International Journal of Engineering Trends and Technology (IJETT) – Volume 33 Number 7- March 2016
Design Considerations for a Dual Band GSM
Signal Jammer Coupled to a Yagi-Uda
Antenna
Joseph, Gani Martins1; Nganya, George2; Madubuike, Fidelia3 and Echegini, Ngozi Silas4.
1,4
Instructor, Mechatronics Engineering Department, Skill G Nig Ltd, Abuja-Nigeria.
2,3
Instructor, Electronics Engineering Department, Skill G Nig Ltd, Abuja-Nigeria
Abstract
Global System for Mobile Communication is the
most widely means of communication today. This,
though useful may pose great nuisance in noise
restricted areas such as classrooms, churches,
mosques, Libraries, hospitals etc. Mobile phone
jammers are employed to prevent mobile phones
from receiving or transmiting from base stations.
The mobile phone signal jammer is used to interfere
with the communication frequency within a specified
radius depending on the strength of the signal
jammer. To achieve this, a radio signal is generated
on the same frequency as the base station of the
mobile phone Network provider and at a higher
power so as to collide and cancel each other out.
The jammer coverage distance hinges largely on the
performance and capacity of the antenna used. This
research employs Yagi Uda antenna (900-1800MHZ)
with great gain for optimal performance. Results of
the match by Gamma match are 50.16Ω. Obtained
value VSWR yagi is 1:46:1n jamming distance that
can be approximately 15m. upon activation all
mobile phones will indicate “No service” and full
service resumes only when the jammer is off.
Keywords: GSM, jammer, yagi, VSWR, Gamma
I. INTRODUCTION
Nowadays, mobile (or cell) phones are becoming
essential tools in our daily life. Here in Nigeria, for
example, with a population around 140 million [1],
four main cell phone carriers are available; namely;
Globacom, MTN, Etisalat, Airtel for GSM’They use
the GSM 900/1800 system. Needless to say, the
wide use of mobile phones could create some
problems as the sound of ringing becomes annoying
or disrupting. This could happen in some places like
conference churches, mosques, rooms, law courts,
libraries, lecture rooms. While most of us just
grumble and move on, some people are actually
going to extremes to retaliate. Cell phones are
basically handheld two-way radios. And like any
radio, the signal can be disrupted or jammed.
Disrupting a cell phone is the same as jamming any
other type of radio communication. A cell phone
works by communicating with its service network
through a cell tower or base station. A Cell tower
divides a city into small areas, or cells. As a cell
phone user drives down the street, the signal is
ISSN: 2231-5381
handed from tower to tower. A jamming device
transmits on the same radio frequencies as the cell
phone, disrupting the communication between the
phone and the cell-phone base station in the tower. It
is called as a denial-of-service attack [1]. The jammer
denies service of the radio spectrum to the cellphone users within range of the jamming device.
1.
EXISTING JAMMING TECHNIQUES
AND TECHNOLOGY
Communication jamming devices 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 commanders) to the receiver (the army
personnel), and vice-versa
In market, there are various types of jamming
devices available which are using different jamming
techniques. Some of those devices are built with
only one feature in it like it will jam only 2G or only
3G network compatible cell phones.[2]
(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
types 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 requires closing an area in a faraday cage so
that any device inside this cage cannot transmit or
receive RF signal from outside of the cage. This area
can be as large as buildings, for example.
(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
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International Journal of Engineering Trends and Technology (IJETT) – Volume 33 Number 7- March 2016
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.
Jamming). This type is using technique EMI
(Electromagnetic Interference) suppression to
make a room into what I called a Faraday cage.
Although labor intensive to construct, the
Faraday cage essentially blocks, or greatly
attenuates, virtually all electromagnetic
radiation from entering or leaving the cage
or in this case a target room.
2.
PROPOSED SYSTEM DESIGN
ss Power
supply
Unit
IF
Unit
RF
Unit
antenna
jamming
signal
Figure 1. Block diagram of Mobile Jammer coupled to
antenna.
Table 1: Jammers classification
a.
[3]
Type "A" Device. This type of
devices transmits only a jamming signal and
has very poor frequency selectivity, which
leads to interference with a larger amount of
communication spectrum than it was
originally intended target.
b. Type
"B"
Device
(Intelligent
Cellular Disablers). Unlike type A, this type
does not transmit an interfering signal on the
control channels. T h e device b a s i c a l l y
w o r k s a s a detector, and it capable to
communicate with the cellular base station.
c.
