The document is a thesis on designing a cell phone detector circuit. It discusses objectives of detecting signals between 0.9-3GHz within 1.5m and notifying when a phone is in use. The circuit consists of an inductor, diodes, transistors, op-amps and an LED. It works by rectifying the RF signal induced in the inductor when a phone is near. The amplified output triggers the LED if above a reference voltage, indicating detection. Applications include areas where phone use is prohibited like petrol pumps, hospitals and exam halls.

1. ROORKEE COLLEGE OF ENGINEERING
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
THESIS ON CELL PHONE DETECTOR
Under guidance of
Miss Priyanka Rana
Submitted by :-Shradha Jha

2. ACKNOWLEDGEMENT
I would like to thank the Almighty God for giving me strength and wisdom
throughout this project.
I would also like to extend my sincere gratitude to my faculty members for their
guidance when I was undertaking this project. My sincere gratitude to the
management of Roorkee College Of Engineering for their insightful and challenging
ideas and the technical staff of the Department of Electronics and Communication
Engineering for their guidance in this work.
I would like to acknowledge my friend and classmate, Arzoo ,Urvashi and Priyanka
for their motivation and challenging ideas to “think without the box”.
To my classmates whom we spent hours brainstorming for ideas, I am very grateful
for your efforts.
At last I would like to thank everyone along with Google without the help of whom
I would have not been able to complete our project on time successfully .

3. ABSTRACT
Cell phones are widely used in the world. While people have to be connected
to one another, there are situations or places where there usage is to be
prohibited either due to security reasons or it may cause health hazards.
Cell phone detection has been on investigation for a long time. There are
techniques which have been formulated or proposed on how cell phones can
be detected. Most of them use the features such as audio system, RF system
and common materials of the phones and try to look into how they can be
used as basis to detect mobile phones.
This project utilizes the RF system of the cell phone as the feature to be used
to detect its presence. A circuit that detects signals of the range 0.9GHz to
3GHz is used to detect a cell phone when in use. When the signal is detected,
an LED blinks to indicate the usage of a cell phone within a radius of
1.5metres.

4. CONTENTS
• Introduction
• Objectives and scope of work.
• Detectability of mobile phones.
• Mobile detectors
• Circuit components
• Working
• Detection techniques
• Advantages
• Disadvantages
• Applications
• Conclusion

5. INTRODUCTION
Cell phones have become an integral part of people’s lives. They are not only used for
call ,sms , emails and internet but advance applications such as remote health
monitoring system and security system have been integrated with mobile phones.
The recent years have seen rapid advancement in the value ,addition , applications in
mobile phones such as high definition cameras and high speed internet connectivity.
Country has also experienced developments in the infrastructure to support the rising
need of faster internet connectivity. Despite the advantages enjoyed by the
advancements in mobile technology , there are threats that have been posed by there
usage.
1. Company data mining
2. Sensitiveness of life support machine
3. At places such as aeroplanes , petrol station , conference hall e.t.c the use of
mobile phone can either lead to failure of sensitive machine or nuisance.
It is therefore reality that mobile usage at some places must be prohibited. Due to the
privacy lose that limits the use of cell phone jammers , cell phone detector must be
designed and installed.

6. OBJECTIVES AND SCOPE OF WORK
• Design a circuit that can detect signals in the range of 0.9 GHz to 3GHz
within a radius of 1 and half meters
• Produce a notification when the signals in the range of 0.9 GHz to 3GHz are
detected.
SCOPE OF WORK
• The project is limited to the detection of a cell phone that is in use, on call ,
communication via sms and internet access.
• The detection of cell phones that are on standby mode , switched off or on
airplane mode will not be included .

7. DETECTABILITY OF MOBILE PHONES
Mobile phones are very versatile device. They are potable and compact and can
perform various functions. Most mobile phones have basic set of comparable
features-
• Microprocessor
• ROM
• RAM
• Radio Module
• Digital signal processor
• Microphone
• Speaker
• Variety of hardware keys and interface
• LCD

8. MOBILE PHONE DETECTOR
The cell phone detectors are mostly hand and pocket size mobile
transmission detectors. It can sense the presence of an activated mobile
phone from a distance of 1 and half meter.
The potential detection point was carried out by looking for internal
oscillators necessary to operate micro-processor and radio frequency
synthesizer. The results were not satisfactory. Hence experiment was carried
out to detect the cell phone by detecting the RF transmitted. This was done
by use of RF signal strength meter, an amplifier, a mixer and a filter.

9. CIRCUIT COMPONENTS
• Voltage source=12V
• Inductance,L1=10µH
• Resistance,R1=1000ΩR4=200Ω
• R2=100KΩR5Ω=100Ω
• R3=3KΩ R6=10
• Transistor
• IC1=LM339
• LED
• Capacitance,C1=100nF

10. CIRCUIT DIAGRAM

11. WORKING
The signals from mobile phone is a radio frequency signal. When a mobile
phone is present near the circuit the RF signal from the mobile induces the
voltage in the inductor via mutual induction.
1. This ac signal of high frequency of the order GHz is rectified by schottky
diode.
2. Output signal is filtered out by capacitor
3. Now when the mobile phone is present near the signal , a voltage is i
induced in the choke and the signal is demodulated by diode
4. This input voltage is amplified by CE transistor
5. The output voltage is more than the reference output voltage. The output of
op amp is thus logic high signal and LED starts glowing to indicate the
presence of mobile phone

12. DETECTION TECHNIQUES
• RF spectrum approach: In this detection approach, a passive circuit listens for
any emissions from a cellular phone when it is transmitting. It does not
require an external signal to detect the phone. This is advantageous areas
where power emission from electromagnetic sources are highly prohibited.
• It has some shortcomings. The I phone propagation range could not be
detected. Even in the absence of cell phone signals could still be detected.
• Frequency jamming: Mobile phone works by transmitting signal between
mobile phone and base station or tower. Therefore one of the method to
detect the mobile phone is to have another device transmitting at the same
frequency as the mobile phone but at a higher power level. As the signal is
interfered by the device service on the phone is blocked . The jamming
device performs well between the two cells to ensure the total denial of
service . The devices consist of following parts in the circuitry-
A. Voltage controlled oscillator
B. Tuning circuit
C. Noise generator
D. RF amplification

13. ADVANTAGES
1. Smaller in size
2. Detection of hidden cell phones
DISADVANTAGES
1. It is very short ranged
2. It does not detect the cell phone when it is switched off or in aeroplane
mode or not transmitting.
APPLICATIONS
It is useful where use of mobiles are prohibited
1. Petrol Pump
2. Gas Station
3. Historical Place
4. Religious Places
5. Examination Hall
6. Military Bases
7. Hospitals