DSBSC report

Lab Project Report on DOUBLE SIDE BAND SUPPRESSED CARRIER 

Carried out and Submitted in partial fulfillment of the requirement of 

 Analog Communications Lab Class: III B. Tech ECE (A

A.!.: "#$%&"#$' i irst Semester 

By G.S.Archana

Roll No. 12311A!1

D.Ar"na

Roll No.12311A!11

S.Bab# $o"n%&a

Roll No.12311A!12

Na'e o( the )ac"lt# In*char+e, L.-.R L.-.R Cha%tan#a Praa/

Assistant Professor, ECE Dept

Department of  Electronics and Communication Engineering SREENID0I INSIUE O) SCIENCE AND EC0NOLOG An A"tono'o" Int%t"t%on "n/er 4NU05

)ac"lt# S%+nat"re

Content

ABSRAC

Chapter 1

Chapter 2

Chapter 3

Concl"%on Re(erence

Intro/"ct%on 1.1

Objective

1.

Components used and !ec"nical specifications

0ar/6are Decr%pt%on .1

Circuit Diagram

.

Components Description

.#

$or%ing Principle

Project I'ple'entat%on an/ Re"lt #.1

&mplementation Procedure

#.

'esults

ABSRAC, Do"ble*%/eban/ "ppree/*carr%er tran'%%on  (DSB*SC) is transmission in *"ic" fre+uencies produced by amplitude modulation (A) are symmetrically spaced above and belo* t"e carrier fre+uency and t"e carrier level is reduced to t"e lo*est practical level, ideally being completely suppressed. &n t"e D-B-C modulation, unli%e in A, t"e *ave carrier is not transmitted/ t"us, muc" of t"e po*er is distributed bet*een t"e sidebands, *"ic" implies an increase of t"e cover in D-B-C, compared to A, for t"e same po*er used. D-B-C transmission is a special case of doublesideband reduced carrier transmission. &t is used for radio data systems.

D-B-C is basically an amplitude modulation *ave *it"out t"e carrier, t"erefore reducing po*er *aste, giving it a 02 efficiency. !"is is an increase compared to normal A transmission (D-B), *"ic" "as a ma3imum efficiency of ##.###2, since 4# of t"e  po*er is in t"e carrier *"ic" carries no intelligence, and eac" sideband carries t"e same information. -ingle -ide Band (--B) -uppressed Carrier is 12 efficient. !"e C1567 is a monolit"ic transistor array arranged as a balanced modulator demodulator. !"e device ta%es advantage of t"e e3cellent matc"ing +ualities of monolit"ic devices to provide superior carrier and signal rejection. Carrier suppressions of 0dB at 189 are typical *it" no e3ternal balancing net*or%s re+uired.Applications include A and suppressed carrier modulators, A and : demodulators, and p"ase detector 

INRODUCION, OB4ECI-E,

!o design and study t"e *or%ing of DO;B0 dB typical

7OR8ING, odulation $e e3plained t"e t"eory of amplitude modulation above, but *"at sort of circuit is actually used !"e symbol for  amplitude modulation is a multiplier, but actual circuits use t"e nonlinearity of  transistors or diodes,

or s*itc"ing operations. :or e3ample, if a modulating signal is input to a circuit using nonlinear amplification, several "ig"er "armonics are generated in t"e output due to t"e amplification c"aracteristics of t"e circuit. !"is "ig"er "armonic contains a sum (or difference) component of t"e information signal fre+uency and carrier fre+uency, and if a suitable filter is used to eliminate t"e un*anted components, t"e correct amplitude modulation *aveform can be obtained. Demodulation Demodulation (detection) met"ods for amplitude modulation on t"e receiving side include sync"ronous detection and async"ronous detection. -ync"ronous detection demodulates t"e received signal by multiplying it *it" a carrier fre+uency *"ic" "as t"e same fre+uency and p"ase as t"e transmission carrier *ave. Async"ronous detection includes envelope detection and rectification detection. $it" async"ronous detection, t"e information signal m(t) must be incorporated in t"e envelope of t"e receiving *aveform. $it" a modulation factor of 12 or more, demodulation is not possible *it" async"ronous detection, but *it" sync"ronous detection, correct demodulation is  possible. 8o*ever, sync"ronous detection re+uires comple3, costly circuits.

I$PLE$ENAION PROCEDURE,

• • • • •

•

Connect t"e circuit as per circuit diagram. Apply m(t) of fre+uency 089 and amplitude greater t"an .1v Apply c(t) of amplitude 0mv and fre+uency 0F89. Observe t"e output D-B-C *aveform at ?o. Plot t"e *aveforms (Amplitude, fre+uency) of m(t) and s(t) to t"e same time base scale. 'epeat t"e e3periment for under modulation, 12 modulation and over modulation by varying t"e 1% potentiometer.

RESUL,

CONCLUSION, !"e design of DO;B