Journal of Microwaves, Optoelectronics and Electromagnetic Applications, Vol. 7, No. 2, December 2008 139 Brazilian Microwave and Optoelectronics Society-SBMO received 25 Feb, 2008; revised 10 Oct, 2008; accepted 27 Jan, 2009 Brazilian Society of Electromagnetism-SBMag © 2008 SBMO/SBMag ISSN 1516-7399 Implementation of an Active Noise Cancellation System in RCS Measurements of Complex Targets in the C Band using an Anechoic Chamber Marcelo A. S. Miacci, Inácio Malmonge Martin Instituto Tecnológico de Aeronáutica 12.288-900 – São José dos Campos – SP – Brasil marcelomiacci@uol.com.br , martin@ita.br Mirabel C. Rezende Divisão de Materiais, Instituto de Aeronáutica e Espaço 12.288-904 – São José dos Campos – SP – Brasil mirabel@iae.cta.br Abstract– This work presents the improvement design of a Radar Cross Section (RCS) measurement system of complex shapes targets (missiles), with the development of an active noise cancellation system. The RCS measurements were carried out in indoor ambient, in a quasi-monostatic condition, using an anechoic chamber, in the frequency range of 5.8 to 6.4 GHz (C-band). Experimental results of missile section characterization in an anechoic chamber show the effort involved in the interpretation of RCS patterns of complex targets. The use of the developed circuit, designed and built in this work, improves the RCS pattern resolution, with the increase of the system sensitivity. It can be cited that the dynamic range increased up to 26 dB in the frequency of 5.9 GHz. Index Terms- Anechoic Chamber, ERAM, Microwaves, Missile, RCS. I. INTRODUCTION The research of the RCS [1] of simple and complex objects is decisively important to identify targets such as aircrafts, missiles and other objects, with the purpose of improving or rendering difficult their radar visibility in various frequency ranges. The use of RCS measurements of targets have expanded to more than solely military applications in the identification and control processes of defense systems [2]. Currently, this technique has been confirmed in the medical area identifying tumors [3] and in the civil defense area, as for instance in controlling attacks and the disarmament of landmines [4]. The C and X frequency bands, which range from 5 to 12 GHz, are widely used by many types of radars in identifying and monitoring targets as aircrafts, missiles and balloons in a particular area. The higher the RCS value is, the easier it becomes to detect and identify it. However, when these targets use different geometrical forms and different types of electromagnetic radiation absorber