Compact, Wideband, Planar Filtenna With Reconfigurable Tri-Polarization Diversity

A compact, wideband, planar filtenna with reconfigurable tri-polarization diversity is presented. The operating mechanisms of its bandpass filter and its bandwidth enhancement are explained through a step-by-step design evolution. Its feed network consists of three J-shaped probes, a Wilkinson power divider, and phase shifters. Reconfigurability is achieved by integrating four pairs of p-i-n (PIN) diodes into it. Three polarization-reconfigurable states: linear polarization (LP), left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP), are dynamically controlled by those PIN diode switches. A prototype was fabricated, assembled, and tested, which has a compact size ( $0.48 \lambda _{0} \times 0.45 \lambda _{0}$ ) and is low profile ( $0.096~\lambda _{0}$ ). The measured results, in good agreement with their simulated values, demonstrate that the filtenna has a wide −10-dB impedance bandwidth ( $\vert \text{S}_{11}\vert \le -10$ dB) of 15.6%, which completely encompasses the axial ratio (AR) bandwidths (AR ≤ 3 dB) of the two circular polarization (CP) states. The realized gain values over this bandwidth: 7.7 ± 0.5 dBi, are very stable for all three dynamical states. Furthermore, the filtenna exhibits good out-of-band rejection performance characteristics.