The Q band is a range of frequencies contained in the microwave region of the electromagnetic spectrum. Common usage places this range between 33 and 50 GHz, but it may vary in term of sourcing. The Q band is in the EHF range of the radio spectrum.
The Q band is mainly used for satellite communications, terrestrial microwave communications and for radio astronomy studies such as the QUIET telescope. It is also used in automotive radar and in radar investigating the properties of the Earth’s surface.
Extremely high frequency (EHF) is the International Telecommunication Union (ITU) designation for the band from 30 to 300 gigahertz (GHz). It lies between the super high frequency band and the far infrared band, the lower part of which is the terahertz band. Radio waves in this band have wavelengths from ten to one millimeter, so it is also called the millimeter band and radiation in this band is called millimeter waves, sometimes abbreviated as MMW or mmWave.
Millimeter waves are used for military fire-control radar, airport security scanners, short range wireless networks, and scientific research etc.
In the new application trending of millimeter waves, the frequency ranges near the bottom of the band are being used in the cell phone networks, 5G networks.
Fig.:Q-band, EHF band Coaxial Circulator