Element-Level Polarization-Switchable Beamforming Empowering Three-Stage Phased Array Antennas

Wireless communication systems require specialized antennas often developed independently, leading to limited applicability and larger footprints. This study develops a 3-stage phased array architecture and associated antennas that support agile radiation for cross-functional scenarios. Beyond simple RF phase adjustments, this work establishes state-mode mappings, with each port generating multiple modes over the same frequency. It allows concurrent activation of multiple ports for effective mode combination, which avoids compromising radiation power during mode switching. First, a pair of dual-port elements enabling polarization selection in the first stage is investigated. Second, a 2stage four-port antenna is designed for polarization-switchable beamforming. Stable active reflection coefficients (ARCs) and cross-polarization discrimination (XPD) levels benefit from the state-mode mappings. Finally, 2-stage phased antennas integrate seamlessly with progressive phases, forming 3-stage phased arrays that allow 3-stage phase superposition without additional phase shifters. Multi-path coupling suppression and grating-lobe-free wide-angle scanning are investigated in two array demonstrations. A 1-by-3 array with 0.83λ element spacing achieves ±60° scanning with -15 dB sidelobe levels (SLLs), while a 1-by-15 array with an average spacing of 1.85λ achieves ±85° scanning ranges with SLLs below -7 dB under 19.6 dBi broadside gain are achieved. Fabricated prototypes and measured results demonstrate its feasibility and potential for MIMO, reconfigurable, phased array antenna systems, offering improved versatility at reduced costs.