Wideband Quad-Polarization-Reconfigurable Bidirectional Antenna With a Simple Wideband Switchable Feeding Network

This letter presents a wideband quad-polarization-reconfigurable bidirectional antenna using a simple wideband switchable feeding network. By cutting a symmetrical fractal slot on the ground, a wideband dual-polarized differential bidirectional circular monopole antenna with high isolation is realized. To achieve reconfigurable quad-polarization diversity, the bidirectional circular monopole antenna is fed by a wideband switchable feeding network, which provides four output states by only using six PIN diodes. For verification, a prototype operating at 1.85 GHz is designed and fabricated. For the two linear polarization states, the measured 10 dB bandwidths are 28.4% and 25.3%, while the measured peak gains are 4.2 and 3.1 dBi, respectively. For the two circular polarization states, the measured bandwidths with 10 dB return loss and 3 dB axial ratio are 26.3% and 17.4%, respectively. The measured peak gains are 2.8 and 2.4 dBi, respectively.