基于介电非线性机制的微带电路无源互调效应研究

微带电路无源互调产生机制尚无定论并且缺乏可靠的理论预测方法，本文基于等效受控源模型，建立了基于介电非线性机制的微带线无源互调的解析计算模型，同时，通过对比测试聚四氟乙烯玻纤布介质微带线和空气介质微带线的三阶互调规律验证了介质非线性是微带电路无源互调的一种主要非线性来源，并提取了非线性参数.实验结果显示聚四氟乙烯玻纤布介质微带线比空气介质微带线的传输互调高了约20dB，反射互调高了约15dB，表明介质非线性是聚四氟乙烯玻纤布介质微带线互调的主要来源.同时，根据本文建立的微带线互调计算解析模型，提取聚四氟乙烯玻纤布介质基板的三阶非线性相对介电常数.本文研究方法可以进一步用于其它微带电路无源互调规律计算研究.

Passive Intermodulation in Microstrip Circuits Due to Dielectric Nonlinearity

To reveal the physical mechanism and establish the prediction model of the passive intermodulation (PIM) in the microstrip circuits,we deduce a closed form PIM model based on the dielectric nonlinearity through the dependent-source equivalence,and demonstrate that the dielectric nonlinearity is one of the major causes of PIM in microstrip circuits comparing the PIM phenomenon in PolyTetraFluoroEthylene (PTFE) fiberglass dielectric and air dielectric microstip lines.The nonlinear dielectric constant was derived as well.The experiments show that the PIM levels of the PTFE fiberglass dielectric microstirp line are about 20dB and 15dB larger than that of the air dielectric microstirp line for forward PIM and reverse PIM,respectively,which indicates that the dielectric nonlinearity is the main cause of PIM in the PTFE fiberglass based microstrip line.The third order nonlinear relative dielectric constant is deduced by the analytical PIM model.The model deduced in this paper can also be extended to study the PIM phenomenon in other microstrip circuits.