high-level ska signal processing description - The Square Kilometre ...

WP2‐040.030.010‐TD‐001
Revision : 1
31
0.8326
1
The radius, , of the Field of View is proportional to .
And the synthetic beam radius, , is proportional to
.
The Earth’s rotation, ω e = 7.92 x 10 ‐5 radians per second
31
0.8326
31 0.98
0.8326 7.92 10 15
200 10
The output rate of the correlator is to be minimised to limit the load on the Imaging Computing. This
is achieved by integrating the Correlation results. However, integration has the effect of smearing
the data and reducing the amplitude from the peak response to a point source due to the effects of
the Earth’s rotation through the fringes.
Currently the DRM calls for less than 2 percent smearing which corresponds to > 0.98
32 ∆
The upper frequency taken to calculate the integration time is either the maximum capability of the
receptor or the upper frequency of the Science requirement depending on which is the lower. On
this basis, more than one receptor technology may be required to provide the required frequency
coverage.
In the more general case, the frequency coverage of individual technologies may differ from the
values quoted and may even provide overlaps in frequency across technologies. This provides the
option of correlation across receptor technologies which are likely to have differing sample rates. In
this case, interpolation of the data streams is required to provide sample level time alignment for
the correlation process. Further work is required to identify the associated processing load and
evaluate the merits of correlating across receptor types.
7.4.2 Correlator Processing Load
The correlator is full Stokes with a processing load proportional to the square of the number of
antennas, N a and signal bandwidth, BW. Nominally, the load is independent of the number of
frequency channels
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