Compact electromagnetic lens antennas using cascaded metasurfaces for gain enhancement and beam steering applications

Abstract

Electromagnetic (EM) lens antenna designs using cascaded metasurfaces for gain enhancement and beam steering applications are proposed. Two different lens aperture designs are proposed and populated with aperiodic unit cells of size 0.2 lambda(o) x 0.2 lambda(o). In lens Design 1, the unit cells of different phases are distributed in concentric circular zones, whereas in lens Design 2, the unit cells of different phases are distributed in vertical linear zones on the aperture of the EM lens. Both lenses are composed of two cascaded metasurfaces with an air gap of 0.047 lambda(o) (where lambda(o) = 51.7 mm at 5.8 GHz). For gain enhancement, the metasurfaces are positioned at an optimum focal distance, f = 0.61 lambda(o) above source patch antenna (f/D = 0.3). Beam steering is accomplished by phase transformation of the source antenna, which can be realized by mechanically sliding the passive metasurfaces in one direction (i.e., +/- x-direction) above the source antenna. The prototype of the two proposed lenses are fabricated and tested. The measured peak boresight gain obtained from Design 1 and 2 are 14.98 and 15.12 dBi, respectively. The experimental results show -25 degrees to +25 degrees and -27 degrees to +27 degrees beam steering range for Design 1 and 2, respectively, with a little gain degradation at other angles.