Abstract
In this article, a novel compact broadband microstrip bandpass filter with high selectivity and wide upper‐stopband performance is proposed using quintuple‐mode stub‐loaded resonator. The proposed resonator can generate two odd‐modes and three even‐modes in the desired band. The open stub and short‐circuited stub at its central plane can not only specially control the even‐mode resonant frequencies, whereas the odd‐mode ones are fixed, but also generate two transmission zeros near the upper and lower cut‐off frequencies, leading to high rejection skirt. Two identical impedance‐stepped open stubs are mainly applied to adjust the high resonant modes (f~m4~, f~m5~) into desired passband and excite one additional transmission zero to deepen the upper‐stopband. A quintuple‐mode broadband filter with the fractional bandwidth better than 64% is simulated, fabricated, and measured. The EM simulated and measured results are presented and excellent agreement is obtained. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:799–803, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25849