Design and Construction of a Remote Controlled Tri–Band Frequency Jammer.

CHAPTER ONE

INTRODUCTION

1.1       BACKGROUND OF THE STUDY

A mobile phone jammer or signal blocker is an instrument used to prevent cellular phones from receiving signals from base stations. The process of blocking the receiver to receive a transmitted signal is called Jamming of the signal. The jammer effectively disallows cellular phone signal when activated. These devices can be used in practically any location, but are found primarily in places where a phone call would be particularly disruptive because silence is expected. Such places include court rooms, meeting venues, lecture theatres or a library environment.

Mobile phone usage is at the increase and globally appreciated as it made the world a global village. In spite of its advantages, mobile phones are sometimes misused especially in the lecture halls, worship centers, movies theatres, concerts, and shopping malls, all suffer from the spread of cell phones because not all phone users know when to stop talking. These boss serious distractions [1].

Jamming in wireless networks is defined as the disruption of existing wireless communications by decreasing the signal-to-noise ratio at receiver sides through the transmission of interfering wireless signals. Jamming is different from regular network interferences because it describes the deliberate use of wireless signals in an attempt to disrupt communications whereas interference refer to unintentional forms of disruptions. Unintentional interference may be caused by the wireless communications among nodes within the same networks or other devices (e.g. microwave and remote controller). On the other hand, intentional interference is usually conducted by an attacker who intends to interrupt or prevent communications in networks. Jamming can be done at different levels, from hindering transmission to distorting packets in legitimate communications[6].

The concept came into existence through military use when one country during war situation did not want their radio transmission to be intercepted by the enemy, with the use of RF jammers to jam near border areas. Although in most parts of the world, the use is restricted based on specificlaws of the country, application is however allowed for research purposes since these jammers actively broadcast radio signals. One of those attempts led to the creation of radio jammers: in World War II, the British used to jam German radio communications [2, 3, 4].

Jammers work by giving a Radio Frequency (RF) signal or a signal at the same frequency expected by the device that’s being jammed, but at a higher power compared to the targeted signal. The jamming signal itself is usually a random noise. Jammers were originally developed for law enforcement and the military to interrupt communications by criminals and terrorists [5]. The device being jammed will then receive the higher power signal which is from the jammer, and then the devices can no longer function correctly (Bhatia 2015). The technology being used in mobile phone jammers or signal blocker is very simple. It breaks down the network between base station and the cell phone and broadcasts a RF signal with frequency range of cell phones leading to the phone displaying no network available. This device can block the frequency range of 800 to 2100 MHz or the band for which it is designed and a coverage radius of few meters so that it does not disrupt the services of other users.