Characteristic Mode Assisted Placement of Antennas for the Isolation Enhancement

In this letter, the isolation between onboard antennas is investigated using characteristic mode analysis, which provides an intuitive insight for the antenna placement on large platforms. An analytical expression of the relationship between the platform modal excitation coefficient and the platform modal charge is derived under the condition of a coaxial feeding mechanism. It is revealed that the deployment position that leads to a maximum isolation is indicated by the platform modal charge. Based on this finding, a simple and efficient method for antenna placement on aircraft-like platforms is developed to enhance the isolation. Two examples with vertically polarized blade antennas are presented, in which two or three blade antennas can be deployed on the platforms. Both the numerical and experimental results show that the isolation is increased remarkably by the proposed method.