This document describes the design and implementation of a mobile signal jammer that can block GSM, CDMA, and 3G networks for a prescheduled time duration using an ARM7 microcontroller. The jammer works by transmitting radio signals on the same frequencies used by mobile networks, interfering with communication between phones and towers. An RTC chip is used to program activation and deactivation times. When activated, phones will show "no network available". The jammer is controlled by an ARM7 microcontroller connected to an RTC, GSM modem, and jamming circuitry. The GSM modem notifies users before jamming begins. Mobile jammers are illegal in most countries due to security and privacy concerns.

1. 1
Advanced mobile signal jammer for GSM, CDMA and 3G
Networks with prescheduled time duration using
ARM7 TDMI processor based LPC2148 controller
Kaku Ramakrishna, Tulasi Sanath Kumar
PG Student, Asst. Professor, Department of Electronics & Communication Engineering, ASCET, Gudur, A.P, India
Abstract : This Paper is designed and implemented for mobile
phone signal jammers for GSM, CDMA and 3G networks with
prescheduled time duration using ARM7.the mobile jammers
block mobile phone use by sending out radio waves along the
same frequencies that mobile phone use .this case enough
interference with the communication between mobile phone
and communicating towers to render the phones unusable
.upon activating mobile jammers all mobile phones will
indicate “NO NETWORK AVAILABLE” . Incoming calls are
blocked as if the mobile phone were off. When the mobile
jammers are turned off, all mobile phones will automatically
re-establish communications and provide full service .the
activation and deactivation time schedules can be programmed
with microcontroller. Real time clock chip DS1307 is used to
set the schedule. In this project we have a jammer section,
microcontroller. RTC and GSM modem .this information is
given to the microcontroller will send data to GSM just before
the select time and GSM will send message to the users whose
number are programmed in the GSM that the jammer is going
to active and communication will be stopped. After message
sent by GSM. Mobile jammer circuit will active and signal are
jammed or blocked.
Keywords: mobile jammer, ARM7.RTC, GSM modem
I. INRODUCTION
Communication jamming device were first developed
and used by military. This interest comes from the
fundamental objective of denying the successful transport of
information from the sender (tactical commander) to the
receiver (the army personnel), and vice-versa. Nowadays,
mobile phones are becoming essential tool in our daily life.
The technology behind cell phone jamming is very simple.
The widely use the mobile phone could create some
problems as the sound of ringing becomes annoying or
disrupting. This could happen in some places like
conference room, aw court, libraries, lecture room and
mosques.
The jamming device broadcasts an RF signal in the
frequency range reserved for cell phones that interference
with the cell phone signal, which results in a “no network
available” display on the cell phone screen. All phones with
in the effective radius of the jammer are science. It should
be mentioned that cell phone jammers are illegal devices in
most countries.
II. RELATED WORK
A. Mobile jammer:
.a mobile phone jammer is an instrument used to
prevent cellular phones from receiver signal from based
station. When used, the jammer effectively disables cellular
phones. This device can be used in practically any location,
but are found primarily in places where a phone call would
be particularly in places where a phone call would be
particularly disruptive because silence is expected. As with
other radio jamming, cell phone jammers block cell phone
use by sending out radio waves along the same frequencies
that cellular phone use. These causes enough interface with
the communication between cell phones and towers to radar
the phones unusable. On most retail phones, the network
would simply appear out of range. Most cell phones use
different bands to send and receive communications from
towers (called frequency division depleting, FDD). Jammers
can work by either disrupting phone to tower frequencies or
tower to phone frequencies. Smaller handheld models block
all bands from 800 MHz to 1900 MHz within a 30-foot
range (9meters). Small devices tend to used the former
method, while larger more expensive models many interfere
directly with the tower
signals
Base station
Figure 1. basic principal mobile signal jammer
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Proceedings of International Conference on Advancements in Engineering and Technology
ISBN NO : 978 - 1502893314
www.iaetsd.in
International Association of Engineering and Technology for Skill Development
58

2. 2
The GSM jammer is a device that transmit signal on the
same frequency at which the GSM system operates, the
jamming success when the mobile phone in the area where
the jammer is located can’t communicate, the basic idea
military use that was called denial of service attack. Mobile
jammer is used to prevent mobile phone from receiving or
transmitting signal with the base stations. When used, the
jammer effectively disables cellular phones. There are
several ways to jam an RF device. The three most common
techniques can be categorized as follows:
i. Spoofing
In this kind of jamming, the device forces the mobile to turn
off itself. This type is very difficult to be implemented since
the jamming device first detects any mobile phone in a
specific area, then the device sends the signal to disable the
mobile phone .some type of this technique can detect if a
nearby mobile phone is there and sends a message to tell the
user to switch the phone to the silent mode (intelligent
beacon disablers).
