mmWave

mmWave refers to radio frequencies roughly from 30 GHz to 300 GHz, corresponding to wavelengths from 10 millimeters to 1 millimeter. The term is used in telecommunications and sensing to describe high-bandwidth transmission and imaging enabled by the large spectrum in these bands. In telecommunications, mmWave is a core component of many 5G networks, with bands around 26-28 GHz, 37-43 GHz, and 60 GHz unlicensed. It is also used for fixed wireless access backhaul, dense urban microcells, and some satellite links.

Propagation: The high frequency yields high free-space path loss and rapid attenuation with distance, plus atmospheric absorption, rain, and foliage. Propagation is largely line-of-sight with limited diffraction, requiring dense deployment or relays. To enable coverage, networks rely on highly directional antennas and beamforming using phased-array or hybrid architectures.

Technology and challenges: Devices require compact high-gain antennas, efficient RF front-ends, and low-noise amplifiers. Oxygen absorption peaks near 60 GHz add loss; rain fade can be significant. Short range and obstruction sensitivity drive indoor or urban backhaul use. Power, cost, and integration with silicon technology are active research areas.

Applications: These frequencies support 5G air interfaces in multiple bands for mobile broadband, fixed wireless access and backhaul, automotive radar (77-79 GHz), imaging and sensing, and some satellite links. Regulatory and standardization efforts shape spectrum allocations and safety guidelines.