Characteristic modes analysis on neutralizing effect of shorted line for two adjacent PIFA elements

Abstract

Two adjacent planar inverted-F antenna (PIFA) elements are used for a beam switchable antenna. But strong mutual coupling between the two closely arranged PIFA elements cannot be ignored. A shorted line connecting the two PIFAs is proved useful to provide neutralizing effect to reduce the mutual coupling. Optimized arrangement of PIFAs and the shorted line is shown, and the theory of characteristic modes is used to analyze that why the optimized shorted line make the mutual coupling reduce and how it works.