On the design and fabrication of a large GTEM cell and its challenges

This paper presents the design of a large Gigahertz Transverse Electromagnetic (GTEM) cell for Electrical/Electronic Sub-Assembly (ESA) testing of a car or other information technology (IT) equipment as well as the challenges of its design and fabrication. The 7.5 meter long and 4 meter width and 4 meter height dimensions of this cell are large enough to test ESAs inside. The operating frequency band is from 30 MHz to 6 GHz based on CISPR standards. To increase the operating frequency of the GTEM and to improve the uniformity of the wave, hybrid absorbers are mounted at the end wall. These absorbers consist of ferrite tile and pyramid absorbers, which have large bandwidth and high performance. The dimensions of the GTEM cell are too large and therefore full wave simulation is difficult and time consuming. In this paper, we have introduced a two-step method to convert a pyramidal absorber into a one-layer flat absorber. This technique simplifies our GTEM cell full wave simulation. On the fabrication side, the effect of distortion of a long metal sheet on the performance of the room are numerically examined. Finally, the acceptable measurement results of the GTEM are reported.