Hello , I am building a PLL based on a resonance frequency of a two port cavity resonator .
The resonator is a basic cylindrical resonator with sapphire core and the inputs and outputs are coupled the basic coax cables .
I have found a resonance with a very high Q.
For some reason the resonant frequency slightly moves all the time which breaks my pll loop because it’s suppose to be a stable source .
what could cause a drift in the resonant frequency ?
How can make the resonator more stable ?
Thanks.
I had a similar task of decoupling 100g shock/ 5g vibration and 50g acceleration from an HC-cut OCXO to meet 1e-10 stability criteria for Doppler. Only allowed 5mm of space, in 1976 I ended up using ESD foam for CMOS which had the necessary low Q resonance yet poor durability. It was just for Black Brandt rockets.
Dual ovens make that task easy.
Identify the source of sensitivity and protect it.
1. Uncouple the oscillator by placing it onto a foam material, for example. Replace your semi rigid cables by soft cables. In other words, reduce coupling of shock and vibration to the cavity.
2. You can heat your cavity to a controlled (regulated) temperature, similar to OCXO for crystal oscilators.
What's time scale and amount of observed drift? It sounds unlikely that a resonator on lab table is exposed to vibrations or larger temperatur variations. I rather guess that instability is caused by your PLL loop. Considering the complex circuit topology, it's not simple to distinguish drift causes.
Hello,there is a circuit shown below taken from the attached article, where we put a YIG signal to a cavity resonator(from A to B) . Then for feedback we lock on the point of the dip. this dip is supposed to be a resonance of a cavity. resonance is when the magnetic energy equals the electric...
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If it's actually a mechanical problem, e.g. broken resonator, you should observe huge effects when slightly knocking it.