# Digital Communication 1

Electronic Engineering MCQ Question Papers: ENTC, IT Interview Placement

Subject: Digital Communication 1

Part 1: List for questions and answers of Digital Communication

Q1. In uniform quantization process

a) The step size remains same

b) Step size varies according to the values of the input signal

c) The quantize has linear characteristics

d) Both a and c are correct

Q2. The process of converting the analog sample into discrete form is called

a) Modulation

b) Multiplexing

c) Quantization

d) Sampling

Q3. The characteristics of compressor in u -law commanding are

a) Continuous in nature

b) Logarithmic in nature

c) Linear in nature

d) Discrete in nature

Q4. The modulation techniques used to convert analog signal into digital signal are

a) Pulse code modulation

b) Delta modulation

d) All of the above

Q5. The sequence of operations in which PCM is done is

a) Sampling, quantizing, encoding

b) Quantizing, encoding, sampling

c) Quantizing, sampling, encoding

d) None of the above

Q6. In PCM, the parameter varied in accordance with the amplitude of the modulating signal is

a) Amplitude

b) Frequency

c) Phase

d) None of the above

Q7. One of the disadvantages of PCM is

a) It requires large bandwidth

b) Very high noise

c) Cannot be decoded easily

d) All of the above

Q8. The expression for bandwidth BW of a PCM system, where v is the number of bits per sample and fm is the modulating frequency, is given by

a) BW is greater than and equal to vfm

b) BW is less than and equal to vfm

c) BW is greater than and equal to 2 vfm

d) BW is greater than and equal to 1/2 vfm

Q9. The error probability of a PCM is

a) Calculated using noise and inter symbol interference

b) Gaussian noise + error component due to inter symbol interference

c) Calculated using power spectral density

d) All of the above

Q10. In Delta modulation,

a) One bit per sample is transmitted

b) All the coded bits used for sampling are transmitted

c) The step size is fixed

d) Both a and c are correct

Q11. In digital transmission, the modulation technique that requires minimum bandwidth is

a) Delta modulation

b) PCM

c) DPCM

d) PAM

Q12. In Delta Modulation, the bit rate is

a) N times the sampling frequency

b) N times the modulating frequency

c) N times the nyquist criteria

d) None of the above

Q13. In Differential Pulse Code Modulation techniques, the decoding is performed by

a) Accumulator

b) Sampler

c) PLL

d) Quantizer

Q14. DPCM is a technique

a) To convert analog signal into digital signal

b) Where difference between successive samples of the analog signals are encoded into n-bit data streams

c) Where digital codes are the quantized values of the predicted value

d) All of the above

Q15. DPCM suffers from

b) Quantization noise

c) Both a & b

d) None of the above

Q16. The noise that affects PCM

a) Transmission noise

b) Quantizing noise

c) Transit noise

d) Both a and b are correct

Q17. The factors that cause quantizing error in delta modulation are

b) Granular noise

c) White noise

d) Both a and b are correct

Q18. Granular noise occurs when

a) Step size is too small

b) Step size is too large

c) There is interference from the adjacent channel

d) Bandwidth is too large

Q19. The crest factor of a waveform is given as –

a) 2Peak value/ rms value

b) rms value / Peak value

c) Peak value/ rms value

d) Peak value/ 2rms value

Q20. The digital modulation technique in which the step size is varied according to the variation in the slope of the input is called

a) Delta modulation

b) PCM

d) PAM

Part 1: List for questions and answers of Digital Communication