144 GHz epsilon-near-zero metamaterial lens

The focusing performance and radiation properties of an all-metallic epsilon-near-zero (ENZ) lens working at 144 GHz are shown. The lens is made of an array of narrow hollow rectangular waveguides working near cutoff, which effectively behaves as an anisotropic ENZ medium. A field enhancement of 5.61 dB and directivity of 17.6 dBi are measured with a good impedance matching with free space.