Optimum Design of Exponentially Varying Helical Antenna with Non Uniform Pitch Profile

Helical antennas finds major applications from VHF to microwaves which requires circular polarisation. Helical antennas can operate in two principal modes of operation: normal (broadside) mode or axial (end fire) mode. They have got high gain in axial direction which makes them suitable for satellite communications. This paper presents optimum design of axial mode helical antenna using non linear pitch profile modeled using Catmull Rom Spline and radius exponentially varied along the axis of the helix. The antenna is optimized for maximising directive gain subject to unity axial ratio. The optimization is done using Particle Swarm Optimization (PSO) and simulation is done usng Numerical Electromagnetics Code NEC2. Original NEC2 source code is suitably modified to incorporate spline modeling and PSO. Simulation result show that antenna designed usng proposed method has better gain characteristics compared to antenna with uniform radius and non linear pitch profile.