ce analog lab

G.H. Raisoni College of Engineering, Nagpur.

Department of Information Technology

ITDC Fifth Semester



ITDC Fifth Semester

List of Experiments

1. To construct the circuit of amplitude modulation on bread board and

observe waveforms.

2. To construct the circuit of frequency modulation on bread board and

observe waveforms.

3. To construct the circuit of amplitude demodulation on bread board &

observe the waveform.

4. To construct the circuit of frequency demodulation on bread board &


5. To construct the circuit of DSBSC on bread board and observe

waveforms.

6.To construct the circuit of Phase Shift Keying on bread board & observe

the waveform.

7.To construct the circuit of Frequency Shift Keying on bread board &


8.To construct the circuit of Pulse Amplitude Modulation on bread board

& observe the waveform.

9.To construct the circuit of Pulse Width Modulation on bread board &


10. To construct the circuit of Pulse Position Modulation on bread board

& observe the waveform.



ITDC Fifth Semester

Experiment No.: - 01

Aim:- To construct the circuit of amplitude modulation on bread board and

observe waveform.

Equipments required:- CRO, CRO probes, Function Generator (2 nos.), Power supply,

Breadboard, connecting wires.

Components:- Transistor: - BC548/549 (1 nos.),Resistor: - 330Ω (2 nos.), Inductor: -

1mH (1 nos.)

Theory:-

In amplitude modulation, the amplitude of the carrier voltage varies in accordance with

the instantaneous value of modulating voltage. Let the modulating voltage be given by

expression,

Vm = Vm cos wmt

Where wm is angular frequency of the signal & Vm is the amplitude. Let the carrier

voltage be given by expression,

Vc = Vc coswct

On Amplitude Modulation, The instantaneous value of modulated carrier voltage is given

by,

V = V(t) cos wct

V(t)=Vc + ka Vm cos wmt

V=Vc[1+ ma cos wm t] cos wct

Where ma is modulation index and the modulation index is defined as the ratio of

maximum amplitude of modulating signal to maximum amplitude of carrier signal.



ITDC Fifth Semester

ma= K Vm / Vc

% modulation is defined as,

%ma=Vm/Vc

Circuit Diagram: -

Procedure: -

1. Assemble components and make connections on the breadboard.

2. Adjust the function generator to obtain the sine wave of frequencies 2 KHz and 1

MHz respectively.

3. Apply the sine wave of modulating signal and carrier signal to the ckt.

4. Observe the resulting amplitude modulated signal on CRO.

5. Calculate Vmax and Vmin from the obtained AM wave and hence calculate

modulation index.

6. Vary amplitude of modulating signal to get overmodulation, 100% modulation

and undermodulation condition.

7. Draw the waveform for overmodulated, 100% modulated, and undermodulated



ITDC Fifth Semester

AM wave on graph paper.

.

Observation Table: -

Table (1):

Sr.No. Voltage signal Frequency Amplitude (Vs )

Modulating signal

Carrier signal

Table (2):

Sr. No. Vmax Vmin Modulation

index

% of

modulation

index

Result: -

When Vm = ……… ma =……….

When Vm = ……… ma =……….

When Vm = ……… ma =……….

Conclusion: - Thus the amplitude-modulated signal is generated and modulation index

for different values of modulating amplitudes is calculated.

Viva Questions: -

1. What are the advantages of AM over FM?

2. What are the advantages of FM over AM?

3. What are the disadvantages of over modulation?



ITDC Fifth Semester

Experiment No.2

Aim: - To construct the circuit of frequency modulation on bread board and

observe waveform.

Equipments Required:- Breadboard ,CRO , function generator, power supply,

CRO probes, connecting wires.

Components:- IC:-XR 3038, Resistors:-100K(2),5.6KΩ,Capacitors :-0.1µf(NO. 2)

Circuit Diagram:-



ITDC Fifth Semester

Theory:-

Frequency modulation consists in varying the frequency of the carrier voltage in

accordance with the instantaneous value of the modulating voltage.Thus the amplitude of

the carrier does not change due to frequency modulation. Let the modulating voltage be

given by expression:

Vm=Vm coswmt.

