Increasing the Test-Volume of Open TEM Cells by Using an Asymmetric Design

Open transverse electromagnetic (TEM) cells offer a low-cost solution for radiated pre-compliance measurements. Usually, available cells are implemented as a symmetric stripline. The main drawback of this technique is the equal distance between the inner and outer conductors, limiting the vertical space for the equipment under test. Throughout this paper, the potential of an asymmetric stripline approach is analyzed to provide test-volume space more efficiently. The main goal was to design a low-cost structure which is easy to build and gives the opportunity to make radiated pre-compliance measurements up to 1 GHz with a budget below 500 C. The initial geometry of the cell was derived analytically, optimized by 3D-EM simulations, and manufactured in-house. For verification purposes, S-parameter and field-probe measurements have been made and compared to simulation results. It is shown that the field homogeneity complies to IEC 61000-4-20 for the desired bandwidth having a cubic test-volume with an edge-length of 100 mm.