Optimum Design of Antennas (Invited)

The paper studies the optimum design of antennas. The objective function to be maximized is the ratio of gain to quality factor (Q) (i.e., the product of gain and bandwidth) in a specified direction. The theoretical upper bounds for the ratio of gain to Q are first re-derived by using a different definition of antenna Q from the traditional one. The ratio of gain to Q may be reduced to an eigenvalue equation which can then be solved, yielding an optimum current distribution that maximizes the ratio of gain to Q in a specified direction. Numerical examples for small antennas have been presented to demonstrate how the theoretical upper bounds for the ratio of gain to Q can be approached by optimizing antenna geometries as well as the current distributions.