On the use of characteristic modes to describe patch antenna performance

This work introduces some preliminary results focused to point out that the theory of characteristic modes may help in the design of microstrip patch antennas, as it brings clear insight of the physical phenomena taking place in it, and presents no limitation over the height of the patch or the dielectric constant of the materials. Characteristic modes are defined as the real currents on the surface of a conducting body that depend on its shape and size, and are independent of the feed point. As characteristic modes form a close and orthogonal set of functions, they can be used to expand the total current. Another advantage of this method, is that for electrically small and intermediate size bodies, only a few modes are needed, and the problem can be dealt with only by considering two or three modes.