communication system (fm) report 2

7/30/2019 Communication system (FM) report 2

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[EP301.DTK5B] September 13, 2012

COMMUNICATION FUNDAMENTAL SYSTEM Page 1

ELECTRICAL ENGINEERING DEPARTMENT

COMMUNICATIONFUNDAMENTALSYSTEM

[EP301]

1. Chong Wei Ting (18DTK10F1036)

2. Zainal Obaidly bin Zainal Abidin (18DTK10F1013)

3. Adlan Bin Abdullah (18DTK10F1034)

4. Mohd Fadzil Bin Mat Arshad (18DTK10F1033)

DTK 5B

Submit date: 13st

September 2012

LAB INSTRUCTOR: MR. NOR AZRIZAL BIN NORAZMI


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LAB 2 : FREQUENCY MODULATOR

Objective:

By the end of this lab, students should be able to:

1) Analyze the relationship between the changes of frequency deviation and the

waveform pattern.

2) Understand the wave pattern for FM.

Equipments:

1. Lab sheet.

2. Digital Synthesized function generator/counter/Arbitrary waveform generator.3. Oscilloscope.

Frequency modulation is the process of varying the frequency of a carrier wave in proportion

to a modulating signal. The amplitude of the carrier remains constant. Figure below

illustrates the signal associated with frequency modulation. Notice how the FM waveform

has both higher and lower frequencies than the carrier frequency and the centre frequency.

INTRODUCTION

FM Modulator

Information/intelligence

signal

Modulating process

Oscillator provides

Carrier signal

Frequency Modulation

signal


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Carrier frequency (fc)

As in AM systems, the carrier frequency in FM systems must be higher than the information signal

frequency for the same reasons.

FM radio Uses carrier frequency between 88 and 108 Mhz

Television Frequency range = 54 806 Mhz

No of Channel = 67channel

Bandwidth = 6 Mhz

VHF 54 -216 Mhz (channel 2- channel 13)

UHF 470 -806 Mhz (Channel 14 channel 69)

608 614Mhz (radio astronomy)

GUIDLINEINTHEEXPERIMENT

Frequency maximum and minimum in FM wave pattern:

Fcs, Carrier swing represents the total change of the frequency from min frequency

to the max frequency.

Frequency maximum

Frequency minimum


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EQUIPMENTSPREPARATION

1. Oscilloscope had been switched ON and calibrated it.

2. After calibration, the equipments had been connected as shown in figure

below.

INPUTSETTING

1. The digital synthesized function generator/Counter/Arbitrary waveform

generator had been set following of the instruction below.

1.1) The power had been switched ON.

1.2) The button of FM had been pressed.

1.3) The button of frequency had been pressed, and then set the carrier

frequency to 1MHz.

1.4) The button of amplitude had been pressed, and then set carrier

amplitude to 2V.

1.5) The button of Shift had been pressed, and then pressed the Sine key.

1.6) The button of MENU had been pressed and then screen would been

displayed:

a. FM DEVIA (Peak frequency deviation)Set FM deviation to 50KHz.

b. FM FREQ (FM frequency)Set FM freq to 5KHz.

c. FM WAVE(FM waveform)press [2] ,[N] (set waveform as square)

d. FM SOURCE (The modulating signal is from internal or external.)INT

2. At display on the oscilloscope record the FM waveform.

3. Repeat the step (1.6) of (a) and (2) for frequency deviations involving 100KHz,

150KHz, 200KHz, and 250KHz.

PROCEDURE

OscilloscopeDigital Synthesized Function Generator /

Counter/Arbitrary Waveform Generator

Input Output


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RESULTS FOR FM


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DISCUSSION

In the experiment of the lab 2 in topic of frequency modulation, we did some

study to determine and observes the output signal wave of frequency modulatedwaveform pattern. At the beginning of the experiment, we prepared two main

equipments involving digital synthesized function generator and oscilloscope. That

the generator act as input that generated information and carrier signal that setting

by frequency deviation and the oscilloscope act as output to display the frequency

waveform generated by the function generator.

Understanding the one of example for FM waveform pattern that show on

below:

The frequency of the waves (how often crests and troughs occur per second)

on the communication medium is modified to represent 0 or 1.


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CONCLUSION

At the end of the laboratory work, we should be able to identify the waveform

pattern for FM after that we achieve the result from display oscilloscope. Besides

that, we also able to understand the wave pattern for frequency modulation after we

analyzed the relationship between the changes of frequency deviation and the

waveform pattern.

As our view for the result of this experiment, we observed the value of

frequency deviation is direct proportional with the value of frequency maximum and

inverting proportional to frequency of minimum, that frequency deviation

represents the amount of change in carrier frequency produced by the modulatingsignal.

At the end of the conclusion, we would be thanking a lot to our lecturer Mr.

Azrizal given most of instruction since we would do it in our LAB EP301.

communication system (fm) report 2

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