Time domain microwave technique for dielectric imaging of multi-layered media

Abstract

In this paper, a novel time domain practical scheme is proposed to reconstruct the dielectric image of the inhomogeneous multi-layered media. The overall process is noninvasive and noncontacting, which employs the measured scattering data of the test media in equivalent time domain. The measurement system consists of a modern vector network analyzer, a wide-band lens horn antenna, and the associated microwave components. The main focus here is to determine both the relative permittivity and the thickness of each layer in terms of the partial reflection coefficient calculated for the corresponding interface. It is also demonstrated here that the proposed approach can be used to characterize the lossy media under some approximation. The proposed approach is quite useful under situations such as the through-wall imaging, where only reflection measurements can be carried out due to restricted access of the object from the other side. The proposed scheme is validated here by determining the permittivity, the thickness, and the effective conductivity of a number of multi-layered media obtained by stacking few reference dielectric samples whose data are available in literature.

Keywords:

• microwave imaging
• time domain reflectometer
• stratified media
• inhomogeneous media

Acknowledgement

The authors would like to thank Prof. Sudhir Misra and his team from Department of Civil Engineering, IIT Kanpur, for providing the cement-based samples.