A General Method for Designing Reduced Surface Wave Microstrip Antennas

Surface-wave excitation from microstrip antennas is of major concern in many practical antenna applications. In this paper, the challenge of reducing the surface-wave excitation from microstrip antennas in a general way is addressed. The proposed approach is based on a theorem called the reduced surface wave (RSW) theorem. The RSW theorem suggests that by properly selecting the permittivity of the filling material inside the patch cavity, the patch will not excite the dominant ${\rm TM}_{0}$ surface-wave mode. A validation of this theorem is demonstrated here for the first time by comparing the mutual coupling between a pair of RSW antennas and a pair of conventional antennas.