PROJECT

FM Transmitter as a JAMMER

Shashank 07436 Kr. Rajeev Ranjan 07438 Kiran Manandhar 07456

LINEAR INTEGRATED CIRCUITS

Synopsis for Project

PROJECT

FM TRANSMITTER AS A JAMMER

CERTIFICATE

We hereby certify that the work which has been presented here as a Project Report

entitled “FM Transmitter as JAMMER” in partial fulfilment of the requirements for the

award of B.Tech and submitted to the Department of Electronics and Communication

Engineering of National Institute of Technology, Hamirpur is an authentic record of our own

work carried during the period of September 2009 to November 2009 under the supervision

of our project guide Er. Vinod Kumar (Lecturer ECED).

Shashank (07436)

Kr. Rajeev Ranjan (07438)

Kiran Manandhar (07456)

This is to certify that the above statement made by us is correct to the best of our

knowledge.

Er. Vinod Kumar Sharma Date: 14th November, 2009 Electronics and Comm. Engg. Department

Project guide

PROJECT

FM TRANSMITTER AS A JAMMER

ACKNOWLEDGEMENT

We would like to express our deep sense of gratitude to our project guide, Er. Vinod

Kumar for encouraging us to undertake this project as well as providing all the necessary

guidance and inspirational support throughout this project. We deem it our privilege to have

carried this project under his valuable guidance.

We are also grateful to other faculty members of our department, who has constantly

watched us and helped us in times of need. We are also indebted to our friends for always

being there with all their help and support.

PROJECT

FM TRANSMITTER AS A JAMMER

Contents

Page No:

A. Abstract 1

1. Introduction 2

2. Terminology Used: 3

3. History associated with Jamming:

4. Fm Transmitter as Jammer (Methodology): 3-7

a. Overview:

b. Modulation:

c. Colpitt Oscillator:

d. Signal Generation and Amplification:

e. Buffer:

f. Transmitter:

g. Capture Effect:

5. Circuit Diagram: 7

6. Result: 8

7. Applications: 9-16

8. Appendices

a. TRAI:

b. Data Sheet of LM 358

9. Bibliography: 17

PROJECT

FM TRANSMITTER AS A JAMMER

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.

FM 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. In Frequency Modulation, frequency of

carrier is varied according to the modulating signal.

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. It 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. We are using this principle here to make a Jammer out of the

FM transmitter.

Major application of Jammer includes in 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.

\

Introduction:

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. [1]

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 not

all 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

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.

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

Signal Generation and its amplification.

Buffer stage

FM modulation

Transmission. 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.

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.

TERMINOLOGY USED:

Following is the brief explanation of the various terms used in the abstract of the project.[2]

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. Voltage Controlled Oscillator: 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. Capture Effect: 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: It’s the difference between the maximum and the minimum frequency

component contained in a signal.

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 the president's motorcade through

London.[3,4]

FM Transmitter as Jammer (Methodology):

1. Overview:

We have split the entire project in four different blocks.

Before entering into the minute details of all the above mentioned blocks, here is a brief description

of the theoretical aspect of FM Generation.

BUFFER

FM

MODULATOR

TRANSMITTER

SIGNAL

GENERATION CUM

AMPLIFICATION

2. 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. 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 + ø ).

Then modulated signal

x(t)= V cos ( wct + Ɵ(t) ) where Ɵ(t)= Kf ʃ m(t) dt.

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.

Frequency Modulated Signal

3. Colpitt 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,

OSCILLATOR

fc m(t) x(t)

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 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).

General diagram of colpitt oscillator is given below:

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 modified as

4. Signal Generation and Amplification:

A mike (or mic ) 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

Oscillation Frequency is given by:

where C = Series comination of C1 and C2

Or,

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.

5. 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.

6. 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= α/4; where α is the wavelength of signal.

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

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

Therefore, L = α/4f;

7. 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 + ø(t) ) A2/A1 cos ( wct + ø(t) )

A1 cos ( wct + ø(t) )

A2 cos ( wct + ø(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 + ø(t) ).

CIRCUIT DIAGRAM:

FM 1

FM 2

RECEIVER

RESULT:

Our intention is to block 101.8 MHz signal which is AIR Hamirpur 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.

The circuit maker simulation of the FM transmitter as jammer is shown in the subsequent plot.

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... don’t be serious)

Appendices

(A) TRAI:

(B) Data Sheet of LM 358

Internal Block Diagram

Bibliography:

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.