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8/10/2019 CommSim File Yoyo

1/20

Roll No.

EXPERIMENT NO. 1

AIM: To simulate AM Modulation.

SOFTWARE USED:VisSim Comm 6.0

THEORY:-MODULATION:-It is defined as the process b !hich the base band si"nal #modulatin" si"nal$

modifies another hi"h fre%uenc si"nal called carrier. The carrier is hi"her in fre%uenc than thehi"hest base band si"nal fre%uenc. The baseband si"nal modifies the amplitude or fre%uenc or

phase of the carrier in modulation process.

AMPLITUDE MODULATION:-In amplitude modulation the amplitude of the carrier is &aried

in accordance to the instantaneous &alue of the modulatin" si"nal 'eepin" fre%uenc and phaseconstant.

(!here) c#t$ is carrier si"nal*

(!here) m#t$ is modulation si"nal*

(!here) #t$ is modulated si"nal*

MODULATION INDEX (m):-The relationship bet!een the amplitude of the modulatin" and

carrier si"nal is e+pressed in terms of their ratio 'no!n as modulation inde+ #m$ and is

mathematicall "i&en as m ,Vm-Vc (1.1)

The modulation inde+ lies bet!een 0 and

CALCULATION OF MODULATION INDEX (m):-

/i".#a$ Modulated a&e

/rom the abo&e fi"ure !e can !rite

(1.2)

= (1.3)

1 2 a " e


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3/20


4/20

Roll No.

/i".#a$ a&eform of AM

% D$4*m:-

/i".#b$ 3loc' 4ia"ram of /M

O5'65':

/i".#c$ 9utput of /M

R+,5': The /re%uenc Modulation has been simulated and &erified.

1 2 a " e


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6/20

Roll No.

W+&%*m:

/i".8#a$ a&eform of AS;

% $4*m

/i".8#b$ 3loc' 4ia"ram of AS;

6 1 2 a " e


7/20

Roll No.

O5'65':

/i".8#c$ 9utput of AS;

R+,5':The Amplitude shift 'ein" #AS;$ has been simulated and studied.

? 1 2 a " e


8/20

Roll No.

EXPERIMENT NO. ;

AIM : To stud and stimulate the /re%uenc shift 'ein" #/S;$ Modulation and

demodulation

S%&'*+ U,+: VisSim Comm. 6.0.

T+%*/:/re%uenc = Shift ;ein"#/S;$ is a fre%uenc modulation scheme in !hich di"ital information

is transmitted throu"h discrete fre%uenc chan"es of a carrier !a&e. The simplest /S; is binar

/S; #3/S;$. 3/S; literall implies usin" a pair of discrete fre%uencies to transmit binar #0s

and s$ information . ith this scheme ) the @ is called the mar' fre%uenc and the @0 is

called the space fre%uenc.

W+&%*m:

/i".#a$ a&eform of /S;

B 1 2 a " e


9/20

Roll No.

%D$4*m:

/i".#b$ /re%uenc Shift ;ein" modulation and 4emodulation

O5'65':

1 2 a " e


10/20

Roll No.

/i".#c$ 9utput of /S; Modulation and 4emodulation

R+,5': The /re%uenc Shift ;ein" #/S;$ Modulation and 4emodulation has

been studied 5 simulated.

EXPERIMENT NO.

A$m:To stud and simulate 2ulse 2osition Modulation.

S%&'*+ 5,+: VisSim Comm. 6.0

T+%*/:-2ulse


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Roll No.

O5'65':-

/i":?#b$ 9utput of 2ulse 2osition Modulation

R+,5':The 2ulse 2osition Modulation has been studied and simulated.

6 1 2 a " e


17/20

Roll No.

EXPERIMENT NO. ?

A$m: To simulate 42S; Modulation.

S%&'*+ U,+:VisSim. Comm 6.0

T+%*/:4ifferential phase shift 'ein" #42S;$) a common form of phase modulation con&es data b

chan"in" the phase of carrier !a&e. In 2hase shift 'ein") Ei"h state contains onl one ccle but

42S; contains one and half ccle. Ei"h state is represented b a M in modulated si"nal and lo!

state is represented b a !a&e !hich appears li'e in modulated si"nal 42S; encodes t!o

distinct si"nals of same fre%uenc !ith B0 de"ree phase difference bet!een the t!o. This

e+periment re%uires t!o B0 de"ree out of phase carrier and modulatin" si"nals. Sine !a&e from

oscillator is selected as carrier si"nal. 4SJ con&erts 4C input &olta"e into pulse trains. These

pulse trains are ta'en as modulatin" si"nals. In actual practice modulatin" si"nal is di"ital form

of &oice or data. Sine !a&e is selected as carrier and B0 de"ree phase shift is obtained usin"

9pamp as sho!n in fi"ure belo!.

% D$4*m:

/i":B#a$ 42S; modulation

? 1 2 a " e


18/20

Roll No.

O5'65':-

/i":B#b$ 9utput of 42S; modulation

R+,5':- The 42S; modulation has been studied and stimulated.

B 1 2 a " e


19/20

Roll No.

EXPERIMENT NO. @

A$m:To simulate 42S; 4emodulation.

S%&'*+ U,+:VisSim. Comm 6.0

T+%*/:4ifferential phase shift 'ein" #42S;$) a common form of phase modulation con&es data b

chan"in" the phase of carrier !a&e. In 2hase shift 'ein") Ei"h state contains onl one ccle but

42S; contains one and half ccle. Ei"h state is represented b a M in modulated si"nal and lo!

state is represented b a !a&e !hich appears li'e in modulated si"nal 42S; encodes t!o

distinct si"nals of same fre%uenc !ith B0 de"ree phase difference bet!een the t!o. This

e+periment re%uires t!o B0 de"ree out of phase carrier and modulatin" si"nals. Sine !a&e from

oscillator is selected as carrier si"nal. 4SJ con&erts 4C input &olta"e into pulse trains. These

pulse trains are ta'en as modulatin" si"nals. In actual practice modulatin" si"nal is di"ital form

of &oice or data. Sine !a&e is selected as carrier and B0 de"ree phase shift is obtained usin" 9p

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