Synopsis Mini Project

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FM TRANSMITTER AS A JAMMER

A

MINI PROJECT REPORT

Submitted by

Mr. KUMAR ABHISHEK (2009EEC13)

in partial fulfilment for the award of the degree

of

BACHLEOR OF TECHNOLOGY

IN

ELECTRONICS & COMMUNICATION ENGINEERING

At

SCHOOL OF ELECTRONICS AND COMMUNICATIONENGINEERING

SHRI MATA VAISHNO DEVI UNIVERSITY

KATRA

NOVEMBER 2011


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A

MINI PROJECT REPORT

Submitted by

Mr. AMAN KUMAR JHA

(2009EEC20)


of


IN


At

SCHOOL OF ELECTRONICS AND COMMUNICATION

ENGINEERING


KATRA

NOVEMBER 2011


3/27


A

MINI PROJECT REPORT

Submitted by

Mr. MOTI LAL

(2009EEC21)


of


IN


At

SCHOOL OF ELECTRONICS AND COMMUNICATION

ENGINEERING


KATRA

NOVEMBER 2011


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Certificate

This is to certify that the Mini project Report entitled FM TRANSMITTER AS A JAMMER beingsubmitted by AMAN KUMAR JHA (2009EEC20) to the School of Electronics and Communication

Engineering, for the award of Bachelor of Technology Degree in Electronics and Communication, is a

bona-fide work carried out by him under the supervision and guidance of the undersigned.His

Seminar-Report has reached the standard of fulfilling of requirements of the regulations related to

degree.

We wish best for his endeavor.

Asst. Prof. S.B KOTWAL Dr. VIPAN KAKKAR

PROJECT CO-ORDINATOR, SECE Director ,SECE


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Certificate

This is to certify that the Mini project Report entitled FM TRANSMITTER AS A JAMMER being

submitted by MOTI LAL (2009EEC21) to the School of Electronics and Communication Engineering,

for the award of Bachelor of Technology Degree in Electronics and Communication, is a bona-fide

work carried out by him under the supervision and guidance of the undersigned.His Seminar-Report

has reached the standard of fulfilling of requirements of the regulations related to degree.





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Certificate

This is to certify that the Mini project Report entitled FM TRANSMITTER AS A JAMMER being

submitted by SHUBHAM SAKHUJA (2009EEC33) to the School of Electronics and Communication

Engineering, for the award of Bachelor of Technology Degree in Electronics and Communication, is a

bona-fide work carried out by him under the supervision and guidance of the undersigned.His

Seminar-Report has reached the standard of fulfilling of requirements of the regulations related to

degree.





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ABSTRACT

Cell phones and radio receivers are used everywhere these days. It's great to be able to call

anyone anytime. But unfortunately, restaurants, movie theatres, concerts, shopping malls and

churches all suffer from the spread of cell phones because not all cell-phone users know

when to stop talking. While most of us just grumble and move on, some people are actually

going to extremes to retaliate.

Communication Jammer can be one of the solutions to this problem.

A transmitter is a device from which signal is transmitted into free space, after insertion of

suitable carrier, i.e. is superimposed on a high frequency-sine wave. Jamming a signal whose

frequency is known, and which is fixed.Every radio broadcast (AM, FM, or short-wave) has a certain characteristic frequency. Each

radio channel has a different frequency, which can be from around 1 million cycles per

second for AM radio to 100 million cycles per second, for FM. This frequency is determined

by the broadcast transmitter and basically is how many times per second the radio signal

wave oscillates.

When we pick up a radio signal, we "tune" our radio to the frequency of the broadcast

transmitter. The way to jam a radio broadcast is to radiate a signal at that same frequency, but

which is stronger than the one of the broadcast transmitter. Then, since the radio is tuned to

that frequency, we'll pick up the jamming signal rather than the one we were hoping to

receive.

