MOBILE PHONE SNIFFER: APPLICATION IN SILENCE ZONE AREA
WAN NURUL NAJMIAH BINTI WAN MAMAT
UNIVERSITI TEKNOLOGI MALAYSIA
2011
PSZ 19:16 (Pind. 1/07)
UNIVERSITI TEKNOLOGI MALAYSIA
DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
Author’s full name : WAN
________________________________________________
NURUL NAJMIAH BINTI WAN MAMAT
Date of birth
: 17
________________________________________________
FEBRUARY 1989
Title
PHONE SNIFFER: APPLICATION IN SILENCE
: MOBILE
________________________________________________
________________________________________________
ZONE AREA
________________________________________________
Academic Session : 2010/2011
________________________________________________
I declare that this thesis is classified as :
√
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Date : 13 MAY 2011
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DR. YUSRI BIN MD. YUNOS
NAME OF SUPERVISOR
Date : 13 MAY 2011
If the thesis is CONFIDENTAL or RESTRICTED, please attach with the letter from
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“I hereby declare that I have read this thesis and in my opinion this thesis is
sufficient in terms of scope and quality for the award of the degree of
Bachelor of Engineering (Electrical – Telecommunication)”
Signature
: ..........................................
Supervisor
: Dr. Yusri bin Md. Yunos
Date
: May 13, 2011
MOBILE PHONE SNIFFER: APPLICATION IN SILENCE ZONE AREA
WAN NURUL NAJMIAH BINTI WAN MAMAT
A Thesis Submitted in Fulfilment of the Requirements
for the Award of the Degree of
Bachelor of Engineering (Electrical - Telecommunication)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
MAY 2011
ii
I declare that this thesis entitled “Mobile Phone Sniffer: Application in Silence Zone
Area” is the result of my own research except as cited in the references.
Signature
: ...............................
Name
: Wan Nurul Najmiah binti Wan Mamat
Date
: May 13, 2011
iii
Special dedicated,
To my beloved family
Thanks for your morale support and understanding
To my lovely friends
Thank you for all your help
May Allah bless all of your kindness
iv
ACKNOWLEDGEMENT
In The Name of Allah, Most Gracious, Most Merciful
Thanks to Allah the All Mighty, All Sovereign and All Supreme for giving
me good health to undergo this project.
I would like to take this opportunity to express my deep gratitude and
appreciation to those people who have helped me to complete my Final Year Project
course, and to individuals to whom I am very much indebted and who, without their
support, this achievement would not have been possible. First of all, special thanks to
my supervisor, Dr Yusri bin Md. Yunos for his great guidance, advice and
encouragement. My greatest appreciations and thanks are dedicated to my parents
from whom I have taken the lesson of life and always pray for my success. I am very
proud of them.
Also, many thanks to my friends with whom I have shared so much fun and
so many good times over the past few years in my campus life especially my
roommate, Nor Aswani Mamat and my fyp-mate Nur Afifah Ahmad Shukri for their
suggestion and help to excellence in all aspect of my project. Although I cannot
mention them all by name, I am grateful to all of them and wish them all the best.
Finally, special thanks to all the members of my family for the warmth and kindness
they always offer, thank you very much.
v
ABSTRACT
Nowadays, the use of mobile phones is becoming a-must-have-list to all
people and not a requirement anymore. People from different age gap such as
students, housewives and government or private worker need to have mobile phones
to use to communicate with each other. While this usage become wider and bigger,
many of the mobile phone‟s users tend to forgot to switch their phones in certain area
that forbid the usage of mobile phones such as lecture halls, examination rooms,
meeting rooms and mosque. While having an important examination or meeting,
somebody needs to make sure that nobody leaks the information to the outside. So,
the idea of this project is to detect the presence of mobile phones in this particular
area so that the users of the phones will have to switch off their phones and make
sure that nobody is using hand phones nearby. By using the principles of radio
frequency and wireless communication, a system is develop and any mobile phones
activities nearby the system will be detected and it will alert the users to switch off
their mobiles phones.
vi
ABSTRAK
Saat ini, penggunaan telefon menjadi keperluan untuk semua orang dan
bukan lagi mengikut kehendak peribadi masing-masing. Tidak kira sama ada dalam
usia yang berbeza seperti mahasiswa, suri rumah tangga dan pekerja kerajaan atau
swasta, mereka semua perlu memiliki telefon yang digunakan untuk berkomunikasi
antara satu sama lain. Apabila penggunaan ini menjadi lebih luas, ramai pengguna
telefon cenderung lupa untuk mamatikan telefon mereka di kawasan – kawasan
tertentu yang melarang penggunaan telefon seperti bilik kuliah, bilik peperiksaan,
bilik mesyuarat dan masjid. Ketika menduduki peperiksaan atau menghadiri
mesyuarat penting, seseorang perlu memastikan bahawa tidak ada kebocoran
maklumat penting ke luar. Jadi, idea dari projek ini adalah untuk mengesan
kewujudan telefon dalam kawasan seperti ini dan pengguna telefon akan di minta
untuk mematikan telefon mereka dan pastikan bahawa tidak ada yang menggunakan
telefon bimbit di situ. Dengan menggunakan prinsip-prinsip frekuensi radio dan
komunikasi wayarles, sebuah sistem direka dan setiap kegiatan telefon di situ akan
dikesan dan akan meminta penggunanya untuk mematikan telefon mereka.
