IOSR Journal of Electronics and Communication Engineering (IOSR-JECE) e-ISSN: 2278-2834,p- ISSN: 2278-8735.Volume 8, Issue 6 (Nov. - Dec. 2013), PP 45-49 www.iosrjournals.org www.iosrjournals.org 45 | Page Contribution to the study and analysis of microwave bandpass filter based on circular Split Rings Resonators Mohammed Berka 1 , Zoubir Mahdjoub 2 , Tarik Bendimered 3 1 (Department of Electrical Engineering / University of Mascara, Algeria) 2 (Department of Electronic / University of Sidi Bel Abbes, Algeria) 3 (Department of Electronic / University of Tlemcen, Algeria) Abstract: The purpose of this article is the analysis and design of a new structure of the bandpass filter, the analysis of the composite structure is made from a bandpass filter using microstrip resonators connected in parallel that are associated with a circular Split Rings Resonators metamaterials present a negative permeability (SRR) to create an environment of retro-propagation of waves. The behavior of the composite filter is also bandpass but around the resonance frequency of (SRR), which is inferior to the center frequency of the first band-pass filter, which allows a good operation of the composite filter in the stop-band of the first bandpass filter with resonators coupled in parallel. Since there’s no scientific or experimental result in the literature for this kind of complicated structure, it was necessary to perform simulations using CST MICROWAVE STUDIO. Keywords: bandpass filter, coupled resonator, CST MICROWAVE STUDIO, permeability, SRR metamaterials. I. Introduction Modern telecommunications are moving towards "wholes wireless", while microwave applications are introduced to meet this need. Among these applications, noting the design of microwave filters, including filters using microstrip resonators coupled in parallel [1] which are widely used because of its low economic cost and also small dimensions during their realizations. The performance of this kind of filter is enhanced with new physical devices that are metamaterials. Metamaterials are artificial pseudo-homogeneous structures with electromagnetic properties not found in nature; an analysis of this kind of structure was originally made by the Russian physicist Victor Veselago [2]. The physical properties of metamaterials are represented by a permittivity ε and permeability μ simultaneously negative [3- 4]. To demonstrate the influence of metamaterials on the quality of microwave filters, we propose in this paper a new structure that includes a coupled resonators filter associated in parallel with metamaterials in Split Ring Resonators (SRR) which are chosen from their circular form and magnetic activity [5], their dimensions are selected to resonate in the X band [8-12] GHz. The dimensions of the filter with resonators coupled in parallel are selected to achieve a center frequency of the bandpass around 21.4GHz which is much higher than the resonance (SRR) in the X band. The choice of number of (SRR) and their position above the parallel coupled resonator filter is very important to allow the composite structure to function outside the passband of the parallel coupled resonators filter. II. Methodology 2.1. Analysis of parallel-coupled resonators filter. Figure 1 shows the band-pass filter consists of a set of five (n = 5) microstrip parallel coupled resonators. Each resonator has a length (λ / 2) at the center frequency f 0 of the bandpass filter and coupled to the other of (λ / 4). We design this kind of filter in a Tchebyshev filtering function , used the synthesis of Matthaei that allows us to determine the impedances even and odd mode for each quarter of symmetric coupled lines, these impedances are also calculated from the elements ( ) of the Tchebyshev lowpass prototype and depending on ripple (r p ) in the passband of this filter. For a filter of n resonators, Matthaei synthesis can be summarized in [6]: -The parameters (i = 1, 2, ......, n) of the standard prototype. , (1) , for i = 2,…, n (2) ; n odd (3) ( ) ; n even (4)