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The W band of the microwave part of the electromagnetic spectrum ranges from 75 to 110 GHz. It sits above the U.S. IEEE designated V band (50 � 75 GHz) in frequency, yet 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 1/64th 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. |
