 01

D. [-4 1 4]

271. A causal system having the transfer function H(s) ? ? is excited with s+21 10u(t). The time at which the output reaches 99% of its steady state value is

A. 2.7 sec

B. 2.5 sec

C. 2.5 sec

D. 2.1 sec

272. An AM signal is detected using an envelope detector. The carrier frequency 2(1+z)

A. co

B.0

C.1

D. ? co

273. Three analog signals, having widths 1200 Hz, 600 Hz and 600 Hz, are sampled at their respective Nyquist rates, encoded with 12 bit words, and time division multiplexed. The bit rate for the multiplexed signal is

A. 115.2 kbps

B. 28.8 kbps

C. 57.6 kbps

D. 38.4 kbps

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