On Sat, 2006-05-27 at 12:16 -0700, Thomas Schmid wrote: > Hi, > > I have a question about the basic RX/TX boards. What should I see if I > hook the basic TX board to an oscilloscope if I send out a QPSK > signal? Here is what I do: > - I generate a QPSK signal in GnuRadio > - I send the signal to a complex file source and the signal looks right > - I send the signal to the complex USRP source and have a BasicTX on > it. The outputs TXA and TXB are hooked up to a oscilloscope on channel > 1 and 2 respectively. > > Now, what should I see on the oscilloscope? Is it the baseband signal? > How does the I and Q phases get mixed together? Does that depend on > the mux values? Unfortunately I couldn't find a good block diagram of > the TX path on the wiki, i.e., the link to [A system block diagram of > the USRP receiver and transmitter path] on the wiki page > "http://www.comsec.com/wiki?UniversalSoftwareRadioPeripheral" is dead.
If you set the carrier frequency to 0 you will see the I signal on the I channel out and the Q signal on the Q channel out. This will only be useful with the LFTX board since the BasicTX will block DC. If you set the carrier frequency to something other than 0, then the I and Q signals will be upconverted and sent to the outputs. As long as the carrier frequency is greater than your signal bandwidth, then you only need either the I output or the Q output since they are now double-sided real signals. You can still use the I and Q connectors with an image-reject mixer if you need. Matt _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio