A Hybrid Optimization Method to Analyze Metamaterial-Based Electrically Small Antennas

A model of an idealized radiating system composed of an electrically small electric dipole antenna enclosed in an electrically small multilayered metamaterial shell system is developed analytically. The far-field radiation characteristics of this system are optimized using a GA-MATLAB based hybrid optimization model. The optimized-analytical model is specifically applied to a spherical glass shell filled with a "cold plasma" epsilon-negative (ENG) medium. These analytical results are confirmed using ANSOFT HFSS and COMSOL Multiphysics simulations; these numerical results include input impedance and overall efficiency values not available with the analytical model. The optimized-analytical model is also used to achieve electrically small nonradiating metamaterial-based multilayered spherical shell designs. The optimized shell properties are exploited to obtain multiband radiating and nonradiating response characteristics. Dispersion properties of the ENG materials are also included in all the analytical models; the bandwidth characteristics of these systems are discussed