Electromagnetic Characterisation of Materials by Using Transmission/Reflection (T/R) Devices

Abstract

An overview of transmission/reflection-based methods for the electromagnetic characterisation of materials is presented. The paper initially describes the most popular approaches for the characterisation of bulk materials in terms of dielectric permittivity and magnetic permeability. Subsequently, the limitations and the methods aimed at removing the ambiguities deriving from the application of the classical Nicolson-Ross-Weir direct inversion are discussed. The second part of the paper is focused on the characterisation of partially conductive thin sheets in terms of surface impedance via waveguide setups. All the presented measurement techniques are applicable to conventional transmission reflection devices such as coaxial cables or waveguides.

Absorption of electromagnetic waves in sandstone saturated with brine and nanofluids for application in enhanced oil recovery

“…Scattering parameters (or S-parameters) describe the input and output parameters between two ports of an electrical system [55]. If we have a two-port system and each port is provided with some voltage and current, then S21 is defined as the power transferred from port 1-2, and S11 is the power transmitted and reflected at port 1 [56].…”

Free-Space Materials Characterization by Reflection and Transmission Measurements using Frequency-by-Frequency and Multi-Frequency Algorithms

“…If the MUT is dispersive but its properties obey a dispersion model, the Debye or Lorentz for example, it can be included in the procedure and its characteristic parameters must be calculated [1,4]. Otherwise, a frequency-by-frequency approach can be used, but this one does not exploit the multi-frequency nature of the measurement, as explained next.…”

“…Characterization of the electric permittivity ε, the magnetic permeability µ and the electric conductivity σ is of fundamental importance in physics and engineering, since these constitutive properties determine the response of the Material Under Test (MUT) to the electromagnetic fields [1,2]. Usually, such properties are extracted from the Scattering (S-) Parameters [1][2][3][4], which can be measured by a Vector Network Analyzer (VNA) [3]. Several measurement setups can be conceived for this purpose, including the Free-Space Method (FSM) [1].…”

“…The FSM consists in connecting antennas to the ports of a VNA and using them to sense the propagation path of interest; in this way, different materials can be characterized by means of proper reconstruction algorithms [1,[3][4][5][6]. The FSM is contactless, requires little sample preparation and is suitable for heterogeneous samples.…”

A Synthetic Aperture Radar (SAR)-Based Technique for Microwave Imaging and Material Characterization

“…Sometimes having an accurate estimate of the constitutive parameters of the surrounding medium can be difficult, such as in Ground Penetrating Radar (GPR) and Through-The-Wall Imaging (TTWI) applications, where ground and wall composition is not homogeneous, and conductivity and permittivity can be affected by moisture levels. In these cases, additional measurements (and hardware) are required for a proper estimation of these parameters, mostly reflectometry [18] and transmission/reflection-based techniques [19,20]. Besides, these constitutive parameters can be also the unknown of the inverse scattering problem, as in security screening systems for detecting weapons and explosives.…”