Question Bank Electronics Communication

Week 1:1 Explain need of modulation2 Draw and explain block diagram of communication system

3 Define amplitude Modulation

4 Define Modulation index and percent modulation for an AM wave.

5 Advantages and disadvantages of analog and digital communication system

Week 2: 1 Explain series tuned circuit

2 Explain parallel tuned circuit

3 A coil has a series resistance of 5, a self capacitance of 7 pF, and an inductance of 1H.

Determine the effective inductance and effective Q-factor when coil forms part of series tuned

circuits resonant at 25MHz.

4 derive equation for Resonance frequency and Q-factor for the parallel tuned circuits.

5 Explain channel effect in detail with their resources. Also explain nyquist information rate and

channel capacity in detail

Week 31 The carrier amplitude after amplitude modulation varies between 4V and 1V. Calculate depth

of modulation.

2 A carrier current is 8A but it is increase to 8.93A when it is modulated Find,

(A) percentage modulation Index

(B) Antenna current when modulation index changes To 0.8

3 Explain Amplitude Modulation with required waveforms. Also give mathematical

representation of Amplitude modulated Wave.

4 Explain Frequency Modulation with required waveforms. Also give mathematical

representation of frequency modulated Wave.

5 State Carson rule.

Week 4

1 Define Single sideband suppressed carrier AM.

2 Explain DSB FC system

3 What are the disadvantages of conventional (or) double side band full carrier

system?

4 Define frequency deviation and deviation ration

5 Explain A FM voltage is represented by v=12sin(6 x 108 t + 5cos 1250t) Find Carrier

Frequency, Modulating Frequency, Modulation Index, Maximum Deviation, Power dissipation

across 10.Week 5 1 What are the complexity remains in SSB ? List the methods of generation of SSB signal and

explain any two of them.2 Explain High level and low level modulation

3 Draw the circuit diagram of Foster seely discriminator and explain its working.

4 Explain in detail about AM detector.

5 List all the basic FM demodulators, Draw and explain ratio discriminator in detail.Week 6

1 Explain Armstrong method of FM generation with neat diagram2 Derive the expression for AM wave. AM modulating signal 8sin (2 x 900t) is used to

modulate a carrier signal 18 sin (2 x 15000t). Find modulation index, percentage modulation,

frequencies of sideband components and their amplitude. Draw the spectrum of AM wave.

3 Draw and discuss schematic diagram for FDM system to combine 4 voice channels

each occupies a bandwidth of 6KHz. The common voice channel has a bandwidth of

24 KHz. (Band- 200 to 224 KHz).4 Discuss the indirect method of generating the FM.

5 Explain Pre emphasis and De emphasis.Week 7 1 Give comparison of FM and PM systems. In FM system, the modulating frequency is

500Hz & modulating voltage is 3.6V with modulating index 65. Calculate maximum

frequency deviation. What will be the modulation index when modulating frequency is

235Hz and modulation voltage is 5V?2 Draw the block diagram of Tuned Radio Frequency (TRF) Receiver and explain its operation. Describe the problems in TRF receiver.3 Define Heterodyning.4 Explain the working of Superheterodyne receiver with its parameters5 What are the advantages of superhetrodyne receiver?Week 8 1 State and prove any three properties of Fourier transform.2 What do you mean by AGC? Draw the circuit diagram of delayed AGC and

explain its operation. What are the advantages of delayed AGC?3 List the standard continuous time and discrete time signal and explain

them with neat sketches.4 Explain Tracking and Adjacent channel selectivity.

5 The frequency span to be received by a receiver is from 525 kHz to 1650 kHz. If Cmin of

tuning circuit is limited to 50 pF, Calculate the value of padder capacitor, if the maximum

value of variable capacitor is 450 pF. The IF used is 465 kHz..Week 9

1 What is Signal to Noise ratio ? Derived equation for Signal to noise

ratio for amplifier

2 Discuss the following:

(i) Energy spectral density

(ii) Power spectral density

(iii) Essential bandwidth of a signal

3 Two resistors 10 k and 25 k are at room temperature (290K) for a

bandwidth of 150kHz.Calculate thermal noise for each resistor, if two resistors

are in series and if two resistors are in parallel.

4 Describe briefly shot noise, partition noise and flicker noise. Why they are

generated?

5 For the periodic signal shown in fig. 1. Find compact trigonometric fourier series and

sketch amplitude spectra.