A study on upper limit frequency of symmetric extended TEM cells

TEM Cells is a commonly used electromagnetic field test device. The upper limit frequency of the TEM Cells is limited to the first resonant frequency. Through the electromagnetic numerical simulation, this paper analyzes the resonant frequency law of high-order modes and studies the resonant frequency characteristics and the upper limit of the frequency of symmetrically extended TEM Cells. Studies have shown that there is an error in the estimated value of the Xmn parameter used in the conventional standard TEM Cells resonant frequency calculation method, which may lead to errors in the order of the resonant modes. Symmetrically extended TEM Cells do not change the original resonant frequency, but because of the coupling modes of even mode and odd mode between two cell units, each of the original resonant frequencies will split two close resonant frequency.