Series expansions for the mutual coupling in microstrip patch arrays

A dominant-mode mutual coupling theory is developed for an array of microstrip patches. One of the key features of the formulation is that only values for isolated self- and mutual impedance are needed in the formulation, making the method suitable for either a cavity model or spectral-domain analysis, or compatible with experimental measurements. The formulation is equivalent with D.M. Pozar´s (1982) moment-method formulation. A series expansion of the solution is derived, allowing for approximate formulas accurate to any specified order. These formulas do not require matrix inversion. Formulas up to third order require less computation time that the exact solution, for single elements of the impedance, admittance, and scattering matrices. These expansions are computationally efficient for large sparse arrays.<>