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Autocorrelation function of an AWGN is independent of the time difference pa- rameter:
a. True
b. False
Assume perfect recovery of carrier component is possible for both SSB-SC and DSB-SC signals. Then the figure of merit of SSB-SC is equal to that of DSB-SC:
a. True
b. False
An AWGN contaminated signal is passed through a filter of bandwidth 500 MHz. If the noise power in the filtered output is 10 nW, then the value of two sided noise No spectral density (0) 2 is:
a. 10-15 WHz-1
b. 10-16 WHz-1
c. 10-17 WHz-1
d. None of these
In a receiver, the power of an input signal is 100 μW, while the power of the additive noise is 20 μW. This noise contaminated signal is passed through an amplifier with power amplification factor 100. However, the amplifier also adds noise to the amplified signal of power 500 μW. The signal power to noise power ratio of the final signal is:
a. 2
b. 4
c. 6
d. None of these
Consider a bandpass noise: n(t) = ni(t) cos(wet) - no(t) sin(wet) where ni(t), no(t) are independent baseband processes each with power P. Then the power of n(t) is given by:
a. 0
b. P/2
c. P
d. None of these
A certain telephone channel has He(w): 10-3 over the signal band. The mes- = sage signal PSD is Sm(w) = BII(w/2a), with a = 8000л. The channel noise PSD is Sn(w) = 10-8. If the output SNR at the receiver is required to be at least 30 dB, what is the value of ẞ corresponding to the required minimum transmitted power?
(Hint: If a signal X(t) with PSD Sx (w) is sent through a LTI channel with transfer function H (w), then the output PSD is given by Sx (w)|H(w)|2)
a. 10
b. 20
c. 30
d. None of these
In the question above, suppose the transfer function of the channel (He(w)) is changed to 10-3/(jw+a) and Sn(w) 10-10. To compensate for the channel distortion, the receiver filter transfer function is chosen to be
의미? jw + a. Hd(w)=
The receiver output SNR is required to be at least 35 dB (~ 3162). Determine the minimum required value of B.
a. 26.96 x 106
b. 25.88 x 106
c. 27.88 x 106
d. None of these
The figure of merit of AM is more than that of DSB-SC
a. True
b. False
An unmodulated carrier of Amplitude A, and frequency fe is added to band-limited white noise and passed through an ideal envelope detector (without DC blocker). Assume the noise spectral density to be of height No/2 and bandwidth 2W, centered about the carrier frequency fe. The output signal-to-noise ratio for the case when the carrier-to-noise ratio is high is:
242
a. NOW
b. A2 NOW
A2 2N.W C.
d. None of these
Consider a DSB-SC coherent demodulator whose local oscillator suffers from a phase error 0. If m(t) is a signal of bandwidth B with power P and channel noise PSD is No/2, the output SNR is:
P sin 0 2N B a.
b. P cos 0 2N B
P cos² 0 2N B C.
d. None of these