A compact three-bit reconfigurable resonator consisting of lumped elements

A two-stage three-bit reconfigurable bandpass filter (BPF) using branch-line type resonators has been proposed to achieve low insertion loss. However, it employed transmission line resonators and has limitation for miniaturization. This paper proposes a three-bit reconfigurable resonator consisting of lumped elements. The circuit replaces the short stub with a LC resonant circuit, while open stubs are substituted with parallel capacitors. A prototype resonator was designed and fabricated with 1005-size chip components. It shows insertion loss of less than 1.1 dB, which is close to that for the transmission line type reconfigurable resonator. The circuit area occupied by the lumped elements is less than 40% comparing with the conventional configuration using transmission lines.