A backward-wave antenna based on negative refractive index L-C networks

Recently, there has been significant interest in materials with simultaneously negative permeability and permittivity, also referred to as negative refractive index metamaterials. Metamaterials comprised of straight metal wires and split ring resonators operating in the long wavelength regime exhibit a microwave frequency range with simultaneously negative values of effective permeability and permittivity. We use a 1D L-C loaded transmission line network supporting fast backward-wave propagation to demonstrate characteristics analogous to "reversed Cherenkov radiation". A novel backward-wave radiating structure inspired by negative refractive index L-C materials is proposed. A CPW-based printed configuration is presented with preliminary method of moments simulation results. The simulated E-plane pattern at 15 GHz shows radiation towards the backfire direction in the far-field pattern, clearly indicating the excitation of a backward wave. Since the transverse dimension of the array is electrically short, the structure is backed by a long metallic trough. The trough acts as a waveguide below cut-off and recovers the back radiation, resulting in unidirectional far-field patterns.