Where wmis angular frequency of the signal & Vm is the amplitude. Let the carrier

voltage be given by expression,

Vc=Vcsin ( wct+θθθθ)

On frequency modulation, the instantaneous value of modulated carrier voltage is given

by,

Vc=Vcsinφφφφ

Where φ=wct+θ;

ϕ ϕ ϕ ϕ=wct+kfVm1/wmsinwmt+θθθθ1

Hence the frequency modulated carrier voltage is given by,

V=Vcsin[wct+kfVm/wm sinwmt]

The modulation index is defined as the ratio of frequency deviation to frequency of

modulating signal mf=d/fm where deviation f(fmax=fmin)/2.

Procedure:-

1. Study the circuit diagram provided in the manual.

2. Study the pin configuration of IC-XR8038.

3. Adjust the function generator to obtain the sine wave of frequency 1KHZ.

4. Apply the sine wave modulating signal to the circuit.

5. Adjust the amplitude & frequency of modulating signal to get the frequency

modulated output.

6. From the carrier sidebands chart find the highest order sideband corresponding to

obtained modulation index.

7. Change the amplitude of modulating signal & repeat step 5 & 6.

8. Draw the waveform on graph paper.



ITDC Fifth Semester

IC 8038

Observation:-

Table1:-

Sr no. Signal Amplitude Frequency

1 Modulating Signal

2 Carrier Signal



ITDC Fifth Semester

Result:- when Vm=…. then B.W.=

Conclusion:-

Thus by changing the amplitude of modulating signal the amount of

deviation willchange, but it remains constant for any change in modulating

signal frequency. Any slight change in deviation for change in modulating

frequency was due to the change in amplitude of generator output.

Viva Questions:-

1)What is frequency deviation in FM?

2)What are the advantages of FM over AM?



ITDC Fifth Semester

Experiment No: - 3

Aim: - To construct the circuit of amplitude demodulation on bread board &


Equipment Required: - CRO, Probes, Connecting wires.

Components: - Diode OA79 (1 no.), Resistor 10 K (1 no.), capacitor 0.1 µF (1 no.)

Theory: -

Envelope detector is also called as linear diode detector. The envelope

detector operates over linear region of the dynamic current voltage characteristic of the

diode. Envelope detector utilizes the rectification characteristics of a diode. The

modulated carrier voltage is applied to the series combination of diode and the load

impendence consisting of resistor R in shunt with capacitor C. During the positive half

cycle the diode conducts thereby charging the capacitor C to the peak value of the carrier

voltage. During the negative half cycle the diode does not conduct and hence discharges

the capacitor through R. Thus the output voltage is spiky in nature but it almost traces the

envelope of the modulated carrier voltage and hence it is nothing but original modulating

voltage. The departure of this output voltage from the envelope may be reduced by

proper choice of R and C depending upon the modulation frequency and depth of

modulation.

Circuit Diagram: -



ITDC Fifth Semester

Procedure: - (1) Assemble the components on the breadboard as shown in the circuit diagram.

(2) Apply the amplitude modulated signal to the input side.

(3) Observe the output on CRO.

(4) Draw the Amplitude modulated signal and demodulated on graph paper.

Observations: -

AM signal:

Carrier frequency=

Vmax=

Vmin=

Demodulated Signal:

Frequency=

Amplitude=

Result: - The demodulated signal at the output of envelope detector was found to be

equal to the modulating signal.

Viva Questions: -

(1) Why envelope detector is also called as linear diode detector?

(2) How by proper choice of R and C the performance of the envelope detector can

be improved?



ITDC Fifth Semester

Experiment No.4

Aim: - To construct the circuit of frequency demodulation on bread board &


Equipment required:-

IC 565, Function generation ,CRO.

Component required:-

R1=560_NO.),R2=10K_,C1=470Pf,C2=0.001µf,C3=0.1µf,C4

=0.01µf.

Theory:-

The process of FM Demodulation is to exact the original modulating voltage

from the frequency modulated voltage. This detection should be done efficiently and

linearly. Further it is desirable that the detector circuit should be in sensitive to amplitude

changes and should not be too critical in its adjustment and operation. The FM

demodulator performs the detection process in two steps:-1)it converts the frequency

modulated voltage into corresponding amplitude modulated voltage using one or more

tuned circuits .2)it rectifies this amplitude modulated voltage in linear diode demodulator

to extract the original modulation frequency voltage. The FM demodulator may be of the

following types:

i) The slope demodulator.

ii) The balanced slope demodulator.

iii) Phase difference discriminator

iv) Ratio detector

v) Foster seeley discriminator

vi) PLL.

PLL -Phase-locked loop principal has been used in application such as FM modulation

,FM demodulator FSK. The PLL IC 565 is used as FM Demodulator IC and it performs

its demodulation operation.



