Investigation on the Mutual Coupling of High-Power Dual-Branch Helical Antennas

Abstract

The mutual coupling in high-power dual-branch helical antennas (DBHAs) is investigated, with the purpose of improving the power capacity of high-power antenna arrays further. Unlike common measures, the maximum <inline-formula> <tex-math notation= LaTeX >${E}$ </tex-math></inline-formula>-field difference between a single antenna element and its array is proposed to evaluate the strength of mutual coupling. This measure is suitable for high-power antenna arrays and validated by comparing with other indexes, such as S-parameter, gain, and axial ratio. Because high-frequency current and the <inline-formula> <tex-math notation= LaTeX >${E}$ </tex-math></inline-formula>-field are closely related, the full-wave method is used to calculate the current amplitude distribution over a single helical antenna and the scattering <inline-formula> <tex-math notation= LaTeX >${E}$ </tex-math></inline-formula>-field of an antenna array. Since the antenna elements mutually coupled through the air, several approaches are discussed for suppressing the mutual coupling. It is verified that using cavity not only isolates the antenna elements well but it is also with high power capacity. The results indicate that each antenna element is able to handle high pulsed power. Besides, it could be seen that the decrease in mutual coupling is helpful for improving the power capacity.