Dielectric resonator Q factor is very high,so why no problems to maintain zero phase?

[Terminator3]

For DRO oscillators, loop gain is >1, and phase must be ~0 or few degrees. I can't understand, at frequencies say 20GHz, tiny change of 0.01mm make difference in phase. So how it still be working? I can imagine someone moving DR puck and looking onto spectrum analyzer and randomly get some good or better result then glue thing to PCB?

 

[Bob60]

It`s up to you where and how do you glue the DRO. To the metal wall to the PCB directly or via ceramics distancer- pedestal to the PCB or something else.

 

[Terminator3]

Problem is why phase maintained right? Isn't it position-related parameter?

 

[Bob60]

Finlay what is your aim, phase or oscillator with wright frequency and performance. Phase and freq depends from everything. Shield material, distance, temperature, position and so on.

 

[BigBoss]

20Ghz has 15cm wavelength in vacuum.On a dielectric substrate this is smaller depending on dielectric coefficient.
A tiny movng can create a significant phase shift.
Just a guess..

 

[Terminator3]

So, what i want to clear out is: if we have very-high-Q resonator, then it is easy to get s21 maximum out of n*360 phase area, so oscillator will not start. How this problem solved for >20GHz oscillators? Hand-placing, machine-placing of DR puck?

 

[Bob60]

20Ghz has 15cm wavelength in vacuum.

just a guess..

Definitely not in a vacuum. Should be 15mm.

 

[BigBoss]

Definitely not in a vacuum. Should be 15mm.

You're right..15mm
On a substratrate , it will be smaller.I meant a tiny movement may change the phase radically..