On Fri, 2011-04-29 at 15:42 -0400, Feng Andrew Ge wrote:
> Could you confirm that switching TX frequency takes "a few ms"? How did
> you get this number? Is it the same for switching TX frequency after
> the code has been running for a while, that is, reconfiguring the TX
> frequency dynamically?
We don't have a guaranteed spec for PLL settling time on the WBX, and we
encourage users to experimentally determine the settling time for their
particular setup and frequency. The figure I gave is based on what I've
seen in the lab, to the best of my recollection. =) It should be pretty
straightforward to determine the settling time for your setup and
frequency step by taking a data capture of a known source.
Any time you retune a PLL VCO, it will take some time to settle. If you
need to avoid that settling time, you can do CORDIC-only tuning with
advanced tuning parameters to shift around within the bandwidth of your
ADC. This will provide a basically instantaneous tuning speed within a
range of 50MHz for USRP2/N2XX, or 32MHz for USRP1/E100.
> On 04/29/2011 12:00 PM, address@hidden
> > Every time you tune the TX you'll have to wait a few ms for it to become
> > stable. For voice transmission purposes, a few ms is effectively
> > instantaneous anyway. And if you aren't retuning, then it will come up
> > instantly, because the LO will still be running in between sample
> > bursts.
> > --n
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