Major application of Jammer includes controlling a hostage situation in which police can

control when and where a captor can make a phone call. Police can block phone calls during

a drug raid so suspects can't communicate outside the area. Cell-phone jammers can be used

in areas where radio transmissions are dangerous, (areas with a potentially explosive

atmosphere), such as chemical storage facilities or grain elevators. Moreover it can be used in

places like Hospitals, restaurants, movie theatres, concerts, shopping malls and churches

where silence is required.


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ACKNOWLEDGEMENTS

I would like to express our deep sense of gratitude to our project guide, Asstt. Prof.

S.B.Kotwal for encouraging us to undertake this project as well as providing all the necessary

guidance and inspirational support throughout this project. I deem it my privilege to have

carried this project under his valuable guidance.

I am also grateful to other members of the ECE department who co-operated with me

regarding some critical issues.

I am also indebted to my friends for always being there with all their help and support.

Last, but not at all the least, i thank God, the almighty for his blessings in the course of this

work.

KUMAR ABHISHEK

2009EEC13


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ACKNOWLEDGEMENTS









work.

AMAN KUMAR JHA

2009EEC20


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ACKNOWLEDGEMENTS









work.

MOTI LAL

2009EEC21


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ACKNOWLEDGEMENTS









work.

SHUBHAM SAKHUJA

2009EEC33


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TABLE OF CONTENTS

CHAPTER NO. TITLE PAGE NO.

ABSTRACT ii

ACKNOWLEDGMENT iii

1. INTRODUCTION

1.1 Jamming : Good or Bad 1

1.2 Terminology Used 2

1.3 History Associated with Jamming 3

2. FM MOULATION AND JAMMING

2.1 Jamming Technique 4

2.2 Blocks in our Project 4

2.3 FM Modulation and Jamming 5

2.3.1 Modulation Technique 5

2.3.2 Colpitts Oscillator 6

2.3.3Signal Generation and Amplification 8

2.3.4 Capture Effect 10

2.3.5 Circuit Diagram 11

2.3.6 Result 11

2.3.7 Application 12

APPENDICES

REFERENCES


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CHAPTER 1: INTRODUCTION

1.1Jamming : Good or Bad

Cell phones are used everywhere these days. According to the Telecom Regulatory Authority

of India (TRAI), almost 300.49 million people were subscribers of Mobile phones at the end

of 2008. This is likely to increase to more than 500 million mobile phone users by 2010

according to a survey conducted by Nokia

It's great to be able to call anyone at anytime. Unfortunately, restaurants, colleges,

Hospitals, shopping malls and churches all suffer from the spread of cell phones because notall cell-phone users know when to stop talking. There comes the need of jamming which is

nothing but blocking the signals.

On one hand, jamming is seen as property theft, because a private company has purchased

the rights to the radio spectrum, and jamming the spectrum is akin to stealing the property

the company has purchased. It also represents a safety hazard because jamming blocks all

calls in the area, not just the annoying ones. Jamming a signal could block the call of a

babysitter frantically trying to contact a parent or someone trying to call for an ambulance.

While on the other hand it is a very handy tool to curb in the theft/emergencies like bomb

tracing (where usually cell phone communication is used) by controlling a hostage situation

in which police can control when and where a captor can make a phone call. Police can block

phone calls during a drug raid so suspects can't communicate outside the area.

It is said that science is a both boon and bane. It all depends upon the person who uses it. So

FM Jammer could also be misused. So there has to be a provision of regular regulation and

monitoring by the government in accordance with very strict guidelines to prevent any

misuse arising from a jammer.

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1.2 Terminology Used

Following is the brief explanation of the various terms used in the abstract of the project.

1. Signal: In the physical world, any quantity measurable through time or over space can be

taken as a signal.

2. Baseband Signal: Baseband signal refers to the message signals (Modulating signal)

which are to be transmitted over long distances using suitable techniques.

3. Carrier: Carrier is a high frequency signal which is used for long distance transmission of

low-frequency message signals.

