Hello, I have built a PLL system based on the article attached.
In the scope photos we see the IF signal of the mixer.
When the servo amplifier is ON as shown in photo 3 then the error signal ripple is much much smaller then photo 5.
but the VCO keeps moving decreasing the frequency.
So ripple wise the amplifier is good but the DC shift is not getting fix.

My only spec is getting a lock on the resonant frequency of the resonator shown in the diagram below.
We drive the FM coil of the YIG for VCO functionality.
My YIG(VCO) FM coil has the following carachteristics:
sensitivity 400(Khz/mA)
3dB BW 2MHz
resistance 1ohm
inductance 1.5uH
How can I see what kind of PID needed in my situation?
What do you think the PID needs to be to lock in resonant frequency?

 

The circuit drawing looks very similar to the drawing in another post that is still fairly current. Two people working on what appears to be the same project. Locking the resonant frequency of a tuned cavity filter and a YIG oscillator.
Is this a class project?? or a senior level final exam??

 

In another thread on a similar, or the same, project, I learned that thermal drift of the frequency setting coil was causing some problems. So probably you also need a servo control function for the frequency setting coil segment.
Basic feedback system theory demands that the fixed blocks do not vary