vii
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF ABBREVIATIONS
xiii
LIST OF APPENDICES
xv
1 INTRODUCTION
1
1.1
Project Background
2
1.2
Objectives
3
1.3
Problem Statement
3
1.4
Scope of Project
3
1.5
Outline of Thesis
4
1.6
Summary of Project
4
viii
2 LITERATURE REVIEW
5
2.1
Introduction
5
2.2
History of Communication System
6
2.2.1 Types of Communication System
6
2.2.2 Block Diagram of Communication
System
2.3
8
Mobile Phones
9
2.3.1 Features of Mobile Phones
2.4
9
Radio Frequency (RF) Signal
11
2.4.1 Application of RF signal
3 RESEARCH METHODOLOGY
12
14
3.1
Project Overview
14
3.2
Research Methodology
15
3.3
Project Implementation
17
3.3.1 Demo Circuit
17
3.3.2 List of Components
18
3.3.3 Schematic Diagram or System Design
Circuit
23
3.3.4 Detecting Process
4 RESULT AND DISCUSSION
25
27
4.1
Introduction
27
4.2
Effects of the Number of Mobile Phones
28
4.3
Effect of Distance between Mobile Phones and
RF Detector
4.4
4.5
29
Effect of Different Activity of Mobile Phones to
the RF Detector Circuit
30
Limitation of the Design
31
ix
5 CONCLUSION
5.1
Conclusion
5.2
Suggestion and Recommendation for Future
Work
32
32
33
REFERENCES
34
APPENDICES
36
x
LIST OF TABLES
TABLE NO.
2.1
TITLE
PAGE
Chronology of Electronic Communication
Technology Development
6
2.2
Frequency Band
13
2.3
Frequency Band and its Applications
13
3.1
Resistor Part List
19
4.1
Differences between Numbers of Mobile Phones
Against Beep Speed Rate
4.2
Differences between Distance and Number of
Beep Speed Rate
4.3
28
29
Effect of Different Type of Mobile Phone Activities to
the Number of Beep Speed Rate
30
xi
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
1.1
Flow Chart of the Design Implementation
4
2.1
Basic Block Diagram of Communication System
8
2.2
The Front and Back of the Circuit Board
11
3.1
Illustration of RF Signal Detector Working System
14
3.2
Methodology Flow Chart
16
3.3
Demo Circuit
17
3.4
RF Signal Detector
18
3.5
Various Type of Capacitors
19
3.6
Electrolytic of Capacitors
20
3.7
CA3130 Operational Amplifiers
21
3.8
Pin Connections of CA3130
21
3.9
TO-92 Outlined of Transistors
22
3.10
Internal Block Diagram of 555 Timers
22
xii
3.11
Piezo Buzzer
23
3.12
Various Type of LED
23
3.13
RF Signal Detector Schematic Circuit
24
3.14
Illustration of Mobile Phone Detector
26
xiii
LIST OF ABBREVIATIONS
ADC
-
Analog to digital converter
AM
-
Amplitude Modulation
dB
-
decibel
DC
-
Direct current
DIP
-
Dual in-line packages
DSP
-
Digital signal processing
EHF
-
Extremely high frequency
ELF
-
Extremely low frequency
FM
-
Frequency Modulation
GHz
-
Gigahertz
GSM
-
Global System for Mobile Communications
HF
-
High frequency
Hz
-
Hertz
IC
-
Integrated Circuits
IR
-
Infrared
kHz
-
kilohertz
LCD
-
Liquid Crystal Display
LF
-
Low frequency
LS
-
Loudspeaker
mA
-
Miliampere
MCMC
-
Malaysian Communications and Multimedia Commission
MF
-
Middle frequency
Op Amp
-
Operational Amplifier
xiv
PCB
-
Printed Circuit Board
PDA
-
Personal Digital Assistant
RF
-
Radio Frequency
ROM
-
Read-only memory
SHF
-
Super high frequency
SID
-
Sound Interface Device
SMS
-
Short messaging system
UV
-
Ultraviolet
TV
-
Television
UHF
-
Ultra high frequency
VCO
-
Voltage-controlled Oscillator
VF
-
Voice frequency
VHF
-
Very high frequency
VLF
-
Very low frequency
WLAN
-
Wireless Local Area Network
xv
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
CA3130 Operational Amplifier
36
B
NE555 Timer
41
C
BC548 Transistor
46
CHAPTER 1
INTRODUCTION
Mobile phones nowadays are major technologies that have been supported by
many peoples. The usage of mobile phones doesn‟t only for business materials but
also for personal use. Because of these, we can see many people including students
in high school already having a mobile phone with them. With instants access from
it, users can send short messages and make a call to others which make the mobile
phones is a must need technology nowadays. This phenomenon also supported by
growth of numerous telecommunication companies such as Maxis, Celcom, Digi, Umobile and others.
