Presentation on Analogue n Digital Signals

8/8/2019 Presentation on Analogue n Digital Signals

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PRESENTATION ON ANALOGPRESENTATION ON ANALOG

AND DIGITAL SIGNALSAND DIGITAL SIGNALS


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COMMUNICATIONCOMMUNICATION

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Communication is the processCommunication is the processofof transferring informationtransferring information

from one entity to another.from one entity to another.


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BASIC ELEMENTS OFBASIC ELEMENTS OF


SENDERSENDER: a sender who creates the: a sender who creates the

message to be transmitted.message to be transmitted.

MEDIUMMEDIUM: a medium which carries: a medium which carriesmessage.message.

RECIEVERRECIEVER: a receiver which receives: a receiver which receives

message.message.


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Point-to-point communicationsPoint-to-point communications

Source Destination

Source: -discrete events (from an alphabet)-waveforms (speech, sound, images, video)

Transmission media: -radio frequency on the air-satellite channel-copper wire-optical fiber


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CONTENTSCONTENTS

Elements of an electricalElements of an electricalcommunication system.communication system.


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A SIMPLIFIED COMMUNICATION MODEL


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DATADATA



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Data communication is the process ofData communication is the process of

electronically sending data from one pointelectronically sending data from one point

to another. In this case the sender andto another. In this case the sender and

receiver are normally machines ,inreceiver are normally machines ,in

particular, computer devices & theparticular, computer devices & the

transmission medium may be telephonetransmission medium may be telephone

lines, microwave links, satellite links etc.lines, microwave links, satellite links etc.


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ADVANTAGES OF DATAADVANTAGES OF DATA


The cost of conveying message, pictures, orThe cost of conveying message, pictures, orvoice over large distance is small.voice over large distance is small.

The message is safe & secured.The message is safe & secured.

The transmission takes place without any doubtThe transmission takes place without any doubtfor the receiver.for the receiver.

The message reaches in a reasonable time.The message reaches in a reasonable time.

The message can be coded that it I understoodThe message can be coded that it I understood

by the sender & the receiver only.by the sender & the receiver only.


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ADVANTAGES OF DATAADVANTAGES OF DATA


The message can be sent in any language,The message can be sent in any language,hindi, punjabi or sanskrit.hindi, punjabi or sanskrit.

A layman can also easily send or receiveA layman can also easily send or receive

messagemessageThe same PC can also be used to getThe same PC can also be used to getinformation from varied sources such asinformation from varied sources such asrailways, weather department, banks, etcrailways, weather department, banks, etc

The same PC can also be used for educatin ,The same PC can also be used for educatin ,entertainment, internet access etc.entertainment, internet access etc.


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FORMS OF DATAFORMS OF DATA

TRANSMISSIONTRANSMISSION

Analog data transmissionAnalog data transmission

Digital data transmissionDigital data transmission


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DATADATA

ENTITIES THAT CONVEY MEANINGENTITIES THAT CONVEY MEANING

ANALOG DATA-ANALOG DATA-

Continuous value with some intervals ,Continuous value with some intervals ,e.g. sound, video etce.g. sound, video etc

DIGITAL DATA-DIGITAL DATA-

Discrete value e.g. text , integersDiscrete value e.g. text , integers


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SIGNALSSIGNALS

BY WHICH DATA ARE PROPAGATEDBY WHICH DATA ARE PROPAGATED

Analog signals-Analog signals-

it is continuously varyingit is continuously varyingelectromagnetic wave that propagateselectromagnetic wave that propagates

over ( a variety of ) mediumover ( a variety of ) medium


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Analog systemsAnalog systems

Analog systems use electrical signals thatAnalog systems use electrical signals thatvary continuously, not having discretevary continuously, not having discrete

valuesvalues Analog signals are electricalAnalog signals are electrical

representations of signals from naturerepresentations of signals from nature

(pressure, light, sound, etc.)(pressure, light, sound, etc.) Examples of analog systems: AM/FM radio,Examples of analog systems: AM/FM radio,

cassettes, telephone, VCR, standardcassettes, telephone, VCR, standardtelevisiontelevision

time

vo

lt

age


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Digital signalsDigital signals

It is a sequence of voltage pulses that areIt is a sequence of voltage pulses that are

transmitted over a wire medium. Thetransmitted over a wire medium. The

signal intensity maintains a constant levelsignal intensity maintains a constant level

for sometime and then changes to anotherfor sometime and then changes to another

constant level .constant level .


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Digital systemsDigital systems

Digital systems use electrical signalsDigital systems use electrical signalsthat represent discrete, binary values.that represent discrete, binary values. Digital signals are not representative ofDigital signals are not representative of

signals that occur in nature (pressure,signals that occur in nature (pressure,

light, sound, etc.).light, sound, etc.). Natural signals must be converted intoNatural signals must be converted into

digital format.digital format.


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Digital signalsDigital signals

Binary digital signals use two discrete voltageBinary digital signals use two discrete voltagelevels to represent binary 1 or 0.levels to represent binary 1 or 0.

