Field theoretical CAD of open or aperture matched T-junction coupled rectangular waveguide structures

The rigorous computer-aided design of rectangular waveguide structures coupled by open or rectangular iris loaded E- or H-plane T-junctions is described. The design theory is based on the full wave mode-matching method for the key-building-block T-junction element associated with the generalized S-matrix technique for composite structures. The waveguide structures may be arbitrarily composed of the T-junction and already known key-building-block elements (such as the double step and the septum discontinuity) combined with homogeneous waveguide sections between them. The E- or H-plane T-junction effect, large apertures, finite iris or septum thicknesses, and higher-order mode interactions at all step discontinuities are rigorously taken into account. Typical design examples, like rectangular iris coupled T-junctions, narrow-stopband waveguide filters, high return loss E-plane T-junction diplexers, an elliptic function E-plane integrated metal insert filter and a simple ortho-mode transducer demonstrate the efficiency of the method. The theory is verified by measurements