radiofrequency

Radiofrequency (RF) refers to the range of electromagnetic radiation with frequencies roughly from 3 kilohertz to 300 gigahertz. It sits between extremely low frequency and infrared in the electromagnetic spectrum and is used to carry information or energy through wireless communications, broadcasting, and various industrial and scientific applications.

Common applications include AM and FM broadcasting, television, cellular networks (2G/3G/4G/5G), Wi-Fi and Bluetooth, satellite communications, radar, and remote sensing. RF heating and induction cooking use higher-frequency RF and microwaves. Medical applications include diathermy and certain imaging techniques.

RF systems consist of a source, an amplifier, a transmission path, and often an antenna. The frequency and modulation determine the channel and data rate. Propagation varies with frequency: lower RF travels further and around obstacles; higher RF yields higher data rates but greater attenuation. Antennas radiate or receive RF energy; common types include dipoles, monopoles, patches, and horns.

RF exposure is regulated by national and international bodies (for example ICNIRP and IEEE). Standards limit exposure to prevent excessive heating. In practice, devices use shielding, interlocks, and proper spacing, and spectrum management minimizes interference. Licensing governs access to certain bands.

Measurement relies on spectrum analyzers, RF power meters, and network analyzers. Key quantities include frequency, power, gain, and impedance. Common units are hertz, watts, dBm, and ohms. Bands are allocated for specific services.

The development traces to late 19th and early 20th century experiments by Hertz, Marconi, and others, and RF technology has since become a core component of modern communications and sensing.