  This paper presents radiation efficiency and gain bounds for microstrip patch
antennas. The presented bounds are shown to be good predictors of antenna
performance. Using the bounds, patch miniaturization techniques based on high
permittivity substrates and geometrical shaping are compared. Further, a
semi-analytic model is developed to approximate the bounds. Measurements are
used to validate the bounds. Finally, maximum bandwidth of a microstrip patch
antenna is linked to its maximum radiation efficiency.
