Analysis of waveguide slot array using virtual cavity method

Conventional design methods for slotted waveguide array antennas synthesize the scattering characteristics of individual slots in a waveguide. We consider the mutual coupling effect of all slots for the rigorous analysis of a longitudinal slot array. The integral equations are solved by Galerkin´s method, where weighting functions are of the same type as the basis functions. When calculating a mutual coupling between slots, the dyadic Green´s functions of H. Seki (1984) are used to avoid the complex calculations of the conventional Green´s functions. The field equivalence theorem enables division into several analysis regions where the dyadic Green´s functions are respectively used. The integral equations for the unknown electric fields are derived on the slot apertures. Furthermore, for the enhancement of calculation time, those coupled-integral equations are derived by the virtual cavity method. The scattered field due to the slot is the field of the slot in the virtual cavity and the magnetic currents on the two walls. The far-field radiation pattern from a slot is obtained by using the Fourier transform of the electric field on the slot. The total field of an array is the superposition of the radiation from all slots. Computed results are compared with an experimental result.