Editing Direction finding (section)

====Electronic analysis of two antennas' signals====
More sophisticated techniques such as [[phased array]]s are generally used for highly accurate direction finding systems. The modern systems are called [[goniometer#radio goniometer anchor|goniometers]] by analogy to [[World War II|WW&nbsp;II]] directional circuits used to measure direction by comparing the differences in two or more matched reference antennas' received signals, used in old [[signals intelligence]] (SIGINT). A modern [[helicopter]]-mounted direction finding system was designed by [[ESL Incorporated]] for the U.S. Government as early as 1972.

[[TDOA|Time difference of arrival]] techniques compare the arrival time of a radio wave at two or more different antennas and deduce the direction of arrival from this timing information. This method can use mechanically simple non-moving omnidirectional antenna elements fed into a multiple channel receiver system.

[[File:B-17F "Tom Paine" of the 388th Bomb Group, WW2.jpg|thumb|upright|right|The RDF antenna on this B-17F is located in the prominent teardrop housing under the nose.]]