B.TECH - Semester 3 analog communication Question Paper 2020 (apr)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Give the mathematical expression for a Single Side Band (SSB) modulated signal.
- What is modulation index of an AM system? How the modulation has classified according to the modulation index value?
- Give the principle of Automatic Gain Control (AGC) of a radio receiver.
- What are factors which depends the selectivity of a radio receiver?
- What is white noise?
- Define the threshold effect in FM receivers.
- Generate a Phase Modulated (PM) signal from a Frequency Modulator (FM).
- A 2 KHz audio signal modulates a 50 MHz carrier causing a frequency deviation of 2.5 KHz . Determine the bandwidth of the FM signal.
- Give four types of pulse modulation methods.
- List the essential component of a standard telephone set. Answer any one question from each module. Each full question carries $\mathbf{2 0}$ Marks.
- (a) The antenna current of an AM transmitter is 6 A , if only the carrier is sent. But this value increase to 6.89 A , When the carrier is modulated with monotonic sinusoidal wave. Determine the percentage of modulation. Also find the antenna current...
- (b) Explain the generation of SSB signal with filter method. Give a neat block diagram.
- (a) Prove that the balanced modulator generates only sidebands at the output and also plot the spectrum.
- (b) A given AM broadcast station transmits a total power of 5 kW , when the carrier is modulated by a sinusoidal signal with a modulation index of 0.707 . Hence compute,
- (i) the carrier power (ii) the transmission efficiency (iii) the peak amplitude of the carrier assuming the antenna to be represented by a $(50+j 0) \Omega$ load.
- (a) Give different aspects for selecting the IF frequency for a super-heterodyne radio receiver.
- (b) What is double spotting? Give the reasons for the same.
- (c) Find the overall noise factor of a three stage cascaded amplifier, each stage having a power gain of 10 dB and noise figure of 6 dB .
- (a) A super-heterodyne receiver is tuned to receive a 1 MHz carrier amplitude by 1 KHz sine wave. It is also assumed that the IF frequency is 455 KHz . Find the frequency components at the input and output of the IF amplifier. Assume the IF bandwidth...
- (b) What is image frequency?
- (c) What is noise temperature? Derive the expression for the noise temperature ' $\mathrm{T}_{\mathrm{n}}$ ' interms of noise factor $F$.
- (a) Discuss about the noise effect in angle modulation. 10
- (b) Differentiate between FM and PM with the help of necessary equations.
- (c) Compare the advantages and disadvantages of AM and FM systems.
- (a) Derive the mathematical expression for the single tone FM modulated signal and hence differentiate the NBFM and WBFM.
- (b) Differentiate between pre-emphasis and de-emphasis for FM signals.
- (c) How the Automatic Frequency Controller (AFC) is functioning in FM receivers? Explain.
- (a) Give the block diagram of a PCM system and Explain the functions of each block.
- (b) Describe the functions of a automated telecommunication switching system.
- (a) Briefly discuss about different types of Pulse Time Modulation (PTM) systems.
- (b) How the cordless telephones systems functions? Explain.
- (c) What is a Local Subscriber Loop? Explain.