Re: [Discuss-gnuradio] Need some answers about FM TX

[mgray]

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
> 
> 
> 
> 
> address@hidden 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:
> >
> >  
> >
> 
> 
> 
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