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?
