Metallo-dielectric Structures for Backscattering Reduction Anuupam R. Chandran (1)* , Thomaskutty Mathew (2) , C.K. Aanandan (1) , P. Mohanan (1) and K. Vasudevan (1) Centre for Research in Electromagnetics and Antennas (1) Department of Electronics, Cochin University of Science and Technology Kochi- 682 022, Kerala, India. (2) School of Technology and Applied Sciences Mahatma Gandhi University Regional Centre, Edappally Cochin 682 024, India. e-mail:anand@cusat.ac.in, Tel: +91 484 2576418, Fax: +91 484 2575800 Scattering behaviour of various metallo-dielectric structures based on the modified design of Sierpinski carpet fractal geometry for the elimination of backscattered power is reported. The reduction in backscattered power is obtained for a wide range of frequencies in X-band. A bandwidth of 1.26 GHz at – 20 dB is obtained for the structure based on octagonal Sierpinski. Simultaneous reduction in backscattered power is obtained for both TE and TM polarisations. Introduction Fractal geometry is an arrangement of identical or similar elements repeated in different magnifications, orientations and positions [1]. Fractal geometries are finding wide applications in electromagnetics, especially in the design of antennas for muti-band applications, due to their inherent self similarity and space filling properties. Other areas of study includes frequency selective surfaces [2], diffraction by band limited fractal screens [3], the reflection and transmission properties of fractal multilayer [4] and the side lobe computation of fractal arrays [5] The structures for elimination of backscattering and specular reflections were studied extensively by many researchers [6, 7]. All these structures employ metallisations on a low loss dielectric substrate based on conventional Euclidean geometry. The use of fractal based metallisations for the elimination of backscattered power is studied and the results are presented in this paper. Methodology and Experimental Set-up The metallo-dielectric structures based on fractal geometries is fabricated by photo etching the metallisation on a reflector backed low loss dielectric substrate (ε r =2.56) of size 30 x30 cm 2 . The schematic diagram of reflector backed metallo-dielectric structure is shown in Fig.1.The metallo- dielectric structure backed with a plane metallic plate is placed on a turn table inside anechoic chamber. The measurements are performed using an HP 8510C vector 0-7803-8883-6/05/$20.00 ©2005 IEEE