Digital Communication - Study Mode
[#96] A BPSK scheme operating over an AWGN channel with noise power spectral density of $$frac{{{N_0}}}{2},$$xa0 uses equiprobable signals $${s_1}left( t
ight) = sqrt {frac{{2E}}{T}} sin left( {{omega _c}t}
ight)$$ xa0 xa0 and $${s_2}left( t
ight) = sqrt {frac{{2E}}{T}} sin left( {{omega _c}t}
ight)$$ over the symbol internal (0, T). If the local oscillator in a coherent receiver is ahead in phase by 45° with respect to the received signal, the probability of error in the resulting system is
Correct Answer
(B) $$Qleft( {sqrt {frac{E}{{{N_0}}}} }
ight)$$
[#97] Consider a sample signal [yleft( t
ight) = 5 imes {10^{ - 6}}xleft( t
ight)sum
olimits_{ - infty }^{ + infty } {delta left( {t - n{T_s}}
ight)} ] where x(t) = 10cos(8π × 10 3 )t and T s =100 μsec. When y(t) is passed through an ideal lowpass filter with a cutoff frequency of 5 kHz, the output of the filter is
Correct Answer
(C) 5 × 10 -1 cos(8π × 10 3 )t
[#98] The Nyquist sampling frequency (in Hz) of a signal given by 6 × 10 4 sinC 3 (400t) ∗ 10 6 sinC 3 (100t) is
Correct Answer
(D) 1000
[#99] In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor
Correct Answer
(B) 12
[#100] Three analog signals, having bandwidths 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
Correct Answer
(C) 57.6 kpbs