The field uniformity and dominant TEM mode performance of the test field acting on the equipment under test(EUT)in gigahertz transverse electromagnetiC(GTEM) cell were studied. The three-dimensional finite-difference time-domain (FDTD) method was used to model the GTEM cell loaded with a metallic EUT in cartesian coordinates. The calculation and analysis frequency is up to 2 GHz. The field distribution performance of a larger EUT and a small EUT were calculated,and the effects of EUT size on field performance were analyzed. Not only the dominant field component uniformity but also the resultant field strength uniformity was studied. Furthermore, the variation trend of average value for each field component with frequency increasing was provided. The obtained results show that the field uniformity for small EUT is perfect,while for the large EUT the field uniformity will decrease when the working frequency is more than its permitted frequency. The results also show that the cross-polar performance will decrease at high frequencies whether for small EUT or for large EUT, which is caused mainly by the increasing of longitudinal component.%研究了GTEM小室中EUT受试电磁场的场均匀性和主TEM模特性.在笛卡尔坐标系中建立了加入金属EUT后GTEM小室的三维FDTD模型,计算分析频率达2 GHz.计算了一个“大EUT”和“小EUT”的场分布特性,分析了EUT大小对场分布性能的影响.不仅研究了主分量的场均匀性,还研究了总场强的场均匀性,此外,还给出了各场分量的平均值随频率变化的趋势.研究结果表明:满足“小EUT”条件时,场均匀性良好,而“大EUT”在超出其许可频率后,场均匀性下降；在高频情况下不论是“大EUT”还是“小EUT”交叉极化特性均有所下降,主要表现为纵向场分量的增加.
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