Novel small folded shorted-patch antennas

The size of a conventional shorted-patch antenna can be reduced by almost a half via folding the shorted patch together with the ground plane. The resonant frequency of the folded shorted-patch antenna may be further lowered by reducing the width of the shorting walls or by moving the folded patch upward. It is shown that the antenna length of a folded shorted-patch can be reduced to less than 1/8 the length of a conventional patch antenna. A practical folded shorted-patch antenna for the Bluetooth ISM band is designed and measured to demonstrate its application potential. This size-reduced antenna can achieve an impedance bandwidth of 4% and has a nearly omnidirectional radiation pattern, which may be suitable for some mobile communications systems.