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

Abstract

In 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 Copyright © 2012 Wiley Periodicals, Inc.