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. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:701–703, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25841