Digital Communication

1. Define companding.

2 What is meant by aliasing?

3. What is the need of prediction filtering? 4. How to overcome the slope overlap?

5. Define correlative level coding.

6. For the binary data 01101001 draw the unipolar and RZ signal.

7. Distinguish coherent vs non coherent digital modulation techniques.

8. Draw a block diagram of a coherent BFSK receiver.

9.

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Generate the cyclic code for (n, k) syndrome calculator.

10. Define channel coding theorem.

PART B-(5 16-80 marks)

11. (a) Illustrate and describe the types of quantizer? Describe the midtread and

midrise type characteristics of uniform quantizer with a suitable (16)

diagram.

Or

(b) Draw and explain the TDM with its applications.

12.

(a)

Describe delta modulation system in detail with a neat block diagram. Also, Illustrate the two forms of quantization error in delta modulation

(16)

Or

(b) Describe Adaptive Delta Modulation with neat sketch and compare with Delta Modulation of ADPCM

it (16)

13.

PMI

&

(a) Explain how Nyquist's Criterion eliminates interference in the absence of noise for distortion-less baseband binary transmission.

(16)

Or

Describe how eye pattern is helpful to obtain the performance system in detail with a neat sketch.

(b)

of the (16)

14 (8)

Describe the generation and detection of Coherent binary PSK Signals.

(10)

(6)

(1) Illustrate the power spectra of binary PSK signal.

Or

Describe the generation and detection of Coherent QPSK Signals.


(12)

(11) Illustrate the power spectra of QPSK signal

(4)

(b) (1)

15. (a) (

Describe the cyclic codes with the linear and cyclic property. Also

represent the cyclic property of a code word in polynomial notation.

List the different types of errors detected by CRC code.

(12) (4)

Or

(b) @ Describe how the errors are corrected using Hamming code with an

(12)

example (2) The code vector [1110010] is sent, the received vector is [1100010) 2 Calculate the syndrome.


 

What is aliasing?

What is companding Sketch the input-output characteristics of a compressor and an expander

What are the advantages of delta modulator!

What is a linear predictor? On what basis are the predictor coefficients determined ?

What are line codes? Name some popular line coles.

What is ISI and what are the causes of ISI?)

Distinguish between coherent and non-coherent reception

What is OPSK? Write the expression for the signal set of QPSK

What is a linear code

10.

What is meant by constraint length of a convolutional encoder

11. (a) (i) State the low pass sampling theorem and explain reconstruction of the signal from its samples (9)

The signal vit) 4 cos400 12 cos360 t is ideally sampled at a frequency of 300 samples per second. The sampled signal is passed through a unit gain low pass filter with a cut off frequency of 220 Hz. List the frequency components present arthe output of the low pass filter? (7) OR

(b) (1) Explain palse ende modulanton system with neat block diagramy. (i) What is TDM ? Explain the difference between analog TDM and digital TOM (10) (6)

12(a) (6) Draw the block diagram of ADPCM system and explain its function (10) fil A delta modulator with a fixed step size of 0.75 V. is given a sinusoidal message signal. If the sampling frequency is 30 times the Nyquist rate, determine the vasesimum perinisite hmplitude of the message signal if slope overload is to be avoided

OR

Draw the Block chagrain of an adaptive delta modulator with continuously variable step sized explain

Compare PCM system with delta modulation system

(19)

(4)

14. (a) Explain the generation and defection of a coherent binary PSK signal and derive the power spectral density of binary PSK signal and plot it

OR

(16)

(b) Explain the non-coherent detection of FSK signal and derive the expression for probability of enor