Reconstruction of the Characteristic Modes on an Antenna Based on the Radiated Far Field

In this paper, we present a method to reconstruct the modal current distribution on an antenna from the radiated far field and general knowledge about the modes involved. The method leads to good results if the radiation mechanism of the antenna can be approximated by the current distribution on a simplified structure. The current distribution of the simplified structure is decomposed into its characteristic modes and the related modal far field is calculated. Assuming that the far field of the actual antenna contains the same modes, their weighting coefficients are calculated by comparing the far field of the actual antenna to the modal far field of the simplified structure. It can be shown that the weighting coefficients of all significant modes can be reconstructed with good accuracy even for complex real structures such as mobile phones.