Optimal positions of loading for a shortened resonant monopole using genetic algorithm

Abstract

The size reduction for resonant monopoles is an important issue for HF and VHF antennas. Unfortunately, size reduction results in degradation in both efficiency and bandwidth, as is well known from the fundamental limits on small antennas. This paper firstly introduces a MATLAB-controlled NEC2 simulation tool with genetic algorithm optimization, and uses this to find the optimal position of inductors for a shortened monopole with L-section matching networks. Trade-offs between bandwidth and efficiency are investigated and demonstrated in a systematic fashion for a single inductor case. Various multi-inductor loading schemes are also investigated; including central symmetrically distributed and arbitrarily distributed two-inductor loading schemes. The ultimate goal of the research is to find an optimal distribution of inductors on a reduced-size resonant monopole.