1.4.2 Artificial Sources
Artificial RF sources are now widespread and support many aspects of modern life. They range from very low-power personal devices to high-power broadcasting transmitters and radar systems.
Communications systems are among the most familiar RF sources. Radio and television broadcasting stations transmit continuously to large geographical areas, while mobile telephone networks employ thousands of base stations to provide wireless coverage. Wi-Fi access points, Bluetooth devices, cordless telephones, satellite terminals, and two-way radios all rely on RF electromagnetic waves to transfer information without physical connections.
Radar systems transmit short-duration pulses of RF energy to detect and track aircraft, ships, vehicles, weather systems, and other objects. Radar is widely used in aviation, maritime navigation, meteorology, defense, and industrial sensing applications. Because radar systems often employ high peak powers and highly directional antennas, they represent an important consideration in occupational RF safety.
Satellite communications systems use RF links between ground stations and orbiting satellites to provide television broadcasting, broadband Internet, navigation, remote sensing, weather forecasting, and military communications. Both satellite earth stations and spacecraft employ highly directional antennas that concentrate RF energy into narrow beams.
Industrial, scientific, and medical equipment also generates RF electromagnetic fields. Examples include induction heating systems, dielectric heating equipment, plasma processing systems, magnetic resonance imaging (MRI) systems, RF ablation equipment, and scientific research facilities. Unlike communications systems, these installations often produce strong RF fields within relatively confined working areas.
Consumer electronics represent another important category of RF sources. Mobile phones, wireless headphones, smart watches, tablets, laptop computers, wireless routers, vehicle keyless-entry systems, and numerous Internet of Things (IoT) devices all employ low-power RF transmitters. Although individual devices generally operate at relatively low power, their widespread use means that RF electromagnetic fields have become a routine part of everyday life.