CAD formula of rectangular microstrip patch antenna on thick substrate

A simple CAD formula of the basic rectangular patch antenna with thick substrate of low /spl epsiv//sub r/ is adapted from that of a basic patch resonator of thin substrate of high /spl epsiv//sub r/. This means that the adapted formula is also based on the cavity model, the fringe field and the radiation loss. The thick substrate of low /spl epsiv//sub r/ is needed to enable the rectangular patch to be made broadband, by the L-probe feed, or other attachments. The CAD formula of the patch antenna has good accuracy (errors< 3%) for /spl epsiv//sub r/<3 and thickness h>0.05 /spl lambda//sub 0/.