Any theory for (off center fed microstrip antennas)?

Hi everyone,

I'll be glad if can provide me with documented materials about "off center fed microstrip antennas".. Theory and preferably about the mechanism, what things have to do with impedance ..I've come across some researches, but they seemed to implement the way with no much theory.
Thank you and God bless you.

Waddah

The classical transmission line model helps. Accordingly it is straightforward to understand that the impedance keeps stable when the feed location varies along the patch width, whereas it becomes quite sensitive when the feed location moves along the patch length.