The GHz Characterisation of Soft Materials скачать в хорошем качестве

The GHz Characterisation of Soft Materials

Paul Ben Ishai (Dept. of Physics, Ariel University) presenting at Interlligent UK's 2023 RF Design Seminar. For most engineers the dielectric constant of a material and its conductivity are parameters characterizing its electrical properties in a particular frequency range. However, for a physicist their origin is in the molecular response of the material to an electromagnetic wave. Consequently, by realizing that the dielectric “constant” is not constant but reflects just how molecular dipoles or charge motion react to their surrounding when perturbed by the EM wave, one has a powerful tool to probe materials. This is especially true for liquids and gels – “soft” materials. Lacking the rigidity of chemical bonds, molecular mobilities are far higher and place the dielectric response in the GHz region at room temperatures. The poster boy example is water, with its dielectric response centered at 18 GHz at 20 °C, and aqueous systems. The dielectric permittivity is a thermodynamic function, influenced by temperature, pressure, composition and mechanical strain. Understanding how to extract the information inherent in the dielectric response Is the aim of all dielectric spectroscopy. This is never more so than for the GHz region of the frequency spectrum. The talk covered the basics of dielectric science, the information available and samples applicable for dielectric research in the GHz range, as well as the methodologies one can use to carry it out. Topics briefly covered included Time Domain Responses, the use of VNAs, the limitations of probes and interaction of biological tissues at these frequencies.