Experimental study of a microstrip array on high permittivity substrate

The results of an experimental study of microstrip patch antennas on moderately thick (0.02-0.03lambda_{0}) substrates with relative permittivities of 10 and 13 are reported. Measured input impedances are qualitatively similar to those of antennas on thinner substrates with lowerepsilon_{r}, but significant differences in resonant resistance are observed for probe-fed and microstripline-fed antennas. Radiation patterns of individual elements exhibit deep scallops that appear to be caused by surface wave diffraction at the edges of the substrate, but four-element monopulse patterns exhibit a usable main beam and tracking null.