-Wireless Telecommunication services are becoming a part of our everyday life because they support a lot of services. However, they are often misused in environments such as hospitals where some patients would require quietness or sometimes they distract medical practitioners from carrying out their duties of saving lives. Therefore, there is a need to use a jammer that prevents mobile phone from working in such an environment. Hence, this paper proposes a cost-effective tri-band mobile phone jammer for hospitals applications. The jammer is designed, constructed, test and found very effective in terms of jamming signal within the bands.
In the last decade, wireless phones has achieved significant global
penetration in both developed and developing countries [
Generally, a cell phone-jammer is a device that block signal from mobile
by creating interference such that it prevents transmission and reception
power at the certain frequency [
Jammers are classified into different types. In this work, we would be focusing on type “A” jammers. This uses the Denial of Service technique. therefore, this section provide an executive summary of the related works in table 1.
scheduled timer with a mobile Jammer. When the ON time reaches, the Jammer is activated through a relay and blocks all GSM and CDMA services within a 5 – 7 m range. The device was successfully able to jam cell-phones using these services.
Nadu, The designed Jammer was able to block 2G and 3G services. However, the challenge faced in this work was that the amplification process did not achieve proper output gain to jam the target services due to issues with the power amplifiers. Because of this, their project is partially designed till date.
The mobile Jammer was able to block cell-phones using 2G and 3G networks. But the jamming device had a poor frequency selectivity and the jamming range was smaller than expected. Also the tuner circuit had poor calibration, this makes difficult to block all frequencies in the applicable bandwidth.
The designed Jammer was able to block GSM 900 services. However in this design, the right amount of current was not provided to the VCO and the Power amplifier which consequently prevented tuning to the desired frequency range for the VCO and also limiting the output power of the Jammer. This limited the jamming range to 10 meters instead of the intended 20 meters.
The designed dual band GSM Jammer used a directional Yagi-uda antenna
instead of the conventional monopole antenna. The Jammer was able to achieve a maximum jamming distance of 16.72 meters when the antenna is at an angle of 10 degrees and a minimum distance of 3.12 meters at an angle of 120 degrees Their cell-phone Jammer works in both the GSM 900/1800 bands and tested Egypt. After full testing, a heat sink was later implemented with the RF power amplifiers in this design to reduce overheating during operation.
The designed Jammer used a different jamming technique by first detecting mobile phones operating in the GSM900 band, and upon detection transmits a jamming signal to block the service within a 2.5 m range. At GSM 900 it was capable of detecting and blocking all the services.
The proposed jamming device consists of three (3) major sections that makes up the Jammer circuit. These include the Power supply, the Intermediate Frequency (IF) and the Radio Frequency (RF). Fig. 1 illustrates the general overview diagram of the Jamming system.
Fig 1. Block diagram of the Jamming device
The circuit schematic for each of these sections and the various electronic components that makes up these sections are critically chosen and selected. Also detailed calculations and measurements is carried out before assembling these different electronic components (resistors, capacitor, transistors, diodes, voltage controlled oscillators, amplifiers, antennas etc.) that forms the Jammer circuit. The range of frequencies that are jammed in this work is provided in table 2: The Network providers considered were: Airtel, MTN. Globacom and 9mobile networks.
890 – 915 935 – 960 1710 – 1785 1805 – 1880 1920 – 1980 2110–2170 ( ) = 32.45 + 20 + 20 . where is the jamming distance in and is the operating frequency in
The Jamming-to-Signal ratio (J/S) of a target system is another important
parameter in mobile jamming. It is the ratio of the jamming signal power at a
specific receiver to the strength of the target signal at that same receiver [
In this paper, we employ the free space path loss model (FSPL). Generally, path loss can be determined using the mathematical model defined in equation (1), that is. (1) (2) (3) (4) (5) where; PJ, PT, GJ, GT, dJ,and dS are the Jammer output power (dBW), Transmitter power (dBW), antenna gains (in dBi) of Jammer and transmitter, distance (in meters) of jammer to receiver and then transmitter to receiver respectively. Applying some mathematical rearrangements, J/S can also be obtain using the equation (5).
( ) = 2
2 where; RTR and RJR is the distance between the transmitter and receiver, and Jammer and receiver, LR and L
J is the signal loss in of the communicating device and signal Loss by the Jammer. BR is the bandwidth of the Receiver and BJ is the bandwidth of the Jamming.
Every radio device has a limit to which they can accommodate noise present
in any signal. This is known as the SNR handling capability of the device. It
is the wanted signal divided by that of noise [
The maximum receive signal power refers to the best or strongest level of
signal a mobile station can possibly receive from another radio device in the
cellular network e.g. the Base station. Table 3 show the maximum power for
each band [
The mathematical models to determine the receiver jamming power and the Jammer output power is given in the equations (6) to (7).
Jamming power at mobile receiver, ≥ −
Maximum Jammer output power, = + (6) (7) For GSM 900 Maximum RSSI, RSSImax = -15dBm Minimum SNR, SNRmin = 9dB Jamming power at mobile receiver ,
For GSM 1800 Maximum RSSI, RSSImax = -23dBm Minimum SNR, SNRmin = 9dB
≥ −32 5.
≥ −15 – 9 Jamming power at mobile receiver, ≥ −23 – 9 This section presents implementation of the Tri-band cell-phone Jammer. The figure 2 depicts the different parts of the Jammer which are developed individually and assembled to form the whole jamming system.
After the successful design and simulation of the Jammer circuit, the design was shifted to a Vero-board to connect all the electronic components. The constructed Jammer device is shown in figure 3.
The testing of the cell-phone Jammer was a full successful as developed device was able to block the four major Mobile operators in Nigeria namely MTN, Globacom, Airtel and 9mobile as shown in Figures 4-6. Although the average jamming range of the system was approximately 10 meters, which is less than the design specification. This limitation can be attributed to the use of telescopic antennas by the jamming system instead of duck antennas that have a good gain. Also the RF power amplifiers that increase the strength of the jamming signal were not able to get the precise voltage supply as specified in their data sheet, as 3.3 volts was provided to them instead of the required 3.5 volts.
During testing, the Jammer was able to block the target services on an average of two (2) minutes after being turned “ON”. Further testing confirmed that, the relationship between the distance between the Jammer and the base station increases proportionally thus blocking more numbers of cell-phones. This is due to the fact that the signal strength at cell-phones are at their strongest when close to the base station, and the farther these cellphones are from the base station, the lesser the amount of power reaching them, thus having a weak signal strength.
The figures 4-6 show the effect of testing the Jammer on different mobile networks. It can be clearly seen that when the Jammer is “OFF”, network services on the different cell-phones were available, but after turning the Jammer “ON”, these services disappears or becomes unavailable.
Fig. 5. Airtel service before and after the Jammer was “ON”.
This project work presents a detailed insight into the implementation of a triband cell-phone Jammer that uses the denial of service jamming technique to inhibit the operation of cell-phones. The aim and objectives initially set out for this work has been achieved as the designed Jammer was relatively able to block GSM 900/1800 and UMTS 2100 services within its jamming range. Further testing of this device shows that its effective jamming distance reduces when tested close to a base station and as we move farther from the base station, this distance increases.