Got it. Saw the earlier message too. Thanks
On Thu, Dec 2, 2010 at 12:12 PM, John Andrews <gnu.f...@gmail.com> wrote: > > > On Wed, Dec 1, 2010 at 5:14 PM, Eric Blossom <e...@comsec.com> wrote: > >> On Wed, Dec 01, 2010 at 04:57:11PM -0600, John Andrews wrote: >> > Hi, >> > Can we change the DDC value to 0 in usrp_fft.py? Why is this not 0 as >> one >> > would expect to input the center frequency same as the baseband >> frequency; >> > i.e. if I know that my signal is on a carrier at 2.4G then I would use >> > usrp_fft.py to display the spectrum by having the center frequency as >> 2.4G >> > instead of typing in 2.404G (as DDC is -4M). >> >> It's non-zero to move the RF DC offset problem away from zero (and in >> most cases out of the range that anybody cares about). See earlier >> message today... >> > > Thanks for your reply Eric but can you please explain what it means or > direct me to a place where I can find out? That will be very helpful of > you. I looked at the messages but I didn't not find which one you were > referring to. > > Thanks > >> >> > In benchmark_tx/rx programs do I have to account for this DDC=-4.0M? If >> one >> > USRP is transmitting at 2.4G ( ./benchmark_tx.py -f 2400M ) then should >> I >> > have the receiving USRP receiving at 2.404G ( ./benchmark_rx.py -f 2404M >> )? >> >> No you don't. If you do -f 2400M then the complex baseband signal is >> equivalent to the RF signal that's centered at 2400M. >> >> Eric >> > >
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