A study of the CTHA based on analytical models

The first electromagnetic analysis of the contra-wound toroidal helix antenna (CTHA) is presented. This very-low-profile antenna is seen to have characteristics derivable from a transmission line with a standing current wave and an array of small loops. Formulas for the far-field radiation and efficiency are given. These are used, in conjunction with a numerical model, to develop some trends relating performance and design parameters.