HFSS Periodic structure fundamental floquet mode

Hello,

I am trying to simulate a periodic structure containing PEC (Metamaterials) using HFSS Eigensolver. And then, I use field calculator to extract the first fundamental floquet mode. In other words, go to spectral domain from spatial domain.

In the spectral domain, for the first mode, we can re-write maxwells equation as follows:
-i beta x H = iwD + J

These field values are volume integrals over unitcell volume mutiplied by exp(+i*beta.r) except for the current which is a surface integral over the PEC.

The problem is that the left hand side and the right hand side of this equation are not equal after I calculate these using field calculator. Using a denser mesh helps with the problem but that's not enough.

Could somebody help please?

M