4. Modulation: Modulation is defined as the superposition of a modulating signal over high

frequency carrier signal so as to change the characteristics of the carrier wave according to

the modulating signal.

5. FM Modulation: In Frequency Modulation, the frequency of carrier is varied by

modulating voltage whose amplitude remains constant.

6. Transmitter: Transmitter as a whole refers to that block which consists of encoder,

modulator and transmitting antennae in which a signal is converted into radio waves.

7. Oscillator: Oscillator is an instrument that generates repetitive alternating current/voltage

waveform of fixed amplitude and frequency without any external input signal.

8. VoltageControlledOscillator: In a Voltage Controlled Oscillator, external input signal

decides the frequency of oscillator. Frequency increase for positive input voltage and

decreases for negative input voltage.

9. Amplifier: Amplifier is a device which boosts the input signal in parameters of either

current or voltage.

10. Buffer: A Buffer is the one that provides the impedance transformation from one circuit

to another.

11. CaptureEffect: The capture effect is defined as the complete suppression of the weaker

signal at the receiver limiter (if it has one) where the weaker signal is not amplified, but

attenuated.

12. Bandwidth: Its the difference between the maximum and the minimum frequency

component contained in a signal.

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1.3 History Associated with Jamming

During World War II ground radio operators would attempt to mislead pilots by false

instructions in their own language, in what was more precisely a spoofing attack than

jamming. Radar jamming is also important to disrupt use of radar used to guide an enemy's

missiles or aircraft. Modern secure communication techniques use such methods as spread

spectrum modulation to resist the deleterious effects of jamming.

Jamming of foreign radio broadcast stations has often been used in wartime (and during

periods of tense international relations) to prevent or deter citizens from listening to

broadcasts from enemy countries. However such jamming is usually of limited effectiveness

because the affected stations usually change frequencies, put on additional frequencies and/or

increase transmission power.

Jamming has also occasionally been used by the Governments of Germany (during WW2),

Israel, Cuba, Iraq, Iran (Iraq and Iran war, 1980-1988), China, North and South Korea and

several Latin American countries, as well as by Ireland against pirate radio stations such as

Radio Nova. The United Kingdom government used two coordinated, separately located

transmitters to jam the offshore radio ship, Radio North Sea International off the coast of

Britain in 1970.

The bombs that blew up commuter trains in Spain in March 2004, as well as blasts in Bali in

October 2002 and Jakarta in August 2003, all relied on cell phones to trigger explosives. It

has been widely reported that a cell-phone jammer thwarted an assassination attempt on

Pakistani President Musharraf in December 2003. When President Bush visited London in

November 2004, it was reported that British police considered using jammers to protect thepresident's motorcade through London.

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CHAPTER 2 : FM MODULATION AND JAMMING

2.1 JAMMING TECHNIQUE

FM Modulated signals are used in the majority of wireless communication uses due to its

superiority in terms of noise rejection and co-channel (or adjacent channel) interference. If

two signals of same frequency (or within some deviation), the signal with the lower

amplitude is attenuated with the factor of the amplitude of that having higher amplitude and

the other remains unaffected. We are using this property to model this Jammer, which is

known as capture effect.

In other words, every radio broadcast (AM, FM, or short-wave) has a certain characteristic

frequency. Each radio channel has a different frequency, which can be from around 1 million

cycles per second for AM radio to 100 million cycles per second, for FM. This frequency is

determined by the broadcast transmitter and basically is how many times per second the radio

signal wave oscillates.

When you pick up a radio signal, you "tune" your radio to the frequency of the broadcast

transmitter. The way to jam a radio broadcast is to radiate a signal at that same frequency, but

which is stronger than the one of the broadcast transmitter. Then, since your radio is tuned to

that frequency, you'll pick up the jamming signal rather than the one you were hoping to

receive.

