A Compact Broadband Filter Using Triple-Mode Stepped-Impedance Stub-Loaded Resonator

摘要

In this paper, a compact broadband bandpass filter (BPF) using triple-mode stepped-impedance stub-loaded resonator (TMSISLR) is proposed. The TMSISLR is composed of an impedance-transforming unit and two asymmetrical open-ended stepped-impedance stubs (SIS) at the center. By simply adjusting the impedances of the SIS, the resonant frequencies of the TMSISLR can be flexibly changed. The interdigital coupled-lines are adopted to feed the proposed TMSISLR. This BPF can realize wide bandwidth, low insertion loss, high selectivity, and deep stopband rejection simultaneously. Finally, the proposed BPF is simulated, fabricated, and measured. The measured results show that the impedance bandwidth under -16.7 dB is 86% from 1.89 to 4.75 GHz, while the insertion loss is smaller than 1.47 dB. The measured insertion loss is larger than 30 dB at both low- and upper-stopband (from 0 to 1.27 GHz and 6.03 to 7.66 GHz). The measured results are in good agreement with the simulated counterpart.