Optimum element spacings for Yagi-Uda arrays

A method is developed for the maximization of the forward gain of a Yagi-Uda array by adjusting the interelement spacings. The effects of a finite dipole radius and the mutual coupling between the elements are taken into consideration. Currents in the array elements are approximated by three-term expansions with complex coefficients which convert the governing integral equations into simultaneous algebraic equations. The array gain is maximized by the repeated application of a perturbation procedure which converges rapidly to yield a set of optimum, generally unequal, element spacings. This method eliminates the need for a haphazard trial-and-error approach or for interpreting a vast data collection. Illustrative examples are given.