Correlator

The correlation scheme in the MWA is of the "FX" variety, in which the voltage samples from the antennas are first Fourier transformed (F) into the frequency domain, then are cross-multiplied (X) pairwise and integrated over time.

The first step of the "F" portion of the correlator is actually done within the receiver, where the digitized signals are transformed into coarse frequency channels, each of 1.28 MHz width. A subset of 24 channels are selected and are then carried along 192 fiber-optic cables, at an aggregate data rate of 320 Gb/s, to the correlator.

At the correlator the signals are converted from optical to electrical format, and are then input to one of 16 PFB boards. These boards perform two essential functions: the coarse channel data are broken into fine channels of only 10 KHz bandwidth, then the data are re-ordered to be suitable for use by the correlator boards.

Further details:

• The cross-multiplication in the correlator boards is a challenging task.
• Running in parallel with the cross-correlation is a digital array beamformer.

[ need correlator diagram ]