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DE LA SALLE UNIVERSITY-DASMARIÑAS

College of Engineering, Architecture an Technolog!

ECET"#$L- %RINCI%LE &' C&MMUNICATI&NS LA(&RAT&RY

E)*t+ No+

Deoulation of A*litue-Moulate .AM/ Signal0

Su1itte (!2

Maria Ro0alina C+ Re!e0

ECE"#

Se*te1er #3, $4#"

Engr+ Conrao D+ Mon5onIn0tructor 

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OBJECTIVES

#+ Too uner0tan the ifferent etho0 of AM eoulation+$+ To o10er6e the !naic characteri0tic of eoulate AM 0ignal

THEORY/DISCUSSION

Deoulation i0 the act of e)tracting the original inforation-1earing 0ignal fro

a oulate carrier 7a6e+ A eoulator i0 an electronic circuit that i0 u0e to reco6er 

the inforation content fro the oulate carrier 7a6e+ There are 0e6eral 7a!0 of 

eoulation e*ening on ho7 *araeter0 of the 1a0e-1an 0ignal are tran0itte in

the carrier 0ignal, 0uch a0 a*litue, fre8uenc! or *ha0e+ 'or e)a*le, for a 0ignal

oulate 7ith a linear oulation, li9e AM, a 0!nchronou0 etector can 1e u0e+

In orer to loo9 at the a*litue eoulation *roce00 it i0 nece00ar! to fir0t loo9

at the forat of an AM 0ignal+ An AM 0ignal con0i0t0 of a carrier 7hich act0 a0 the

reference+ An! oulation that i0 a**lie then a**ear0 a0 0ie1an0 7hich 0tretch out

either 0ie of the 0ignal - each 0ie1an i0 a irror iage of the other+

The ain eleent of AM eoulation i0 to create the 1a0e1an 0ignal+ Thi0 can

1e achie6e in a nu1er of 7a!0 - one of the ea0ie0t i0 to u0e a 0i*le ioe an

rectif! the 0ignal+ Thi0 lea6e0 eleent0 of the original R' 0ignal+ :hen other for0 of 

eoulation are u0e, the! too lea6e 0oe eleent0 of an R' 0ignal+  The filtering

reo6e0 an! un7ante high fre8uenc! eleent0 fro the eoulation *roce00+ The

auio can then 1e *re0ente to further 0tage0 for auio a*lification, etc+

 An AM 0ignal encoe0 the inforation onto the carrier 7a6e 1! 6ar!ing it0

a*litue in irect 0!*ath! 7ith the analogue 0ignal to 1e 0ent+ There are t7o

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etho0 u0e to eoulate AM 0ignal0+ The en6elo*e etector i0 a 6er! 0i*le

etho of eoulation+ It con0i0t0 of a rectifier .an!thing that 7ill *a00 current in one

irection onl!/ or other non-linear that enhance0 one half of the recei6e 0ignal o6er the

other, an a lo7-*a00 filter+ The rectifier a! 1e in the for of a 0ingle ioe, or a! 1e

ore co*le)+ Man! natural 0u10tance0 e)hi1it thi0 rectification 1eha6iour, 7hich i0

7h! it 7a0 the earlie0t oulation an eoulation techni8ue u0e in raio+ The filter 

i0 u0uall! a RC lo7-*a00 t!*e, 1ut the filter function can 0oetie0 1e achie6e 1!

rel!ing on the liite fre8uenc! re0*on0e of the circuitr! follo7ing the rectifier+ The

cr!0tal 0et e)*loit0 the 0i*licit! of AM oulation to *rouce a recei6er 7ith 6er! fe7*art0, u0ing the cr!0tal a0 the rectifier, an the liite fre8uenc! re0*on0e of the

hea*hone0 a0 the filter+

The *rouct etector ulti*lie0 the incoing 0ignal 1! the 0ignal of a local

o0cillator 7ith the 0ae fre8uenc! an *ha0e a0 the carrier of the incoing 0ignal+ After 

filtering, the original auio 0ignal 7ill re0ult+ Thi0 etho 7ill ecoe 1oth AM an SS(,

although if the *ha0e cannot 1e eterine a ore co*le) 0etu* i0 re8uire+

 An AM 0ignal can 1e rectifie 7ithout re8uiring a coherent eoulator+ 'or 

e)a*le, the 0ignal can 1e *a00e through an en6elo*e etector .a ioe rectifier an a

lo7-*a00 filter/+ The out*ut 7ill follo7 the 0ae cur6e a0 the in*ut 1a0e1an 0ignal+

There are for0 of AM in 7hich the carrier i0 reuce or 0u**re00e entirel!, 7hich

re8uire coherent eoulation+

DATA AND RESULTS

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Diagram 1. Moulating an Deoulate Signal for DS('C .'i)e %ha0e Relation/

 ADa); $+"

Table 1. %ha0e Re0*on0e of the DS(

 .egree0/ᶲ  AD .6olt0/ AD

@3 $+#$ 4+= 4+=#

>" #+3$ 4+>? 4+>?

$ 4+== 4+@$ 4+@#

?4 4+#3 4+43 4

#4= 4+= 4+$? 4+@#

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Diagram 2. Deoulate Signal a0 'unction of %ha0e ᶲ

:hat o the0e 0ignal0 re*re0ent

The final 7a6e re*re0ent0 *ilot tone fro the oulator an the 0econ

7a6efor re*re0ent0 the recei6e *ilot tone fro the eoulator+

Diagram 3. Tran0itte an Recei6e %ilot Tone

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Diagram . In*ut an &ut*ut Signal0

:hat o the0e 0ignal0 re*re0ent

The fir0t 7a6efor 7a0 fro the tran0itter it re*re0ent0 the in*ut 0ignal annthe

0econ 7a6efor re*re0ent0 the 0ignalthe ha0 gone through the oulator+

DSBSC, SSB Demodulation

Diagram !. Moulating an Deoulate Signal0 of DS(SC

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Diagram ". Moulating an Deoulate Signal0 of SS(RC

Diagram ". Moulating an Deoulate Signal0 of SS(SC

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OBSERVATION/CONCLUSION

In the e)*erient conucte, eoulating AM 0ignal0 can 1e one u0ing

6ariou0 techni8ue0 li9e u0ing ioe0, filter0 an the li9e+ %ha0e re0*on0e of the DS(

7a0 al0o o10er6e+ Deoulation of DS( 0ignal0 i0 one 1! ulti*l!ing the DS(-SC

0ignal 7ith the carrier 0ignal+ 'or eoulation, the eoulation o0cillatorB0 fre8uenc!

an *ha0e u0t 1e e)actl! the 0ae a0 oulation o0cillatorB0, other7i0e, i0tortion

an