analog-communications-lab manual and viva

8/13/2019 Analog-Communications-Lab Manual and VIVA

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Analog Communications Lab

INDEX

Signature of Lab-In-charge HOD

INSTRUCTIONS TO STUDENTS

Turbomachinery Institute Science & Technology 1 Dept. ofECE

S.No Name of the Experimentage

No

Date of

erformance

Date Of

Submission

Assessment

of mar!s

"#ax $%#&

Sign. Of

'acult(

1.Amplitude Modulation &

Demodulation

2. Diode Detector Characteristics

.!re"uency Modulation &

Demodulation

#. $alanced Modulator

%. re'(mphasis & De'emphasis

). Mi*er Characteristics

+. Digital hase Detector

,. hase -oced -oop

/. Synchronous Detector

10 AC Characteristics

11 !re"uency Synthesier

12. S"uelch Circuit

A)erage mar!s


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Students shall read the points given below for understanding the theoretical concepts and Practical applications.

1. Listen carefully to the lecture given by teacher about importance of subject, curriculum philosophy, Learning

structure, skills to be developed, information about equipment, instruments, procedure, method of continuous

assessment, tentative plan of work in Laboratory and total amount of work to be done in a semester.

2. Students shall undergo study visit of the laboratory for types of equipment, instruments and material to be

used, before performing experiments.

3. Read the write up of each experiment to be performed, a day in advance.

4. Organize the work in the group and make a record of all observations.

5. Understand the purpose of experiment and its practical implications.

6. Student should not hesitate to ask any difficulty faced during conduct of practical / exercise.

7. Student shall develop maintenance skills as expected by the industries.

,. Student should develop the habit of pocket discussion / group discussion related to the experiments/

exercises so that exchanges of knowledge / skills could take place.

9. Student should develop habit to submit the practical, exercise continuously and progressively on the

scheduled dates and should get the assessment done.

10. Student shall attempt to develop related hands - on - skills and gain confidence.

11. Student shall focus on development of skills rather than theoretical or codified knowledge.

12. Student shall visit the nearby workshops, workstation, industries, laboratories, technical exhibitions trade fair

etc. even not included in the Lab Manual. In short, students should have exposure to the area of work right in the

student hood.

13. Student shall develop the habit of evolving more ideas, innovations, skills etc. those included in the scope of

the manual.

14. Student shall refer to technical magazines, proceedings of the Seminars, refer websites related to the scope

of the subjects and update their knowledge and skills.

15. The student shall study all the questions given in the laboratory manual and practice to write the answers to

these questions.

Turbomachinery Institute Science & Technology 2 Dept. ofECE


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Exp No* $ Date*

A#LI+,DE #OD,LA+ION DE#OD,LA+ION

AI#* To study the function of Amplitude Modulation & Demodulation 3under modulation4 perfect

modulation & o5er modulation6 and also to calculate the modulation inde*.

AAA+,S E/,IED*

S. No. Component Specification /uantit(

1 Transistor $C10+ 2

2 7esistors

10089 2

#.+89 2

2+0 9 1

9 1

Capacitors#.+:! 2

0.001:! 1# Diode 0A+/ 1

% !unctions enerator 1Mh 2

) 7egulated o;er Supply 30'06< 1

+ $read $oard 1

, Cathode 7ay =scilloscope 0'20M> 1

/ Connecting ?ires Single Strand As 7e"uired

+HEO0*

Modulator sectionillustrates the circuit of modulating amplifier employing a transistor as an acti5e de5ice

in C( mode. 71& 72establish a "uiescent for;ard bias for the transistor. The modulating signal fed at the

emitter section causes the bias to increase or decrease in accordance ;ith the modulating signal. Cis bypass

capacitor for carrier. Thus the carrier signal applied at the base gets amplified more ;hen the amplitude of

the modulating signal is at its ma*imum and less ;hen the amplitude of the modulating signal is small. C2

couples the modulated signal to output of the modulator. Demodulationin5ol5es t;o operations.

i6 7ectification of the modulated signal and

ii6 (limination of 7! components of the rectified signal.

The diode in the circuit diagram of demodulator does half ;a5e rectification. The rectified signal is applied

to a lo; pass filter to e*tract the modulating signal.

