On 12/28/2010 08:05 PM, James Jordan wrote:
Hi Alexander, where the filter perform? In gnuradio?
Since there is a filter, openbts must set it, how openbts set the filter?
Regards.
The OpenBTS software likely sets the incoming decimation rate to match
as closely as possible the desired receive bandwidth,
then it likely applies an FIR bandpass filter on the software side.
This is, after all, Software Defined Radio, so it should be no surprise
to anyone that applications (OpenBTS, or whatever) use
filters implemented in software to condition the signals before
further processing. None of that requires the analog filtering to
work in anything other than an anti-alias mode. Filtering and
bandwidth reduction is performed first in the FPGA, in the digital
domain, and then on the host, with software, again in the digital
domain. Either Gnu Radio, or OpenBTS, or whatever.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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