PIERS ONLINE, VOL. 4, NO. 6, 2008 641 Abnormal Radiation Pattern of Metamaterial Waveguide A. N. Lagarkov, V. N. Semenenko, A. A. Basharin, and N. P. Balabukha Institute for Theoretical and Applied Electromagnetics of Russian Academy of Sciences (ITAE RAS) Izhorskaya 13, Moscow 125412, Russia Abstract— The idea to inverse the radiation pattern of the microwave antenna due to appli- cation of the isotropic metamaterial screen with negative refractive index in S band is demon- strated at the first time in this investigation. The electromagnetic simulation of waveguide antenna patterns by moment’s methods demonstrates an agreement modeling antenna patterns with measured antenna diagrams for values of metamaterial effective parameters (permittivity and permeability) extracted from measured S-parameters of metamaterial sheet sample. 1. INTRODUCTION The prediction of left handed materials (LHM) by V. G. Veselago in 1967 [1] can be considered as a new stage in the development of electromagnetics of continuous media. Recently a lot of papers [2, 3] related to the artificial magnetoelectric media with anomalous electromagnetic properties have been appeared. Among these papers there are ones on 2-D, 3-D media with the negative permittivity and permeability [4, 5] and, hence, negative refractive index. The abnormal antenna patterns of a rectangular open waveguide loaded by a rectangular cross-section magnetoelectric tube made of the metamaterial with the negative refractive index in S frequency band for different thicknesses of tube are demonstrated at first in this paper. 2. SCHEME OF WAVEGUIDE RADIATOR The geometry of open waveguide loaded by the metamaterial screen having a shape of a rectangular cross-section tube (modified open waveguide radiator ) is shown in Figs. 1–2. A standard coaxial-waveguide adapter of the S-band with the waveguide window of 50 × 25 mm in sizes is used in the measurements of antenna patterns of modified waveguide radiator. metamaterial feedline waveguide 180 0 0 0 Figure 1: Schematic diagram of the waveguide radi- ation structure. Figure 2: A view of the waveguide radiator. The metamaterial under investigation is an isotropic 2D lattice made of nichrome spiral wires (helixes) positioned randomly on the polyurethane substrate with 0.2 mm in thickness. To exclude chiral properties of the metamaterial sample is used an identical combination of left- and right handed helixes. The helixes were wound of the 0.4mm nichrome wire with the number of turns 3 and coil pitch 1 mm. The helix external diameter is 5 mm. In the experiments an isotropic metamaterial sheet sample named as LR-5I (see Fig. 3 — 1/3 part of helixes set is positioned along rectangular coordinate axes of x, y and z respectively) with 5.2 mm in thickness is used.