CIC,I+ DIA1A#*


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71 7

C2

=utput

C1 $ C -1100 >

7! Input $C 10+

72 (

7# C

A! Input

Demo2ulator*

D1

AM Input A! =utput

=A +/ 18

1n!

E3EC+ED 4A5E'O#S*-

OCED,E*

1. Made the connections according to Circuit Diagram.

2. Measure and note do;n the fre"uency & amplitude 3p'p6 of the fi*ed carrier signal.

Turbomachinery Institute Science & Technology # Dept. ofECE


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. Measure and note do;n the fre"uency & amplitude 3p'p6 of the fi*ed message signal.

#. Apply fi*ed fre"uency carrier signal to 7! input terminals.

%. Apply modulating signal to A! input terminals.

). ote do;n and trace the modulated signal en5elope on the C7= screen.

+. !ind the modulation inde* by measuring


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/,ES+IONS

Turbomachinery Institute Science & Technology ) Dept. ofECE

m


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1. AM is Defined as EEEEEEEEEEEE

2. Dra; its spectrumEEEEEEEEEEE

. Dra; the phase representation of an amplitude modulated ;a5eEEE

#. Modulation inde* is defined asEEEEE

%. The different degrees of modulation EEEEEEE

). ?hat are the limitations of s"uare la; modulator

+. Compare linear and nonlinear modulators

,. Compare base modulation and emitter modulation

/. AM Demodulator is EEEEEEEEEEE

10. Detection process EEEEEEEEE

11. The different types of distortions that occur in an en5elop detector areEEEEEEEEEE

12. (limination of distortions in (n5elope Detector EEEEEEEEEEEEEEEEEE techni"ue ;e use.

Turbomachinery Institute Science & Technology + Dept. ofECE


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Turbomachinery Institute Science & Technology , Dept. ofECE


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Turbomachinery Institute Science & Technology / Dept. ofECE


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Turbomachinery Institute Science & Technology 10 Dept. of

ECE


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Exp No* 6 Date*

DIODE DE+EC+O CHAAC+EIS+ICS

AI#* To perform demodulation of an amplitude modulated signal using

3i6 Simple diode detector and 3ii6 ractical diode detector

AAA+,S E/,IED*


1 Transistor $C10+ 2

2 7esistors

10089 2

#.+89 2

2+0 9 1

9 1

Capacitors

#.+:! 2

0.001:! 1

1

/ otentiometer 1008 9 1

10 Connecting ?ires Single Strand As 7e"uired

+HEO0* Demodulation in5ol5es t;o operationsF

3i6 7ectification of the modulated ;a5e and

3ii6 (limination of 7! components of the rectified modulated ;a5e

Simple Dio2e Detector

The diode is the most common de5ice used in AM demodulator. Signal 3AM modulated signal6 is

applied to anode and output is taen from cathode. Diode operates as half ;a5e rectifier and passes only

positi5e half cycle of the modulated ;a5 e. !urther signal is applied to a parallel combination of resistor

37d6 and capacitor 3Cd6 ;hich acts as a lo; pass filter. This -! allo;s only lo; fre"uency signal to output

and it by passes 7! component to the ground.

This simple diode detector has the disad5antage that the output 5oltage4 in addition to being

proportional to the modulating signal4 also has a dc component4 ;hich represents the a5erage en5elope

amplitude 3i.e. carrier signal6 and a small 7! ripple. >o;e5er these un;anted components are remo5ed in a

practical detector lea5ing only A! signal.

CIC,I+ DIA1A#*


ECE


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E3EC+ED 4A5E'O#S*-

AM Modulated signal

ractical Dio2e Detector*


ECE


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In practical diode detector the cathode terminal of the diode is connected to one end of the secondary

of I! transformer. The other end is grounded. Secondary is tuned ;ith the capacitor C1. The capacitors C2

and C are used for 7! filtering.

The modulated signal is applied at the input of I! transformer. The 5oltage applied is negati5e and

hence the cathode of the diode passes is connected to the I! transformer. So the diode passes both the

positi5e and negati5e half cycles. The 7! filtering is done by C2and C. The output is taen at the 5olume

control.

OCED,E*-

1. Connect the circuit as per the circuit diagram and s;itch on the po;er supply. 3 Measure the

po;er supply 5oltage4 12< and '12 fre"uency.. o; connect the modulator output to the simple diode detector input.