ITDC Fifth Semester

Circuit diagram:-

Procedure:-

1) The output of FM is forward to the input of demodulator.

2) Set deviation control R1fully clockwise for maximum deviation .Also set the

generation frequency control to be 200HZ.

3) Connect your oscilloscope to pin 7 of the 565 phase locked loop .set the time/cm

control to 2ms/cm and the vertical input to 0.5v/cm.At this point ,you may or may not

have an audio output signal displayed on the oscilloscope. You must adjust the 565

PLL to the correct operating frequency .To do this adjust R2 until you obtain a sine

wave output on the oscilloscope.

4) Using the generation frequency control and R the deviation control, verify that the

output of the phase locked loop is directly proportional to the modulating signal.

Result:-

The demodulated signal was found equal to the modulating signal.

Viva Question:

1. What is Frequency Discriminator?

2. What is the advantage of using PPL for FM Demodulation?



ITDC Fifth Semester

Experiment No.:- 5

Aim: - To construct the circuit of DSBSC on bread board and observe

waveform.

Equipment Required:- Function Generator, CRO, Connecting wires.

Components: - IC 1496 (1 nos.), Resistors: 1KΩ (3 nos.), 100Ω (2 nos.)

Theory: -

The amplitude-modulated signal is simple to produce but has two practical

drawbacks in application to many real communications systems: the bandwidth of the

AM signal is twice that of the modulating signal and most of the power is transmitted in

the carrier, not in the information bearing sidebands. To overcome these problems with

AM, versions on AM have been developed. These other versions of the AM are used in

applications were bandwidth must be conserved or power used more effectively.

If the carrier could somehow be removed or reduced, the transmitted signal would consist

of two information-bearing sidebands, and the total transmitted power would be

information. When the carrier is reduced, this is called as double sideband suppressed

carrier AM or DSB-SC. Instead of two third of the power in the carrier, nearly all being

the available power is used in sidebands.



ITDC Fifth Semester

Procedure: -1. Assemble components and make connections of the breadboard

.2. Adjust the function generator to obtain the sine wave of frequencies 2 KHz and 1

MHz respectively.

3. Apply the sine wave of modulating signal and carrier signal to the ckt.

4. Observe the resulting DSB-SC signal on CRO.

5. Draw the time domain and frequency domain representation of DSB-SC on graph

paper.

Observation Table : -

Sr. No. Signals Frequency Amplitude in Vs

Modulating signal

Carrier signal

Result & Conclusion: - The Balanced modulator IC 1496 can be used for the

generation of DSB-SC signal. The frequency domain representation of DSB-SC signal

shows that DSB-SC signal do not contain the carrier component and it consists of two

symmetrically placed sidebands.

Viva Questions: -

1. What is the bandwidth of the DSB-SC signal?

2. How SSB signal could be generated from DSB-SC signal?

3. What is ring modulator?

4. what is use of DSB-SC ?



ITDC Fifth Semester

Experiment No.:-6

Aim: - To construct the circuit of Phase Shift Keying on bread board & observe

the waveform.

Equipment Required: - PSK kit, Function generator dual channel, CRO, Digital

multimeter, IC1496.

Theory: -

The original source of information, text, speech, the most commonly used

coding scheme is binary sequence such as 0011101011. For transmission purpose this has

to be converted to a continuous electrical waveform, conversion process is referred to as

the modulation .The o/p of the PCM system is also a binary data. If they are to be

transmitted over copper wires, they can be Directly Transmitted as two voltage levels +v

and –v. But if they are to be transmitted through space using antenna, Phase Modulation

is used. As the modulating signal consists of only two levels the modulation technique is

known as Phase Shift Keying. Phase Shift Keying is a modulation in which the phase of

the carrier signal changes with respect to the digital signal. The binary signal to be

transmitted changes the phase of the sine wave carrier depending upon whether 0 or 1 is

transmitted. It is also called as Binary Phase Shift Keying (BPSK).

The BPSK can be implemented by using a Balanced Modulator. IC1496 is used as a

Balanced Modulator for implementing BPSK. The circuit diagram is shown in the

manual. The carrier is applied to pin no.8 and Modulating Binary signal is applied to pin

no.1 The BPSK O/P is taken from pin no. 12.IC 1496 internally consists of differential

amplifier configuration .its carrier suppression is rated at a minimum of –5db with a

typical value of –65db at



ITDC Fifth Semester

500khz.

Procedure: -

1) Study the circuit provided on the front panel of kit.

