Shielding Effectiveness of I-D Periodic Composite Screens in the Presence of Electric Line Sources: Full-Wave Analysis and Limits of Homogenization Giampiero Lovat Electrical Engineering Department, "Sapienza" University of Rome Via Eudossiana 18,00184 Roma, Italy Email: giampiero.lovat@uniromal.it z considerable attention in the EMC community thanks to their weight savings with respect to solid metallic panels and different approaches have been proposed for their study [3]-[6]. Moreover, periodic screens may offer significant advantages in terms of frequency selective properties, which have also been studied and characterized through generalized sheet transition conditions [7]-[8]. Figure 1. Examples of 1-D periodic screens in the presence of an electric line source. (a) MSG based (w = 5 mm) and (b) WM based (N = 4, ro = 0.1 mm, d = 1 mm, t = b = 0.5 mm). Other parameters: e; = 2.2, h =4 mm,p = 10 mm. Abstract-The near-field shielding effectiveness of composite screens characterized by spatial periodicity along one dimension is investigated in the presence of an electric line source (i.e., an aperiodic source) placed in proximity of the screen. The metal strip grating and the wire-medium screen supported by a dielectric board are studied as exampIes of one-dimensional periodic screens. Both full-wave analyses and approximate homogeneous models are adopted in order to investigate the limits of the homogenization techniques for the study of the interaction between a finite source and a periodic screen. Moreover, differences in shielding-effectiveness values for such periodic structures are discussed when considering finite- source or plane-wave excitations. Keywords: Aperiodic sources, near field, periodic structures, shielding effectiveness. I. INTRODUCTION Recently, there has been significant research activity related to the development of composite periodic structures such as electromagnetic bandgap (EBG) structures and artificial materials (including metamaterials) [1]-[2]. On the other hand, wave propagation in periodic structures has been an important subject in electromagnetics for many decades. The idea that has stimulated most of the recent research activities in this old subject is the possibility of designing composite media which allow for controlling the electromagnetic propagation, with application to the design of, e.g., modeless substrates and highly directive antennas. if---:::--+ P o o J j (x ',Z ') o (a) (b) x The properties of artificial periodic materials are scalable with wavelength and are applicable over wide frequency ranges, from radio frequency up to optical regimes. Fabrication of RF and microwave periodic structures is relatively straightforward with respect to optical applications thanks to printed-circuit technology, which is versatile, easy to fabricate, low weight and low cost. Advanced composite screens made of microstructured periodic structures have received 978-1-4244-4108-2/09/$25.00 ©2009 IEEE The goal of the present paper is the study of the shielding effectiveness (SE) of one-dimensional (I-D) periodic screens in the presence of two-dimensional (2- D) near-field sources. In contrast to common analyses, which consider either homogeneous models for the screens or the canonical plane-wave excitation, the problem addressed here involves the presence of a single (nonperiodic) finite source in an infinite inhomogeneous periodic environment.