Compact polarization-reconfigurable AFSIW array with integrated biasing network

A polarization-reconfigurable antenna array with an integrated biasing network is demonstrated using air-filled substrate-integrated waveguide (AFSIW) technology for the [7.75–8.25] GHz sub-band of Frequency Range 3 (FR3). The antenna element features a compact 0.6${\lambda }_0\times 0.6{\lambda }_0$ footprint, utilizing a U-shaped slot within a quarter-mode AFSIW topology. Two PIN diodes enable +45°/-45°polarization switching by electrically shorting the slot at well-defined positions. Their DC bias is provided through inductive vias, which are isolated by capacitive gaps, allowing seamless integration without additional biasing components. The stand-alone antenna prototype was fabricated using low-cost printed circuit board (PCB) technology. Moreover, a 2 × 2 array was fabricated to validate the platform’s scalability. Measurements reveal a -10 dB impedance bandwidth of 590 MHz (7.46%) for both the single element and the array. The stand-alone antenna achieves a peak gain of 5.18 dBi, 91% efficiency, and 16.5 dB boresight cross-polarization discrimination across the entire frequency band. The array achieves a peak realized gain of 9.5 dBi, with embedded element radiation patterns closely matching the single-element patterns owing to mutual coupling remaining below -15 dB. 2D steering was demonstrated in simulation for a 4 × 4 array up to 40$°$. Measurement results align closely with simulations, confirming effective polarization reconfigurability, making the design well-suited for next-generation FR3 communication systems.