Basic Resonator Problem.

[oldsamples]

Hello Experts,

I am trying to simulate very basic structure and I cannot get it right.
My structure is a regular cylindrical resonator. I want the TE11 mode. My resonance frequency is 2.0 GHz. The dimensions are: radius 0.05m, length of the cylinder 0.156m. I have checked the formulas and I have Eigenmode simulation confirming the mode. So next I want to make the driven modal solution for the same structure and obtain the s11 parameter for frequency around the resonance frequency. So I make a sweep and instead of drop of s11(in dB) I get values that are close to zero..no resonance found whatsoever. The critical frvalue of this particular waveguide is around 1.75GHz. When I sweep from 0.1 to 2 Ghz I get drop of S11 until the critical frequency and after that 0 (see the picture). Shouldn't be the opposite since the all power is reflected when the critical waveguide frequency is not met. For the sweep I use the "discrete" setting. The discretization is made for 4Ghz setting.

Thanks in advance,

 

[gasingh]

Hello Experts,

I am trying to simulate very basic structure and I cannot get it right.
My structure is a regular cylindrical resonator. I want the TE11 mode. My resonance frequency is 2.0 GHz. The dimensions are: radius 0.05m, length of the cylinder 0.156m. I have checked the formulas and I have Eigenmode simulation confirming the mode. So next I want to make the driven modal solution for the same structure and obtain the s11 parameter for frequency around the resonance frequency. So I make a sweep and instead of drop of s11(in dB) I get values that are close to zero..no resonance found whatsoever. The critical frvalue of this particular waveguide is around 1.75GHz. When I sweep from 0.1 to 2 Ghz I get drop of S11 until the critical frequency and after that 0 (see the picture). Shouldn't be the opposite since the all power is reflected when the critical waveguide frequency is not met. For the sweep I use the "discrete" setting. The discretization is made for 4Ghz setting.

Thanks in advance,
View attachment 88049

Hi oldsamples , Would you mind sharing the structure you are simulating , How are you coupling the input to the resonator , Do you expect 50ohms input impedance from resonator at resonance ( that seems to be the case as you expect S11 to dip) , If the loss component of the resonator is very small say 1ohm , then there is no way that you will see S11 dipping at resonance feeding with a 50ohm feed , it will stay at zero , We need transform the Resonators input impedance to match the feeds output impedance at resonance , for both S11 to dip and the power transfer

 

[flanello]

Can you plot the real and imaginary part of the input impedance over the frequency?

 

[biff44]

increase the probe coupling until the resonance is seen.

 

[oldsamples]

Hello guys,

First of all thanks for your response!

For feeding the structure I use a wave port with an integration line defined.
I don't use normalization to 50 Ohm.
As far as I understand not using renormalization is the same as providing the resonator with matched signal whatever is its impedance. It is like inherently matched. The next step for me is of course to match it to the 50 Ohm real world but for now I just want to see the resonances as I see them in the eigenmode solver. I provide you the file attached.

thanks again guys