A dual-mode dual-band bandpass filter using a tri-stubs loaded multimode resonator (TSLMR)

Abstract

This paper presents a tri-stubs loaded multimode resonator (TSLMR) for designing dual-band bandpass filters. The TSLMR produces four spitting modes and the modal character is analyzed by using odd- and even-mode methods. A pair of even–odd modes is used to form the first passband, while another pair is used to produce the second passband. This resonator structure provides sufficient degrees of freedom to control the central frequencies and bandwidth of each passbands. Meanwhile, multi-transmission zeros are properly tuned for the rejections between the two passbands and in the upper stopband. A dual-band BPF operating at 1.57 and 3.5 GHz is designed and fabricated. Without a shorted structure and extra resonator, the measured filter shows good performance for both in band matching and outside rejections of the desired dual-passbands.

Keywords:

• dual-band bandpass filter
• multimode resonator
• even-mode
• odd-mode