USING A 3D METAMATERIAL TO ENHANCE THE SURFACE WAVE PROPAGATION FOR HIGH FREQUENCY OVER-THE-HORIZON RADARS: FROM SIMULATION TO OUTDOOR MEASUREMENTS

This article is about the characterization of a 3D metamaterial structure arranged to reinforce the surface wave radiation of antennas relevant to High Frequency (HF) surface wave radars. The use of a corrugated surface with a negative equivalent permittivity placed in the vicinity of the antenna increases the surface wave component of the radiated field. In order to confirm the anticipated performance of that metamaterial antenna, near-field measurements have been realized. Also, an original near far-field transformation technique, taking the surface wave into account, is applied to derive the radiation pattern of the antenna. Measurements were first achieved at reduced scale in UHF band and at full scale in HF band. At 1.1 GHz, they were operated on a small scale mock-up in a semi-anechoic chamber. An electric field acquisition setup installed in an Unmanned Aerial Vehicle (UAV) is used to characterize this antenna under outdoor conditions. This measuring system was especially designed for this application. The obtained results are discussed and enable us to validate the expected behavior of the antenna.