2.2 BLOCKS IN OUR PROJECT

We have four major blocks in our project which are as follows:-

1. Signal Generation and its amplification.2. Buffer Stage3. FM Modulation4. Transmission.

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With the help of mike (or mic) we shall be converting speech signal to some voltage level

and its amplification is done using OPAMP (LM-358). Then with the help of buffer which is

basically a voltage follower we give this signal to oscillator. Clapped oscillator modifies its

frequency according to incoming signal given, thus modulation of frequency takes place in

this stage. Finally this signal is transmitted through antenna of proper dimensions.

We have split the entire project in four different blocks.

2.3 FM MODULATION AND JAMMING

2.3.1. MODULATION TECHNIQUE

Modulation is defined as the superposition of a modulating signal over high frequencycarrier

signal so as to change the characteristics of the carrier wave according to the modulating

signal. In Frequency Modulation, the frequency of carrier is varied by modulating voltage

whose amplitude remains constant. In other words argument of carrier is varied according to

modulating signal.

Mathematically, let m(t) be the modulating signal and v(t) be the carrier signal such that

m(t) = A cos ( wmt )and

v(t)= V cos ( wct + ).

Then modulated signal

x(t) = V cos ( wct + (t) ) where (t)= Kfm(t) dt.

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Signal

Generation and

Amplification

Buffer FM Modulator Transmitter


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Simply if Wx(t), is the frequency of modulated signal, it varies as

Wx(t) = wc + Kf wm

Oscillator is an instrument that generates repetitive alternating current/voltage waveform of

fixed amplitude and frequency without any external input signal. In a Voltage Controlled

Oscillator, external input signal decides the frequency of oscillator. Frequency increases for

positive input voltage and decreases for negative input voltage. So if modulating signal is

applied to the input of VCO, the output of Oscillator will have a varying frequency signal

which is nothing but the frequency modulated signal.

2.3.2 Colpitts Oscillator

A crystal Oscillator provides constant stable frequency at higher frequencies but we cannot

vary the frequency by applying input bias voltage or simply it cannot act as a VCO. A colpitt

oscillator provides relatively stable frequencies in which the output frequency can be

obtained as a simple function of modulating voltage. A Colpitts oscillator is one of a number

of designs for electronic oscillator circuits using the combination of an inductance (L) with a

capacitor (C) for frequency determination, thus also called LC oscillator. The basic Colpitts

circuit has two capacitors and one inductor to determine the frequency of oscillation. The

feedback needed for oscillation is taken from a voltage divider made by the two capacitors.

As with any oscillator, the amplification of the active component should be marginally larger

than the attenuation of the capacitive voltage divider, to obtain stable operation. Thus, using

the Colpitts oscillator for a variable frequency oscillator VFO is best done by using a variable

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Oscillator fcm(t) x(t)


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inductance for tuning, instead of tuning one of the two capacitors. If tuning by a variable

capacitor is needed, it should be a third one connected in parallel to the inductor (or in series

as in the Clapp oscillator).

Oscillation frequency is given by

where C = Series comination of C1 and C2

Or

Here base of transistor is grounded, that implies the frequency of oscillator is constant. If

some input is applied to this frequency will increase or decrease depending upon the

amplitude of bias applied is positive or negative. Moreover this deviation in frequency is

proportional to the amplitude of bias. Thus if modulating signal is applied to this base, output

of the oscillator will be a frequency modulation signal. Circuit is becomes as shown

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2.3.3. Signal Generation and Amplification:

A microphone is used to generate signal from audio signal. Some other signal generator with

high Bandwidth could be used if we are to cover the maximum of BW of a signal that we

intend to block. This signal is very week so it needs to be amplified. An operational amplifier

has a very high gain which can be used to amplifying such weak signal. We have used here

LM 358 which has a high gain and has internally frequency compensated operational

amplifiers which are designed specifically to operate from a single power supply over a wide

range of voltages. [5]

We are using LM 358 as non-inverting amplifier. Further to reduce the effect of noise and

stabilize the circuit we are using voltage divider circuit at input.

