A Dual Polarization-Independent Tunable Active Second-Order Filter Featuring Wideband Phase and Polarization Reconfigurable Functions

The paper introduces a novel broadband second-order filter characterized by an angularly stable, polarization-independent switchable working window. In contrast to traditional designs limited to dual polarization and a single function, this innovative filter allows independent and continuous tuning or phasing of TE and TM waves. This capability is enabled by adopting a via-hole jump layer structure, facilitating the independent manipulation of TE and TM waves at different frequencies. This resolves challenges related to conflicting electromagnetic waves in co-layer orthogonal polarization directions on a single metasurface. Moreover, the design achieves a structural broadband second-order filter by splitting and layering the middle layer. This approach not only broadens the filter's operational bandwidth but also ensures independent dual-polarization feeding, thereby guaranteeing polarization independence across a wide frequency range. Furthermore, the implementation of a gap capacitor through a single-layer branch plays a crucial role. It effectively shifts the transmission passband frequency to the lower frequency band, resulting in significant miniaturization. As a result, the unit size is reduced to a mere 10.4% the central working wavelength. Overall, these advancements represent a substantial leap forward in filter technology, offering enhanced versatility, polarization independence, angular stability, and compact size. AFSS structures with these capabilities demonstrate significant potential applications in beam space aperture antennas.