Type "C" Device (Intelligent Beacon
Disablers). Like type B, this type does not
transmit an interfering signal on the control
channels. The device, when located in a
specific silent room, function as a beacon and
any compatible terminal is ordered to
disable its ringer or disable its operation.
d. Type "D" Device (Direct Receive and
Transmit Jammers). This type is similar to
type A, but with
a receiver, so that
jammers is predominantly in receive mode and
when the device detects the presence of a
mobile phone in the silent room, it will
intelligently choose to interact and block the
cellular phone by transmitting jamming signal.
e.
Type "E" Device (EMI
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Shield-Passive
Power Supply Unit
Power Supply energizes the whole system.
Generally mobile phone jammers use 5V DC to
operate. Thus we used Lithium-ion battery to
supply our creation.
IF Section
Noise
Signal
Generator
Tuning
Circuit
Fig 2. IF block diagram
The IF-Section of the Mobile Jammer generates
the tuning signal for the Voltage Controlled
Oscillator (VCO) in the RF-Section, which will
sweep the VCO through the desired range of
frequencies. This tuning signal is generated by a
noise generator, and then offset by proper amount
so as to sweep the VCO output from the minimum
desired frequency to a maximum. Basically, it is
just a triangle or sawtooth-wave generator
Noise Generator
Produces random electronic output in a specified
frequency range to jam the cell phone network
signal (part of the tuning circuit). Without noise, the
output of the VCO is just an un-modulated sweeping
RF carrier. So, we need to mix the triangular signal
with noise (FM modulating the RF carrier with
noise). To generate noise signal, we used the Zener
Diode operated in reverse mode. Operating in the
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International Journal of Engineering Trends and Technology (IJETT) – Volume 33 Number 7- March 2016
reverse mode causes what is called avalanche effect,
which causes wide band noise
Tuning Circuit
Tuning circuit is an open-loop which is quite simple
and requires just a few op-amps with additional
passive components. It is a sawtooth wave generator
which makes VCO to go from lowest to highest
frequency.
Voltage
Controlled
Oscillator
driven element field. Basic construction is consists
of driven added element parasitic, reflector (element
parasitic), driven (element with powered) and
director (also called array parasitic). [6]
Power
Amplifier
D
DE
R
Fig 3 RF block Diagram
The RF-section consists of a voltage controlled
oscillator VCO, and power amplifier
Voltage controlled oscillator (VCO)
The voltage controlled oscillator (VCO) is the heart
of the RF-section. It is the device that generates the
RF signal which will interfere with the cell phone.
The output of the VCO has a frequency which is
proportional to the input voltage, thus, we can
control the output frequency by changing the input
voltage[4 ]. Triangular waveform is required to give
an output that will span a specific frequency range.
In our design, we need to find a VCO for GSM 900
and GSM 1800. The selection criteria for
selecting a VCO for this application are; a VCO that
should cover the required frequency bands that we
need, it should be readily available at low cost, and it
should run at low power consumption.
Power Amplifier
Since 5 dBm output power from the VCO does not
achieve the desired output power of the GSM
jammer, we had to add an amplifier with a suitable
gain to increase the VCO output to 34 dBm. We
obtained our amplifier IC (PF08109B ) which has a
gain of 35 dB[ 5]. As datasheets illustrated that this
IC is designed to work in dual band GSM & DCS,
this IC does not work at the two bands
simultaneously so we used two power amplifier IC’s
instead of one amplifier.
Fig 4. Yagi Antenna parametric elements
The dual-band Yagi-Uda antenna comprises of the
director, driver and reflector. In order to operate in
two application bands, the antenna is designed with
simple and easy fulfilled branch structure that are
made up some short and long elements.
Firstly, to make an antenna, we must know the
frequency as expected. In this research, we use
GSM frequency are 855-1945MHz and then
calculate the wavelength value (λ = 0.33m-0.66m).
In designing a Yagi antenna, length and spacing of
each element has its own formulation. But there
is no specific formula to make the best Yagi
antenna on any band, however a lot of good Yagi
design and can be tried was made [6]. Below is a
Yagi antenna design according to some references
as follows:
a. Constantine A Balanis (Antenna
Analysis and Design)[7]
Theory
b.Yagi Antenna Design (NBS Technical Note
688)[8]
c.YC0PE by Ridwan Lesmana[9]
From three references above, we get parameters
that suitable with formulation in respectively, see
table 1
Transmitting Antenna
In this design we couple our jammer to a Yagi
Antenna. In Yagi antenna, increase of antenna
alignment without power on all elements is
expected. Elements that are not powered have
parasitic character and receive signals from coupling
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International Journal of Engineering Trends and Technology (IJETT) – Volume 33 Number 7- March 2016
Based on Figure 3, it is shown that radiation pattern
has main lobe that is wide enough on the X axis, a
back lobe and 2 sidelobe. From this radiation
pattern, expected signal could jamming in long
distance. Gain found at a frequency of 900 MHz is
11.2 dBi, where the gain is greatest at a frequency
of 890-910 MHz and the smallest gain 10.9 dBi at a
frequency of 960MHz. It means that Yagi antenna
could be operation with the range frequency
desired.
