Millisecond‐Switching Dual‐Band/Dual‐Polarization Ka‐Band Wavefront Control Enabled by a Complementary Liquid‐Crystal Metasurface

Abstract Nematic liquid crystals (LCs) offer significant advantages for reconfigurable millimeter‐wave (mmWave) devices, but many implementations remain limited to single‐band or single‐polarized operation and slow switching due to thick LC layers. This work presents a dual‐band, dual‐polarized reconfigurable metasurface for Ka‐band applications operating at 28 and 38 GHz. The design features a symmetric complementary patch/slot metasurface with via‐based biasing, integrating a 10 µm LC layer and operating down to a 2 µm gap. This thin profile is achieved through the strong electromagnetic coupling between a patch array and a complementary cross‐slot array topology. A key design feature is a 45°‐rotated slot in the lower‐frequency element that suppresses a parasitic dark‐mode resonance, preserving weak inter‐band coupling at oblique incidence. Full‐wave simulations predict independent phase control at 28 and 38 GHz, and measurements confirm dual‐band phase tuning with millisecond‐scale switching. This approach provides a practical route to compact, high‐performance reconfigurable components for advanced mmWave communication and sensing using LCD‐compatible fabrication.