Microstrip antennas excite surface waves and produce lateral radiation, and these fields deteriorate the radiation pattern due to diffraction and also couple with neighboring patches in an array environment. Recently, microstrip antennas denoted as ldquoreduced-surface-waverdquo (RSW) antennas were developed that minimize the surface-wave excitation and lateral radiation (D. R. Jackson, et al., August 1993) (M. A. Khayat, et al., Oct. 2000). However, these antennas have the disadvantage of being physically larger than conventional microstrip antennas. The design proposed here realizes a reduced-surface-wave microstrip antenna that is smaller than the previous design by using via loading of an annular ring configuration.