The U-band, as defined by IEEE, is a frequency range from 40 to 60 GHz. IEEE uses letters to signify a range of frequencies from 1 to 110 GHz. This frequency band lies between the IEEE Q-band (33-50 GHz) and V-band (50 to 75 GHz). As the U-band’s frequency range is shared by Q and V bands, it also shares most of the same applications as well.

U-band frequency was originally used for signaling in telegraph networks but with technological advancements, telegraphy became more and more obsolete over the years with the arrival of several faster modes of communication. Hence U-band frequencies are mostly unused at the moment. Higher U-band frequencies i.e., above 55 GHz, which are also part of the V-band, are used for some wireless high capacity, Line-of-Sight (LOS) communications. In fact, U-band is entirely considered a part of the lower range of the V-band recently making it a single band ranging from 40 to 75 GHz.