Experimental and theoretical studies of a DR loaded helical antenna

A DR loaded helical antenna was studied both experimentally and theoretically. The DR was made as a cylindrical core and placed inside the helix. Particular interest was paid to the effect of the positioning of the DR core along the helix. In other words, we moved, instead of fixed, the DR core inside of the helix. We found that when the DR core was moving further and further away from the ground plane, the gain of the resulting antenna was increasing while the bandwidth and the input impedance were less affected. We used a multiple equivalent current sources technique to simulate the presence of the DR core. This removes the error in using an infinite structure approximation. The current distribution along the helix and the radiation patterns were then calculated.