Extremely high frequency

Extremely high frequency (EHF) is the <a href="/facts/International_Telecommunication_Union/Yn8UKKkw">International Telecommunication Union</a> designation for the band of radio frequencies in the <a href="/facts/Electromagnetic_spectrum/24LARvFY">electromagnetic spectrum</a> from 30 to 300 gigahertz (GHz). It is in the <a href="/facts/Microwave/HmVSN31Y">microwave</a> part of the radio spectrum, between the <a href="/facts/Super_high_frequency/Bqrg4fcy">super high frequency</a> band and the <a href="/facts/Terahertz_band/729QecPK">terahertz band</a>. <a href="/facts/Radio_wave/XmB6WPpF">Radio waves</a> in this band have <a href="/facts/Wavelength/kcJU0ymz">wavelengths</a> from ten to one millimeter, so it is also called the millimeter band and radiation in this band is called millimeter waves, sometimes abbreviated MMW or mmWave. 
Some define mmWaves as starting at 24 GHz, thus covering the entire <a href="/facts/5G_NR_frequency_bands/PBFAA5nA">FR2</a> band (24.25 to 71 GHz), among others.
Compared to lower bands, radio waves in this band have high <a href="/facts/Atmospheric/oUpLaGRF">atmospheric</a> <a href="/facts/Attenuation/XP4vX360">attenuation</a>: they are absorbed by the gases in the atmosphere. Absorption increases with frequency until at the top end of the band the waves are attenuated to zero within a few meters. Absorption by humidity in the atmosphere is significant except in desert environments, and attenuation by rain (<a href="/facts/Rain_fade/p91Euggs">rain fade</a>) is a serious problem even over short distances. However the short propagation range allows smaller <a href="/facts/Frequency_reuse/8zA0jQJ9">frequency reuse</a> distances than lower frequencies. The short wavelength allows modest size antennas to have a small <a href="/facts/Beamwidth/45klmvIl">beam width</a>, further increasing frequency reuse potential. Millimeter waves are used for military <a href="/facts/Fire-control_radar/Dgpf47AH">fire-control radar</a>, <a href="/facts/Millimeter_wave_scanner/vEdV0YI0">airport security scanners</a>, short range <a href="/facts/Wireless_network/yr4SWTdl">wireless networks</a>, and scientific research.
In a major new application of millimeter waves, certain <a href="/facts/5G_NR_frequency_bands/PBFAA5nA">frequency ranges</a> near the bottom of the band are being used in the newest generation of <a href="/facts/Cell_phone/H3EcqD9h">cell phone</a> networks, <a href="/facts/5G/yVb460m4">5G</a> networks. The design of millimeter-wave circuit and subsystems (such as antennas, power amplifiers, mixers and oscillators) also presents severe challenges to engineers due to semiconductor and process limitations, model limitations and poor <a href="/facts/Q_factor/NNjGLb5b">Q factors</a> of passive devices.

Extremely high frequency open-in-new

Extremely high frequency