Combining multiple bits into words permits usCombining multiple bits into words permits us

to represent larger values.to represent larger values.Digital circuits operate on digital signalsDigital circuits operate on digital signals

performing logic and arithmetic functions.performing logic and arithmetic functions.

time

vo

lt

age

0 V

5 V

1 0 1 01 1


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Digital examplesDigital examples


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Comparision b/wComparision b/wanalog and digitalanalog and digital

datadata

communicationcommunication


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Comparision b/w analog andComparision b/w analog and

digital data communicationdigital data communication

Continuous overContinuous over

an interval likean interval like

sound, light &sound, light &

radio wavesradio waves

Cost ofCost of

transmission istransmission ishighhigh

Efficiency is lowEfficiency is low

It is in the form ofIt is in the form of

discrete quantitiesdiscrete quantities

Cost of transmissionCost of transmission

is lowis low

Efficiency is highEfficiency is high


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Comparision b/w analog and digitalComparision b/w analog and digital

data communicationdata communication

MaintenanceMaintenance

cost is highcost is high

Effect of noise isEffect of noise ishighhigh

Error rate is highError rate is high

Data rate is lowData rate is low

Maintenance costMaintenance cost

is lowis low

Effect of noise isEffect of noise is

lowlow

Error rate is lowError rate is low

Data rate is highData rate is high


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Advantages of digital signalsAdvantages of digital signals

The most important advantage of digitalThe most important advantage of digitalcommunications is noise immunity.communications is noise immunity.

Receiver circuitry can distinguish between aReceiver circuitry can distinguish between a

binary 0 and 1 with a significant amount ofbinary 0 and 1 with a significant amount ofnoise.noise.

1 0 1 01 1

digital signal with noiseanalog signal with noise


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Advantages of digital signalsAdvantages of digital signals

Digital signals can be stripped of any noise inDigital signals can be stripped of any noise ina process called signal regeneration.a process called signal regeneration.

Consider a network of relay stations.Consider a network of relay stations.

microwave

relay stations


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Advantages of analog signalsAdvantages of analog signals

An analog signal is received, amplified andAn analog signal is received, amplified andretransmitted at each station.retransmitted at each station.

However, the noise is also amplified eachHowever, the noise is also amplified each

link.link.

microwave

relay stations

original analog signal

signal at repeater 1




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Whats the difference?Whats the difference?


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Advantages of Digital SystemsAdvantages of Digital Systems

More resilient to interference andMore resilient to interference and

imperfectionsimperfections

Longevity: data can be stored overLongevity: data can be stored oververy long periods of time.very long periods of time.

Information can be stored as numericalInformation can be stored as numerical

data: data storage cheapdata: data storage cheap


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Disadvantages of Digital SystemsDisadvantages of Digital Systems

Digital signal will not be an exactDigital signal will not be an exact

copy of the original analoguecopy of the original analogue

signal: sampling errorsignal: sampling error

Takes time to doTakes time to do

Complex processing involvedComplex processing involved


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Transmission of digitalTransmission of digital

datadataThere are two ways to move bits from oneThere are two ways to move bits from one

place to another:place to another: Transmit all bits of a word simultaneouslyTransmit all bits of a word simultaneously

((parallel transferparallel transfer).).

Send only 1 bit at a time (Send only 1 bit at a time (serial transferserial transfer).).


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Serial transmissionSerial transmission

In serial transmission, each bit of a word isIn serial transmission, each bit of a word is

transmitted sequentially, one after another.transmitted sequentially, one after another.

The least significant bit (LSB) isThe least significant bit (LSB) istransmitted first, and the most significanttransmitted first, and the most significant

bit (MSB) last.bit (MSB) last.

Each bit is transmitted for a fixed intervalEach bit is transmitted for a fixed intervalof time.of time.


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Serial data can be transmitted faster andSerial data can be transmitted faster and

over longer distances than parallel data.over longer distances than parallel data.Serial buses are now replacing parallelSerial buses are now replacing parallel

buses in equipment where very highbuses in equipment where very high

speeds are required.speeds are required.


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Parallel transmissionParallel transmission

Parallel data transmission is extremely fastParallel data transmission is extremely fastbecause all the bits of the data word arebecause all the bits of the data word are

transferred simultaneously.transferred simultaneously. There must be one wire for each bit ofThere must be one wire for each bit of

information to be transmitted. Multi-wire cableinformation to be transmitted. Multi-wire cable

must be used.must be used.


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Parallel transmissionParallel transmission

Parallel data transmission is impractical for long-Parallel data transmission is impractical for long-distance communication because of:distance communication because of:

Cost of laying multi-wire cables.Cost of laying multi-wire cables.

Signal attenuation over long distances.Signal attenuation over long distances.

At high speeds, capacitance and inductance ofAt high speeds, capacitance and inductance of

multiple wires distorts the pulse signal. To reducemultiple wires distorts the pulse signal. To reduce

this, line lengths must be severely shortened.this, line lengths must be severely shortened.

To achieve clock speeds up to 400 MHz, lineTo achieve clock speeds up to 400 MHz, linelengths must limited to a few incheslengths must limited to a few inches


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Parallel data transmission byParallel data transmission by

radio would be complex andradio would be complex andexpensive.expensive.

One transmitter and one receiverOne transmitter and one receiverfor each bit.for each bit.


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Conversion fromConversion fromanalog to digitalanalog to digital


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Before we can use digital transmission, we mustBefore we can use digital transmission, we must

convert the signal of interest into a digital format.convert the signal of interest into a digital format.

Translating an analog signal into a digital signal isTranslating an analog signal into a digital signal iscalled analog-to-digital (A/D) conversion, digitizing acalled analog-to-digital (A/D) conversion, digitizing a

signal, or encoding.signal, or encoding.

The device used to perform this translation is knownThe device used to perform this translation is known

as an analog-to-digital converter or ADC.as an analog-to-digital converter or ADC.


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An analog signal is a smooth orAn analog signal is a smooth or

continuous voltage or current variation.continuous voltage or current variation.

Through A/D conversion theseThrough A/D conversion these

continuously variable signals arecontinuously variable signals are

changed into a series of binary numbers.changed into a series of binary numbers.

01101010100111001101010101111


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Thanks for your kindThanks for your kind

attention!attention!

Questions are welcome!Questions are welcome!

Thank you

Date post:	29-May-2018
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Presentation on Analogue n Digital Signals

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