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 wire-medium 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.