J. of Electromagn. Waves and Appl., Vol. 19, No. 10, 1407–1421, 2005 ANALYSIS AND DESIGN OF WAVEGUIDES LOADED WITH SPLIT-RING RESONATORS S. N. Burokur and M. Latrach RF & Microwave Group Ecole Sup´ erieure d’Electronique de l’Ouest BP 30926, 49009 Angers, France S. Toutain IREENA, Ecole Polytechnique de l’Universit´ e de Nantes BP 50609, 44306 Cedex Nantes, France Abstract—This paper presents the study of composite media, based on a one-dimensional periodic array of conducting non magnetic Split Ring Resonators (SRRs) and waveguides. Previous studies have shown that the SRRs possess in a given frequency band, a negative permeability. Here, we are going to study the properties of these small resonant particles in a waveguide configuration. It will be observed that the response of the SRRs depends on the resonant frequency of the SRRs with regard to the cut-off frequency of the waveguide. They can then show either a band-stop property, if the resonant frequency is located above the waveguide’s cut-off frequency, or a band-pass property if the resonant frequency is below. The effective medium is referred to as a Negative Permeability Medium (NPM) in the case of the band-stop phenomenon, and as a Backward Wave Medium (BWM) in the case of the band-pass phenomenon. These two media have been designed, simulated, fabricated and tested experimentally. The two different phenomena of the waveguides loaded with SRRs are experimentally confirmed. The influence of the mechanical etching accuracy of the SRRs on the response of such structures is also studied.