16454 communication

8/3/2019 16454 Communication

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ANALOG

COMMUNICATIONHARAMARDEEP SINGH

LPU


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ANALOG SIGNALS: THE BASICS

Cycle

Time

Signal

Amplitude

Frequency = Cycles/

Second

A typical

sine wave


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AMPLITUDE AND CYCLE

AmplitudeDistance above reference line

CycleOne complete wave


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FREQUENCY

FrequencyCycles per second

Hertz is the unit used for expressingfrequency

Frequency spectrumDefines the bandwidth for differentanalog communication technologies


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ANALOG TO DIGITAL CONVERSION

1 0 1 1 0 1 0 0

A to D Converters, Digital Signal Processors (DSP) etc.


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DATA TRANSMISSION USING

ANALOG TECHNOLOGY

Digital

0s and 1s

Analog

0s and 1s

Digital-to-Analog Modulation and vice versa

ComputerModem


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FREQUENCY SPECTRUM DEFINED

Available range of frequencies for communicationStarts from low frequency communication such as

voice and progresses to high frequency

communication such as satellite communication

The spectrum spans the entire bandwidth ofcommunicable frequencies


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FREQUENCY SPECTRUM

Low Frequency High Frequency

Radio

Frequency

Coaxial

Cable

MHz

Satellite

Transmission

MicrowaveMHz

Voice

KHz


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FREQUENCY BANDS

BAND Hz

4ELF 30 - 3004AF 300 - 3 k 4VLF 3 k - 30 k4LF 30 k - 300 k 4MF 300 k - 3 M4HF 3 M - 30 M

BAND Hz

4VHF 30M-300M4UHF 300M - 3 G4SHF 3 G - 30 G4EHF 30 G - 300G

Wavelength, = c/f


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BANDWIDTH DEFINITION

Bandwidth, in general, represents a range of frequencies

300 MHz 700 MHz

Bandwidth is 400 MHz


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USAGE OF THE TERM BANDWIDTH

To specify the communication capacityA medium such as a coaxial cable is

associated with a bandwidthTo indicate the bandwidth of a technologyVoice grade circuits have a bandwidth

of 4 KHz (0-4000 Hz)


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ELEMENTS OF A COMMUNICATION SYSTEM

Communication involves the transfer ofinformation or intelligence from a source to

a recipient via a channel or medium.Basic block diagram of a communication

system:

Source Transmitter Receiver Recipient


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BRIEF DESCRIPTION

Source: analogue or digitalTransmitter: transducer, amplifier, modulator,

oscillator, power amp., antennaChannel: e.g. cable, optical fibre, free spaceReceiver: antenna, amplifier, demodulator,

oscillator, power amplifier, transducerRecipient: e.g. person, speaker, computer


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MODULATION

Modulation is the process of impressing information ontoa high-frequency carrier for transmission.

Reasons for modulation:to prevent mutual interference between stationsto reduce the size of the antenna required

Types of analogue modulation: AM, FM, and PMTypes of digital modulation: ASK, FSK, PSK, and QAM


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TIME AND FREQUENCY DOMAINS

Time domain: an oscilloscope displays theamplitude versus time

Frequency domain: a spectrum analyzer displaysthe amplitude or power versus frequency

Frequency-domain display provides information onbandwidth and harmonic components of a signal


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CLOCK SPEED AND PULSE DURATION

Pulse

Duration

MHz


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CLOCK SPEED AND EXECUTION SPEED

Pulse duration is inversely proportionalto the clock frequency

Faster the clock speed, the smaller thepulse duration

Smaller the pulse duration, the faster theexecution in general


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CLOCK SPEED AND COMMUNICATION

SPEED

Faster the clock speed, smaller the pulseduration

Smaller the pulse duration, smaller the timetaken to transmit one bit of information

Therefore, faster the clock speed measured inMHz, faster the communication speed measured

in Mbps in general


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CLOCK SPEED AND COMPUTER

OPERATION

Computer operations are timed by a clock, namelyby the clock speed measured in HZ

Faster the speed, the smaller the pulse durationComputer operations are timed by the pulse

durationTherefore, faster the clock speed, faster the

computer operationA 3 GHz computer is faster than a 2 GHz computer


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AMPLITUDE MODULATION


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INTRODUCTION

Amplitude Modulation is the simplest and earliest form oftransmitters

AM applications include broadcasting in medium- and high-frequency applications, aircraft communications


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BASIC AMPLITUDE MODULATION

The information signal variesthe instantaneous amplitude of

the carrier


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AM CHARACTERISTICS

AM is a nonlinear processSum and difference frequencies are created

that carry the information


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FULL-CARRIER AM: TIME DOMAIN

Modulation Index - The ratio between theamplitudes between the amplitudes of the

modulating signal and carrier, expressed by

the equation:

m=E

m

Ec


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OVERMODULATION

When the modulation index is greater than 1,overmodulation is present


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ASK VS FSK VS PSK


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