“…Moreover, as application of principle of passive cancellation for electromagnetic (EM) wave, the artificial magnetic conductor (AMC) and perfect electric conductor (PEC) surfaces or two AMCs were combined together for RCS reduction of waveguide slot antenna [4]. Then, two AMCs with different metamaterial structures were theoretically analyzed and easily implemented using the common printed circuit board fabrication methods for ultra-thin and broadband radar absorber material design [1], [5][6][7]. Nevertheless, in those cases, the RCS is reduced in boresight direction but increased in other directions.…”