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:
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