Surface wave radiation from a shorted elliptical patch antenna

Surface wave radiation from microstrip antennas is known to be source of many inconveniences, such as undesirable coupling between elements of an array, radiation efficiency reduction and radiation pattern perturbations due to the surface wave diffraction on dielectric truncations. For this reason, research on reduced surface wave (RSW) patch antennas has been receiving an increasing consideration. In particular, the shorted annular patch (SAP) antenna (Jackson, D.R. et al., IEEE Trans. on Antennas and Propag., vol.41 no.8, 1993) has been revealed as a microstrip radiator that can be designed to produce a small amount of surface wave radiation. The conditions for designing a dual band reduced surface wave antenna are outlined considering a shorted elliptic ring antenna. Following the resonating analysis presented by Jackson et al., the surface wave emission from an elliptic distribution of magnetic current, defined in terms of angular Mathieu functions, is studied. It is proved that, at variance with the circular case, the zero-emission condition cannot be determined and only a minimum for the surface wave power can be achieved.