Features Snapshot

The EVN MkIV data processor can currently correlate/provide:

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1- and 2-bit sampling (2-bit observations are by far the more common).

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parallel- and cross-polarization products if desired in dual-polarization observations.

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up to 4096 frequency points per baseline (see the discussion following equation 1 below).

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fan-out modes, where 1 channel is written onto 2 or 4 tracks during recording, increasing bandwidth without using higher tape speeds.

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MkIII, MkIV, VLBA, and Mk5 recordings.

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sustained 512Mb/s recordings, a capability that is currently unique to the EVN (full 1Gb/s awaits deployment of the disk-based Mk5 recorders, owing to cross-talk within the playback heads in the tape-playback units at 320ips).

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oversampling at 2 or 4 times the Nyquist frequency in order to provide subband bandwidths, $BW_{\rm sb}$, down to 500kHz (the maximum Nyquist-sampled $BW_{\rm sb}$ is 16MHz).

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multi-pass correlation (i.e., for observations having $>$16 stations at any given time).

Capabilities whose development is still underway or not yet fully tested include:

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pulsar gating.

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multiple field centers (correlation of $>$1 phase centers in one pass) -- most likely to be implemented in the PCI (cf §2.3).

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playback at a tape speed different than that used in recording.

Capabilities that are yet to come include:

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phase-cal extraction.

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sub-netting.

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recirculation -- achieving greater equivalent correlator capacity for observations that don't use the maximum bandwidth per channel (see the discussion following equation 1).

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space VLBI.