Miniaturized narrow band‐pass filter with quarter‐wavelength short stubs using U‐shaped folded transmission line

Abstract

ABSTRACTIn this article, the miniaturized narrow band‐pass filter (BPF) with 90° short stubs using a U‐shaped folded transmission line is suggested. A U‐shaped transmission line is adopted instead of a conventional transmission line to reduce the size of the BPF on the low dielectric substrate. The size of the conventional narrow BPF is reduced by more than 70% due to the reduction of the length of the transmission line within the inverter. The experimental results show that the insertion loss and return loss are 1.61 dB and 15.4 dB, respectively, with bandwidth of 5% at the center frequency of 5.8 GHz. The designed BPF shows a harmonics rejection up to third (3f0) and fifth (5f0), with more than 18 dB rejection level in the simulation and experimental results. The size of the filter is 19 × 8.6 mm2. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2862–2865, 2015