Low-RCS, High-Gain, and Wideband Mushroom Antenna

In this letter, a high-gain and wideband mushroom antenna with wideband low radar cross section (RCS) is presented. The mushroom structure is resonant at the antenna operating frequency, and the in-band RCS can be reduced significantly. The bandstop frequency selective surface (FSS) designed at the operating frequency of the antenna is used to replace the metallic ground of the antenna so that the out-of-band RCS of the proposed antenna can be reduced while maintaining the high gain. Furthermore, square metallic patches printed periodically below the cells of the FSS are utilized to add a new zero-degree reflection phase in the desired frequency range to enhance the bandwidth of RCS reduction. As a result, a wideband RCS reduction can be achieved both in and out of antenna operating frequency band. The results show that the RCS of the proposed antenna is dramatically reduced over a wide frequency range, compared to the traditional patch antenna.