<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
<font size="-1"><br>
</font><font size="-1"><tt><big>It seems to me that majority of work to
implement proposed functionality is on the CMIB. <br>
<br>
CM would have to pass to CMIB the following parameters: <br>
- Enable/Disable "WBC data for slope corrector" <br>
- Specify averaging time (if enabled)<br>
- destination address for generated XML messages (depending on the CMIB
implementation this may not be needed).<br>
<br>
In addition, when this function is active, WBC can not be configured to
produce other products (wideband cross and auto - correlation
products). (Comment for Bruce: It would be nice if CMIB schema could be
defined so that all products are either part of element
vciConfiguration or element wbc.)<br>
<br>
Should we allow VCI user to enable/disable this function and to specify
averaging time (and destination address) ? <br>
Or should CM enable this for all Antennas/Basebands with 3-bit IQ ? <br>
<br>
If needed, CM could collect data for all the basebands/antennas and
forward it to the Executor, but is probably more efficient to avoid
such "intermediate" step.<br>
<br>
Sonja <br>
</big></tt></font><font size="-1"><br>
</font><br>
Barry Clark wrote:
<blockquote cite="mid:4C59F022.4060809@aoc.nrao.edu" type="cite">
<pre wrap="">To set the baseband slope correctly, the least complicated approach
is to use the Wide Band Correlator on the station board to see the
overall shape of the spectrum, and have it report the correction
needed to the Executor, which would then forward it to the slope
corrector in the T304 modules.
This is because the required slope is a function of antenna, band,
and location within the band. To do it by tabulation would require
maintenance of a very large table which would change from time to
time as receivers are serviced or replaced. (The slope required
may also be a function of which T304s are installed, although these
are believed to be much more uniform than the receivers.)
The Executor could handle this information in the same way it currently
handles reference pointing, phasing, and, indeed, setting T304 levels.
What the Executor would like to see is just an rms and slope from
the WBC, one for each baseband in the array. I suggest the following
XML descriptor.
<xsd:complexType name="WbcDataType">
<xsd:sequence>
<xsd:element name="rms" type="xsd:float" />
<xsd:element name="slope" type="xsd:float" />
</xsd:sequence>
<xsd:attribute name="antId" type="xsd:string" />
<xsd:attribute name="baseBand" type="xsd:string" />
<xsd:attribute name="avg" type="xsd:double" />
<xsd:attribute name="time" type="xsd:dateTime" />
</xsd:complexType>
These would probably come packaged in an envelope, either for a lot
of antennas if they come from some collector in the correlator, or
with just a couple if they come directly from the station board.
Worst case is eight basebands from 28 antennas, 224 elements in all.
The whole works might fit in a 16K datagram. I think a reasonable
averaging time (avg above) would be 10 seconds. (The consideration
is only to keep the traffic at a low level while still getting answers
on a script-type timescale.) I guess CM will need to send this
averaging time to the StB.
These need only be sent when in three bit mode.
The rms above is just the lag zero autocorrelation, divided by
averaging time and suitably scaled.
The slope is a little more difficult. If computation is not a
consideration, you calculate the spectrum and see which slope
corrector works best, calculating the goodness of fit of
a*10^{0.1*n*(f/bw)}
for, say, n in the range -10 to 10 and reporting the best n.
If calculation is a problem, a reasonable guess can be made directly
from the lags. (The lag beyond which the correlation is low is
a measure of the magnitude of the slope; whether there are nulls
before then gives the sign.)
_______________________________________________
evla-sw-discuss mailing list
<a class="moz-txt-link-abbreviated" href="mailto:evla-sw-discuss@listmgr.cv.nrao.edu">evla-sw-discuss@listmgr.cv.nrao.edu</a>
<a class="moz-txt-link-freetext" href="http://listmgr.cv.nrao.edu/mailman/listinfo/evla-sw-discuss">http://listmgr.cv.nrao.edu/mailman/listinfo/evla-sw-discuss</a>
</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="90">--
Sonja Vrcic
Software Engineer
National Research Council
Herzberg Institute of Astrophysics
Penticton, BC, Canada
Tel: 250-497-2309 / 250-497-2300
<a class="moz-txt-link-abbreviated" href="mailto:Sonja.Vrcic@nrc.gc.ca">Sonja.Vrcic@nrc.gc.ca</a>
<a class="moz-txt-link-freetext" href="http://www.nrc-cnrc.gc.ca/eng/ibp/hia.html">http://www.nrc-cnrc.gc.ca/eng/ibp/hia.html</a>
</pre>
</body>
</html>