Effects of geometrical parameters, loading, and feeding on nonuniform helical antennas

Abstract

In this paper, analysis and design methods are applied on helical antenna by using the NEC commercial code based on the method of moments. When adding a ground plane, the linear helix gives a 20 dB gain compared to a 17 dB gain obtained from exponential helix without a ground plane. The feeding of the helix is changed by varying the pitch and studying its effect on the radiation characteristics. Also the helices of uniform and nonuniform profiles are loaded at different positions by different values of resistances and inductances. In this case, the current distribution is computed, and the electric field in the vertical plane and the gain are investigated. Finally, many exponential profiles have been examined for improved characteristics by changing the pitch angle /spl alpha/ of the exponential helix and studying the resulting effect on the antenna characteristics.