太赫兹科学与电子信息学报, 2020, 18 (2): 273, 网络出版: 2020-05-28
基于传输反射法的等离子体相对复介电系数测量
Measurement of relative complex permittivity of plasmas based on transport reflection method
等离子体 相对复介电系数 神经网络 传输反射法 在线测量 plasma relative complex permittivity neural network transmission reflection method on-line measurement
摘要
为解决微波激发等离子体参数诊断存在的困难问题,提出利用二端口传输反射法测量微波激励产生的低温等离子体的等效相对复介电系数。使用有限元方法设计了基于BJ22标准波导的样品测试结构,该 结构能在较大的介电系数范围内,保证介电系数和端口的|S11|,φS11和|S21|参数保持较好的单调性,避免产生多值问题;通过人工神经网络对计算获得的各介电系数对应的S参数进行训练,达到足够的精确度;最后 通过实验,将测量获得的S参数利用神经网络反演获得待测物质的相对复介电系数。该方法对今后测量类似等离子体、复介电系数实部为负的特殊材料的介电常数具有一定的指导意义。
Abstract
To solve the problem of parameter diagnosis of microwave excited plasma, the equivalent relative complex permittivity of low-temperature plasma excited by microwave is measured by the two-port transmission reflection method. Firstly, the sample-test structure is designed based on the standard BJ22 waveguide structure with the finite element method. The structure can ensure that the permittivity and port parameters of |S11|,φS11,|S21| keep good monotonicity in a large range of permittivity, avoiding multi-value problems. Then, artificial neural network is utilized to train the S parameters which are corresponding to each permittivity obtained by simulation, and the training results achieve sufficient accuracy. Finally, through experiments, the measured S parameters are inverted by neural network to obtain the relative complex permittivity of the substance to be measured. This method can be applied to measure the permittivity of materials like plasma which has negative real part of complex permittivity.
吴晓明, 杨帆, 解田, 吴丽, 朱铧丞, 杨阳, 黄卡玛. 基于传输反射法的等离子体相对复介电系数测量[J]. 太赫兹科学与电子信息学报, 2020, 18(2): 273. WU Xiaoming, YANG Fan, XIE Tian, WU Li, ZHU Huacheng, YANG Yang, HUANG Kama. Measurement of relative complex permittivity of plasmas based on transport reflection method[J]. Journal of terahertz science and electronic information technology, 2020, 18(2): 273.