Meta-reflector antenna with annular pattern for electromagnetic orientation in UAS applications

Unmanned Aerial Systems (UAS) often use GPS for navigation, but there are many scenarios in which GPS is inaccessible or inaccurate. GPS-denied navigational systems using optical and radar technologies have been proposed to supplement GPS. We present a novel antenna that produces an annular beam pattern ideal for down-looking navigational radar. This pattern is achieved using a monopole over a metasurface ground. The design uses a planar, focusing reflector technique based on a sub-wavelength grating to achieve a high gain pattern with a low profile antenna, and a null in the direction normal to the antenna plane. The annular radiation pattern reduces specular returns from the nadir direction below the UAS that can overdrive the radar electronics. The performance of a GPS-denied navigation system is simulated using the antenna pattern of the planar meta-reflector antenna.