With the increasing users and subscribers for this Telco companies, many of
the subscribers tend to forgot to silence their hand phones in the restricted areas such
as mosque, meeting rooms, library and others. This phenomenon tends to become a
habit and it can disturb the other people who want to be in silence environment.
The idea of this project is to create a system that can detect the active signal
from a mobile phone and alert the user to not use their phones in those particular
areas.
2
1.1
Project Background
With a growing technology of mobile phones, people will always carry these
devices to anywhere and everywhere at anytime because they need to be updated the
news time to time. However, mobile phones tend to cause interruptions because of its
noise coming from the ringtone or the message tone that have been set by the users.
Some places such as prayer halls, library and meeting rooms, the use of hand phones
is strictly forbidden because of they need these areas to be in silent for the people‟s
here can perform their activities in peace.
Mobile phones need to transmit and receive the RF signal in order to operate.
This means there are possibility of jamming (make the system become stuck or inoperable) these RF signals in mobile phone restricted area. However, jamming
communication signal is illegal in many countries, even when confined to privatelyowned spaces or secure facilities. Shielding might be used to block RF signals from
the area of interest. However, is expensive and requires maintenance. It is also not
allowing the user to use their phone in term of emergency case.
So, the best way is that by designing this circuit, any active signal from the
mobile phones will be detected and will alert the users to not use their phones in
these particular areas.
3
1.2
Objectives
The main objective of this project is to design a sensor that can be used to
detect mobile phones which in active mode which are used to make incoming or
outgoing calls or send SMS. This system can be used to alerts the users to not use
their phones when they in these silences zone area.
1.3
Problem Statement
i. Detect phone so that to remind the prayers/crowd to switch off or silent
mode their phone.
ii. Interruption of wireless mobile phone in public area such
- Mosque
- On board airplane
- Bank etc
1.4
Scope of Project
The project scopes are:
1. To investigate basic electronic components involve in RF circuit design
2. To design, testing and simulate analogue RF signal detector circuit
4
1.5
Outline of Thesis
This thesis consists of five chapters. Chapter 1 in this thesis will present some
introduction to mobile phones and define the objective and the scope of the project.
Chapter 2 present some review on RF signal and its use in mobile phones and its
application. Chapter 3 discusses about the methodology and approach for the
hardware part including sensing part. Chapter 4 shows how the measurement is done
and some analysis on the result. Lastly, Chapter 5 discusses the conclusion from and
some suggestion for future works.
1.6
Summary of Project
The implementation of this project can be summarized as follows:
Design the signal conditioning
circuit
Design the hardware of the system
Test the design
Analysis the result
Figure 1.1: Flow chart of the design implementation
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction
This chapter contains a brief overview of mobile phone features, fundamental
study of communication principles as well as the basic theory of radio frequency
(RF) signal including frequency and electromagnetic spectrum, and electronic
components involved in the construction of the analogue RF signal detector, such as
antennas, operational amplifier and 555 timers.
2.2
History of Communication System
Communication is a process where the data or signal been send from one
point to another point. The first information conveyed showed by the history is by
direct method through people‟s conversation. After realizing that distance has
6
become the barrier, peoples start using smoke, letters or noise as a medium to send
the signal. When the era changes and people start to globalize, the technologies also
start to grow to become more updated and make the users easier to use it. The new
era of electronic communication also been trigged as time move on. The electronic
communication system that has been created is a telegraph, telephone, fax, radio,
satellite and mobile phone. The brief history of communication system can be seen
as follows:
Table 2.1: Chronology of Electronic Communication Technology Development
Year
Event
1844
Samuel Morse invented telegraph
1876
Alexander Graham Bell invented telephone
1904
Radio communication system was invented
1923-1938
1936
Television was invented
FM radio
1938-1945
Radar and microwave system was invented for World War II
1962
Beginning of the satellite communication system
1972
Creation of a mobile phone by Motorola
1988-1989
2.2.1
Optical communications and Internet
Types of Communication Systems
There are many types of communication systems such as optical
communication, radio communication, power line communication and duplex
communication.
i) Optical communication system
This communication system involved with light that is used as the
medium of transmission. Optical communications consists of a
7
transmitter, which encodes a message into an optical signal, a channel,
which carries the signal to its destination, and a receiver, which
reproduces the message from the received optical signal. Fibre-optic
communication systems transmit information from one place to another
by sending light through an optical fibre. The light forms an
electromagnetic carrier wave that is modulated to carry information.
ii) Radio communication system
A radio communication system is a communication sends using radio.
