AbstractIn this article, series‐LC resonator loaded coupled lines are proposed to implement microstrip bandpass filters. The proposed loaded coupled line can generate three tunable transmission zeros. Conditions for the transmission zeros of the series‐LC resonator loaded coupled lines are analyzed and discussed. To demonstrate the applications, two second‐order bandpass filters using the proposed loaded coupled‐lines are designed with wide stopband rejections. The measured results show a good agreement with the simulations. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1273–1276, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27542