The measurement of the properties of materials

Microwave Open Resonator Techniques – Part II: Applications

“…Figure 11. Resonant circuit for the computation of frequencies f 1,2 They can be easily expressed as:…”

“…The accurate modelling of dielectric and impedance features [1,2] is an essential need for the efficient design of microstrip circuits and antennas. The increasing demand for miniaturization and high-frequency operation strongly imposes the accurate characterization of low-loss thin dielectric surfaces [12,14], both in the form of simple laminated substrates [ 6 ,9 ,1 9 ,2 3 ] ,a sw e l la si nm o r ec o m p l e xc o n fi g u r a t i o n so fm i c r o s t r i pg r i d st ob eu s e d for reflectarray/transmitarray structures [3,21].…”

Electromagnetic Shielding Features in Lightweight PVDF-Aluminum Based Nanocomposites

“…Metals are particularly suitable as shielding material against electromagnetic fields due to their high electrical conductivity (order of magnitude 10 6 Siemens/cm) [2]. Depending on the electromagnetic properties, the material can be either used as an absorber or a reflector of electromagnetic radiation [3,4]. However, there are few drawbacks when metal is used as a shielding material, its weight as well as its easiness to corrosion being the most important ones.…”

Electric and Magnetic Characterization of Materials

“…For example, from the knowledge of the frequency dependence of the complex relative permittivity and magnetic permeability of a material, the shielding effectiveness of a structure made of that material can be predicted; similarly, signal interconnects can be accurately designed when the frequency dependence of the dielectric substrate is known; from dielectric property information of tissues the spatial distribution of an incident electromagnetic field and the absorbed power can be accurately determined. Although the complex relative permittivity and magnetic permeability are quantities not directly measurable, they are reconstructed from the measurement of a sensor reflection coefficient or scattering parameters, which can be obtained with a number of different techniques proposed and developed over the last decades (Afsar et al (1986); Baker-Jarvis et al (1995); Faircloth et al (2006); Ghodgaonkar et al (1990); Queffelec et al (1994) is limited by its own constraint to specific frequencies, materials (e.g., liquid, malleable or solid material; isotropic or anisotropic) and applications. Regardless of the technique used for the measurement, the common challenge is the extraction of the complex relative permittivity and/or magnetic permeability from measured data by expressing the measured quantities as a function of these parameters.…”