Quasi-Lumped Coplanar Waveguide Diplexers for a Multichroic Polarimeter

Abstract

This article presents a multichroic Kinetic Inductance Bolometer (KIB) polarimeter that utilizes coplanar waveguide (CPW) diplexers. The CPW diplexers function as filters, providing two passbands centered at 220 GHz and 280 GHz. The high-quality-factor resonant units deliver excellent transmission and isolation characteristics. Additionally, the quasi-lumped-element resonator design enables a significant reduction in size compared to conventional microstrip diplexers. The entire polarimeter—comprising orthomode transducer (OMT) probes, diplexers, KIBs, and CPW feed lines—is integrated on a single plane, allowing for one-layer superconducting thin-film fabrication with a simplified process. The compact size, superior frequency response, and streamlined fabrication process make the proposed pixel scheme suitable for integrated array development.