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There are two equations that are useful when planning observations
that will be correlated on the EVN MkIV data processor. The first relates
to total correlator capacity:

(1) 
Here, from right to left, is the recirculation factor (see
next paragraph).
is the number of polarization
combinations wanted in the correlation (1, 2, or 4).
represents the number of different
frequency subbands, counting lower and uppersidebands from
the same BBC as distinct subbands, but not multiple polarizations in the same
sideband (these enter via ). The value to use for
is ``granular" in multiples of 4: e.g., if you have 58 stations,
use ``8". Independent of this equation, the maximum (
is 16
(a stationunit limitation), and the
maximum is 4096 (a single baseline/SB/pol must
fit onto a single correlator board).
You should pick the various parameters in designing
your observation such that the equation holds, otherwise you will have
to compromise on at least one of them when it's time to correlate.
Some examples of configurations that would
use the full correlator capacity (without recirculation) include:

8sta 
1SB 
1Pol 
2048Frq 
(EVN spectralline) 

16sta 
8SB 
4Pol 
16Frq 
(global crosspolarization mapping) 

12sta 
14SB 
1Pol 
64Frq 
(geodesy) 
When recirculation is operational, the constant term 131072 can be
multiplied by recirculation factor, , for observations that
don't use the full (Nyquistsampled) 16MHz bandwidth per SB/polarization
channel. In principle,
would be set by
, but there may be a smaller absolute limit
depending on the actual implementation.
would still be
subject to the maximum limit of 4096, as discussed above.
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Up: Capabilities
Previous: Features Snapshot
Bob Campbell
20030922