Compact Triple-Band High-Temperature Superconducting Filter Using Coupled-Line Stepped Impedance Resonator

Abstract

A compact triple-band high-temperature superconducting filter using a coupled-line stepped-impedance-resonator (C-SIR) has been proposed in this paper. Compared with the typical SIR, the proposed C-SIR can control transmission zeros effectively by changing the gap parameter g of the coupled line. In order to enhance the selectivity of the proposed filter, an interdigital structure between the C-SIR and feed lines has been utilized. Furthermore, to achieve better coupling of a two-order resonator, spiral-shaped lines are applied to the high-impedance transmission line section. The resultant filter shows a competitive merit in size miniaturization and high selectivity. For demonstration purposes, a triple-band filter operating at 1.57 GHz (GPS band), 3.5 GHz (WiMAX band), and 5.5 GHz (WLAN band) is designed, fabricated, and measured. Good agreement between the simulated and the measured results is observed.