Broadband characteristics of cylindrical antennas with exponentially tapered capacitive loading

Experimental results are presented demonstrating the electrical characteristics of a cylindrical antenna loaded with capacitive elements whose reactance increases exponentially with the distance from the feed end. The results show that the antenna reported has good broadband characteristics. One of the antennas yielded radiation pattern constancy over a 3:1 bandwidth with VSWR varation of less than 3:1 with respect to 50 ohms. For impedance constancy only, a model has achieved greater than 10:1 bandwidth. Qualitative design considerations to achieve required broadband characteristics are included. Finally, the approximate current distribution along the antenna is obtained theoretically, and it is predicted that the current decays very rapidly toward the free end when the loading is sufficiently large. Experimental results are presented in order to confirm the theoretical prediction.