EM lens design using thin planar metasurfaces for high antenna gain and low SLL applications

Abstract

A novel electromagnetic (EM) lens with high gain, suppressed side-lobe level (SLL) and low profile is designed using thin planar metasurfaces. The proposed design consists of a source patch antenna and an EM lens based on two thin planar metasurfaces. The two thin metasurfaces with an air gap are placed at the focal distance H of about lambda/2.25 above the source patch antenna. This configuration forms a thin planar lens in which the source patch antenna emitted quasi-spherical wave in order to transform into plane wave. The total size of source antenna and an EM lens is same. The miniaturised EM lens antenna faces high SLL, which can be reduced by maintaining the uniform transmission phase coefficient and tunable transmission amplitude coefficient of metasurface unit cells. By implementing this topology on metasurfaces, the SLL of the proposed EM lens can be reduced without affecting the boresight gain of source patch antenna. The measured results of the proposed EM lens achieve 7 dB gain enhancement at designed frequency (5.8 GHz) with the SLL suppression of -24 dB. The total volume of planar lens antenna is 1.17 lambda x 1.17 lambda x lambda/2.25 mm(3), which is very compact compared with other reported planar lens designs.