A Simulation-Assisted Non-destructive Approach for Permittivity Measurement Using an Open-Ended Microwave Waveguide

A new convenient and non-destructive permittivity measurement method is presented. No physical cut of specimens is needed here for material characterisation. In the setup, the material under test is placed in the near-field region of a microwave open-ended waveguide. An electromagnetic model of the setup is built in the Computer Simulation Technology simulation software. Employing optimisation, the permittivity is obtained from the measured reflection coefficients. Using the same technique, the effect of the model size is investigated that could reduce the modelling effort for large structures. The efficiency of a traditional method (i.e., Newton) and an intelligent algorithm (i.e. particle swarm optimisation) for permittivity calculation is thoroughly studied and compared. The proposed methodology is validated by experimental data. It is demonstrated that the proposed method can provide more accurate permittivity results than the intrusive in-waveguide measurement. The proposed methodology can contribute to electromagnetic analysis, thickness measurement and non-destructive evaluation.