Influence of the wall geometry on reflection and transmission in an -plane sectoral horn

For a gradual waveguide-sectoral horn junction excited in the TEM mode, the influence of the wall geometry on reflection and transmission is investigated. The wall profile of the junction has the shape of a circular arc. When increasing the circle radius from zero, an abrupt junction changes to a smooth one. The magnitude of the reflection coefficient is reduced in a broadband manner whereas the phase variation increases. Clearly, the transmission increases too, but the ratio of dominant horn mode to the next higher mode will be diminished considerably. The analysis is rigorous and combines the "generalized telegraphist\´s equations" with a mode matching technique. This method is particularly suited for the calculation of waveguide-horn junctions.