Toroidal helical antennas-analysis and optimisation

We present some results from our comprehensive study on toroidal antennas, including verification of the claimed behaviour, analysis and explanation on its radiation mechanism. Moreover, we have found that the reported contrawound toroidal helical antenna (CTHA) has an inherent drawback and a new of type open toroidal antenna structures are proposed and simulation studies show that the proposed open CTHA can achieve both satisfactory radiation and impedance performance. Optimal design of the open CTHA is also conducted and a very near isotropic radiation performance has been obtained with pattern fluctuation within /spl plusmn/1 dB. The Numerical Electromagnetic Code (NEC) and an optimisation tool based on genetic algorithm were used for the computer simulation study.