Abstract
In this article, a new triβband microstrip bandpass filter (BPF) is proposed. The BPF is composed of two folded, rectangularβshaped threeβsection SIRs (TSSIRs) whose first three resonant frequencies can be tuned to locate in the desired passbands. The BPF are 0Β° fed and the end sections of the TSSIRs are designed in an antiparallel fashion to produce zeros at appropriate frequencies for improving passband selectivity. In addition, by embedding spur lines and defected ground structures (DGS) in the BPF, extra transmission zeros around the first spurious passband are introduced to widen the upper stopband. The designed BPF is fabricated on an RT/Duroid 6010 substrate. The measured fractional bandwidths (minimum insertion losses) for the 1.57 GHz (GPS), 2.45 GHz (ISM), and 3.5 GHz (WiMAX) bands, respectively, are 11.5% (1 dB), 4.6% (2.19 dB), and 10.9% (1.3 dB), which agree well with those predicted by simulation. It also shows that for miniaturization purposes, the TSSIRs are made meandered to give an overall circuit size of only 23.29 Γ 10.94 mm^2^ for the designed BPF. Β© 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 989β991, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24208