Research in microwave/RF passive devices at UMH-UA Enrique Bronchalo, ´ Angela Coves, Germ´ an Torregrosa and ´ Angel A. San Blas Departamento de Ingenier´ ıa de Comunicaciones Universidad Miguel Hern´ andez de Elche Avda. de la Universidad s/n 03202 Elche, Alicante, Spain Email: ebronchalo@umh.es Stephan Marini Departamento de F´ ısica, Ing. Sistemas y Teor´ ıa de la Se˜ nal Universidad de Alicante 03690 San Vicente del Raspeig, Alicante, Spain Abstract—The Radiofrequency Systems Group at UMH (Uni- versidad Miguel Hern´ andez of Elche), in collaboration with Dr. Stephan Marini from the University of Alicante, has worked in the last years in different research lines. On one hand, we have studied the dispersion properties of periodic structures, in the case of both open and guiding media, through their Brillouin diagram, which provides their allowed and forbidden frequency bands of propagation, and it has been successfully compared to the transmittance of the corresponding periodic lattices of finite dimensions. On the other hand, a very efficient procedure to determine the wideband generalized admittance matrix representation of complex waveguide filters (e.g. in-line direct-coupled-resonator filters with tuning screws, evanescent- mode filters with cylindrical conducting posts, as well as folded configurations of real comb-line filters) has been developed, which can also integrate a standard (vertical) or collinear coaxial excitation. In a different field dealing with high-power devices, we have developed a Montecarlo algorithm for studying the multipactor effect in microwave waveguides partially loaded with dielectric layers. In particular, the dependence of the multipactor effect in a parallel-plate dielectric-loaded waveguide on the different geometrical and electrical parameters of the waveguide has been investigated. In addition, we are developing a simulation tool to analyze the multipactor effect in a rectangular waveguide loaded with dielectric layers, including corrugated surfaces. I. I NTRODUCTION The Radiofrequency Systems Group is formed by Ph. D. En- rique Bronchalo, Ph. D. ´ Angela Coves, Ph. D. Germ´ an Torre- grosa and Ph. D. ´ Angel A. San Blas from the Departamento de Ingenier´ ıa de Comunicaciones of UMH (Universidad Miguel Hern´ andez of Elche), This research group, in collaboration with Ph. D. Stephan Marini from the Departamento de F´ ısica, Ingenier´ ıa de Sistemas y Teor´ ıa de la Se ˜ nal of UA (Universidad de Alicante), has worked in the last years in different research lines which are developed separately in the next sections. II. FULL-WAVE ANALYSIS OF PERIODIC STRUCTURES A novel full-wave method for the modal characterization of dielectric electromagnetic band-gap structures under oblique plane wave excitation has been developed [1], showing the dielectric lattice periodicity in both the longitudinal and the transverse propagation directions, as shown in Fig. 1. In this method, an eigenvalue problem is obtained in terms of the e r1 e r2 D y h h ...... ...... ...... D y D z ...... e rh h p l 2 y x q l 1 z f k inc Fig. 1. Two-dimensional dielectric electromagnetic band-gap structure under oblique plane wave excitation given by the wave-number vector k inc with an angle of incidence θ. The dashed-line rectangle represents an elemental cell of the lattice with a double periodicity Dy and Dz in the y and z directions, respectively; the material is uniform in the x axis. generalized ABCD matrix of the periodic cell, whose solution provides not only the propagation constant of the fundamental Floquet mode, but also of the higher order modes of the global periodic structure. In order to check the accuracy and efficiency of the proposed formulation, we have computed and represented in Fig. 2(a) the Brillouin diagram of the first three Floquet modes of an EBG material whose transmittance was studied in [2]. The proposed analysis technique has been successfully validated with HFSS (a commercial software based on the frequency domain finite element method) (see Fig. 2). The transmittance of a finite number of unit cells is also success- fully verified in Fig. 2 for 100 periods through comparisons with theoretical results reported in [2]. In addition, we have studied the case of a finite EBG that has a periodic defect in the middle of the structure with two possible configurations, denoted as donor and acceptor defect. We present the case of a finite length 2D EBG made of N L = 25 rod layers with identical characteristics to that described in Fig. 2 in which the defect results from the modification of the depths h p and