Compact microstrip low‐pass filter using complementary split ring resonators with ultra‐wide stopband and high selectivity

Abstract

Abstract The transmission characteristic of the microstrip with complementary split ring resonator (CSRR) is researched. Compared with the conventional structure, this filter can achieve a wider bandgap by shifting the gap of CSRR from the side of the microstrip to the underside. And then, a lower transmission zero can be realized by loading a pair of narrow slots in the gap of the ring. The equivalent circuit model of the structure is provided. By cascading CSRR cells with different transmission zeros, a ultra‐wide bandgap low‐pass filter (LPF), which has a cutoff frequency at 4.3 GHz is designed. The designed LPF has a high performance with an insertion loss lower than 0.3 dB in pass band, a high out‐band suppression more than 20 dB (4.55–25 GHz), and a very sharp transition band about 0.25 GHz (4.3–4.55 GHz). © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 430–433, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24942