Shipboard NVIS radiation system design using the theory of characteristic modes

This paper presents a systematic approach for the shipboard Near Vertical Incident Sky Wave (NVIS) radiation system design. In this approach, characteristic mode analysis to the shipboard platform is performed first. A multi-objective optimizer is then applied to find the optimal weighting coefficient to each mode. Besides the NVIS radiation patterns that realized in the optimal design, we also localize the intense current distribution only in a very small part of the shipboard platform. The localized currents facilitate the excitation of the synthesized current distribution on the platform. Conformal embedded slots are proposed to excite the platform currents with very good impedance matching. The shipboard platform itself thus serves as the radiator, and the radiation efficiency is maximized. Unlike conventional methods, the proposed approach does not require additional antennas and does not need to consider the antenna placement issue. Due to the simplicity and very clear physical concept, this new method can be easily implemented in other platform integrated radiation system designs.