Quarter-Wavelength Two-Section Coaxial Stepped Impedance Resonators With Parallel Central Sections for Constraint Reduction in Compact Tx Bandpass Filters

This article presents a novel two-section coaxial stepped impedance resonator (SIR) based on the integration of parallel coaxial sections in the central part of the structure. Compared with the classical approach, this topology adds a new degree of freedom to the design, allowing an improvement of the quality factor, multipactor threshold, and fabrication tolerances. To demonstrate these advantages, we designed an example of a fourth-order filter in the
$L$
-band. This filter was fabricated in aluminum and measured. The experimental results are presented and discussed.