Theoretical And Experimental Researches On Open-ended Coaxial Probe Measurement Techniques For Simultaneously Determining Complex EM-parameter

Because of its broadband-capability, opened-structure and wide-compatibility, the open-ended coaxial probe(OECP) is essentially applicable for in-vivo testing of materials' electromagnetic(EM) parameters and has tremendous potentials of applications in material science, and in non-destructive test as well.In combination with a "Ninth Five" project and a "Tenth Five" project, supported by the General Armaments Department of the people's liberation army(PLA), the OECP measurement techniques to simultaneously determine the complex EM parameters of stratified materials have been systematically and deeply investigated in both theory and experiment. Laying particular stresses on providing novel ideas and giving consideration to solving practical problems are the distinguishing features of this dissertation.The researches on the simultaneous EM-parameters measurement techniques with an OECP can be classified into two parts, in this dissertation. The first one is dedicated to studying the theoretical modeling and design of OECPs. We firstly formulate the spectral domain model for OECP measurement configuration in detail. Then some problems in modeling computation are carefully discussed. These problems include the calculation of improper integrals, the proper selection of high-order modes in coaxial line, etc. Finally, an analysis of the near-fields radiated from coaxial probe is carried out in order to determine the appropriate dimension of the mounted flange. The second part of this dissertation is mainly involved in investigating the simultaneous EM-parameters characterization techniques. An uncertainty analysis system for "Thickness-Varying Method"(TVM)/"Sample-Adding Method"(SAM) is firstly established to study the relations between the measurement accuracy and experimental parameters. Experiments on several typical radar absorbing materials(RAMs) are conducted to validate theeffectiveness of such analysis. Then the frequently-occurring problem--"ambiguities in characterizing the EM parameters" is particularly discussed while some useful solutions are given for that. Furthermore, a novel in situ measurement technique, named "Probe-Varying Method"(PVM), is proposed for simultaneously determining the complex EM-parameters of radar absorbing coatings. Key techniques in PVM are thoroughly discussed with the experimental validation of several typical RAMs. Meanwhile, we proposed a new idea, which could reduce the requirements in test instruments preparation. That is to merely measure the scalar reflections (modulus) of the sample-loaded OECP instead of the vector ones in the previously proposed methods. As an example, "Scalar Thickness-Varying-Method" is investigated based on uncertainty analysis techniques and validated with some experiments as well.In the summary of this dissertation, we put forward two trends for the further development of the simultaneous measurement techniques for determining the complex EM-parameters with an OECP. One is to further extend its application in on-line, in vivo and in situ measurement fields. The other is to look for some additional experiment conditions to constitute some novel EM-parameters characterization method.