Application of wire-based metamaterials for antenna miniaturization

This paper reviews recent numerical and experimental investigation of application of wire-based ENZ metamaterials in miniaturization of waveguide horn antennas, undertaken at University of Zagreb. Two representative examples of prototyped shortened horn antennas that operate in 10 GHz band are described: the horn with embedded single-wire ENZ slab and the horn with embedded double-wire ENZ slab. These two horn antennas had lengths of 52% and 33% of the length of the optimal horn, respectively. Measured gain was found to be very similar to the gain of the full length optimal horn (within 0.1 dB), but in a narrow band (5% - 12%). Finally, the results of numerical study of applicability of a simple Drude model of wire medium in the design of shortened horn antennas are presented. The results show that Drude model of wiremedium is not accurate if the wires are not connected to the metallic plates at an angle of 90 degrees. However, even in this case a Drude model is good starting point for the initial design, while the required antenna characteristics should be achieved by an additional numerical optimization.