20-09-2009, 03:33 PM
MOBILE DETECTION AND JAMMING
INTRODUCTION:-
The aim of this project is to build a device which can detect the presence of a active mobile phone in a given area and upon detection, activate the jamming device which jams the phone hence disrupting communication.
This objective is achieved by splitting the working of the device into two parts-
1) Mobile detection
2) Mobile jamming
· MOBILE DETECTION:-
The Mobile detection project is an advanced device which finds various applications in the modern fields of communication and surveillances. Mobile detection project is designed to detect the mobile phone in a closed room / place which is in active transmission mode. This project is very useful for the private meetings, defense establishments, military camp, Hospitals; Petrol pumps etc., where the uses of an active Mobile Communication (GSM) device are prohibited. With the aid of this project, one can detect the active mobile device like Cell Phone and GPS systems. Here the Mobile detection project can be used like a metal detector and the project is capable of detecting the Cell phone like device from the range of few centimeters to few inches depending upon the Cell phoneâ„¢s transmission strength and other parameters. Here the project is waved near the person / place where the presence of a GSM device is to be detected.
Further, the project also incorporates a vary unique feature of remote paging & indication. In this part when the project is installed on the frame of a door or entrance, (like metals detectors) it scans incoming personâ„¢s mobile activity and if the person is carrying an Active mobile phone, then instead of activating an alarm, it sends a wireless message using Infra-Red signal to a Microcontroller unit which is monitored by a person. So whenever the project detects the active phone carried by a person, it can be made to display an alert message about the same to watchman / security personnel silently, without alarming the person carrying the phone.
METHODOLOGY:
Here the project consists of a set of high sensitive electronic wave detection antenna, pre-amplifier, filter, Schmitt trigger, switching stage and an alarm. The project is exactly same as that of a metal detector in principle and operation. The project is also similar to operation and detection like the Metal / Explosive Detector, only with a difference being that, the Metal / Explosive Detector is going to detect the passive parameters, but where as this project is aimed to detect the active signals like GSM signal source like mobile phone which operates in the frequency band of 900 MHz or 1800 MHz typically.
The project mainly consists of the following Block elements as listed below;
1) Active Antenna
2) Pre-Amplifier
3) Amplifier & Filter
4) Schmitt Trigger Driver
5) Tone Generator & Alarm Circuit OR
6) TRx cum Microcontroller.
BLOCK DIAGRAM
· MOBILE JAMMING
The Basics of Cell Phone Jamming
Cell phones work by communicating with a service network through the utilization of cellular towers or base stations. Individual towers partition cities into small sections called cells. As a cell phone user traverses the cells in an area, the signal is passed from tower to tower.
Jamming devices take advantage of this fact by transmitting on the spectrum of radio frequencies used by cellular devices. Through its concurrent transmission, the jamming device is able to disrupt the two-way communication between the phone and the base station. This form of a denial-of-service attack inhibits all cellular communication within range of the device.
WORKING
Through the transmission of a high power signal on the same frequency of a cell phone, the jamming device creates a competing signal that collides with, and, in effect, cancels out the cellular signal. Cell phones, which are designed to increase power in the case of low levels of interference, react to this interference. Consequently, jamming devices must be aware of any increases in power by the cellular device and match that power level accordingly.
As cellular telephones are full-duplex devices utilizing two separate frequencies (one for talking, one for listening, where all parties to a call can talk at the same time as opposed to half-duplex walkie-talkies and CBs), any removal of one of these frequencies tricks the phone into thinking there is no cellular service. Consequently, the jammer need only block one of the frequencies.
The less complex jammers can only block a specific frequency group while the more complex jammers can block several different networks thus preventing dual- or tri-mode phones from switching to a different network with an open signal. Jammers are able to broadcast on any frequency and can interrupt AMPS, CDMA, TDMA, GSM, PCS, DCS, iDEN and Nextel systems. The effective range of a jammer is dependent upon the strength of its power source and the immediate pysical environment (hills or walls which may block the jamming signal). Lower powered jammers have a call-block range of about 30 feet while higher power units can create a cellular signal-free zone about the size of a football field. In addition, certain units applied by law enforcement have been known to shut down cellular service approximately 1 mile from the jamming device.