Vout = Vin

Vin

Vout

Buffer:-

Voltage follower is used as buffer here. Voltage follower used here is a simple unity gain amplifier

realised with same LM 358 operational amplifiers. This is used to match the impedance

transformation from one circuit to another.

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1+R2/R1

R2


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Transmitter:-

A transmitter is an electronic device which, usually with the aid of an antenna, propagates an

electromagnetic signal such as radio, television, or other telecommunications.

Generally in communication and information processing, a transmitter is any object (source)

which sends information to an observer (receiver). When used in this more general sense,

vocal chords may also be considered an example of a transmitter. In radio electronics and

broadcasting, a transmitter usually has a power supply, an oscillator, a modulator, and

amplifiers for audio frequency (AF) and radio frequency (RF). The modulator is the device

which piggybacks (or modulates) the signal information onto the carrier frequency, which is

then broadcast.

Size of transmitting antenna should be comparable to that of wavelength of signal.

Mathematically, size of antenna

L= /4; where is the wavelength of signal.

Wavelength of the signal used is related to its frequency f by

= c/f where c is velocity of light in vacuum.

Therefore, L = /4f

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2.3.4 Capture Effect

In telecommunication, the capture effect, or FM capture effect, is a phenomenon associated

with FM reception in which only the stronger of two signals at, or near, the same frequency

will be demodulated. The capture effect is defined as the complete suppression of the weaker

signal at the receiver limiter (if it has one) where the weaker signal is not amplified, but

attenuated. When both signals are nearly equal in strength, or are fading independently, the

receiver may switch from one to the other and exhibit picket fencing. The capture effect can

occur at the signal limiter, or in the demodulation stage, for circuits that do not require a

signal limiter. Some types of radio receiver circuits have a stronger capture effect than others.

The measurement of how well a receiver can reject a second signal on the same frequency is

called the capture ratio for a specific receiver. It is measured as the lowest ratio of the power

of two signals that will result in the suppression of the smaller signal.

A1 cos ( wct + (t) )

A2/A cos ( wct + (t) )

A1 cos ( wct + (t)

A2 cos ( wct + (t) )

If amplitude A1> A2, the signal received at the receiver due to FM2 is attenuated by a factor

of A1. Therefore, signal due to FM2 will be A2/ A1 cos ( wct + (t) ).

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FM 1

FM2

RECEIVER


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2.3.5 Circuit Diagram

2.3.6 Result

Our intention is to block 101.8 MHz signal which is AIR Jammu in vicinity. From circuit

diagram we have C9 =33 pF and L=112 uH

C= 2.22 uF.

Therefore, the value at which Varicap is to be tuned is equal to 33.02 pF which is

approximately equal to 33 pF

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2.3.7 Applications

1. During a hostage situation, police can control when and where a captor can make a phone

call. Police can block phone calls during a drug raid so suspects can't communicate outside

the area.

2. Cell-phone jammers can be used in areas where radio transmissions are dangerous, (areas

with a potentially explosive atmosphere), such as chemical storage facilities or grain

elevators.

3. It can be used in places like Hospitals, restaurants, movie theatres, concerts, shopping

malls and churches where silence is required.

4. Examination Halls, where there are chances of high some fraud, can install this system to

block this radio signal so that no communication can take place from outside. (To stop

Munna Bhai Effect... dont be serious)

APPENDICES

Data Sheet of I C LM 358

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REFERENCES

1. Annual Report 2008, Telecom Regulatory Authority of India (TRAI).

2. Electronic Communication Systems by Kennedy and Davis.

3. www.wikipedia.org

4. www.howstuffworks.com

5. Linear Integrated Circuit by Ramakant A. Gayakward.

6. Signals and systems By B.P. Lathi

7. FM Transmitter (Google Search)

8. Electromagnetic Field Theory by KD Prasad.

9. Circuit Maker Manual.

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