Types of radio communication systems depend on technology, standards,
regulations, radio spectrum allocation, user requirements, service
positioning, and investment. The radio equipment involved in
communication systems includes a transmitter and a receiver, each having
an antenna and appropriate terminal equipment such as a microphone at
the transmitter and a loudspeaker at the receiver in the case of a voicecommunication system.
iii) Power line communication system
Power line communications systems operate by impressing a modulated
carrier signal on the wiring system. Different types of powerline
communications use different frequency bands, depending on the signal
transmission characteristics of the power wiring used. Since the power
wiring system was originally intended for transmission of AC power, the
power wire circuits have only a limited ability to carry higher frequencies.
The propagation problem is a limiting factor for each type of power line
communications.
iv) Duplex communication
A system composed of two connected parties or devices which can
communicate with one another in both directions. The term duplex is used
when describing communication between more than two parties or
8
devices. Duplex systems are employed in nearly all communications
networks, either to allow for a communication "two-way street" between
two connected parties or to provide a "reverse path" for the monitoring
and remote adjustment of equipment in the field.
2.2.2
Block Diagram of Communication Systems
The block diagram for communication systems is basically consisting of
transmitter, receiver, transmission medium (channel) and noise which can be seen as
follows:
Transmitter
Channel
Receiver
Noise
Figure 2.1: Basic block of communication systems
Transmitter
Function to process the signal information to be transmission signal. This signal
generated will be tailored to the characteristics of transmission medium used. Also
used to filter and strengthen the signal.
Transmission medium (channel)
Connecting the transmitter and the receiver that enable the modulated signal
propagate through the medium
Receiver
As inverse of the process that occurs at the transmitter block, the receiver work to
recover the original signal. In this project, this part/process plays an important role
9
where it concept is used as foundation/ basis of the idea for designing RF detector
circuit. This topic will be discussed further in the next section.
2.3
Mobile Phones
Before proceeding to the RF detector circuit concept, it is better to understand
the concept of mobile phones and its overview and how it is related to the principle
of radio frequency concept.
2.3.1
Features of Mobile Phones
The key components of a mobile phone include:

Antenna

RF switch

Power amplifier (PA)

Low-noise amplifier (LNA)

Mixer

Voltage-controlled oscillator (VCO)

Filter (bandpass, low-pass)

Converter (ADC, DAC)

Digital base band processor
10
Antenna
An antenna (or aerial) is an electrical device which couples radio waves in free space
and converts it to electrical current to use by a radio receiver or transmitter. The
antenna intercepts some of the power of an electromagnetic wave at the reception in
order to produce a tiny voltage that the radio receiver can amplify. Alternatively, a
radio transmitter will produce a large radio frequency current that may be applied to
the terminals of the same antenna in order to convert it into an electromagnetic wave
(radio wave) radiated into free space. Antennas are thus essential to the operation of
all radio equipment, both transmitters and receivers. They are used in systems such
as radio and television broadcasting, two-way radio, wireless LAN, mobile
telephony, radar, and satellite communications.
Power Amplifier
An RF power amplifier is a type of electronic amplifier used to convert a low-power
radio-frequency signal into a larger signal of significant power, normally for driving
the antenna of a transmitter. It is usually optimized to have high efficiency, high
output power (P1dB) compression, good return loss on the input and output, good
gain, and optimum heat dissipation.
Voltage-controlled oscillator (VCO)
A voltage-controlled oscillator or VCO is an electronic oscillator designed to be
controlled in oscillation frequency by a voltage input. The frequency of oscillation is
varied by the applied DC voltage, while modulating signals may also be fed into the
VCO to cause frequency modulation (FM) or phase modulation (PM); a VCO with
digital pulse output may similarly have its repetition rate (FSK, PSK) or pulse width
modulated (PWM).
11
Figure 2.2: The front and the back of the circuit board
Figure 2.2 shows the PCB of mobile phone with several computer chips
attached on the board. The analogue-to-digital and digital-to-analogue conversion
chips translate the outgoing audio signal from analogue to digital and the incoming
signal from digital back to analogue. The digital signal processor (DSP) is a highly
customized processor designed to perform signal-manipulation calculations at high
speed.
The microprocessor handles all of the housekeeping chores for the keyboard
and display, deals with command and control signalling with the base station and
also coordinates the rest of the functions on the board.
2.4
Radio Frequency (RF) Signal
Radio frequency is a term that refers to alternating current (AC) having
characteristics such that, if the current is input to an antenna, an electromagnetic
12
(EM) field is generated suitable for wireless broadcasting and/or communications.
These frequencies cover a significant portion of the electromagnetic radiation
spectrum, extending from nine kilohertz (9 kHz),the lowest allocated wireless
communications frequency (it's within the range of human hearing), to thousands of
gigahertz (GHz) [11].
