Mutual coupling in finite coplanar rectangular waveguide arrays

Mutual admittance expressions are given for all possible combinations of mode coupling in an array of identical collinear rectangular waveguides opening into an infinite ground plane. Specific results are presented for the worst case of E-plane coupling between identical square waveguide to show that significant high-order mode excitation can occur. Some of these modes are a source of crosspolarisation, making mutual coupling important to the prediction of the crosspolar pattern of a rectangular waveguide array.