AbstractA novel planar microstrip triple‐mode bandpass filter is proposed by introducing slits into λ/2 traditional microstrip resonator in this article.The slits cannot only perturb the traditional resonator for the multimode operation but also generate transmission zero point at stopband for the stopband control. By using different kinds of slits, different kinds of responses triple‐mode bandpass filter can be realized. For method validation, a filter operating at 2.45 GHz is fabricated and measured. Both the simulated results and the measured results are presented. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1260–1262, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25965