When an RF current is supplied to an antenna, it gives rise to an
electromagnetic field that propagates through space. This field is sometimes called
an RF field; in less technical jargon it is a "radio wave." Any RF field has a
wavelength that is inversely proportional to the frequency. In the atmosphere or in
outer space, if f is the frequency in megahertz and λ is the wavelength in meters,
then;
λ = 300/f
(1)
The frequency of an RF signal is inversely proportional to the wavelength of
the EM field to which it corresponds. At 9 kHz, the free-space wavelength is
approximately 33 kilometres (km). At the highest radio frequencies, the EM
wavelengths measure approximately one millimetre (1 mm). As the frequency is
increased beyond that of the RF spectrum, EM energy takes the form of infrared
(IR), visible, ultraviolet (UV), X rays, and gamma rays.
2.4.1
Application of RF signal
Many types of wireless devices make use of RF fields. Cordless and cellular
telephone, radio and television broadcast stations, satellite communications systems,
and two-way radio services all operate in the RF spectrum. Some wireless devices
operate at IR or visible-light frequencies, whose electromagnetic wavelengths are
shorter than those of RF fields. Examples include most television-set remote-control
13
boxes, some cordless computer keyboards and mice, and a few wireless hi-fi stereo
headsets.
The RF spectrum is divided into several ranges, or bands. With the exception
of the lowest-frequency segment, each band represents an increase of frequency
corresponding to an order of magnitude (power of 10). The table depicts the eight
bands in the RF spectrum, showing frequency and bandwidth ranges. The SHF and
EHF bands are often referred to as the microwave spectrum.
Table 2.2: Frequency band
Designation
Frequencies
Free-space wavelength
Very Low Frequency (VLF)
9 kHz – 30 kHz
33 km – 10 km
Low Frequency (LF)
30 kHz – 300 kHz
10 km – 1 km
Medium Frequency (MF)
300 kHz – 3 MHz
1 km – 100 m
High Frequency (HF)
3 MHz – 30 MHz
100 m – 10 m
Very High Frequency (VHF)
30 MHz – 300 MHz
10 m – 1 m
Ultra High Frequency (UHF)
300 MHz – 3 GHz
1 m – 100 mm
Super High Frequency (SHF)
3 GHz – 30 GHz
100 mm – 10 mm
Extremely High Frequency
30 GHz – 300 GHz
10 mm – 1 mm
(EHF)
Table 2.3: Frequency band and its application
Application
Frequency Band
TV (channel 2-6)
54 - 166 MHz
TV (channel 7-13)
174 - 216 MHz
Mobile Phone
806 – 901 MHz
Bluetooth
2.4 – 2.48 GHz
802.11a WLAN
5.15 – 5.85 GHz
CHAPTER 3
RESEARCH METHODOLOGY
3.1
Project Overview
This project is mainly about the designation of a RF detector sensor
that will sense the presence of mobile phones in the particular areas. The illustration
of the system can be represented as follows:
Signal received
Signal received
RF
detector
Send data
Host
Signal received
Send message to user
Figure 3.1: Illustration of RF signal detector working system
15
3.2
Research Methodology
Based on the illustration before, to achieve the design specification, a
thorough research must be done and in order to achieve the objectives, the following
protocol had been set up.
 Do a literature review about mobile phones, RF signal, wireless
communication and others
 List and find out the suitable components for circuit design
 Components selection
 Design the RF detector circuit
 Test the circuit to check whether can work properly or not
 Result and analysis
16
START
Do a literature review about mobile phones, RF signal,
wireless communication and others
List and find out the suitable components for circuit design
Components selection
Design the RF detector circuit
Test the circuit
whether function
properly or not
YES
Result analysis
END
Figure 3.2: Methodology Flow Chart
NO
17
3.3
Project Implementation
This section will further discuss the project design of the RF signal
detector circuit. But before that, let first discuss about the demo circuit of this
project.
3.3.1
Demo Circuit
R1 1M
IC 3130
C1 0.22
LED
R2 100K
R3 1M
C2 47 UF
Figure 3.3: Demo circuit
IC1 is designed as a differential amplifier. Non-inverting input is connected
to the potential divider R1, R2. Capacitor C2 keeps the non-inverting input signal
stable for easy swing to positive or negative while R3 is the feedback resistor.
IC1 functions as a current to voltage converter, since it converts the tiny
current released by the 0.22 capacitor as output voltage.
At power on output go high and LED lights for a short period. This is because
positive input gets more voltage than the negative input. After a few seconds, output
goes low because the output current passes to the negative input through R2.
18
Meanwhile, capacitor C1 also charges. So that both the inputs gets almost equal
voltage and the output remains low. 0.22μF capacitor (no other capacitor can be
substituted) remains fully charged in the standby state.
When the high frequency radiation from the mobile phone is sensed by the
circuit, 0.22μF capacitor discharges its stored current to the positive input of IC1 and
its output goes high momentarily. (In the standby state, output of the differential
amplifier is low since both inputs get equal voltage of 0.5 volts or more). Any
increase in voltage at positive input will change the output state to high.
