A phase switch is a device used to increase the discrimination and sensitivity of an
interferometer
Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...
, especially at radio frequencies; an extra half-wave path difference is switched in, at well defined frequency, between the two interfering signal sources. In-phase signals then become out of phase and vice versa, so that the signal output becomes modulated by the switching frequency, and can be more easily filtered from the internally generated noise. (The discrimination is highest for sources which are small compared with the interferometer-fringe spacing)
Its use in
radio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming f ...
is generally credited to
Martin Ryle
Sir Martin Ryle (27 September 1918 – 14 October 1984) was an English radio astronomer who developed revolutionary radio telescope systems (see e.g. aperture synthesis) and used them for accurate location and imaging of weak radio source ...
, and used extensively in the
1C radio survey.
Interferometry
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