Using the wfm receive module I notice increased sensitivity using the
halfband filter load. I have not played with the various decimations or
tried to do anything other than standard stuff so far but this is an
improvement. I can't wait to look at GPS with the DBS_RX to see if the
sensitivity there sees a similar improvement.
Bob
Eric Blossom wrote:
Matt's been hard at work on the halfband filter for the FPGA, and it's
in pretty good shape. As long as you're not using a decimation factor
of 10, everything looks good. The FPGA code along with the relevant
host side mods are checked in.
With this change the usrp decimation factor must be EVEN and in the range
8 <= decim <= 256. We've got proper gain over the full range.
If you're tracking CVS, you should update:
usrp
gr-usrp
and install this .rbf file http://comsec.com/usrp/usrp_fpga_rev2_2005_10_24.rbf
as $prefix/share/usrp/rev2/usrp_fpga.rbf
If you update some, but not all of these items, you'll be hosed ;)
[The halfband code is pretty gnarly. Take a look at
usrp/fpga/sdr_lib/hb/halfband_decim.v for some serious brain twisting...]
Also, there's some work-in-progress to support inbound 8-bit samples
across the USB. The interfaces are in (u.set_format(...)), but it's
not all sorted out yet.
Eric
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