Robert McGwier wrote:
This is not quite right. The DIFFERENT oscillators on the USRP boards
have different frequencies and thus constantly changing phase angle
with respect to each other and with probability 1, the frequencies of
both oscillators will change with changing temp, air flow, etc.. The
only way to avoid this is the buffer the clock from one board and use
it to drive the other board. The system will NOT be coherent unless
it IS coherent. ;-).
Bob
This raises a question I've always had about phase-coherence of PLL
oscillators that use a common
clock source. Will they be coherent "enough" for things like
astronomical interferometry?
The individual PLLs will still have "close in" phase noise components
that are unrelated to
on another. I suppose that given that you typically integrate over
several seconds, such
artifacts get cancelled out. But at very fine timescales, I imagine
that PLLs locked to
a common clock are *not* a good way to get decent coherency?
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