Formulation, Validation, and Extensibility Study on the Impedance of Underwater Dipole Antennas

Abstract

This paper describes the theoretical formulation for half sheath dipole antenna(HSDA) and adaption area of this formulation with comparison between simulation results and formulation results. HSDA which conductor length is 2m and sheath length is 1m could be defined as small antenna electrically in the seawater at 10kHz because current in the sheath is constant, current out of sheath is operated as Hertz dipole antenna, and electric field near antenna is electrostatic. Therefore, HSDA is replaced with equivalent circuit and each element is calculated with electrostatic analysis, so that impedance of HSDA was formulated theoretically. Accuracy of this formulation and adaption area is indicated by comparison between HFSS simulation results and formulation. Additionally, this formulation method is adopted to full sheath dipole antenna(FSDA). Each element consisting FSDA impedance is calculated with electrostatic analysis for inside sheath because electric field in the sheath is dominant. This electrostatic formulation for FSDA is also found effective by comparing with simulation and formulation results.