Comsim Lab File

8/10/2019 Comsim Lab File

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EXPERIMENT NO 01

AIM:-To Study And Simulate transmission and recetion o! Amlitude Modulation"

SO#T$ARE %SE&:-'issim ("0

T)EOR*

MO&%+ATION:-It is defined as the process by which the base band signal (modulating signal) modifies

another high frequency signal called carrier. The carrier is higher in frequency than the highest base band

signal frequency. The baseband signal modifies the amplitude or frequency or phase of the carrier in

modulation process.

AMP+IT%&E MO&%+ATION:-In amplitude modulation the amplitude of the carrier is varied in

accordance to the instantaneous value of the modulating signal keeping frequency and phase constant.

#i,ure:-Amlitude Modulation

MO&%+ATION IN&EX m.:-The relationship between the amplitude of the modulating and

carrier signal is expressed in terms of their ratio known as modulation index (m) and is

mathematically given a

m = 1"1.

The modulation index lies between and !


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/A+/%+ATION O# MO&%+ATION IN&EX m.:-

"rom the above figure we can write

1".

2 1"3.

#mplitude $odulation

Result: #mplitude $odulation has been studied and waveform detected.


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EXPERIMENT NO 0

AIM:-To study and simulate transmission and reception of frequency modulation.

SO#T$ARE %SE&:-%is&im 'omm .

T)EOR*:-

#RE4%EN/* MO&%+ATION:-In frequency modulation the frequency of the carrier is varied in

accordance to the instantaneous value of the modulating signal keeping amplitude and phaseconstant.

"igure!*"requency modulation

= t+

= )( where t+ #t t= , = t) (

)Instantaneous angular frequency of frequency

modulation wave after modulation is given as = + t)where is the constant of

proportionality which represents the frequency conversion factor.The total instantaneous phase of


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frequency modulated wave is

=

5+O/6 &IA7RAM:-

"requency $odulation

O%TP%T:


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RES%+T:The frequency modulation has been simulated and waveform is recorded.


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EXPERIMENT NO 03

AIM: To study and simulate transmission and reception of #&-.

SO#T$ARE %SE&: %is&im 'omm .

T)EOR*:

The Transmission of digital signals is increasing at a rapid rate. ow*frequency analog signals are

often converted to digital format (/#$) before transmission. The source signals are generally referred

to as baseband signals. In the modulation process, the baseband signals constitute the modulating

signal and the high*frequency carrier signal is a sinusoidal waveform. There are three basic ways of

modulating a sine wave carrier. "or binary digital modulation, they are called binary amplitude*shift

keying (0#&-), binary frequency*shift keying (0"&-) and binary phase*shift keying (0/&-).

5inary Amlitude-S8i!t 6eyin, 5AS6.:

#mplitude*shift keying (#&-) is a form of modulationthat represents digitaldataas variations in the

amplitudeof a carrier wave. #ny digital modulation scheme uses a finitenumber of distinct signals to

represent digital data. #&- uses a finite number of amplitudes, each assigned a unique pattern of

binary digits. 1sually, each amplitude encodes an equal number of bits. 2ach pattern of bits forms the

symbol that is represented by the particular amplitude. The demodulator, which is designed

specifically for the symbol*set used by the modulator, determines the amplitude of the received signal

and maps it back to the symbol it represents, thus recovering the original data.

# binary amplitude*shift keying (0#&-) signal can be defined by

3 t 3 T 4.!
http://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wiktionary.org/wiki/finitehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Symbol_(data)http://en.wikipedia.org/wiki/Demodulatorhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wiktionary.org/wiki/finitehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Symbol_(data)http://en.wikipedia.org/wiki/Demodulatorhttp://en.wikipedia.org/wiki/Modulation


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where # is a constant, m(t) = ! or , fcis the carrier frequency, and T is the bit duration. It has a power

so

that # = 5/ . Thus,

s(t) = 5/ cos 56fct, 3 t 3 T 4.5

= /T cos56fct 3 t 3 T 4.4

= 2 cos 56fct, 3 t 3 T 4.7

where 2 = / T is the energy contained in a bit duration. If we take 8!(t) = 5Tcos 56fct as the orthonormal

basis function,

applicable signal space diagram of the 0#&- signals is shown in figure below.

/onstellation dia,ram o!

5AS6:

#i,ure: a. 5inary data

9. /arrier a;e!orm

c. AS6 a;e !orm

ogic levels are represented by different amplitudes of signals. 1sually, one amplitude is 9ero forlogic digital logic 9ero while is logic ! represented by the actual amplitudes of some sine wave

signal. "igure shows the expected waveforms in #&-. %d(t) is the message signal, %c(t) is the


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carrier signal,%ask(t) is the output.

The #&- waveform looks like an :;*:"" of the signal therefore is also known as :;*:""

keying(::-).

#&- is generated by applying the binary data and sinusoidal carrier to the two inputs of the product

modulator. The #&- signal has a power spectral density (/&


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enhance the immunity to noise. &o the coding technique can be used to detect, correct and encrypt

the signal.