ii. Shielding attacks:
This is known as TEMPEST or EMF shielding. This kind
required closing an area in a faraday cage so that any device
inside this cage cannot transmit or receiver RF signal from
outside of the cage. This area can be large as buildings.
iii. Denial of service
This technique is referred to DOS. In this technique, the
device transmits a noise signal at the same operating
frequency of the mobile phone in order to decrease the
signal -to-noise ratio (SNR) of the mobile under its
minimum value. This kind of jamming technique is the
simplest one since the device is always on. Our device is of
this type.
Figure2. Block diagram of the jammer device
B. Component of mobile jammer:
Electronically speaking, cell-phone jammers are very basic
device. The simplest just have an on/off and a light that
indicates it’s on. More complex device have switches to
activate jamming at different frequencies. Components of
jammer include:
a. Power supply:
Smaller jamming device are battery operated. Some look
like cell-phone batteries. Stronger device can be plugged
into a standard outlet or wired in to a vehicle’s electrical
system.
b. Circuitry:
The main electronic components of a jammer are:
Voltage-controlled oscillator--generates the radio signal that
will interface with the cell phone signal.
Tuning circuit – controls the frequency at which the jammer
broad cast its signal by sending a particular voltage to the
oscillator
Noise generator: -- produces random electronic output in a
specified frequency range to jam the cell-phone network
signal (part of the tuning circuit)
RF amplification (gain stage)—boost the power of the radio
frequency output to high enough level to jam a signal
Check your phone: -- if the battery on your phone is okay
and you’d like to continue your conversation, try walking
away from the the area. You may be able to get out of the
jammer’s range with just a few steps.
c. Antenna:
Every jamming device has an antenna to send the signal.
Some are contained rical cabinet. On stronger device,
antennas are external to provide longer range and tuned for
individual frequencies.
The effect of jamming depends on the jamming-to- signal
ratio (j/s), modulation schema, channel coding and
interleaving of the target system. Generally jamming-to-
signal ratio can measure according to the following equation
=
Pj=jammer power,Pt-transmitter power, Gjr=antenna gain
from jammer to receiver , Grj=antenna gain from receiver to
jammer , Gtr=antenna gain from transmitter to receiver ,
Grt=antenna gain from receiver to transmitter,
Br=communication receiver bandwidth, Bj=jamming
transmitter bandwidth, Rtr=rang between communication
transmitter and receiver, Rjt=range between jammer and
communication receiver, Lr=jammer signal loss,
Lr=communication signal loss
Jammers simply overflow the frequency used by wireless
phones with radio waves. Jamming signal needs enough
power to collide and cancel GSM signal. Cell phones are
Power
supply
IF
section
RF
section
Jamming
signal
Proceedings of International Conference on Advancements in Engineering and Technology
ISBN NO : 978 - 1502893314
www.iaetsd.in
International Association of Engineering and Technology for Skill Development
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3. 3
designed to increase their power when facing low level
interface. Jammer should recognize that power. Power of
jamming signal should match the power increase from the
phone.
Sophisticated jammers can block several networks to head
off dual or tri-mode phone that automatically switch among
different network to find open signal.highend device can
block all frequencies.
GSM(global system for mobile communication) ranges
erope900 MHz, asia-1800 MHz, USA-1.9 MHz
C. Micro controller:
This section forms the control unit of the whole project.
This section basically consists of a microcontroller with its
associated circuitry like crystal with capacitors, reset circuit,
pull up resistors (if needed) and so on.
The microcontroller forms the heart of the project
because it controls the drives begins interfaced and
communicates with the drives according to the program
being written. a microcontroller is a small computer on a
single integrated circuit consisting of a relatively simple
CPU combined with support function such as crystal
oscillator ,timers, watchdog timer, serial and analog i/o etc.
microcontroller are also used in specific, high technology,
and aerospace projects. Microcontrollers are designed for
small or dedicated application.
D. ARM7TDMI:
ARM is the abbreviation of advanced RISC machines,
it the names of a class of processor, and is the name of kind
technology too. The RISC instruction set, and related
decode mechanism are much simpler than those of complex
instruction set computer (CISC) design.
E. Liquid-crystal display (LCD):
A flat panel display electronic visual display that uses
the light modulation properties of liquid crystal. Liquid
crystals do not emit light directly.LCD are available to
display arbitrary image or fixed image which can be
displayed or hidden, such as preset words, digits, and 7-
segment displays as in a digital clock. They use the same
basic technology, except that arbitrary image is made up of a
large number of small pixels, while other displays have
large elements.
