I believe the filtering used does change with the decimation - per an earlier posting by Matt Ettus: if the decimation is a factor of four there are two half-band filters + CIC filter, if it is a multiple of two (i.e. even, but not a factor of four) then there is only one half-band filter + CIC, and if it is an odd number, just a CIC filter. Doug
On Mon, Oct 26, 2009 at 4:20 PM, Jordan J Riggs <[email protected]> wrote: > Folks, > > I have been trying to get a better understanding the noise characteristics > of the USRP2/RFX2400 platform. To get an idea of the noise floor at various > bandwidths, I connected the SMA's on the RFX2400 to a 50ohm load and > averaged out the FFT at various bandwidths. Naturally, I would expect the > floor to drop at lower bandwidths (higher decimation), but this is not > always the case. For example, the floor at decim 100 is slightly lower than > it is at 128. This is counterintuitive. The only explanation I can come up > with is some filtering quirk in the FPGA. Does anyone have any ideas? > > I've attached screenshots at decim 100 and 128. > > Thanks, > Jordan > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- Doug Geiger [email protected] _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
