Modal source reconstruction based on radiated far-field for antenna design

We present a mathematical technique to reconstruct the modal current distribution on arbitrary antennas from the radiated far-field and general knowledge about the modes involved. The method leads to good results if the radiation mechanism of the actual 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.