A geometrical theory of the resonant frequencies and radiation

-factors of

, and

triangular microstrip patch antennas is developed, based upon the rereflection of rays making up the field underneath the patch. Extremely simple formulas for

are obtained, which enables an extensive comparison of relative radiation

for various patch shapes to be made. This theory replaces other much more cumbersome expressions from the literature, or gives new formulas for some cases for the first time.