Multipolarization-Reconfigurable Air-Filled Substrate Integrated Waveguide Cavity-Backed Slot Antenna

A novel single-feed ultrawideband cavity-backed slotantenna with a reconfigurable polarization capability is demon-strated in substrate-independent air-filled substrate integratedwaveguide (AFSIW) technology for Internet-of-Things applica-tions in the [5.15-5.85] GHz frequency band of the unlicensednational information infrastructure. The antenna achieves an ul-trawide impedance bandwidth by exploiting a double ring of slotsand supports four switchable linear polarization states (±45°,0°,+45°,and 90°) by leveraging four quartets of p-i-n diodes. Byelectrically shorting the slots at well-defined positions by these p-i-ndiodes, dynamic polarization reconfiguration is achieved by switch-ing their dc bias current, supplied at the antenna feed through anexternal bias tee and routed from the antenna's back to front cavityplane via the AFSIW sidewalls. This new simple, yet effective, biasnetwork enables the integration of all polarization control electron-ics inside the antenna cavity to protect them from environmentaleffects. Finally, measurements prove that the prototype exhibits anoverlapping impedance bandwidth of 29%, from 4.85 to 6.45 GHz,and a stable conically shaped radiation pattern across the operating band width with a 3 dB beamwidth of 45°and a peak gain of 6.5 dBi for all four states.