Here is an article that discusses using this technique in a radio: http://img.cmpnet.com/commsdesign/csd/2002/oct02/eamon-fig3.jpg
Here is a graphic that shows the various images that are present in the spectrum. http://img.cmpnet.com/commsdesign/csd/2002/oct02/eamon-fig3.jpg This is not a clock leakage or a DAC non-linearity problem. It is just Nyquist digital sampling theory. http://en.wikipedia.org/wiki/Shannon-Nyquist_sampling_theorem On Sat, 1 Oct 2005, Robert McGwier wrote: > Thanks for all the comments but I still have my doubts. I am more like > to believe in clock leakage and DAC nonlinearities causing this than I > am with square wave harmonic activity. I will investigate further with > the spec-an if I have time. > > The pico-board looks great. I recently acquired the AD9954 eval board > (two 9954's sync'd for I/Q) and a AD9958 eval board to learn what was > going on. AD is a serious believer these days in DAC nonlinearities and > clock leakage causing all sorts of issues that are mistaken for other > things and as such they are truly seriously pushing the 9958 with its 10 > bit DAC and smaller accumulator and phase word which seems so > counterintuitive but as you all say, measurements will tell the tale. > Their app engineers are all over you when you talk to them at length > about the problems attributed to phase truncations which mathematically > cannot be and which they have tracked down to DAC/clock leak issues. > > I will post a note here with some results. > > Bob > > > > > [EMAIL PROTECTED] wrote: > > >The same does apply to a DAC as well as an ADC. They are both sampling > >systems. A DAC typically has a low pass filter to cut all the alias > >images. But you can also bandpass filter those images to produce the > >desired signal. The system is very linear and isn't a mixer. > > > >Here is my original post: > > > > > > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
