Multibeam-Assisted Cross-Polarization Suppression With Ka-Band 64-Element Four-Beam Reconfigurable Phased Array Implementation

This article proposes a multibeam-assisted active cross-polarization (X-Pol) suppression technique that leverages auxiliary beams to effectively mitigate X-Pol leakages, thereby supporting polarization-division multiplexing (PDM). Amplitude and phase relationships for optimal cancellation are established, and performance limitations under practical residual array-level errors are quantified through theoretical analysis. To validate the technique, a compact Ka-band 64-element receive (RX) phased array with four fully connected beams is designed and fabricated using an 18-layer printed circuit board (PCB). It integrates 16 eight-channel four-beam beamformers (BFs), a dual-polarized (DP) slot-fed patch antenna array, and four sets of high-isolation 16:1 Wilkinson combining networks. The phased array demonstrates four independently steerable beams with 41.8-dB interbeam isolation at 29.5 GHz. It achieves scanning coverage up to ±50° in both planes with reconfiguration capability between circular [left-handed circular polarization (LHCP)/right-handed circular polarization (RHCP)] and linear (H/V) polarization (Pol) states. The measured gain-to-noise-temperature ratio (G/T) exceeds <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {-7}$</tex-math> </inline-formula> dB/K across all scan angles at 29.5 GHz. Measurement results show that the proposed technique effectively enhances steerable X-Pol discrimination from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {\sim }20$</tex-math> </inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {\gt }40$</tex-math> </inline-formula> dB at the target frequency within a wide bandwidth across the scanning range and significantly improves the error vector magnitude (EVM) under strong interference. To the authors’ best knowledge, this work presents the first Ka-band phased array supporting four concurrent beams with Pol reconfigurability, advancing high-capacity concurrent co-site communication systems with robust interference resilience.