Planar transmission line excitation of dielectric resonator antennas

An approximate theory is derived for all the modes in a cylindrical dielectric resonator antenna. The air-dielectric interface is approximated as a perfect magnetic conductor and expressions for the resonant frequency and radiation from the equivalent surface magnetic currents are presented. A broad beam with a maximum normal to the ground plane is obtained for the lowest mode. A more directive beam or a beam with a single sharp null is obtained for the next mode depending on the cylinder geometry. Good agreement is obtained between theory and experiment. An experimental investigation was also undertaken to demonstrate the microstrip transmission line and the coplanar waveguide as effective excitation mechanisms for the cylindrical dielectric resonator antenna. Results showing the coupling behavior and the radiation patterns for various cylinder aspect ratios, dielectric constants, and feed positions are presented. The results show these feed structures result in efficient and practical antenna systems.