Mutual coupling between shorted annular ring-reduced surface wave antennas

Jackson et al. (1993) developed a new microstrip patch, the shorted annular ring-reduced surface wave (SAR-RSW) antenna. This microstrip antenna produces only a small amount of surface-wave excitation. In addition, if printed on an electrically thin substrate (so that /spl beta/(TM/sub 0/)/spl ap/k/sub 0/), this antenna only weakly excites lateral waves (the space-wave fields that propagate along the air-dielectric interface). In this presentation we summarize our study of the mutual coupling between SAR-RSW antennas. The mutual coupling between conventional circular patches is used as a comparative reference, since these results are representative of the coupling between typical microstrip antennas. The same analysis is used for both antennas, since the SAR-RSW antenna becomes a conventional circular patch in the limiting case when the inner radius goes to zero. We present numerical results from a theoretical analysis of the mutual coupling, along with experimental results. The mutual coupling behavior is then explained using an asymptotic analysis, which demonstrates how the mutual coupling varies with patch separation. Finally, a theoretical investigation of both lateral- and surface-wave contributions to the coupling is performed to investigate the importance of these two contributions to the mutual coupling.