Spherical-multipole analysis of the field within a canonical GTEM-cell

The GTEM-cell has been a subject of extensive research. However, due to its relatively large dimensions and to the sharp edges of the septum, numerical treatment of the cell´s field may become very difficult. Furthermore, numerical simulation to determine the distortion of the empty cell´s field by a device under test becomes even more complex. This paper introduces a mostly analytical model for the GTEM-cell that is obtained by changing the geometry of the cross section from rectangular to elliptical. This allows an exact solution for the empty cell´s field by means of a problem-adapted dyadic Green´s function in sphero-conal coordinates. The solution may be combined with other numerical methods to obtain a more realistic modelling of the coupling phenomena. First numerical results are also shown.