Composite right/left‐handed‐coupled line bandpass filter using the first negative resonant mode

In this letter, a high-order composite right/left-handed (CRLH)-coupled line bandpass filter using the first negative resonant mode is presented. The unit-cell structure of a half wavelength resonator is composed of an interdigital capacitor for a series capacitance and a shorted stub for a shunt inductance, respectively. The design equations are derived from those of a conventional coupled line filter. The even-mode and odd-mode impedances of a CRLH-coupled line section are obtained using full wave simulation to complete the design equations. An insertion loss of a CRLH filter is suppressed from 2.1 to 1.1 dB by adding via hole in the end of resonators. The size of a CRLH filter is reduced by 53%, compared with that of conventional coupled line bandpass filter. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:943–947, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25856