Abstract:
In this paper the helical antenna is considered with different helix diameters; uniform,
linear, conical and exponential diameter variations are loaded at different positions. All
helices are mounted on infinite ground planes and analyzed using NEC commercial
code based on the moment methods. 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
conical helix gives better performance. Fabrication of uniform and conical helices is
accomplished by their accurate dimensions .The results clarify that the laboratory
measured values is very close to the computed results.