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"&- $odulation

O%TP%T:

RES%+T:The frequency shift keying ("&-) has been simulated and waveform is recorded


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EXPERIMENT NO 0=

AIM: To study and simulate transmission and reception of /&-.


T)EOR*:/hase*shift keying (/&-) is a digital modulation scheme that conveysdataby modulating

thephaseof thecarrier wave. #ny digital modulation scheme uses a finitenumber of distinct signals to

represent digital data. /&- uses a finite number of phases, each assigned a unique pattern of binary

digits. 1sually, each phase encodes an equal number of bits. 2ach pattern of bits forms the symbolthat

is represented by the particular phase.

0/&- (also sometimes called /D-, /hase Deversal -eying, or 5/&-) is the simplest form of phase

shift keying (/&-). It uses two phases which are separated by !EF and so can also be termed 5*/&-.

The and ! bits shift the carrier phase by !EF.
http://en.wikipedia.org/wiki/Data#Uses_of_data_in_computinghttp://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Carrier_wavehttp://en.wiktionary.org/wiki/finitehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Symbol_(data)http://en.wikipedia.org/wiki/Data#Uses_of_data_in_computinghttp://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Carrier_wavehttp://en.wiktionary.org/wiki/finitehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Symbol_(data)


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signal sequence of 0/&- that shows a carrier sinCc t

al data

- signal.

where ! is represented by and is represented by

Thebit error rate(02D) of 0/&- in #BG;can be calculated as

or

&ince we define the bandwidth as the range occupied by the baseband signal from A9 to the first

9ero*crossing point, we have 0 A9 of bandwidth for the baseband signal and 50 A9 for the 0/&-

signal.

This is
http://en.wikipedia.org/wiki/Bit_error_ratehttp://en.wikipedia.org/wiki/AWGNhttp://en.wikipedia.org/wiki/Bit_error_ratehttp://en.wikipedia.org/wiki/AWGN


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the frequency spectrum of a 0/&- signal.

This constellation diagram shows an axis where each phasor represents the amplitude of the carrier and

the direction represents the phase position of the carrier.

The general form for 0/&- follows the equation

This yields two phases, and 6. In the specific form, binary data is often conveyed with the following

signals

for binary HH

where fc is the frequency of the carrier*wave.

Aence, the signal*space can be represented by the single basis function

BLOCK DIAGRAM:


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/&- $odulation

O%TP%T:


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RES%+T: /hase* shift keying has been studied and waveform detected.

EXPERIMENT NO 0(

AIM: To &tudy and simulate transmission and reception of


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"ig 0lock diagram of


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O%TP%T:


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AIM:To &imulate J/&- (Juadrature /hase &hift -eying) $odulation.

T)OER*:

In fig shows a block diagram of a typical J/&- transmitter. The unipolar binary message (data)

first converted into a bipolar non*return*to*9ero (;DK) sequence using a unipolar to bipolar

converter. The bit stream is then split into two bit streams I(in*phase) and J(Juadrature) .The bit

stream in*phase(I) is called the LevenM stream and quadrature (J) is called L:ddM stream. The two

bit stream fed to the ow pass filter (/").Then the two bit stream after filtering fed to the

modulator. The filter at the output of the modulator confines the power spectrum of the J/&-signal

within the allocated band. The two modulator bit stream are summed and fed to the band pass filter

(0/") and produce the J/&- output.

J/&- $odulation

$a;e!orms:
http://http/turboblogsite.com/qpsk-theory.htmlhttp://http/turboblogsite.com/qpsk-theory.html


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Juadrature /hase &hift -eying $odulation Baveform

Result:Juadrature /hase &hift -eying $odulation has been &imulated and Baveforms

Decorded.

EXPERIMENT NO ?

AIM: To study and simulate transmission and reception of (/#$) $odulation.


T)EOR*:/#$ is pulse modulation system in which the signal is sampled at regular intervals in each

sample is made proportion to amplitude of the signal at the instant of sampling. /#$ in which a fixed dc

level is added to the signal to ensure that pulses are always positive.


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a) $odulating signal

b) $odulated signal

5+O/6 &IA7RAM:-


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O%TP%T:-


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RES%+T:-/ulse #mplitude $odulation has been studied and waveform detected.

EXPERIMENT NO @

Aim: To study and simulate transmission and reception of //$.

So!tare %sed:%is&im 'omm. .

T8eory:


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/ulse position modulation (//$) is a pulse modulation technique that uses pulses that are of

uniform height and width but displaced in time from some base position according to the amplitude

of the signal at the instant of sampling. /ulse position modulation is also sometimes known as

pulse*phase modulation. /ulse position modulation has the advantage over pulse amplitude

modulation (/#$) and pulse duration modulation (/


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$a;e!orms:


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Result:The //$ has been simulated and waveform is recorded.

/ulse position modulation (//$) is a pulse modulation technique that uses pulses that are of uniform height

and width but displaced in time from some base position according to the amplitude of the signal at the

instant of sampling. /ulse position modulation is also sometimes known as pulse*phase modulation. /ulse

position modulation has the advantage over pulse amplitude modulation (/#$) and pulse duration

modulation (/

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