2) Apply the sine wave of 400Hz to pin no. 8.

3) Apply the square wave i.e. non linear binary data minimum 200Hz pin no.1

4) Connect CRO at the o/p i.e. pin no. 12.

5) Switch ON the power supply.

6) Observe the PSK O/P on the CRO.

7) Draw the observed waveform on the graph paper.



ITDC Fifth Semester


Result: -

The carrier signal changes phase as Binary signal changes its state from logic 0

to logic 1.

Viva Questions:-

1. What is the advantage of PSK over FSK?

2. What is the difference between PSK, FSK and ASK?



ITDC Fifth Semester

Experiment No.:-7

Aim:- To construct the circuit of Frequency Shift Keying on bread board &


Requirements:- Breadboard , CRO dual channel, function generator, power supply,

CRO probes, connecting wires.

Components:- IC:-XR2206, Resistors:-22K,1K(2),100K(2),220ΩCapacitors-1µf,10µf

Theory:-

Frequency shift keying is the digital system of frequency modulation .Digital

signal generated in system like telegraphy is not transmitted as it is instead

they are transmitted using keying techniques .In FSK the nominal

unmodulated carrier frequency .Corresponding to mark condition and space

condition is transmitted for logic level 1 and logic level 0

respectively.

Procedure:-



ITDC Fifth Semester

1. Assemble components and make connection on breadboard as shown in fig.

2. Get it checked before turn on the power supply .

3. Apply square wave input.

4. Observe the waveform on CRO & note down mark & space frequencies.

Observation:-

The standard mark frequency f(mark)= 1/R1C3

Space frequency f(space)= 1/R2C3

Observe I/P square wave

Frequency=

Amplitude =

Observe O/P sine wave

Mark frequency=

Space frequency=

Result:-

Mark frequency is ……. And Space frequency is ……

Conclusion: -

Mark frequency is greater than space frequency. FSK system is used for

digital data transmission.

Viva question:-

1) What is FSK?

2) What are mark and space frequencies?

3) Which component in the circuit governs the mark and space frequencies?



ITDC Fifth Semester

Experiment No.8

Aim: - To construct the circuit of Pulse Amplitude Modulation on bread board &


Equipment required:-

PAM kit, dual channel CRO, signal generator.

Component required:-

R1=39K, R2=18K, R3=R4=10K,R5=10K pot

C1=0.01µf,C2=0.01µf,C3=1µf,IC1=555,IC2=4016 CMOS

switch.

Theory:-

In pulse modulation some characteristics of pulse (carrier) is change in

accordance with the sample of the modulating signal .Such type of modulation is called

as Pulse Modulation. It is applied in many types .But some of common types are Pulse

Amplitude modulation (PAM) ,Pulse width modulation (PWM),and Pulse position

modulation (PPM).If the characteristics of pulse such as amplitude ,duration(width),

position is change in accordance with the modulating signal than it is called as

PAM,PDM or PWM and PPM respectively. Pulse Amplitude Modulation the amplitude

of the pulse is varied in accordance with the modulating signal then it is called as pulse

Amplitude modulation .Its waveform is shown in fig 1.PAM gives dual polarity (AC

type) PAM output called as natural PAM sampling .But If DC level is introduced to the

modulating signal then it results single polarity PAM.



ITDC Fifth Semester

Procedure:-

1. Assemble components and make connection on breadboard as shown in fig.

2. Switch on the power supply and note the amplitude and frequency of sample

pulse internally generated by IC555 connect the same at pin 13 of CMOS IC

by using patch cord.

3. Apply a sine wave modulating signal of around 5-VPp, 70 Hz at the point marked

as I/P 4.Connect dual Channel CRO for at i/p and o/p side.

4. Adjust the amplitude and frequency of modulating i/p to get Dual polarity PAM

output.

5. Note DC voltage V2 given potential divider R3 and R4 now introduced DC

voltage V2 by shorting points A and B by patching repeat. In the above step keep

CRO in DC mode.

6. Vary the input frequency and amplitude of the modulating signal and observe the

corresponding change in PAM output.



ITDC Fifth Semester

Conclusion:- As the amplitude of sampling pulse is changed in accordance with the

modulating signal so it is called as pulse amplitude modulation (PAM). By introducing

DC voltage it gives single polarity PAM output.

