0

I have this question that has been haunting me for a week now. I was given a measurement file of a previous student. Allegedly, they are the measurements of the admittance of a circuit that is supposed to behave as an capacitive circuit. When I plot the values measured, I get the following figure:

enter image description here

What I don't understand, is why is there two resonance frequencies. I was expecting only one, the one due to the resonance of the parasitic inductance and the capacitance C? Any ideas why is that and how can I interpret this behavior?

Thanks in advance

EDIT: the measurements were performed on a cylindrical conductor that has dielectric layer on top. In order to measure the capacitance created by this dielectric layer, another layer of Galium was used as a second conductive cylindrical plate for us to be able to quantify the capacitive coupling. So basically the measured capacitance is a cylindrical one and The measured admittance is that of a parallel RC circuit because of the presence of dielectric losses. So Yc is the module of the measured admittance of the circuit that could be modelled as an RC circuit and $\phi$ is the phase.

Wallflower
  • 449
  • 3
  • 10
  • 1
    Can you show us the circuit? – Jan Eerland Apr 27 '21 at 08:14
  • @Jan It was a cylindrical conductor that has dielectric layer on top. In order to measure the capacitance created by this dielectric layer, another layer of Galium was used as a second conductive cylindrical plate for us to be able to quantify the capacitive coupling. So basically the measured capacitance is a cylindrical one. – Wallflower Apr 27 '21 at 08:23
  • 1
    could you give us a mathematical formula of what I am looking at or how you would expect the circuit to behave 'normally'?. What are the |Yc|? amplitude maybe? and what is Φ in degrees? I see its 100deg until 10^7 Hz. what does this mean? (add these info to your question, not as comment). It would help for someone like me, of limited knowledge. – Christianidis Vasileios Apr 27 '21 at 10:36
  • 1
    @ChristianidisVasileios Done! Thank you for your remark ^_^ – Wallflower Apr 27 '21 at 10:59
  • 1
    It is tricky to do these measurements. The inductance you are measuring is probably more due to the fixture than the device. You are obviously seeing extra resonances. This could be due to transmission line effects or extra capacitance in your fixture. To understand this better, you might draw the measurement fixture and show us what it looks like. Or, you can model the measurement setup with a 3D EM simulator. – user69795 Apr 27 '21 at 17:47

0 Answers0