Higher-order mode coupling effects in shunt-series coupling junctions of planar slot arrays

While the design of linear slot array antennas has been completely automated, the use of an insufficient theoretical description of the coupling junctions in the design of two-dimensional planar slot arrays has delayed the total automation of this design procedure. It has been determined that this problem in the design process is due to the higher-order mode coupling between the closely spaced slots in the coupling junction region. A theoretical model for a shunt-series coupling junction has been created to take into account all of the higher-order mode coupling effects, and then the method of moments was used to calculate the electric field distributions for the coupling slot and the straddling radiating slots. The results of this theoretical approach are validated by comparing the theoretical results to experimental data obtained from a waveguide test fixture.