#. =bser5e the A! signal at the output to the simple diode detector at appro*imately %0G

modulation using C7=.

%. Compare it ;ith the original A! and obser5e that the detected signal is same as the A! signal

applied. Thus no information is lost in the process of modulation. 3oteF =nly ;a5e shape and

fre"uency ;ill be same4 amplitude ;ill be attenuated and phase may change6

). To obser5e AM ;a5e at different fre"uencies4 connect A! signal from e*ternal signal generator

to the input of modulator and obser5e demodulated ;a5e at different fre"uencies.

+. 7epeat the e*periment using practical diode detector circuit.

ECA,+IONS*

ES,L+*


ECE


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A! output

/,ES+IONS

Turbomachinery Institute Science & Technology 1# Dept. of

ECE


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1. Selecti5ity of recei5er is defined as EEEEEEEEEEEEE

2. Sensiti5ity of a recei5er is defined as EEEEEEEEEEEE

2. The purpose of diode in diode detector circuit is EEEEEEEEEE

. The disad5antages of simple diode detector circuit are EEEEEEE

#. The factors influencing the choice of intermediate fre"uency in recei5ers EEEEE

%. The ad5antages of practical diode detector areEEEEEEEE

Turbomachinery Institute Science & Technology 1% Dept. of

ECE


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Turbomachinery Institute Science & Technology 1) Dept. of

ECE


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Turbomachinery Institute Science & Technology 1+ Dept. of

ECE


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Turbomachinery Institute Science & Technology 1, Dept. of

ECE


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Exp No* 7 Date*

'E/,ENC0 #OD,LA+ION AND DE#OD,LA+ION

AI#*To study the functioning of fre"uency modulation & demodulation and to calculate the modulation

inde*.

AAA+,S E/,IED


1 ICs H7 220)4 -M %)% 1 (ach

2 7esistors

100894 #.+89 2 (ach

1089 1

2209 1

#+89 1

Capacitors

0.01:!40.001:! 2

0. 1:!4 #+0p!4 0.01p! 1

1:!410:! 1# !unctions enerator 1Mh 2

% 7egulated o;er Supply 30'126< 1

) $read $oard 1

+ Cathode 7ay =scilloscope 0'20M> 1

, Connecting ?ires Single Strand As 7e"uired

+HEO0*

1. A! eneratorF

This is an op'amp placed ;ein bridge oscillator. A !(T input "uad =p'Amp 3ICT-0,#6 is used here

to generate lo; fre"uency signals of %00 > and %8> to use as modulating signal. In this

e*periment4 a s;itch is pro5ided to change the fre"uency. 7e"uired amplification is pro5ided to

a5oid loading effect.

2. 7egulated po;er supplyF

This consists of bridge rectifier4 capacitor filters and three terminal regulators to pro5ide re"uired dc

5oltages in the circuit i.e. 1%


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#.+ 10 !B)5

1008 #+8 8

A! IB! !M =B

108

0.1

!

220

0.01 !

1 !B)5

're8uenc( Demo2ulation Circuit Diagram*

%5

108 108!

0.1 !A! Input

),0 18!

A! =utput

),0 #+0!

% !re"uency to use

as carrier signal in this e*periment. AdJustments for Amplitude and !re"uency are pro5ided in panel for

ease of operation.

2. AF Generator:

-o; !re"uency signal of appro*imately %8> is generated using ='AM based ?ein' $ridge oscillator.

IC T- 0,# is used as an acti5e component T- 0,# is !(T input general purpose "uad ='AM integrated

circuit. =ne of the ='AM has been used as amplifier to impro5e signal le5el. !acility is pro5ided to

change output 5oltage.

3. Regulated Power Supply:

This consists of bridge rectifier4 capacitor filters and three terminal regulators to pro5ide re"uired DC

5oltage in the circuit i.e. 1254 ',5 1%0 MA each.

