An improved technique for the evaluation of transverse slot discontinuities in rectangular waveguide

The scattering from a slot discontinuity in rectangular waveguide can be described by an integral equation. This equation can be reduced to matrix form by application of the well-known moment method technique. The success of this approach depends on the convergence of the kernel, i.e., the Green's dyadic. When the Green's dyadic is structured using waveguide modes,
\hat{z}\hat{z}
component convergence is assured. However,
\hat{x}\hat{x}
component convergence is uncertain in the source region. This condition is most clearly demonstrated by the transverse series slot. An image technique can be employed to overcome this difficulty, with the penalties of slow series convergence and loss of waveguide modal association. A superior approach results when an edge condition is introduced to retain a waveguide mode description and, at the same time, assure
\hat{x}\hat{x}
component convergence. The radiating transverse slot is analyzed using this edge condition. Results compare favorably with Oliner's experiments.