Shorted Patch Antenna with PIN Diode Operating Band Switching

An improved design of a shorted patch antenna with electronic switching of the operating bands is proposed. PIN diodes are used as switches for connecting four shorting posts to the ground plane. With reverse biased diodes the antenna operates at 2 GHz, while with forward biased diodes the operating frequency is 4 GHz. Two electronically switched impedance matching networks are designed, one for each band. The impedance matching networks are electronically switched with the same bias voltage used for switching the patch resonant frequency. The E- and H-plane co-polarization and cross-polarization radiation patterns are measured in both bands. The results show good radiation characteristics and lower cross-polarization levels in comparison to previous designs