The following are materials that are used to design
a Yagi antenna, namely:
a.
Table 2: antenna parameters on Yagicad
[10]Software used to design a Yagi antenna and for
the simulation is YagiCad 6.2 and Sigview. After
performing the simulation with YagiCad and
Sigview for three different parameters, it can be
seen the value of impedance, SWR and frequency
along the greatest gain, as in the following table 2
.
Table 3 Simulation results comparison
From the table 2 above, it can be seen that the best
parameters are according to NBS Technical Note
688 with a smaller value of SWR and gain the
resulting greater. So these parameters are used for
further design. To reduce the SWR value, we use a
gamma match that is tuned and connected with the
SWR analyzer[11].
Aluminium Rod for elements, length 1
meter and a diameter of 5 mm.
b. Pipe boom 55 cm with a diameter of 2 cm
c. 5 Brackets with diameter 7/8 inch x 5 mm.
This bracket is used to set elements (R, D1,
D2, D3, and D4) on the pipe boom.
d. A bracket connector diameter 7/8 inch x 5 mm.
This bracket is used to set DE and gamma match
on the pipe boom.
e. N chassis connector is placed on the bracket
connector.
f.
Gammas match tube and Coaxial RG8
50Ω
g. N male and SMA male RG58 crimping 50.
known to simulated impedance of Yagi antenna
in free space without the gamma match are 24 +
j3.73…………………………………1
The diameter of the driven element
and gamma match tubes 5 mm (0.015λ=2a)
and 7.3 mm (0.022λ=2a'), respectively.
The separation between the driven element
and gamma rod is 17.2 mm (0.052λ).
Then it can be calculated impedance
values obtained as follows:
Determine the current division factor α by using
equation (2), (3), and (4).
…....2
The free-space impedance (without the
gamma match) designate it as Za
Za = 24 +j3.73
3. Find the value of Z2 by using equation
…………3
Fig 5 Radiation Pattern
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International Journal of Engineering Trends and Technology (IJETT) – Volume 33 Number 7- March 2016
Determine impedance Z0 by using (2.21).
...........4
1.
Normalize z2 by Z0, then:
6. ANALYSIS
From Figure 8 we got the radiation of
jamming using helical antenna below. Maximum
distance of jamming is 4.6 at 190 degree. From
measurement that has been done, it can be seen
that the average of area jamming is 3 to 4 meters.
Fig 8 the Jammer Pattern
Figure 6. Radiation Pattern of Helical Antenna
The maximum distance of 16.72 meters jamming
largest found at an angle 10 degrees and a minimum
distance of 3.12 meters at an angle of 120 degrees.
Distance at every angle is different, this is because
the characteristics of Yagi antenna as directional
antenna which is the antenna with the radiation in
one direction. Direction of the antenna radiation
focused in one direction so that the resulting gain
Yagi is greater.
Fig 9 Jammer Swept Frequency (900MHZ)
Figure 7. Radiation Pattern of Yagi Antenna
Fig 10. Jammer Swept Frequency Response
(1800MHZ)
The following can be viewed on YagiCad below
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International Journal of Engineering Trends and Technology (IJETT) – Volume 33 Number 7- March 2016
CONCLUSION
The jammer cancels out any GSM transmission
within a given perimeter as designed. Once it is
switched on all mobile stations showed No network
as service is cancelled. Once it is switched off service
resumes and network is restored. Voltage Standing
Wave Ratio of the designed Yagi antenna is 1.46:1
with RL = 14.51 dB. Bandwidth that achieved by
Yagi antenna is about 120 MHz, this is more than
range of GSM.
Impedance matching using gamma match achieved ±
50.16Ω and the capacitance is± 6 pF and Designed
Yagi antenna can jam mobile phones up to 15 meters
with a fourfold increase compared with helical antenna.
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on
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Gamma
match
antenna Access on
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http://273k.net/gsm/designing_and_building_a
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