Patch antenna miniaturizing with a shorting pin near the feed probe-its physical mechanism and the design on Smith chart

Miniaturizing patch antennas by a shorting pin near the feed probe has been successful in hardware experiments. The physical mechanism is now given. The mechanism points out that a feed probe with the shorting pin is equivalent to a folded dipole antenna in an admittance formula. This equivalence makes it possible to use the Smith chart to: (1) aid the selection of the feed and pin dimensions and (2) provide the limit of possible miniaturization. The mechanism also points out that the efficiency of patch can be quite low due to the high Q of the miniaturized mode