Figure 3.4: RF signal detector
Technical Specifications – Characteristics
Supply Voltage: 9V (DC)
Detection range: GSM (860-965MHz)
Indication: Buzzer and LED
19
3.3.2
List of components
a) Resistor
Table 3.1: Resistor part list
Resistor
Value
R1
2.2 MΩ
R2
100 kΩ
R3
2.2 MΩ
R4
1 kΩ
R5
12 kΩ
R6
15 kΩ
b) Capacitor
Figure 3.5: Various type of capacitors
Ceramic capacitor
C1 – 22 pF
C2 – 22 pF
C3 – 0.22 μF
C5 – 47 pF
C6 – 0.1 μF
C7 – 0.1 μF
C8 – 0.01 μF
20
Electrolytic capacitor
Figure 3.6: Electrolytic capacitor
C4 – 100 μF/ 16V
C9 – 4.7 μF/ 16V
c) Operational Amplifiers ICs
The CA3130 is a 15MHz BiMOS operational amplifier with
MOSFET input/CMOS output. This operational amplifier is combination
of both CMOS and bipolar transistor. Gate-protected P-channel MOSFET
(PMOS) transistor is used in the input circuit to provide very high input
impedance, very low input current and exceptional speed performance.
The use of PMOS transistors in the input stage results in common
mode input-voltage capability down to 0.5V below the negative-supply
terminal, an important attribute in single-supply applications. A CMOS
transistor-pair, capable of swinging the output voltage to within 10mV of
either supply-voltage terminal (at very high values of load impedance), is
employed as the output circuit.
The CA3130 Series circuits operate at supply voltages ranging
from 5V to 16V, (±2.5V to ±8V). They can be phase compensated with a
single external capacitor, and have terminals for adjustment of offset
voltage for applications requiring offset-null capability. Terminal
provisions are also made to permit strobing of the output stage.
21
Figure 3.7: CA3130 Operational Amplifier
Figure 3.8: Pin Connections of CA3130
Application for this IC:
i) Ground-Referenced Single Supply Amplifiers
ii) Fast Sample-Hold Amplifiers
iii) Long-Duration Timers/Monostables
iv) High-Input-Impedance Comparators (Ideal Interface with Digital
CMOS)
v) High-Input-Impedance Wideband Amplifiers
vi) Voltage Followers (e.g. Follower for Single-Supply D/A Converter)
d) Transistor
22
T1- BC548
Figure 3.9: TO-92 outlined of transistor
This transistor is actually NPN General Purpose Amplifier. This device is
designed for use as general purpose amplifiers and switches requiring
collector current to 300mA.
e) 555 Timers
Figure 3.10: Internal block diagram of 555 timers
This NE555 is highly stable controller capable of producing accurate
pulses. With a monostable operation, the time delay is controlled by one
external resistor and one capacitor. With an astable operation, the
frequency and duty cycle is accurately controlled by two external resistor
and one external capacitor.
f) Antenna
23
Wire type – detection area until 1.5m
Alternative – telescopic antenna radio type, detection area until 20m
g) Piezo-buzzer
This used as the indication of the mobile phone detection. It will sound
according to the signal of mobile phones.
Figure 3.11: Piezo buzzer
h) Light Emitting Diode (LED)
Also used as indication, can use any colour such as red, green or yellow.
Figure 3.12: Various type of LED
i) On-off switch
For convenience of the user when doesn‟t want to use the detector.
3.3.3
Schematic Diagram or System circuit Diagram
24
Figure 3.13: RF signal detector schematic circuit
This detector circuit detects an RF signal ranging from 860 MHz until 965
MHz which is previously had been discussed in the chapter before which is in GSM
band. When a mobile phone been detected, the buzzer will sound and the LED will
blinking and this will alert the other people that someone at the particular area had
using their mobile phones.
Mobile Bug
Normally IC1 is off so IC2 will be also off. When the power is switched on,
as stated above, IC1 will give a high output and T1 conducts to trigger LED and
Buzzer .This can be a good indication for the working of the circuit.
Circuit Description
An ordinary RF detector using tuned LC circuits is not suitable for detecting
signals in the GHz frequency band used in mobile phones. The transmission
frequency of mobile phones ranges from 0.9 to 3 GHz with a wavelength of 3.3 to 10
cm. So a circuit detecting gigahertz signals is required for a mobile bug. Here the
circuit uses a 0.22μF disk capacitor (C3) to capture the RF signals from the mobile
25
phone. The lead length of the capacitor is fixed as 18 mm with a spacing of 8 mm
between the leads to get the desired frequency. The disk capacitor along with the
leads acts as a small gigahertz loop antenna to collect the RF signals from the mobile
phone.
