Hi all,
I have a multi-phase input signal (1 to 3 phases), all components have the same frequency, but unknown (yet constant) phase offsets. All the offsets can be 0. Each phase can suddenly disappear and re-appear. The input is from mains, but any crazy combination is allowed: a proper +/-120 degrees 3-phase system, all inputs connected to the same phase, two inputs connected to the same phase and the remaining one to a different one, a +/-180 deg input, etc. I would like the system to maintain the combination (once discovered) and stay phase-locked to something invariable in the reference signals.
Additionally, I want to produce a *single* signal of ~1000 times the frequency of a single phase. What would be the best way to implement a seamless switchover?
One obvious solution is to have 3 separate PLLs, but then each of them would produce its own multiplied signal and these signals should not be expected to be seamlessly switchable. This could be either because of tracking the inherent phase shift of the reference signals or just because of noise.
So what else? A single 6-phase NCO (3 phases for lock detection), each phase equipped with a tunable phase shifter? Might work, but seemst to be an overkill.
I think I am not the first person having this kind of requirements, there must be a neat solution. Any ideas?
Best regards, Piotr