NEC2 Based Optimum Design of Circularly Polarized Axial Mode Helical Antenna with Non-linear Pitch Profile Modeled using Catmull–Rom Spline and Particle Swarm Optimization
S. Santhosh Kumar1, Monisha Menon A2

1Dr. S. Santhosh Kumar, Assoc. Prof., Department of Electronics and Communication, Government Engineering College Idukki (Kerala), India.
2Monisha Menon A, Asst. Prof., Department of Electronics and Communication, Marian Engineering College, Thiruvananthapuram (Kerala), India.

Manuscript received on 15 December 2015 | Revised Manuscript received on 25 December 2015 | Manuscript Published on 30 December 2015 | PP: 68-72 | Volume-5 Issue-2, December 2015 | Retrieval Number: B4349125215/15©BEIESP
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Abstract: This paper presents a novel method for design of circularly polarized axial mode helical antenna with maximum directive gain. In this work helical antenna is modeled by eight parameters – helix radius (a), number of turns (N) and nonlinear pitch profile represented by a Catmull-Rom spline curve. This spline curve consists of six pitch angles, α1, α2, α3, α4, α5 and α6 at six equidistant points along the axial length of the helix. For a given number of turns optimum value of radius and pitch profile is determined for maximizing the gain subject to unity axial ratio. The gain and axial ratio are determined using NEC2 (Numerical Electromagnetics Code) simulation and optimization is performed using Particle Swarm Optimization (PSO). The original NEC2++ source code has been modified to incorporate Catmull-Rom spline modeling and PSO to suite the requirement of this work. Simulated and experimental results show that there is significant improvement in gain characteristics compared to design based on Kraus method which uses constant pitch profile.
Keywords: Helical Antenna, Axial mode, Catmull-Rom spline, Method of Moments, Particle Swarm Optimization, NEC2.

Scope of the Article: Microwave Antenna