Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Simulating resistive losses in Time-domain RF model

Please login with a confirmed email address before reporting spam

Hello, I have built a model for a microwave cavity resonator using the Electromagnetic Waves, Frequency Domain (emw) physics, where the cavity is a volume of air with the external boundaries using an Impedance Boundary Condition to account for the resistive losses in the cavity's copper walls. This model works well and I have confirmed experimentally the Q-factor and eigenfrequencies.

However, I now want to model the time-domain response of the cavity when driven by microwave pulses. To this end I have added Electromagnetic Waves, Transient (temw) physics to the model. The problem is that this module does not allow me to add an Impedance Boundary Condition or a Transition Boundary Condition to account for resistive losses.

I have tried to explicitly include the cavity walls in the model, specifying the material as copper, but this overestimates the resistive losses by several orders of magnitude (I think because the minimum element size of my mesh is still much larger than the skin depth at the operating frequency). It would be unpractical to have mesh elements small enough to accurately simulate the skin effect.

How should I set up my model to allow time-domain solving while accounting for resistive losses (which are the prevalent dissipation mechanism controlling the cavity dynamics)?

Regards, Louis Haeberle

-------------------
-- Louis Haeberle
MSc Student (Physics)
Silicon Spintronics Research Group (Pr. Pioro-Ladrière)
Université de Sherbrooke

1 Reply Last Post 1 mag 2018, 17:02 GMT-4
Edgar J. Kaiser Certified Consultant

Please login with a confirmed email address before reporting spam

Posted: 6 years ago 1 mag 2018, 17:02 GMT-4

Louis,

you might consider to do a frequency sweep with suitable resolution and frequency range according to the pulse and then Fourier transform into the time domain using a suitable window function.

An approach like this worked for me in an acoustical model.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Louis, you might consider to do a frequency sweep with suitable resolution and frequency range according to the pulse and then Fourier transform into the time domain using a suitable window function. An approach like this worked for me in an acoustical model. Cheers Edgar

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.