Gain pattern of a terminated - waveguide slot antenna by an equivalent circuit method

The terminated - waveguide slot antenna consists of a slot cut in the wall of a waveguide terminated in a known load. The gain pattern of such a slot is a function of the waveguide termination and may change markedly for different load values. The slot field can be regarded as composed of two independent field types arising from symmetric and antisymmetric electric field excitations of the slot, respectively; the relative intensities of the two excitations depend on the waveguide termination. Each of these constituent fields has its own characteristic radiation pattern, and the total gain pattern is obtained by superposition. The determination of the constituent slot fields from which the radiation fields may be computed is an extremely difficult task. it is desirable, therefore, to employ a technique which enables one to find the radiated field as a function of the incident field in the waveguide without a detailed knowledge of the slot field.