Comparison of square array directivity formulas

Directivity of rectangular planar arrays is often approximated using the directivity of two constituent linear arrays, either of dipoles or isotropic elements. A result has been derived for directivity of a rectangular planar array of short dipoles (in the plane of the array) using a method from Forman. The severe approximate directivity calculations are compared with this more accurate result. Curves of exact directivity of square arrays of from 4 to 20 elements on a side using short dipoles are presented.