## Principles of Analog & Digital Comm. - May 2017

### MU Information Technology (Semester 3)

Total marks: --

Total time: --
INSTRUCTIONS

(1) Assume appropriate data and state your reasons

(2) Marks are given to the right of every question

(3) Draw neat diagrams wherever necessary

### Solve any four question from Q.1(a, b, c, d, e)

**1(a)**Compare analog and digital communication system. 5 marks

**1(b)** Define modulation. Explain and Justify any two need of modulation.
5 marks

**1(c)** Explain in brief Pre-emphasis and De-emphasis in FM.
5 marks

**1(d)** Explain in brief the process of quantization.
5 marks

**1(e)** What is line coding. Draw the NRZ and Manchester signal for the following binary signal 10111010.
5 marks

**2(a)** Explain the term thermal noise. Prove that the noise voltage Vn√4kTBRVn4kTBR V_{n}\sqrt{4kTBR} / For electronic device operating at a temperature of 17°C with a bandwidth of 10 KHz, determine

1. Thermaol noise power in dBm. 2. RMS noise volatage for a 100Ω internal resistance and a 100Ω load resistance.
5 marks

**2(b)** State and prove time scaling property of Fourier transd 01m. Determine the Fourier transform for a rectangular pulse of amplitude 'A' and time period 'T' is from-T/2 to T/2
5 marks

**3(a)** An AM signal appears across a 50Ω load and has the following equation [v(t)= 12(1+sin12.566×10^{3}t) sin 18.85×10^{6}t volts br> i) Sketch the envelope of this signal in time domain.

ii) Calculate modulation index, sideband frequencies, total power and bandwidth.
5 marks

**3(b)** What are the limitations of 'TRF' receiver. Explain how these limitations are avoided using super heterodyne receiver.
5 marks

**4(a)** With the help of neat circuit diagram explain the working of Ratio detector.
5 marks

**4(b)** What is multiplexing in communication system. Draw and explain in brief the transmitter and receiver of FDM.
5 marks

**5(a)** State and prove sampling theorem for how pass band limited signal. Explain aliasing error.
5 marks

**5(b)** What are the various pulse modulation techniques? Explain how PPM is obtained from PWM.
5 marks

**6(a)** Explain in brief the generation and detection of Delta modulation.
5 marks

**6(b)** Explain the generation and detection of ASK signal with block diagram and waveforms.
5 marks