TEM小室高次模及谐振抑制的有限元分析

Finite-element Analysis on Suppression of Higher-order Modes and Resonances in TEM Cell

采用全波有限元法分析了TEM小室开纵向缝隙对高次模和谐振的抑制效果。计算、分析了用于IC(集成电路)辐射发射测试的TEM小室主传输段两维模型在3 GHz频率内的高次模模式,并与TEM小室内、外导体分别切割纵向缝隙以及内、外导体同时切割纵向缝隙时的高次模模式进行了对比。建立了标准TEM小室和外导体开纵向缝隙的TEM小室的三维模型,分析了三维谐振模式及电压驻波比。研究结果表明:TEM小室内外导体开纵向缝隙可有效抑制高次模的产生;尽管改进后的TEM小室谐振模式仍较为复杂,但谐振现象有明显改善,电压驻波比性能较为满意,上限工作频率可达到2.5 GHz。

The efficiency of suppressing higher-order modes and resonances in TEM cell by cutting longitudinal slots was calculated and analyzed by full-wave finite-element method. The higher-order modes of the 2-D model for the main section of TEM cell, which is used in IC （integral circuit） radiated emission measurement, were calculated up to the frequency of 3 GHz, and compared with the modified TEM cell slotted septum and external walls separately and all together. Further more, the standard TEM cell and the TEM cell slotted external walls were modeled in 3-D geometry to analyze their resonance modes and voltage standing wave ratio. The obtained results show that slotting the septum and external walls of TEM cell can effectively suppress the higher-order modes. And, although the resonance modes in modified TEM cell are still complex, the resonance phenomena are improved remarkably, in particular the performance of voltage standing wave ratio is fairly satisfied, so that the upper limited frequency can reach up to 2.5 GHz.