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EC 5Communication Engineering Lab

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

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Course pre-requisites

Good Knowledge in both Analog and Digital

communication techniques.

Knowledge in sampling theorem.

Basic circuit design & building skills.

Matlab programming skills.

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Course Layout

Cycle 1 : Analog Communication (5 experiments)

Cycle 2 : Digital Communication (5 experiments)

Cycle 3 : Software Simulation ( 4 experiments)

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Cycle 1

Exp. 1 : Amplitude Modulation

Exp. 2 : Frequency Modulation

Exp. 3 : Pulse Width Modulation

Exp. 4 : Pulse Position Modulation

Exp. 5 : Pulse Amplitude Modulation & Sampling

Theorem

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Cycle 2

Exp. 6 : Amplitude Shift Keying

Exp. 7 : Frequency Shift Keying

Exp. 8 : Binary Phase Shift Keying

Exp. 9 : Pseudo random Noise Sequence

Exp. 10: Line Coding Techniques

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Cycle 3

Exp. 11 : Simulation of Amplitude Shift Keying

Exp. 12 : Simulation of Frequency Shift Keying

Exp. 13 : Simulation of Binary Phase Shift Keying

Exp. 14 : Simulation of Direct Sequence Spread Spectrum

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Amplitude Modulation

Aim:To modulate a 120 kHz carrier with a 1kHzmessage signal with 60 % modulation indexand successfully demodulate it.

Equipment Required:

Signal generator (2 MHz)2 Nos.

Dual Channel Osilloscope (5 MHz)1 No.

Breadboard1 No. Transistor (BC147)1 No.

Resistors, Capacitors and other components.

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Circuit Diagram (AM Modulator)

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Circuit Diagram (AM Demodulator)

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DesignTransistor Biasing

VCC= 12 V

VB 2 V R1 = 6 * R2

100

Carrier Coupling (HPF) C1*(R1R2)

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Frequency Modulation

Aim: To frequency modulate an 20 kHz career with 2 kHz

message with a frequency deviation of 3 kHz, using

XR2206

Equipment required: Signal generator (2 MHz)1 No.

Dual Channel Oscilloscope (5 MHz)1 No.

Breadboard1 No.

IC - XR2206 - 1No. Resistors, Capacitors and other components

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Circuit Diagram (FM Modulator)

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Design

Carrier Frequency:

Frequency Deviation:

2

1

CRfC

ppmvf )(

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FM Demodulator Circuit

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Measurements & Readings

Input Message Signal:

Frequency & Amplitude

Output FM Signal:

Amplitude (VPP)

fMAX

fMIN

Carrier Frequency:

Frequency Deviation:

2MINMAX

C fff

2

MINMAX fff

Demodulated Signal: Frequency & Amplitude

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Pulse Amplitude Modulation

Aim:

To amplitude modulate a discrete pulse waveform

of 8000 pulse per second with a message signal of 2

kHz and successfully demodulate it.

To vary the frequency of the message signal and

verify the sampling theorem

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Circuit Diagram (Sampling)

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Circuit Diagram ( De-Sampling)

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Design

De-samplingkHz

RCfCO 4

2

1

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Measurements and Reading

fM fS Demodulated

Amplitude

Demodulated

Frequency

2 kHz 8 kHz

3 kHz 8 kHz

4 kHz 8 kHz

5 kHz 8 kHz

6 kHz 8 kHz

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PULSE WIDTH MODULATION

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PULSE POSITION MODULATION

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Pulse width modulation

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Pulse position modulation