Network parameters of a waveguide broad wall-slot radiator

It is found from experimental investigation that the equivalent network of a thin displaced longitudinal slot in the broad wall of a rectangular waveguide changes from a parallel element to a series element a back to parallel element again as the length of the slot is increased from about ¿/2 to about 3¿/2. In the paper, analytical experssions for the immitance variations in the series and shunt forms of representations have deen found. The electric-field distribution in th aperture plance of the slot is replaced by suitable magnetic-curent distribution. The field distribution in the aperture plane of a slot, representable as a shunt element, is an even function and produces a discontinuity in modal current. The analytical expression for the complex admittance in the shunt form of equivalent network has been found from the reaction of the magnetic field due to the slot with the magnetic current exciting the slot and the discontinuity in modal current. A slot, whose equivalent network is a series element, has an odd distribution of electric field in its aperture plane, and such a slot produces a discontinuity in modal voltage. The analytical expression for the impedance in the series form of equivalent network is found from the power radiated by, and power stored in the vicinity of, the radiating slot and the discontinuity in modal voltage. The analytical expression for the impedance in the series form of equivalent network is found from the power radiated by, and power stored in the vicinity, of the radiating slot and the discontinuity in modal volage. The theoretical results are in good agreement with experimental observations.