ANALOG ANALOG COMMUNICATIOCOMMUNICATIO

NSNS

UNIT-I UNIT-I INTRODUCTIONINTRODUCTION

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Definition of Signal, Analog and Digital Definition of Signal, Analog and Digital signalsignal

Waveform of Analog and Digital signalWaveform of Analog and Digital signal Differences between Analog and Digital Differences between Analog and Digital

signalsignal Frequency Spectrum used in communicationFrequency Spectrum used in communication Introduction to Communication SystemIntroduction to Communication System Need for ModulationNeed for Modulation Types of ModulationTypes of Modulation

Signal, Analog & Digital Signal

In electronics a In electronics a signalsignal is an electric  is an electric current or electromagnetic field used to current or electromagnetic field used to convey data from one place to anotherconvey data from one place to another

Analog signalAnalog signal which is a continuous signal which is a continuous signal that contains time-varying quantitiesthat contains time-varying quantities

Digital signal Digital signal refers to an electrical signal refers to an electrical signal that is converted into a pattern of that is converted into a pattern of bits.digital signal has a discrete value at bits.digital signal has a discrete value at each sampling point.each sampling point.

Analog and Digital Signal Waveform Analog and Digital Signal Waveform

Analog Vs Digital signal

Cont..Cont..

Frequency Spectrum used in communication

Introduction to Communication System

Communication is a process of conveying Communication is a process of conveying message at a distancemessage at a distance

Three basic components.Three basic components.

TransmitterTransmitter

ChannelChannel

ReceiverReceiver

..

TransmitterTransmitter is the equipment which is the equipment which converts physical message, such as sound, converts physical message, such as sound, words, pictures etc., into corresponding words, pictures etc., into corresponding electrical signal.electrical signal.

ReceiverReceiver is equipment which converts is equipment which converts electrical signal back to the physical electrical signal back to the physical messagemessage

ChannelChannel may be either transmission line or may be either transmission line or free space, which provides transmission free space, which provides transmission path between transmitter and receiver.path between transmitter and receiver.

Communication is the ability to send and receive messages.

1.People to people

2.People to machine

3.Machine to people

4.Machine to machine

Need for modulation Need for modulation

Modulation:Modulation:

Modulation is defined as the process by which Modulation is defined as the process by which some characteristics (i.e. amplitude, frequency, some characteristics (i.e. amplitude, frequency, and phase) of a carrier are varied in accordance and phase) of a carrier are varied in accordance with a modulating wave.with a modulating wave.

Modulation is performed at the transmitting endModulation is performed at the transmitting end

Demodulation:Demodulation:

Demodulation is the reverse process of Demodulation is the reverse process of modulation, which is used to get back the original modulation, which is used to get back the original message signal. message signal.

Demodulation is performed at the receiving endDemodulation is performed at the receiving end

In In analog modulation sinusoidal signal is analog modulation sinusoidal signal is used as carrier used as carrier where as in where as in digital digital modulation pulse train is used as carriermodulation pulse train is used as carrier..

Need for modulation:Need for modulation:

Modulation is needed in a communication Modulation is needed in a communication system to achieve the following basic needssystem to achieve the following basic needs

1) Multiplexing1) Multiplexing

2) Practicability of antennas2) Practicability of antennas

3) Narrow banding3) Narrow banding

Types of ModulationTypes of Modulation

Continuous wave modulation (CW): Continuous wave modulation (CW):

When the carrier wave is continuous in When the carrier wave is continuous in nature the modulation process is known as nature the modulation process is known as continuous wave modulation.continuous wave modulation.

Pulse modulation: Pulse modulation:

When the carrier wave is a pulse in nature When the carrier wave is a pulse in nature the modulationthe modulation

process is known as Pulse modulationprocess is known as Pulse modulation