micromachined rectangular patch antenna on a synthesized substrate ( Al2O3 with air)

Hello
I'm working on designing a micromachined rectangular patch antenna on a synthesized substrate ( Al2O3 with air) but the problem that i'm facing is the inset width is coming bigger than the width of the patch itself for some reason! After synthesizing my primittivity, I use the new value to calculate my L and W of the rectangular patch but using the new primittivity I'm getting an inset width bigger than the width of the patch....

Does anyone have any information on micromachined patch antennas?

I appreciate you guys help in advance.