boundary conditions and electric energy

Hello,

I am using HFSS to simulate a device and I would like to compute the total energy in and around the device, I have nevertheless several questions some related to HFSS, and particularly, to boundary conditions, another is more general and concerns electric energy. I hope the community can help:

1- In electrostatics, the total electric energy is obtained by calculating We = 1/2 \int_Vol E dot D dVol inside the air box, If I understand well, the radiation box does not contain the energy, then how can I compute the electric energy outside the radiation box using HFSS?

2- At high frequency, if I understand well, a too small radiation box will cause reflections and therefore increase the energy inside and decrease the radiated power, but at low frequencies, what does the use of a radiation box implies in terms of energy?

3- How does the total electric energy relate to capacitance? Once again, at low frequency, We is equal to 1/2 C U^2, as frequency increases and in harmonic regime, is We still equal to 1/2 C U^2?

Thanks for your inputs,

3 Why not? Apply to each V(f). or U(f)

I will do that, thank you. Then again, the energy inside the radiation box does not account for all the energy, nevertheless, it is perhaps a good approximation.