Efficient Excitation of Characteristic Modes for Radiation Pattern Control by Using a Novel Balanced Inductive Coupling Element

A design strategy exploiting the characteristic mode (CM) analysis (CMA) is described for improving the radiation efficiency of a mounted-on-platform radiator. To this aim, a novel balanced inductive exciter (BIE) is introduced to improve the modal excitation purity of some CMs. In fact, even if the optimal position of the exciters on the hosting platform is determined by using the CM theory, the excitation purity of each mode plays a fundamental role in the radiation efficiency of the radiating system. In particular, achieving a good level of excitation purity strongly reduces the reactive power (P
_reac
) stored in the near-field zone and hence maximizes the amount of the radiated power (P
_r
). To better highlight the benefits offered by the presented approach, a set of BIEs is applied on a platform to obtain a fully reconfigurable radiation pattern. The evaluation of the P
_reac
, P
_r
, and equivalent isotropically radiated power provided by the BIE reveals the importance of a pure modal excitation. To assess the reliability of the proposed BIEs, some prototypes have been manufactured and tested.