Digital Communications_quiz_bits_A S Rao - Quiz Quiz Bits 1...

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A. S. Rao A. S. Rao Page 1 of 11 Dept. of Electronics & Communication Engineering Balaji Institute of Balaji Institute of Technology & Science Technology & Science Technology & Science Quiz Quiz Quiz Quiz Bits Bits Bits 1 Subject: Digital Communication Branch: 3 rd B.Tech, ECE -------------------------------------------------------------------------------------------------------------------- 1. The system which does not require Synchronization is a ) Delta b) PCM c) PDM 2. One chief advantage of Continuous Variable Slope Delta Modulation over PCM is a) its high S/N ratio b) its high efficiency c ) it can handle voice, at about half the bit rate 3. In delta modulation, in order to keep S/N ratio nearly constant, the step size ‘ δ ’ is kept small but increases as the input signal a ) increases b) decreases c) remains unaffected 4. In continuous variable slope delta modulation, the squaring circuit makes a) the gain of the feedback amplifier to increase with signal amplitude b) power to vary linearly with input signal variations c ) both of these 5. One chief advantage of CVSD as compared to PCM is that it is not suitable for a) frequency sharing among multiple channels b ) time sharing among multiple channels c) none of these 6. As compared to message bandwidth, the PCM bandwidth is a) much smaller b) same c ) much larger 7. As compared to ideal communication system, the PCM system a) has less complex circuitry b ) compares most favorably with ideal system c) requires 8 dB less power 8. Near threshold, the pulse system which gives most superior performance is a) Delta modulation b) PDM c ) PCM 9. Regeneration capability are found in a) delta modulation b) PDM c ) PCM 10. In PCM, increasing the transmitted power beyond threshold value of (S/N) leads to a) improvement in (S/N) b ) no improvement in (S/N) c) both of these 11. In PCM, only decision at the receiver is required to be made is about the a) amplitude of the pulse b) width of the pulse c ) presence of the pulse 12. In PCM, the high noise immunity is achieved with a ) increased bandwidth b) decreased bandwidth c) none of these 13. A sample and hold circuit placed before A/D converter a ) reduces the aperture time b) increases the aperture time c) none of these 14. In PCM, quantization noise appears as a) thermal noise b) shot noise c ) white noise 15. Non uniform quantization is used for a ) weak signals b) strong signals c) all types of signals 16. For weak signals, the step size is reduced for a ) smaller sample amplitudes b) large sample amplitudes c) all sample amplitudes 17. One chief advantage of Continuous Variable Slope Delta Modulation over PCM is
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A. S. Rao A. S. Rao Page 2 of 11 Dept. of Electronics & Communication Engineering Balaji Institute of Balaji Institute of Technology & Science Technology & Science Technology & Science a) its high S/N ratio b ) its high efficiency c) it can handle voice, at about half the bit rate 18. In PCM system, if the bandwidth of a channel is increased, the S/N ratio would a) decreases b) remains unaffected c ) increases 19. To generate PCM, the signal is sampled and converted into a) PWM b) PPM c ) PAM 20. In PCM, for 128 standard quantizing levels, the maximum error will be a) 1/128 of the total amplitude range b
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