dc

code No: 56026 :2: Set No. 2
II Fill in the blanks
11. A Matched filter is used to __________________________
12. A signal extending over -4v to +4v is quantized into 8 levels. The maximum possible
quantization error obtainable is _____________V.
13. The advantage of DPCM over Delta Modulation is _________________________
14. The phases in a QPSK system can be expressed as ______________________
15. The Synchronization is defined as _______________________
16. The sampling rate in Delta Modulation is _______________than PCM.
17. The bit error Probability of BPSK system is __________________that of QPSK.
18. Non-coherent detection of FSK signal results in ____________________
19. _____________ is used as a Predictor in a DPCM transmitter.
20. The Nyquist's rate of sampling of an analog signal S(t) for alias free reconstruction is
5000samples/sec. For a signal x(t) = [S(t)]2 ,the corresponding sampling rate in
samples/sec is __________________
-oOo-
Code No: 56026 Set No. 3
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
III B.Tech. II Sem., I Mid-Term Examinations, February – 2012
DIGITAL COMMUNICATIONS
Objective Exam
Name: ______________________________ Hall Ticket No.
Answer All Questions. All Questions Carry Equal Marks.Time: 20 Min. Marks: 10.
I Choose the correct alternative:
1. Companding results in [ ]
A)More S/N ratio at higher amplitudes of the base band signal
B) More S/N ratio at lower amplitudes of the base band signal
C) Uniform S/N ratio throughout the base band signal
D) Better S/N ratio at lower frequencies
2. A uniform quantizer is having a step size of .05 volts. This quantizer suffers from a
maximum quantization error of [ ]
A) 0.1V B) 0.025 V C) 0.8 V D) 0.05 V
3. In Non-Coherent demodulation, the receiver [ ]
A) relies on carrier phase B) relies on the carrier amplitude
C) makes an error with less probability D) uses a carrier recovery circuit
4. The advantage of Manchester encoding is [ ]
A) less band width requirement B) less bit energy required for transmission
C) less probability of error D) less bit duration
5. Granular Noise in Delta Modulation system can be reduced by
A) using a square law device B) increasing the step size
C) decreasing the step size D) adjusting the rate of rise of the base band signal
6. The minimum band width required to multiplex 12 different message signals each of band
width 10KHz is [ ]
A) 60KHz B) 120KHz C) 180KHz D) 160KHz
7. In 8-PSK system, adjacent phasors differ by an angle given by ( in degrees) [ ]
A) n/4 B) n/8 C) n/6 D) n/2
8. Band Width efficiency of a Digital Modulation Method is [ ]
A) (Minimum Band width)/ (Transmission Bit Rate)