Use of multi-length TDR data aimed to infer the dispersion law of nonmagnetic materials

This contribution presents a method of multi-length transmission lines, filled with or embedded in the material under test (MUT), based on time domain reflectometry (TDR), to measure the dispersion law of a nonmagnetic material. This approach is essential and can be exploited in both radiofrequency and microwave applications. The proposed technique expands on studies presented in [1-2], where dielectric, magnetic and conductive losses are accounted for by the complex relative permittivity and permeability of the MUT.

Many materials of interest in geophysical [3-4] and biomedical [5-6] applications are non-magnetic but preliminary measurements with the proposed technique can help to determine if the MUT indeed has magnetic properties. Moreover, it is shown that establishing the non-magnetic nature of the MUT constitutes meaningful a-priori information that allows disambiguating experimental results, even with limited data in the frequency range of interest.

Results relative to two different types of multi-length measurement data, namely data acquired by considering different lengths of a TDR probe entirely embedded in (or embedding) the MUT and data achieved from a sequential progressive embedding of the probe in the MUT (or, vice-versa, of the MUT in the probe) are presented to illustrate the method. The pros and cons of presented cases are also discussed.  

Acknowledgements

This work is supported by the European Cost Action “Mywave” CA17115.

References

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