On Fri, Nov 19, 2010 at 09:19:04PM +0900, Songsong Gee wrote: > I understan what you told me... > Then... however, why they have same sign? > One is for up conversion, and the other is for down conversion > they might have opposite signs. > one is MINUS 4 MHz, and the other is PLUS 4 MHz > > and one another... > They meet in frequency by DXC, > but, in my opinion, they are basically different in baseband frequency... > I really really cannot understand this magic :(
Try drawing a picture... Eric > 2010/11/19 Eric Blossom <e...@comsec.com> > > > On Fri, Nov 19, 2010 at 05:17:53PM +0900, Songsong Gee wrote: > > > I use USRP sink and source and set frequency with 2.6 GHz > > > When I run a flow graph, I see like below: > > > ============================================== > > > A: Flex 2400 Tx MIMO B > > > r.baseband_frequency = 2604000000.0 > > > r.dxc_frequency = -4000000.0 > > > r.residual_frequency = 0.0 > > > r.inverted = False > > > > > > A: Flex 2400 Rx MIMO B > > > r.baseband_frequency = 2596000000.0 > > > r.dxc_frequency = -4000000.0 > > > r.residual_frequency = 0.0 > > > r.inverted = False > > > =============================================== > > > Both of baseband frequency are near 2.6 G, but they do not match up > > > Can it be problmeatic for communicating each other? > > > > The actual frequencies on the air will be 2.6 G +/- oscillator tolerance. > > > > In the Tx case, the LO is set 4MHz higher than the target, and the > > DUC is used to adjust the baseband -4MHz. > > > > In the Rx case the LO is set 4MHz lower than the target, and the DDC > > is used to move the digitized IF signal 4MHz lower prior to decimating. > > > > This is easy to confirm with a siggen and a spectrum analyzer. > > > > Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
