Wideband designs of proximity fed regular shape microstrip antennas using bow-tie and H-shape ground plane profile are proposed in 1000 MHz frequency range. The modified ground plane alters the quality factor of the patch cavity which enhances the impedance bandwidth. In terms of the results obtained for bandwidth and gain together, circular and square patches backed by bow-tie shape ground plane, followed by circular patch backed by H-shape ground plane yield optimum results. For substrate thickness of 0.097λg, against the conventional ground plane, bow-tie shape gives 12% and 24% bandwidth increment for circular and square patches, respectively, and H-shape ground plane yields bandwidth increment by 17% in circular patch. All these wideband designs offer peak gain around 6 dBi with a broadside radiation pattern. Further, modified ground plane profile helps in optimizing the proximity fed antennas on lower substrate thicknesses. Amongst all the configurations, for ~0.03λg reduction in the substrate thickness, SMSA using bow-tie shape ground plane yields 19% increase in the impedance bandwidth against the equivalent thicker substrate design with a peak broadside gain of above 6 dBi. Thus, proposed modified ground plane antennas yields bandwidth improvement but for a smaller substrate thickness.
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