Discussion Forum

Hello,

What I am trying to do :

I have been trying to simulate a bowtie antenna structure in time domain. The operating frequency is around - 10 GHz and I have designed the antenna dimension according to that.

Boundary Conditions in Time domain :

I have selected boundary condition (PMC, PEC, SBC) on the side walls of the big air box. I have used excitation plane waves which is coming from the top of the big air box using SBC and the excitation plane waves E (1,1,0).

Problem I am facing with the Result:

In the result section, I am checking how the E-field at the center of the gap is changing with time (ns). The problem I am facing right now is - The electric field, E, at the center of the gap seems to be unstable (as you can see in the attached figure). It seems to be there is an amplitude modulation going on in E-field. Whereas, the expected E-field should be steady with time (pure sine wave).

I thought there might be an issue related to the reflection of the wave from the boundary of the air box. But since, the dimension of my air box is around 5*lamda (wavelength); therefore, I don't get the point why the E-field shows a standing wave pattern at the gap.

I would like to know why E-field in my model is unstable and how can I fix it? Please kindly let me know. I have been trying to fix this thing for more than a week. Please feel free suggest if you think the model can be improved by doing it in any other way. I have attached the my Comsol model for your convenience.

Thanks for your patience and cooperation.

Regards,