A Shape Synthesis Method for Unidirectional Electrically Small Antennas Using Characteristic Modes

A shape synthesis method for unidirectional electrically small antennas (ESAs) is proposed using characteristic mode (CM) concepts. Eigenvalues and eigenfields, which are feed-independent CM quantities, are used as the objective functions and preconditions to synthesize the antenna shape. As a result, the feed location does not need to be specified in advance, and design freedom is increased. The inclusion of the eigenfields makes the choice of the starting shape more arbitrary and flexible, encouraging a wider range of effective unidirectional antenna designs. A unidirectional ESA with a fairly high gain and an extremely low back lobe is designed using the proposed shape synthesis method.