Novel compact quad-mode wideband bandpass filter with wide stopband using T-shaped resonator

Abstract

A novel compact wideband bandpass filter (BPF) with wide stopband is presented to use T-shaped resonator in this paper. The main block of the BPF is a quad-mode stub-loaded resonator which consists of three open-ended stubs loading on a high impendence resonator symmetrically. The transmission characteristics of the quad-mode resonator are analyzed and explained. The upper and lower cut-off frequencies of the passband can be adjusted through simply tuning the dimensions of three open-stubs. A T-shaped resonator is added before the feeding line to create an additional transmission zero which can improve the upper stopband performance. Finally, a BPF with a fractional bandwidth of 43.3% at the center frequency of 3 GHz is designed and measured. Measured results show good agreements with the simulated ones.

Keywords:

• quad-mode resonator
• wideband bandpass filter
• high selectivity
• wide stopband
• stub-loaded resonator