truncated patch antenna

Hi all,

I am designing a square microstrip patch antenna with truncated/chamfered (circularly-polarized single-feed).

Does anyone know of closed-form design equations for the basic antenna design, patch size, chamfer size, frequency offset, etc, or if they exist. I would like to derive a simple MathCAD or Excel spread sheet to calculate these antennas.

I have found various design methods incorporating design plots but not closed-for equations.

Thanks.