Figures of Merit for Field Homogeneity in TEM Waveguides

The homogeneity of the transverse electromagnetic (TEM) field in a TEM device is a necessary condition for the compliance of emission and immunity measurements in TEM test facilities with standards. Under these conditions, the behavior of the TEM mode over the desired frequency range has to be verified. This homogeneity, indeed a figure of merit of the waveguide, is investigated using the generalized postulates presented in this work in combination with some calibration procedures defined in the standards. Verification of the postulates provides a valuable insight into the field distribution within the considered TEM line facility, since the obtained results are in excellent agreement with the measured fields. The maximum transverse and longitudinal polarization errors, which can be normally tolerated in order for the field to be considered as a TEM wave, are derived from the copolar field. As a result, the savings in the measurements are achieved. Finally, the consistency obtained upon direct comparison of different TEM test facilities confirms the applicability of the model.