Internal admittance elements of a rectangular waveguide longitudinal slot using the image method

The internal admittance matrix elements that are needed during the Method of Moments analysis of a longitudinal slot in a rectangular waveguide have been evaluated by considering the slot images in waveguide walls. The contribution from all the sources (real and virtual) has been evaluated by adopting the technique of Fast Matrix Generation (FMG). The contribution from all the image terms has finally been evaluated using a simple closed-form expression and a rapidly converging series. This leads to a faster, intuitive and more efficient analysis. The results calculated using this simple method are shown to be in excellent agreement with measured results and with other theoretical results. This method is useful in the efficient design of waveguide fed slot arrays.