The W band of the microwave part of the electromagnetic spectrum ranges from 75 to 110 GHz, wavelength ~2.7-4 mm. It sits above the U.S. IEEE-designated V band (50–75 GHz) in frequency, and overlaps the NATO designated M band (60–100 GHz). The W band is used for satellite communications, millimeter-wave radar research, military radar targeting and tracking applications, and some non-military applications.
A number of passive millimeter-wave cameras for concealed weapons detection operate at 94 GHz. A frequency around 77 GHz is used for automotive cruise control radar. The atmospheric radio window at 94 GHz is used for imaging millimeter-wave radar applications in astronomy, defense, and security applications.
Less-than-lethal weaponry exists that uses millimeter waves to heat a thin layer of human skin to an intolerable temperature so as to make the targeted person move away. A two-second burst of the 95 GHz focused beam heats the skin to a temperature of 130 °F (54 °C) at a depth of 1/64 of an inch (0.4 mm). The United States Air Force and Marines are currently using this type of Active Denial System.
In terms of communications capability, W band offers high data rate throughput when used at high altitudes and in space. (The 71–76 GHz / 81–86 GHz segment of the W band is allocated by the International Telecommunication Union to satellite services.) Because of increasing spectrum and orbit congestion at lower frequencies, W-band satellite allocations are of increasing interest to commercial satellite operators, although no commercial project has yet been implemented in these bands.
The design of a real-time 94 GHz passive millimetre-wave imager for helicopter operations, R. Appleby, R. Anderton, N. Thomson, J. Jack, Proc. SPIE, 5619, pp. 38 (2004). doi:10.1117/12.581336
Zhiming Chen, Chun-Cheng Wang, and Payam Heydari, "A BiCMOS W-Band 2×2 Focal-Plane Array With On-Chip Antenna," IEEE Journal of Solid-State Circuits, vol. 47, no. 10, pp. 2355-2371, Oct. 2012.
Leland Gilreath, Vipul Jain, and Payam Heydari, "Design and Analysis of a W-Band SiGe Direct-Detection-Based Passive Imager Using a Balanced LNA with an Embedded Dicke Switch," IEEE Journal of Solid-State Circuits, vol. 46, no. 10, pp. 2240-2252, Oct. 2011.