Study on the Multiple tuning for VLF Umbrella Antenna

The purpose of this paper is to investigate the electrical properties of multiple tuning and single tuning on input resistance and input current of VLF Umbrella. Owning to the adverse conditions of low radiation resistance of the singled tuned antenna, the coupling network that provide the impedance transformation is need in feeders. We propose a multiple-tuned method of increase the impedance of VLF Umbrella Antenna to eliminates the coupling network. A model of a trideco-tower umbrella antenna (the NWC antenna) is established in the FEKO simulation software. Using the multiple-tuned, the radiation resistance of multiple-tuned VLF antenna is the square of n times that of a single-tuned antenna, where n is the number of elements. Meanwhile, the current in tuning inductance is 1/n times that of a single-tuned antenna. The antenna voltage of the multiple-tuned is the same as for the single-tuned condition.