A method of analyzing coupled antennas of unequal sizes

The impedance parameters of coupled antennas are calculated by a variational method. The unknown coefficients pertaining to the trial functions for the current distributions on various elements are shown to satisfy a set of linear equations involving the excitation conditions, but the final formulas for the impedance parameters involve only the trial functions and the geometry. The method is directly applicable to the analysis of Yagi-Uda antennas, and the technique can be extended to coupled slots inside a waveguide or coupled radiating slots excited by waveguides.