Longitudinally Independent Matching and Arbitrary Wave Patterning Using $\varepsilon$ -Near-Zero Channels

We experimentally verify the unusual radiation properties of sources placed inside and in the neighborhood of effective ε-near-zero narrow (ENZ) channels. By utilizing the unique properties of a narrow waveguide channel operated at cutoff, a static-like uniformly enhanced electric field distribution can be induced at microwave frequencies over long distances. First, we show how this field uniformity provides a mechanism for position-invariant impedance matching for localized sources placed within the channel, enabling a unique coaxial-to-waveguide matching highly invariant to discontinuities. We then extend these concepts to sources placed outside the ENZ channels, realizing a microwave lens with unique radiation patterning properties. The realized ENZ lens is experimentally demonstrated under several excitation conditions, highlighting the possibility of tailoring the impinging wavefront with large flexibility.