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

Abstract

A novel single-feed ultrawideband cavity-backed slot antenna with a reconfigurable polarization capability is demonstrated in substrate-independent air-filled substrate integrated waveguide (AFSIW) technology for Internet-of-Things applications in the [5.15-5.85] GHz frequency band of the unlicensed national information infrastructure. The antenna achieves an ultrawide impedance bandwidth by exploiting a double ring of slots and supports four switchable linear polarization states (+/- 45 degrees, 0 degrees, +45 degrees, and 90 degrees) by leveraging four quartets of p-i-n diodes. By electrically shorting the slots at well-defined positions by these p-i-n diodes, dynamic polarization reconfiguration is achieved by switching their dc bias current, supplied at the antenna feed through an external bias tee and routed from the antenna's back to front cavity plane via the AFSIW sidewalls. This new simple, yet effective, bias network enables the integration of all polarization control electronics inside the antenna cavity to protect them from environmental effects. Finally, measurements prove that the prototype exhibits an overlapping impedance bandwidth of 29%, from 4.85 to 6.45 GHz, and a stable conically shaped radiation pattern across the operating bandwidth with a 3 dB beamwidth of 45 degrees and a peak gain of 6.5 dBi for all four states.