Investigation on the EM-Coupled Stacked Square Ring Antennas With Ultra-Thin Spacing

Stacked electromagnetically coupled square ring antennas with extremely thin spacing are studied. The separation between rings is kept very small so that they do not increase the overall antenna height, yet can provide multiband operation. The coupling effects among these very closely placed rings are studied based on substrate parameters so that they can be practically implemented using commercially available microwave substrates. It is observed that with an asymmetric arrangement of the stacked rings, different polarizations can be obtained for different resonances. However, if a fixed polarization is desired, a concentric stacked rings configuration has to be used. Experimental investigations are conducted to confirm simulation results.