exp
Full Member level 1
I have a very system-level question: If, in my application, the synthesized frequency does not to be precise but it would be sufficient to know the actual frequency (e.g. by measuring it): Can I get away without PLL (VCO only) or is a PLL always strictly required?
For example:
1.) Does phase noise improve with PLL? (I guess no because PN of PLL should even be higher due to PD)
2.) A PLL definitely accounts for temperature drift of a VCO ... but how critical is this? Is it possible to build a VCO (LC Oscillator) in a modern CMOS process that is sufficiently temperature/"long term" stable? With long term ... hours range. That means: If my control signal is exactly 1.234V and after 2 hours I apply the same 1.234V - can an LC oscillator be built that will produce the same frequency?
For example:
1.) Does phase noise improve with PLL? (I guess no because PN of PLL should even be higher due to PD)
2.) A PLL definitely accounts for temperature drift of a VCO ... but how critical is this? Is it possible to build a VCO (LC Oscillator) in a modern CMOS process that is sufficiently temperature/"long term" stable? With long term ... hours range. That means: If my control signal is exactly 1.234V and after 2 hours I apply the same 1.234V - can an LC oscillator be built that will produce the same frequency?