Digital Communications Laboratory Viva Questions - Part 3

Theory_Questions:

1. The bandwidth of TV video plus audio signal is 4.5MHz. If the signal is converted to PCM bit stream with 1024 quantization levels, the number of bits/sec generated by the PCM system will be________. (Assume the signal is sampled at the rate of 20% above the nyquist rate).

1. 108*10⁶ bits/sec
2. 72*10⁶ bits/sec
3. 54*10⁶ bits/sec
4. 90*10⁶ bits/sec
   
   
    
   

2. A 7 bit PCM system employing uniform quantization noise has an overall signaling rate of 56 kbps. Calculate signal to quantization noise ratio that would result when its input is sine wave with peak to peak amplitude equal to 5v.

1. 31.8 dB
2. 38.8 dB
3. 43.8 dB
4. 48.8 dB

3. If ∆ is the step size of a stair case approximation of a signal than what is tha maximum approximation of a signal?

A)

B)

C) ∆

D)

4. If number of quantization levels increases what will be the signal to noise ratio?

A) Remains constant

B) Increases

C) Decreases

D) None of these

5. In non uniform quantization what will be the relation between amplitude of a signal and step size?

A) Variation in ∆ is high at minimum amplitude of a signal and low at maximum amplitude of a signal

B) Variation in ∆ is high at maximum amplitude of a signal and low at minimum amplitude of a signal

C) No variation will occur in ∆ But sudden variation will occur at maximum amplitudes of a signal

D) There is no relation between amplitude of a signal and step size

6. In a n bit PCM using midriser quantizer, the number of levels will be_______

A) 2n

B) 2ⁿ

C) 2ⁿ-1

D) 2^n-1

7. What is the result of taking more samples during the quantization process?

A) More errors in the analog-to-digital conversion B) More bit requirements C) More accurate signal representation D) More bit requirements and more accurate signal representation

8. If sampling frequency doubles then

A) Quantization noise decreases
B) Quantization density decreases
C) Quantization noise increases
D) Quantization density increases

9. If the number of bits per sample in a Pulse Coded Modulation (PCM) system is increased from 5 bits to 6 bits,the improvement in signal to quantization noise ratio will be

A) 3 dB

B) 6 dB

C) 2pi dB

D) 0 dB

10. A television signal with bandwidth of 4.2 MHz is transmitted using binary PCM. The number of quantization levels is 512. Calculate code word length

A) 3 bits

B) 6 bits

C) 9 bits

D) 12 bits

Answers

1. A
2. C
3. D
4. B
5. B
6. C
7. D
8. C
9. B
10. C