MICROSTRIP PATCH DESIGNS THAT DO NOT EXCITE SURFACE-WAVES

Two variations of a circular microstrip patch design are presented whi ch excite very little surface wave power. Both of the proposed designs are based on the design principle that a ring of magnetic current in a substrate (which models the patches) will not excite the dominant TM 0 surface wave if the radius of the ring is a particular critical valu e. Numerical results for radiation efficiency and radiated field stren gth from a ring of magnetic current are shown to verify this basic des ign principle. The proposed patch designs are chosen to have a radius equal to this critical value, while maintaining resonance at the desig n frequency. These patch designs excite very little surface-wave power , and thus have smoother radiation patterns when mounted on finite-siz e ground planes, due to reduced surface-wave diffraction. These new pa tch designs also have reduced mutual coupling, due to the reduced surf ace-wave excitation. Measured results for radiation patterns and field strength within the substrate are presented to verify the theoretical concepts.