Op-amp IC CA3130 (IC1) is used in the circuit as a current-to-voltage
converter with capacitor C3 connected between its inverting and non-inverting
inputs. It is a CMOS version using gate-protected p-channel MOSFET transistors in
the input to provide very high input impedance, very low input current and very high
speed of performance. The output CMOS transistor is capable of swinging the output
voltage to within 10 mV of either supply voltage terminal.
Capacitor C3 in conjunction with the lead inductance acts as a transmission
line that intercepts the signals from the mobile phone. This capacitor creates a field,
stores energy and transfers the stored energy in the form of minute current to the
inputs of IC1. This will upset the balanced input of IC1 and convert the current into
the corresponding output voltage. Capacitor C4 along with high-value resistor R1
keeps the non-inverting input stable for easy swing of the output to high state.
Resistor R2 provides the discharge path for capacitor C4. Feedback resistor R3
makes the inverting input high when the output becomes high. Capacitor C5 (47pF)
is connected across „strobe‟ (pin 0 and „null‟ inputs (pin 1) of IC1 for phase
compensation and gain control to optimise the frequency response.
When the mobile phone signal is detected by C3, the output of IC1 becomes
high and low alternately according to the frequency of the signal as indicated by
LED1. This triggers monostable timer IC2 through capacitor C7. Capacitor C6
maintains the base bias of transistor T1 for fast switching action. The low-value
timing components R6 and C9 produce very short time delay to avoid audio
nuisance.
3.3.4
Detecting Process
26
Firstly, the detector is placed in the middle of the particular areas which are
library, mosque, meeting rooms and others. Then, the switch must be turn on and the
antenna must be outside of the box. Within 1.5 meter, if there are active mobile
phones that are making a call, receive calls or sending SMS, the RF detector circuit
will sense it and the buzzer will sound continuously with the blinking of LED. The
indications will only ceases when no other active signal from nearby.
Figure 3.14: Illustration of mobile phone detector
CHAPTER 4
RESULTS AND DISCUSSIONS
4.1
Introduction
Several experiments had been conducted/ performed to assure that this device
can be used in the future.
i)
To identify the effects of difference number of mobile phones used in
the particular areas to the beep speed rate of the RF detector
ii)
To investigate the effect of the distance between phones and the
detector beep speed rate
iii)
To determine the difference of beep speed rate between the usage of
mobile phone when making or receiving a call and sending message
or SMS
28
4.2
Effects of the number of mobile phones
Table 4.1: Difference between numbers of mobile phones against beep speed rate
No. of phones
No. of beeps sound per minute
Beep speed rate (beep/sec)
0
-
-
1
116
1.9333
3
118
1.9667
5
120
2.0
Table 4.1 above shows that the effect of having different number of mobile
phones with the beep speed rate. This experiment was conducted using oscilloscope
and the signal shown on the oscilloscope indicate that the number of beep and will be
divided by 60 to get the number of beep speed rate which is in beep per second. In
this experiment, all the mobile phones were located at 5cm radius from the detector
circuit. Although having difference number of mobile phones, but the beep speed
rate are almost the same. From the table above, it shows that when there are three
mobile phones, the beep sounds as much as 118 within a minute while only having
difference with 118 for five mobile phones detected. This shows that having
difference number of mobile phones in the detection areas doesn‟t affect much the
beep speed rate.
Thus, from this experiment, it can be concluded that the number of beep
speed rate is almost the same for difference number of mobile phones. So, this means
that the rate of detector beep speed does not depend on the number of mobile phones,
which indicate that this circuit only sense the frequency of mobile phones not the
phone itself. From this result, it can say that the objective of this project has been
achieved, but the scope could not be proceed further because the RF detector circuit
cannot be used to detect the number of mobile phones used.
29
Thus, more dynamic and stable circuits required in order to detect the number
of mobile phones in those particular areas.
4.3
Effect of distance between mobile phones and RF detector
Table 4.2: Difference between distance and number of beep speed rate
Distance (radius)
No. of beeps per minute
Beep speed rate (beep/sec)
5 cm
116
1.9333
0.5 m
92
1.5333
1m
47
0.7833
1.5 m
18
0.3
Second experiment was conducted to find the effect of difference distance
(between the mobile phone and the detector) to the number of beep speed rate. The
table above shows that the data taken when the experiment been conducted. For
distance of 5 cm, the number of beeps per minute is 116 which give the beep speed
rate is 1.9333 beep/sec, while for 1.5 m, the number of beeps per minute is 92, at 1 m
the number of beep speed rate is 0.7833 beep/sec and lastly at 1.5 m, the number of
beeps per minute is 18 and gives 0.3 beep/sec.
From this finding, it is shown that, as the distance increases, the signal
detected by the RF signal sensor will decreases as maybe there are some blocking
between the mobile phones and the detector. Thus it can be concluded by saying that
the number of beeps per minute is inversely proportional to the distance. This beep
30
speed rate is depending on the distance between the mobile phone and the detector.
The closer the distance between the sensor and the mobile phones, the faster the
buzzer will be buzzing and the LED blinking.
