CS6304 Analog & Digital Communication B.E Question Bank : dsirt.ac.in
Name of the Institute : Dhanalakshmi Srinivasan Institute of Research and Technology
University : Anna University
Degree : B.E
Department : Computer Science & Engineering
Subject Code/Name : CS6304 Analog & Digital Communication
Year : 2nd
Semester : 3rd
Document Type : Question Bank
Website : dsirt.ac.in
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DSIRT Digital Communication Question Paper
Analog Communication :
Unit – I
1.Define modulation? :
Modulation is a process by which some characteristics of high frequency carrier signal is varied in accordance with the instantaneous value of the modulating signal
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2.Define depth of modulation :
It is defined as the ratio between message amplitude to that of carrier amplitude.
3.what is the need of modulation? :
** Ease of transmission
** multiplexing
** reduce noise
** narrow bandwidth
** reduce the equipments limitations
4.What is the degree of modulation? :
** Under modulation, m<1
** Critical Modulation, m=1
** Over modulation, m>1
5.What are the two types of modulator? :
** linear modulator
** Non-Linear modulator
6.What are the advantages of VSB-AM? :
** It has bandwidth greater than SSB but less than DSB system.
** Power transmission greater than DSB but less than SSB system
** No low frequency component loss. Hence it avoids phase distortion
7.How will you generating DSBSC-AM? :
There are two ways of generating DSBSC-AM such as,
** Balanced modulator
** Ring Modulator
8.Define frequency modulation :
Frequency Modulation is a process by which frequency of carrier signal is varied in accordance with the instantaneous value of the modulating signal.
9.Define modulation index of frequency modulation :
It is defined as the ratio of maximum frequency deviation to the modulating frequency.
10.State the Carson’s rule :
An approximate rule for the transmission bandwidth of an FM signal generated by a single tone modulating signal of frequency.
11. What are the types of FM detector? :
** Slope detector
** Phase discriminator
Unit – II
Digital Communication :
1.What are the advantages of digital communication/
** transmission quality high
** Effect of noise, distortion and interference is less in a communication system.
** Digital circuits are more reliable and cheaper compared to analog circuits
2.What are the disadvantages of digital communication? :
** Large System Bandwidth
** System Synchronization
3.What are the performance measure of communication systems? :
** Spectral Efficiency
** Bit Error Rate
** Bandwidth Utilization
4.Define Sampling :
The process of conversion of analog signal into digital signal is called sampling. There are two types of sampling 1.Impulse sampling 2. Natural Sampling
5.What is meant by Alaising effect? :
Alaising effect takes place when the sampling frequency is less than nyquist rate. During this condition the spectrum of sampled signal overlaps itself. So high frequency takes the form of low frequency. This interference is called as aliasing effect.
6.What is meant by quantization? :
The process of transforming continuous samplied amplitude values m(nTs) of a message signal m(t) at time t=nTs into discrete amplitude value mq(nTs) from finite set of possible amplitude is referred to as quantization.
7.What are the types of quantization? :
** Scalar quantization
** vector quantization
8.Mention the pulse modulation techniques? :
** Pulse Amplitude Modulation
** Pulse Width Modulation
** Pulse Position Modulation
9.What are the types of Adaptive Delta modulation? :
** Discrete type
** Continuous type
10.What is meant by sub band coding? :
Sub band coding is a method of controlling and distributing quantization noise across the signal spectrum.
Unit – III
Data And Pulse Communication :
1.What is PAM? :
PAM is the pulse modulation. In PAM the amplitude of a carrier consisting of a periodic train of rectangular pulse is varied in proportion to sample values of a message signal.
2.What is PCM? :
PCM is a process used to convert analog signal to digital data. In PCM ,the analog signal is first sampled then quantized then each sample is replaced with n bits binary data.
3.What do you mean by nonlinear encoding in PCM system? :
Nonlinear encoding is a technique used to increase the performance of PCM system. In nonlinear encoding the quantization levels are not equaled spaced. That is greater number of quantization levels for signals of low amplitude and smaller number of quantization levels for signals of high amplitude.
4.What is called processing gain? :
Processing gain is defined as the ratio of the bandwidth of spread message signal to the bandwidth of unspreaded data signal.
5.What is meant by PCM? :
PCM is a method of signal coding in which the message signal is sampled, the amplitude of each sample is rounded off to the nearest one of a finite set of discrete levels and encoded so that both time and amplitude are represent in discrete form.
6.Define quantization error?:
It is the difference between the output and input values of quantizer.
7.Define quantization process?:
The conversion of analog sample of the signal into digital form is called quantization process.
8.Define PPM?:
The position of a constant width pulse with in a time slot is varied according to the amplitude of the sample of the analog signal.
9.Define PWM?:
The width of a constant amplitude pulse is varied proportional to the amplitude of the analog signal at the time the signal is sampled.