Effects of narrow slits on frequency response of a microstrip square loop resonator and dual‐mode filter applications

Abstract

AbstractIn this letter, the effect of narrow slits on resonance characteristics for a microstrip square loop resonator (SLR) with mitered bends is investigated and a new formula to calculate the resonance frequency of SLRs loaded inductively by means of slits is derived as a function of the number of slits.A novel dual‐mode SLR configuration performing a slow‐wave characteristic obtained by using narrow slits is proposed to use in design of microstrip dual‐mode bandpass filters. Also, a new perturbation technique based on the change of electrical lengths is presented for the excitation of two degenerated modes of these type resonators. Additional, two dual‐mode bandpass filters having linear phase and elliptical frequency characteristics have been designed, fabricated and tested to verify the proposed filter topology. Experimental results agree with simulated results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:143–146, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27237