BW Enhancement using Proximity Coupling

Proximity coupling is basically a feeding mechanism which gives the highest bandwidth and low spurious radiation. In general, we use two substrates of different thicknesses and permittivity. A short tuning stub is connected in shunt with feedline at some distance from edge of the patch. The fabrication of such an antenna is difficult. Length of feeding stub and the width-to-line ratio of the patch is used to control the match.