A Metasurface-Based Folded Transmitarray Antenna for 77 GHz Automotive Radar Applications

In this article, a 77 GHz low-profile folded transmitarray antenna (FTA) for automotive radar applications is presented based on well-designed top and bottom metasurfaces The top metasurface is employed to reflect the x-polarized wave and simultaneously convert the y-polarized wave to x-polarized transmitted wave with arbitrary phase modulations. A bottom metasurface is applied to reflect the incident wave with polarization conversion. A horn is set on the center of bottom metasurface as the feed source. The final configurated FTA is numerically simulated with a maximum aperture efficiency of 44.1%, and a 3-dB gain bandwidth of 16.6%. Moreover, the H/D ratio is drastically reduced to 0.18 by introducing the folded ray-tracing structure.