Low-RCS Frequency-Reconfigurable Fabry–Perot Antenna Based on Liquid Metal Metasurface

A frequency reconfigurable Fabry–Perot (F-P) antenna with low radar cross section (RCS) is proposed in this work. A multifunctional liquid metal high impedance surface (HIS) is employed on the ground plane of the feed antenna. By altering the filling states of liquid metal within the HIS cells, the frequency reconfiguration can be achieved. Moreover, among the aforementioned HIS states, 180° phase difference can also be obtained, thus leading to an integrated in-band low RCS property. A liquid metal partially reflective surface is located directly above the feed antenna to reduce the out-of-band RCS according to the phase cancellation theory, as well as enhance the radiation gains. To verify the design method, an antenna prototype is fabricated and measured. The measured results indicate that the operating frequency can be tuned in the range of 8.7 GHz – 10.6 GHz (19.7%). At the same time, the RCS reduction is achieved in 6 GHz – 20 GHz (107.69%).