EC2252 Communication Theory – Most Important Questions 2014 Editions

Anna University

Department of ECE

4 Semester

EC2252 Communication Theory

(Regulation 2008)

Most Important Questions – 2014 Edition

UNIT-1 AMPLITUDE MODULATION

1. Explain the principles of operation of balanced modulator used for generating DSBSC

2. How SSB is generated? Explain

3. Explain in detail the methods of generating AM signal and derive the frequency spectrum of AM signal

4. Describe how AM generation is done using nonlinear circuits. Derive the output voltage expression for the circuit

5. Write short notes on VSB generation

6. Explain the working principles of linear modulators for generating AM.

7. Explain the principle of synchronous detection

8. Discuss the different distortions that occur in diode detectors

UNIT-2 ANGLE MODULATION

  1. Derive an expression for a single tone FM signal and draw its frequency spectrum With a help of neat circuit explain Armstron method of generating FM signal
  2. Explain the indirect method of generation of FM wave &any one method of demodulation of FM wave
  3. Explain in detail the tansmission bandwidth of FM signal with diagrams
  4. Explain how FM to PM and PM to FM is obtained
  5. Explain the operation of direct FM tewrasmitter
  6. Obtain the expession for narrow band and wide band FM
  7. Explain how amplitude limiting is obtained in an FM ratio detectors
  8. Explain the Wide Band Frequency Modulation
  9. Explain the detection of FM using Foster Seely Discriminator

UNIT-3 NOISE PERFORMANCE OF DSB- SSB RECEIVERS

  1. Explain the following terms 1) shot noise 2)noise temperature 3)noise figure
  2. Derive the quadrature and in phase components of a narrow band process Explain how various noise are generated and method of representing them
  3. Write short notes on noise temperature & noise figure
  4. Derive the effective noise temperature of cascaded amplifier.
  5. Explain the narrow band representation of noise in terms of envelope and phase components

UNIT-4 NOISE PERFORMANCE OF AM AND FM RECEIVERS

  1. Derive the noise power spectral density of the FM demodulator and explain its performance with diagram
  2. Explain the noise performance of AM system using envelope detection
  3. Compare the performance of noise in AM & FM
  4. Obtain the expresion for SNR in PM system
  5. Obtain the expresion for SNR in AM system using envelope detector in the receiver

UNIT -5 INFORMATION THEORY

  1. Derive the channel capacity of binary symmetric channel
  2. Write a notes on binary symmetric channel ,discrete channel capacity , continous channel capacity &channel capacity theorem
  3. Find the mutual information &channel capacity of the channel shown.
  4. Give the algorithm for Shanon -Fano coding
  5. Give the algorithm for Huffman coding
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