Helical antennas with nonuniform helix diameter

On this paper the helical antenna is considered with different helix diameters, uniform, linear, exponential and logarithmic diameter variations are considered. In each case, the radiation fields in the principal planes, the gains, axial ratio and current distributions are obtained. Also the input impedance is calculated as the frequency varies around the design values for each case. In all cases the pitch is taken constant. The numerical evaluations indicate that the exponential helix gives better performance.