I've got a student intern (Undergrad Senior) who's doing a project for me where he's trying to synchronize (and syntonize) two 1 pps ticks, generated from different oscillators using some modules in an FPGA. One oscillator is a run of the mill 66 MHz clock oscillator the other is a 49.x MHz TCXO. (and, of course, because he's working in a breadboard, I can swap in a signal generator for either.. I've got a stack of 3325Bs and 8663s, etc.) The objective is to get two signals that are 1 pps (or 10 pps) ticks (each derived from a different oscillator) that align I'm looking for info to point him to on evaluating the performance of his implementation. I've got a HP 5335 (which works quite nicely with a Prologix and John Miles's tools... thanks John!). I've got oscilloscopes. I've got access to more exotic stuff if need be (although, since my intern budget is skinny, stuff I happen to have in the lab, like my uncalibrated 5335, is better) I also have a bunch of Wenzel 10 MHz OCXOs sitting around (although for this, why not use one of the instrument's internal oscillator and distribute it around) I do have a hydrogen maser derived reference in the lab, but I'm more interested in him measuring the two oscillators against each other. (that is, measuring the performance of the TCXO, by itself, isn't particularly interesting) What he needs is some suggestions on things that he can measure that would be meaningful figures of merit for the application. He's not doing a PhD dissertation, though.. And he has to be done before the end of the spring semester. No million second Allan Deviation measurements.

Hi Jim, On 03/09/2012 10:27 PM, Jim Lux wrote: > I've got a student intern (Undergrad Senior) who's doing a project for > me where he's trying to synchronize (and syntonize) two 1 pps ticks, > generated from different oscillators using some modules in an FPGA. > One oscillator is a run of the mill 66 MHz clock oscillator the other is > a 49.x MHz TCXO. (and, of course, because he's working in a breadboard, > I can swap in a signal generator for either.. I've got a stack of 3325Bs > and 8663s, etc.) > > The objective is to get two signals that are 1 pps (or 10 pps) ticks > (each derived from a different oscillator) that align > > I'm looking for info to point him to on evaluating the performance of > his implementation. > > I've got a HP 5335 (which works quite nicely with a Prologix and John > Miles's tools... thanks John!). I've got oscilloscopes. I've got access > to more exotic stuff if need be (although, since my intern budget is > skinny, stuff I happen to have in the lab, like my uncalibrated 5335, is > better) For the application, the 5335 will be more than adequate. > I also have a bunch of Wenzel 10 MHz OCXOs sitting around (although for > this, why not use one of the instrument's internal oscillator and > distribute it around) > > I do have a hydrogen maser derived reference in the lab, but I'm more > interested in him measuring the two oscillators against each other. > (that is, measuring the performance of the TCXO, by itself, isn't > particularly interesting) > > > What he needs is some suggestions on things that he can measure that > would be meaningful figures of merit for the application. He should measure: - Lock-in transient - Lock-in time/time-constant - Lock-in overshot - Estimate control loop bandwidth and Q-value/resonance He should then also have a "lock" detector, possibly several lock levels and illustrate them in the transient waveform. Then, he should measure the lock-in deviation pattern and measure bias and RMS noise. Maybe even do a nice ADEV/TDEV set of plots. MTIE plots is always nice as well. Showing good control of model parameters and actual performance remains a good thing. It is usually good to attempt to improve things. A good exercise is trying to figure out ways to get quick and dead safe lock-in while also get good in-lock performance. :) I strongly recommend having a digital scope in parallel with the counter. > He's not doing a PhD dissertation, though.. And he has to be done before > the end of the spring semester. No million second Allan Deviation > measurements. Should be a good project for him. Keep me posted on the progress. Cheers, Magnus