On Mon, 01 May 2006 17:24:30 GMT, "Michael A. Terrell"
wrote:

My point about microwave is that without filtering you have aditional
noise to deal with in the system. We offered IF bandwidths from 10 KHz
to 20 MHz, and video amps with matching bandwidths to keep as much noise
out of the received signal as possible.


The same receivers are used by NOAA for their weather sat downlinks.
With the improved doppler compensation they are able to lock onto the
sat before it comes over the hrizon five minutes faster than the old
Harris equipment it replaced.

Ah! I see what you mean. Of course matching a receive filter to the
necessary bandwidth means that you neither lose much-needed signal,
nor let in unwanted noise. That goes for IF and baseband. As for RF,
presumably you have a range of input frequencies to deal with, so you
can't implement a channel-width filter there. But what you can do is a
roofing filter and image filters.

I presume your Doppler compensation was predictive, offsetting the
receiver by 17000MPH worth of frequency in anticipation of
acquisition.

d

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Pearce Consulting
http://www.pearce.uk.com