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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
COMMUNICATIONCOMMUNICATION
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
COMMUNICATIONCOMMUNICATION
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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
COMMUNICATIONCOMMUNICATION
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
COMMUNICATIONCOMMUNICATION
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
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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
signal at repeater 2
signal at repeater 3
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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