Eigenanalysis-based Port Synthesis of Multifeed Antenna for Power Combining

In this paper, a method for synthesizing multi-feed antennas is proposed. The Eigenvalue analysis of the scattering matrix of a multi-feed antenna has been used to synthesize different types of excitations. We have shown that the eigenvectors in the null space of the scattering matrix act as the building blocks of the excitation vectors for optimum power combination. To bring more flexibility, we propose two different scenarios to fit the design restrictions: (A) antenna ports with different input power levels and equal input impedances, and (B) equal input power levels and different input impedances. Based on simulation results of a four-port half-wavelength dipole both scenarios yield the same power combining for the multi-feed antennas. Also, we studied the effect of the feeds' weighting vector on equivalent isotropic radiated power (EIRP). It can be concluded that the EIRP in the multi-feed antenna is not a linear function of input power.