Design and analysis of a helical spherical antenna using the theory of characteristic modes

Electrically small dipole antennas with ka less than 0.5 exhibit low radiation resistance, high capacitive reactance and high Q factor which is inversely proportional to antenna bandwidth. Here, the k is the free space wave number and a is the radius of an imaginary sphere which circumscribes the whole antenna. Spherical dipole antennas potently have higher effective volume if compared to other small antennas with maximum dimension equal to a. The higher the effective volume the lower the Q if proper feeding is used. Characteristic mode theory, as formulated in (Harrington and Mautz, 1971), will be used to analyze the input impedance and currents of a one-turn four-arm spherical antenna to improve the antennapsilas broadband behavior.

Introduction

Electrically small dipole antennas [1] with less than 0.5 exhibit low radiation re-sistance, high capacitive reactance and high Q factor which is inversely proportional to antenna bandwidth. Here, the is the free space wave number and is the radius of an imaginary sphere which circumscribes the whole antenna. Spherical dipole antennas potently have higher effective volume if compared to other small antennas with maximum dimension equal to . The higher the effective volume the lower the Q if proper feeding is used. Characteristic mode theory, as formulated in [2], will be used to analyze the input impedance and currents of a one-turn four-arm spherical antenna [3] to improve the antenna's broadband behavior.