A Polarization Reconfigurable Microstrip Circular Patch Filtering Antenna

A polarization reconfigurable microstrip filtering antenna is proposed in this paper. The proposed antenna is composed of a microstrip circular patch radiator which is probe-fed by a PIN-diode-controlled switchable network on the other side of its ground plane to provide four different states of polarization. The feeding network is successively coupled to two additional microstrip resonators and the input microstrip line. Together with the resonant mode of the circular patch, a 3rd order equal-ripple filtering response is achieved. The measured fractional bandwidth of the proposed antenna is around 6.5% centered at 2.45 GHz. Measured in-band maximum antenna gain is 3.1 dBi. The proposed antenna has the advantages of multi-function, small dimension and simple structure for 2.4 GHz WLAN applications.