Characteristics of the shorted annular-ring patch antenna

A recent paper by Jackson et al (see IEEE Trans. Antennas Propagat., vol.41, no.8, p.1026-1037, 1993) discussed the design of a class of microstrip patch antennas that excite very little surface wave power. Their design is based on the principle that a ring of magnetic current of a particular critical radius should not excite the dominant TM/sub 0/ surface wave in the substrate. This property would allow for the design of more efficient individual patch radiators as well as provide for reduced mutual coupling in an array environment. Unfortunately, this critical radius is larger than that required for the usual dominant mode resonance for a conventional circular patch. Thus, new designs must be developed that both are resonant and satisfy the critical radius criteria. One such design, the shorted annular-ring microstrip patch, is the subject of this investigation.<>