COMPACT TRIPLE-MODE STUB-LOADED STEPPED IMPEDANCE RESONATOR AND BANDPASS FILTER

A compact microstrip triple-mode stub-loaded stepped impedance resonator (SIR) and bandpass filter (BPF) are proposed in this letter. As a starting part of designing a triple-mode BPF, the initial miniaturization dual-mode folded T-type open stub-loaded SIR characteristic is investigated to choose its proper dimensions. Based on these predetermined dimensions of this dual-mode resonator, a short-circuited stub at the center plane is introduced in this resonator to generate an even mode and four transmission zeros which lead to a high rejection skirt and wide upper stopband outside the desired passband. A compact BPF with the triple-mode SIR is simulated, fabricated and measured. The electromagnetic (EM) simulated and measured results are presented and an excellent agreement is obtained. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53: 701-703, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25841