4.4
Effect of different activity of mobile phones to the RF detector circuit
Table 4.3: Effect of different type of mobile phone activities to the number of beep
speed rate
Activity
No. of beeps per minute
Beep speed rate (beep/sec)
SMS
16
0.2667
Receive/Making calls
118
1.9667
From the table above, the data were collected when the user using the mobile
phone to sending a message or making a call or receiving a call. As we can see
above, there are huge differences of beep speed rate between these two activities.
When sending a message, the beep speed rate is 0.2667 beep /sec while when making
or receiving a call, the number of beep speed rate is 1.9667 beep /sec.
This huge difference is because when a user sending a message, it only take
less than a minute to make a successful transaction which is mean the number of
beep detected also is lower than while making a call or receiving a call. Thus, it can
be concluded that the number of beep speed rate also depends on the type of
activities the user is doing.
31
4.5
Limitation of the design
The prototype design has only limited range of 1.5 meters. But if a
preamplifier stage using JFET or MOSFET transistor is used as an interface between
the capacitor and IC and the range can be increased.
CHAPTER 5
CONCLUSION
This chapter will further discuss the conclusion for this project and future
works for the design. Some recommendation also will be provided to improve the
design for the next future works.
5.1
Conclusion
As a conclusion, this project had successfully detected the mobile phones
when it is located at particular areas such as mosque, library, meeting rooms and
lecture halls. But the problems for this design is that it can only sense the frequency
of the mobile phones, it cannot detect how many of mobile phones been used.
However, by detecting the presence of the mobile phones, it can alert to user to silent
or switch off their mobile phones from those particular areas.
By designing this project, it can be used to help the management system for
preventing the usage of mobile phones for those particular areas. This design can
33
help to prevent the noise interruption and maintain the peace environment to the
other people in those areas.
This RF detector circuit also can help to discipline the people from using the
mobile phones in the prohibited areas. The users also can helping each other to alert
between themselves to respect the other person and not being a selfish for using the
mobile phones in those areas. By this, a new environment can be created and make
the Malaysian peoples become more respectful to other nationality.
5.2
Suggestion and Recommendation for Future Work
This project has been developed and implemented. However, it can be
improved to target more advanced and better application in the next stage of
research. For future improvement, there are several suggestions stated below:
1. Another sensor design can be develop to detect how many phones available
in that particular zone / area
2. Increase the range of the detection area (range can be wider)
3. Develop automatic system :
a) Single way transmission - host will give message to receiver
b) 2 ways transmission and receive - host need to know the mobile status
c) 2 ways transmission and receive + automatic with phone preset
d) 2 ways + automatic switch mode (2 ways)
e) Automatic switch to silent in silent mode zone
f) Away silent zone, switch back to previous/ general
34
REFERENCES
1. ITT Technology (2007). “Detecting and Locating Mobile phones in
Correctional Facilities”. EVI Technology, LLC 7065 Columbia Gateway
Drive Columbia, MD 21046.
2. Ian Poole (2006). “Cellular Communication Explained: From Basics to 3G”
Elsevier Ltd, Oxford, UK.
3. Rozeha A. Rashid (2007). “Prinsip Kejuruteraan Telekomunikasi”. Penerbit
UTM.
4. William C. Y. Lee (2009. “Wireless and Cellular Telecommunications: 3rd
Edition”. McGraw-Hill Engineering.
5. J. C. Joseph (2001). “Secrets of RF Circuit Design, 3rd Edition”. TAB
Electronics.
6. John S. Seybold (2005). “Introduction to RF Propagation”. John Wiley &
Sons, Inc
7. Reinhold Ludwig, Gene Bogdanov (2009) “RF Circuit Design: Theory and
Applications”, Second Edition. Pearson International Edition.
8. Johari Kasim, Camallil Omar, Abd Hamid (2009). “Sistem Elektronik”. Edisi
Ketiga. Penerbit UTM.
9. P. Manian (2009). “Cell Phone Detector aka Mobile Bug”. Available at
http://electroschematics.com/1035/mobile-bug-detector-sniffer/
35
10. Online on http://www.techlib.com/electronics/cellhelp.htm. “Cell Phone
Helper”
11. http://searchnetworking.techtarget.com/definition/radio-frequency. “What is
Radio Frequency”
12. Aaron
Alai
(2009).
“EMF
Detector”.
Available
at
http://www.aaronalai.com/emf-detector
13. Online at http://en.wikipedia.org/wiki/History_of_mobile_phones
14. B.
Kainka
(2002).
“Mobile
Phone
Sniffer”.
Available
http://www.electronics-circuits.net/mobile-phone-sniffer-vt39.html
15. Cell phone detector available at http://www.circuit-projects.com/
at
36
APPENDIX A
CA3130 Operational Amplifier
37
38
39
40
41
APPENDIX B
NE555 Timer
42
43
44
45
46
APPENDIX C
BC548 Transistor
47
48