Ultracompact Self-Shielded Rectangular Patch Bandpass Filter Based on CRLH and Meander-Line Resonators

This paper presents a hybrid rectangular patch filter composed of two half-mode rectangular patch resonators, one composite right/left-handed resonator (CRLHR), and one meander-line resonator (MLR). By introducing an array of metallized vias with a coupling window on the symmetry plane of the rectangular patch resonators, the symmetric fundamental mode of the rectangular patch is split to exhibit dual-mode behavior. Meanwhile, the CRLHR and MLR offer the merits of small size, adjustable frequency, and opposite phase shift characteristics, and can be embedded separately or jointly into the dual-mode rectangular patch structure to realize third- or fourth-order bandpass filters. In addition, a periodic metallic via array is introduced around the hybrid patch structure to reduce insertion loss. Effectively, two third-order and fourth-order hybrid bandpass filters are fabricated and verified. Compared with similar filters featuring a hybrid substrate integrated waveguide structure, the size of the proposed filters is reduced by approximately 50%. Overall, this self-shielded hybrid patch filter offers low insertion loss, small size, and high selectivity.