F. Global system for mobile communication
(GSM):
GSM/GPRS RS232 modem from rhydoLABZ is built
with SIMCOM make sim900 quad-band GSM/GPRS engine
.GSM, which stands for global system for mobile
communication, reigns (important) as the world’s most
widely used cell phone technology. Cell phones use a cell
phone service carrier’s GSM network by searching for cell
phone towers in the nearby area.
Global system for mobile communication (GSM) is
globally accepted standard for digital cellular
communication. GSM is the name of a standardization
group established in 1982 to create a common European
mobile telephone standard that would formulate
specification for a pan-European mobile cellular radio
system operating at 900 MHz it is estimated that many
countries outside of Europe will join the GSM partnership.
Table 1: Operating frequency bands
In our design, the jamming frequency must be the same the
downlink, because it needs lower power to do jamming then
the uplink rang and there is no need to jam the base station
itself. So, our frequency design will be as follows:
UPLINK
(Handset
transmit)
DOWNLINK
(handset
receive)
USED IN
JORDAN
BY:
GSM
900
890-915
MHz
935-960MHZ Zain+orange
DCS
1800
1710-1785
MHz
1805-1880
MHz
Ummiah
Proceedings of International Conference on Advancements in Engineering and Technology
ISBN NO : 978 - 1502893314
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International Association of Engineering and Technology for Skill Development
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4. 4
GSM 900---- -- 935-960 MHz
GSM 1800 1805-1880 MHz
The CDMA frequency range will be 860-894 MHz
(Asia&Europe) and 850-894 MHz (United States).
III. HARDWEARE IMPLEMENTATION:
The below fig.3 is the block diagram of the system that to
set the scheduled time duration for mobile jammer. The
activation and deactivation time schedules can be
programmed with microcontroller. In order to run the RTC
(real time clock) one crystal oscillator is externally
interfaced, an oscillator is an electronic circuit that produces
a repetitive electronic signal. The power supply interfaced it
is used to battery backup for the purpose of update the time
when the absence of power. The A.C input i.e., 230v from
the mains supply is step down by the transformer to 12v and
is fed to a rectifier. One reset button interface, Reset is used
for putting the microcontroller into a ‘known’ condition.
That partially means that microcontroller can behave rather
inaccurately under certain undesirable condition. In order to
continuous its proper functioning it has to be reset. Relay is
an electrically controllable switch widely used in industrial
controls, automobile and appliances.
One LCD (liquid crystal display) also interface in this
micro controller, it is flat electronic visual display that used
that use the light modulating properties of liquid crystals.
These components are specialized for being used with the
microcontrollers, which means that they cannot be activated
by standard IC circuits.
RTC (real time clock) is interface because it is widely
used device that provides accurate time and date for many
applications. LED indicator interface in this microcontroller
it have a life of at last ten years and consumer 90 percent
less power than conventional indicators, depend on the type
of the materials (Ga, AS, p).
IV. LEGAL ISSUES:
India: government and schools use jammers. United States:
illegal to operate, manufacture, import, or offer of up to
$11,000 and imprisonment of up to one year. Pakistan: legal
inside bank, often used also in libraries. United Kingdom:
illegal to use, but legal to
V. CONCOLUSION:
This paper is successfully completed using mobile
jammer and ARM7.by this system we can deactivate all the
mobile signals at any locations. We designed a device that
stops phone ringing in particular time period. This device
could be used in places where ringing is not desired at
specific times, as these ringing may disturb people in such
place. The design drive works in dual band. It jams both the
GSM900 and GSM1800 bands. The device was able to jam
the three main cell phone carriers in Jordan
VI. REFERENCE
[1] www.howstuffwork.com
[2] en.wikipedia.org/wiki/mobile_phone_jammer
[3] multitopic conference2008.INMIC 2008.
[4]ccnga.uwaterloo.ca/jscouria/GSM/gsmreporter.html
[5]ieeee explore.com
[6]”zone of scilence[cell phone jammer],”spectrum, ieee
Vol.42,no.5,18,may2005.
Figure: block diagram system
LCD
Driver
I2C
ARM7
LPC2148
Micro
controller
Jammer circuitry
Relay
Driver
LCD
LED
indicators
RTC
RS232
interface
Crystal
Oscillator
Relay
GSM
modem
Reset
Power supply
Proceedings of International Conference on Advancements in Engineering and Technology
ISBN NO : 978 - 1502893314
www.iaetsd.in
International Association of Engineering and Technology for Skill Development
61