> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract — This paper presents the design, fabrication and characterization of a planar broadband chessboard structure to reduce the radar cross-section (RCS) of an object. The chessboard like configuration is formed by combining two artificial magnetic conductor (AMC) cells. The bandwidth limitations intrinsic to AMC structures are overcome in this work by properly selecting the phase slope versus frequency of both AMC structures. 180 degrees phase difference has been obtained over more than 40% frequency bandwidth with a RCS reduction larger than 10dB. The influence of the incidence angle in the working bandwidth has been performed. A good agreement between simulations and measurements is achieved. Index Terms — Artificial Magnetic Conductor (AMC), Electromagnetic Band Gap (EBG) technology, Radar Cross- Section (RCS). I. INTRODUCTION roadband radar cross section (RCS) reduction in a low profile configuration is a challenging objective to designers. At the same time, easy integration with any target which needs to be hidden or with any object for which reflection requires to be minimized is also desired. Different techniques have been proposed in literature to reduce RCS: shaping, radar absorbing materials, passive or active cancellation. Several solutions have been implemented in each of these RCS reduction techniques [1-10], but narrow band behavior seems to be their common characteristic in low profile designs. The shaping principle is based on modifying the shape or the surface of the device under test (DUT) in order to redirect the scattered energy away from the source. One way of achieving this scattering goal using a planar configuration was proposed by the authors in [10-11]. The planar structure used, based on a combination of Artificial Magnetic Conductors (AMC) and Perfect Electric Conductors (PEC) in a chessboard Manuscript received December, 2012. This work was supported by the Spanish Ministry of Economy and Competitiveness Project Nos.TEC-2009- 11995, CSD 2008-00066 and INNPACTO IPT-2011-0960-390000 Juan Carlos Iriarte, Amagoia Tellechea, José Luis Martínez de Falcón, Iñigo Ederra, Ramón Gonzalo are with the Electrical and Electronic Engineer Department, Universidad Pública de Navarra, 31006, Pamplona, Spain (e- mail: ramon@unavarra.es). Peter de Maagt is with the Antenna and Submillimetre Wave Section, Electromagnetics & Space Environments Division, European Space Agency (ESA-ESTEC) (e-mail: peter.de.maagt@esa.int) like configuration, has shown the possibility of narrow band RCS reduction. The main advantages of the mentioned structure are its low profile and the possibility to conform it to any object shape while retaining its properties. In addition to this, the structure was simple to manufacture with standard printed board technology. The working principle of the chessboard configuration is based in the destructive interference between the reflected wave produced by the AMC and PEC cells which compose the chessboard configuration. Metallic cells reflect incident waves with a 180° phase change while AMC cells introduce a 0º phase change to the reflected wave at its working frequency. Combining these effects a 180° phase difference is created between the contribution of the PEC and AMC cells, obtaining destructive interference and achieving a null in the specular direction [10]. The main limitation of the chessboard configuration is the narrow band behavior of the AMC structure. Outside this bandwidth, the AMC behaves as a PEC and the condition for destructive interference is not satisfied anymore. This limitation can be overcome by substituting the PEC cell by another AMC structure operating at a different resonance frequency. This substitution allows the destructive interference condition to be complied with, at least, at the resonance frequency of both AMCs. Consequently, a dual band design can be obtained [12, 13]. Apart from the previous results published by the authors in [12, 13], other authors have also presented similar structures with the same goals. For instance in [14, 15] the combination of two AMCs structures for reducing the RCS is presented. These AMCs structures avoid the use of complex via-hole unit cell configurations achieving frequency bandwidths below 4%. In another work [16], a high permittivity dielectric is used to replace the AMC cells, with the dielectric-AMC and PEC combination acting the same as the one in [12]. However, since the bandwidth of the AMC over which it maintains a zero reflection phase is relatively narrow, it cannot function effectively over a wide frequency band. On the other hand, in [17-18] a method which uses the effective phase differential between two different types of AMCs was developed. In this case the operational bandwidth has been significantly increased, but only normal incidence was studied. As a matter of fact, the performance of the AMC degrades for off-normal incidence. In this paper a novel design, where the AMC Broadband Radar Cross-Section Reduction Using AMC Technology Juan Carlos Iriarte, Amagoia Tellechea, José Luis Martínez de Falcón, Iñigo Ederra, Ramón Gonzalo, Member, IEEE, and Peter de Maagt, Fellow Member, IEEE B This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication. The final version of record is available at http://dx.doi.org/10.1109/TAP.2013.2282915 Copyright (c) 2013 IEEE. Personal use is permitted. For any other purposes, permission must be obtained from the IEEE by emailing pubs-permissions@ieee.org.