Mutual Coupling Considerations in Linear-Slot Array Design

A study was made of the mutual coupling between two resonant waveguide fed slots on a finite ground plane. The size of the ground plane and the relative spacing of the slots were such that the geometry corresponded to that of a pair of adjacent longitudinal shunt slots on the broad face of a rectangular waveguide. A null bridge method of measurement was used to determine accurately the relative field strength excited in the second waveguide by mutual coupling between the slots when the generator was applied to the first waveguide. The change in input slot admittance of the driven slot arising from the presence of the parasitic slot was also measured for matched terminations of the ends of the parasitic slot waveguide. The changes in slot input admittance and excitation arising from mutual coupling were determined. It is shown that the changes may be neglected in the design of the great majority of linear-slot arrays.