Viva Questions:-

1. What is the difference between single polarity and dual polarity PAM signal?

2. How single polarity PAM signal is generated from dual polarity PAM?



ITDC Fifth Semester

Experiment No.:-9

Aim: - To construct the circuit of Pulse Width Modulation on bread board &


Equipment Required: - Pulse width modulator, pulse width demodulator, CRO,

Patch cords.

Components: - R1=560_, R2=1K, R3=100_, R4=1K+1M pot, R5=2.7K, R6=10K,

Q1=Q2=BC 148, C1=C2=0.1µF, C3=C4=0.22µF.

Theory: -

In PWM, the width of the pulses of the carrier pulse train is varied in

accordance with the modulating signal. The pulse width demodulator circuit can be

formed by using transistorized circuit with OP-AMP low pass filter. A PWM i/p signal is

applied to the base of Q1 and demodulated o/p is obtained from OP-AMP o/p. The

transistor Q1 works as a inverter. Hence during the time interval when the PWM is high,

the input to the transistor Q2 is low. Therefore, during this time interval the transistor Q2

is cut-off and the capacitor C1 gets charged through resistor R4. During the time interval

when the PWM i/p is low the input to the transistor Q2 is high and it gets saturated. The

capacitor C1then discharges very rapidly through Q2. The collector voltage of Q2 during

this interval is then low. Thus the waveform at the collector of Q2 is more or less a saw-

tooth waveform whose envelope is same as the modulating signal. This signal is then

passes through OP-AMP low pass filter to smooth the shape of envelope and finally it

gives o/p whose envelope is nearly equals to the modulating i/p signal.



ITDC Fifth Semester

Procedure: -

1. Study the circuit provided in the manual switch on the power supply.

2. Apply a PWM i/p to the base of the transistor Q1.

3. Connect one channel of CRO to observe modulating signal and other to

demodulated o/p.

4. First verify and note the PWM i/p signal.

5. Adjust the amplitude and frequency to obtain the demodulated o/p whose

envelope is nearly equals to the modulating signal.

6. Vary the amplitude and frequency of modulating i/p and observe the

corresponding change in demodulated o/p.

Result: - The envelope of the sawtooth waveform can be set equals to the modulating

signal hence through OP-AMP IC 741 low pass filter we obtained

demodulated o/p equals the modulating signal the circuit can be used for pulse

width demodulator.

Viva Questions:-

1) What is PWM ?

2) What is function of summing amplifier ?



ITDC Fifth Semester

Experiment No.10

Aim: - To construct the circuit of Pulse Position Modulation on bread board &


Equipment Required: - Breadboard, CRO, Signal generator, CRO probes,

connecting wires.

Components: - IC 555 (1 no.), Resistors:- 18K (2 no), 10k (1 no), 1K (2 no.),

Capacitors- 0.1µF (2 no.), 10 µF (1 no.).

Theory:-

Pulse Position Modulation (PPM) is the type of pulse modulation in which

the amplitude and width of the pulse is kept constant but the position of each pulse in

relation to the position of a recurrent reference pulse is varied by each instantaneous

sampled value of the modulating wave. PPM has the advantage over PWM of requiring

constant transmitter power output but has the disadvantage of dependence on transmitter

receiver synchronization.

PPM may be obtained from PWM. In PWM each pulse has a leading edge and a trailing

edge but the location of the leading edges are fixed whereas those of trailing edges are

not but are dependent on the pulse width, which in turn is dependent on the signal value

at that instant. Thus, we may state that the trailing edges of PWM pulses are position

modulated. Thus PPM may be obtained from PWM by simply getting ride of the leading

edges and flat tops of PWM pulses.

Circuit Diagram: -



ITDC Fifth Semester

Procedure: -

1. Study the circuit diagram and the pin configuration of IC 555.

2. Assemble the components on the breadboard to build the circuit of PPM as given

in circuit diagram.

3. Apply sine wave modulating signal to pin number 5 of IC 555 and observe the

same signal on CRO and note down its amplitude and frequency.

4. Observe the PPM signal on CRO.

5. Simulate the circuit to generate PPM in microcap.

6. Draw the modulating signal and PPM signal on graph paper.


Sr.No. Signal Amplitude Frequency

Result:-

PPM signal is generated using IC 555 and observed on CRO. The same circuit

is simulated in microcap. Both PPM waveforms were compared and were

found same.

Conclusion:-

PPM signal can be generated by first generating PWM by using

differentiator and diode clipper.

Viva Questions: -

1) What is the advantage of PPM over PWM?

2) What is the difference between pulse modulation and CW modulation?

ce analog lab

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