Wide Band Beam Steering Digital Metasurface Reflectarray Antenna for Millimeter Wave Applications

Abstract

A compact wideband digital metasurface reflectarray antenna for millimeter-wave application is presented in this article. The metasurface reflectarray is composed of periodic arrangements of metabit unit cell elements. The metabit consists of a dipole with end stub loading, exhibiting wideband reflection characteristics. The metabit is quantized to generate two discrete reflection phase levels, resulting in binary states of 0 and 1, respectively. The binary bits are distributed over the reflector surface using uniform phase quantization to achieve a highly directive beam in the desired direction. A digital metasurface reflector array composed of $20\times20$ metabits is analyzed, fabricated, and characterized. The digital reflector is illuminated by a Ka-band horn antenna placed at a miniaturized focal point, resulting in compactness with high gain. The specialized digital coding sequence on the reflector surface results in a highly directive beam towards 0°, ±15°, and ±30° operating in the frequency band of 26 GHz - 35 GHz with a maximum achievable gain of 21.5 dBi. The measured results of the digital metasurface reflectarray antenna depict the wideband characteristics of having a 3 dB gain bandwidth of 29.5% and a peak aperture efficiency of 30%in the frequency band of 26 GHz - 35GHz. The proposed digital metasurface reflectarray antenna finds its application in millimeter-wave communications such as 5G and beyond, satellite, and defense applications.