CIC,I+ DIA1A#*

Turbomachinery Institute Science & Technology 2, Dept. of

ECE


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4. Modulator:

Turbomachinery Institute Science & Technology 2/ Dept. of

ECE


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The IC MC 1#/) is used as Modulator in this e*periment. MC 1#/) is a monolithic integrated circuit

balanced modulatorBDemodulator4 is 5ersatile and can be used up to 200 Mh. MultiplierF A balanced

modulator is essentially a multiplier. The output of the MC 1#/) balanced modulator is proportional to the

product of the t;o input signals. If you apply the same sinusoidal signal to both inputs of a ballooned

modulator4 the output ;ill be the s"uare of the input signal AM'DS$BSCF If you use t;o sinusoidal signals

;ith deferent fre"uencies at the t;o inputs of a balanced modulator 3multiplier6 you can produce AMDS$B

SC modulation. This is generally accomplished using a high' fre"uency NcarrierO sinusoid and a lo;er

fre"uency NmodulationO ;a5eform 3such as an audio signal from microphone6. The figure 1.1 is a plot of a

DS$'SC ;a5eform4 this figure is the graph of a 1008> and a % 8> sinusoid multiplied together. !igure

1.2 sho;s the circuit that you ;ill use for this e*periment using MC 1#/) balanced modulatorBdemodulator.

Note: In re!uen"y dou#l$ng I t%e $nput t$&e per$od $' ()* ater re!uen"y dou#l$ng t%e t$&e per$od '%ould

#e %aled.$.e+*),2*.

OCED,E*-

I-Fre!uen"y ou#ler

1. Connect the circuit as per the gi5en circuit diagram.

2. S;itch on the po;er to the trainer it.

. Apply a % 8> signal to both 7! and A! inputs of 0.1


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ECE


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ECE


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ES,L+*

/,ES+IONS

1. The t;o ;ays of generating DS$ESC are EEEEEEEE

2. The applications of balanced modulator are EEEEEEEE

. The ad5antages of suppressing the carrier EEEEEEEE

#. The ad5antages of balanced modulator EEEEEEEEEE

%. The ad5antages of 7ing modulator EEEEEEEEEE

). The e*pression for the output 5oltage of a balanced modulator is EEEEEEEEE

Turbomachinery Institute Science & Technology Dept. of

ECE


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Turbomachinery Institute Science & Technology % Dept. of

ECE


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Turbomachinery Institute Science & Technology ) Dept. of

ECE


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Exp No* ; Date*

E-E#HASIS DE-E#HASIS

AI#* To study the functioning of re'(mphasis and De'(mphasis circuits.

AAA+,S E/,IED*


1 7esistors 189 2

2 Capacitors0.1:! 2

0.001:! 1

!unctions enerator 1Mh 2

# 7egulated o;er Supply 30'06< 1

% $read $oard 1

) Cathode 7ay =scilloscope 0'20M> 1

+ Connecting ?ires Single Strand As 7e"uired

+HEO0*

!re"uency modulation is much immune to noise than amplitude modulation and significantly more

immune than phase modulation. A single noise fre"uency ;ill affect the output of the recei5er only if it falls

;ith in its pass band.

The noise has a greater effect on the higher modulating fre"uencies than on lo;er ones. Thus4 if the

higher fre"uencies ;ere artificially boosted at the transmitter and correspondingly cut at the recei5er4

impro5ement in noise immunity could be e*pected. This booting of the higher fre"uencies4 in accordance

;ith a pre'arranged cur5e4 is termed pre'emphasis4 and the compensation at the recei5er is called de'

emphasis. If the t;o modulating signals ha5e the same initial amplitude4 and one of them is pre'emphasied

to 3say6 t;ice this amplitude4 ;hereas the other is unaffected 3being at a much lo;er fre"uency6 then the

recei5er ;ill naturally ha5e to de'emphasie the first signal by a factor of 24 to ensure that both signals ha5e

the same amplitude in the output of the recei5er. $efore demodulation4 i.e. ;hile susceptible to noise

interference the emphasied signal had t;ice the de5iation it ;ould ha5e had ;ithout pre'emphasis4 and ;as

thus more immune to noise. Alternati5ely4 it is seen that ;hen this signal is de'emphasied any noise

sideband 5oltages are de'emphasied ;ith it4 and therefore ha5e a correspondingly lo;er amplitude than

they ;ould ha5e had ;ithout emphasis again their effect on the output is reduced. The amount of pre'

emphasis in P.S !M broadcasting4 and in the sound transmissions accompanying tele5ision4 has been

standardied at +% microseconds4 ;hereas a number of other ser5ices4 notably CCI7 and Australian T

analog-communications-lab manual and viva

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