Correlator

This article covers signal processing circuits. The term correlator is also used for the abstract mathematical operator , e.g. B. used in quantum field theory .

A correlator performs the function of cross-correlation for the precise determination of the time offset between two signals. Possible forms are special computers, analog circuits , brain structures or computer programs . The signals can be technically coded radio signals , radar , sonar or optical echoes or signals of natural origin.

The principle is explained using three different applications as an example,

• a direction measurement: measurement of the earth's rotation by VLBI interferometry on quasars ,
• the speed measurement by means of a pair of sensors arranged offset in the direction of movement, and
• a distance measurement : localization with the satellites of the Global Positioning System (GPS).

In the correlation, two signals are shifted against each other by calculation until the characteristics of the two signals match. The shift found is then the time difference

• either between the transit times from a radiation source (quasar) to two ground stations
• or the signals of the two sensors that move one after the other over a structure
• or between the code received from a satellite and the code calculated in the receiver.

As long as the radiolocation receiver after switching (position-dependent!) The orbits of satellites and knows his own movement in space only very roughly, his correlators have because of the Doppler shift signals not only time- shifting , but also different stretch . This two-dimensional search is considerably more complex.

Correlators in comparison

• The Atacama Large Millimeter / submillimeter Array (ALMA) correlator performed 17 PetaFLOPS in December 2012.
• The computing power of the WIDAR correlator on the Expanded Very Large Arrays (EVLA) is given (June 2010) as 40 PetaFLOPS.
• The planned correlator of the Square Kilometer Array (SKA) (construction period 2016 to 2023) should be able to carry out 4 ExaFLOPS (4000 PetaFLOPS) (information as of June 2010).

See also

• Optimal filter
• Equalization calculation
• Astrometry , radio astronomy

Individual evidence

1. ↑ Powerful Supercomputer Makes ALMA a Telescope .
2. ↑ The highest supercomputer in the world compares astronomy data . Heise online.
3. ↑ ^{a b} Cross-Correlators & New Correlators - Implementation & choice of architecture . (PDF; 9.4 MB) National Radio Astronomy Observatory, p. 27.
4. ^ The Expanded Very Large Array Project - The 'WIDAR' Correlator . (PDF; 13.2 MB) National Radio Astronomy Observatory, p. 10.