Experimental demonstration of metamaterial flat lens at F-band

We experimentally demonstrate a metamaterial flat lens based on split-ring resonators at 120 GHz based on the gradient index optics theory. The gap of the SRRs that were used as a unit cell of the lens was varied to obtain desired reflective index at a specific place in the lens. In this work, a far-field radiation pattern of an open-ended waveguide antenna was measured with and without the metamaterial flat lens, and we experimentally determined the improvement in the beam directivity on the antenna gain to be approximately 11 dB, with a 3-dB relative bandwidth of 15% or more.