© 2021 EurAAP.In this article, we propose a design of aperture coupled antenna with ultra-wideband low radar cross section (RCS) characteristics for X band applications. The RCS reduction ranging from 8 to 24 GHz has been realized with two novel artificial magnetic conductor (AMC) unit cells that are placed around the patch antenna. The AMCs have been designed with a 180 ± 38° phase difference within a frequency range in order to provide an effective phase cancellation. The proposed antenna's operating bandwidth is 8.9-9.8 GHz, corresponding to an impedance bandwidth of 9.6%, and the RCS reduction is mainly in the Ku band. The maximum out-of-band RCS reduction is 37 dB at 12.7 GHz, while the maximum in-band RCS reduction is 27 dB at 9.2 GHz. The monostatic RCS results of the reference antenna and proposed antenna have been investigated under both θ and -polarized plane wave incidence.