Computation of electrodynamic properties of structures with liquid components

Computation of electrodynamic properties of structures with liquid componentsAnatoliy T.Ponomarenko, Nataliya G.Ryvkina, Igor A.Tchmutin, Carl Klason*, Vitaliy G.ShevchenkoInstitute of Synthetic Polymeric Materials, ISPM RAS, Profsoyuznaya 70, Moscow 1 17393, Russia*Chmers University ofTechnology, Gothenburg, Sweden, S-412 96 Gothenburg, SwedenABSTRACTThe paper investigates absorption of electromagnetic waves by radio engineering structures, filled with liquiddielectrics, in which characteristic size of heterogeneities is much less compared to the wavelength. These structures canbe treated as composite materials, possessing effective dielectric constant. Their electrodynainic properties can becomputed using equations, derived for composites. An approximate computation method is offered, allowing to computeelectrodynamic properties of the structure in analytical form, using equations for the effective dielectric constant oflaminated composites. Computed dependencies of electrodynamic properties as a function of structure geometry anddielectric properties of liquids are presented in explicit form, making it easier for analysis, compared to numericalresults, obtained by rigorous electrodynamic methods.For a wide range of structures effective dielectric constants and reflection coefficients for the case "absorbingstructure on metal" have been computed. A good agreement of computed and experimental results has been observed.KEYWORDS: liquid dielectrics, absorption, reflection, computation.INTRODUCTIONThere is a number of investigations now on design of effective structures, absorbing electromagnetic waves in awide range of frequencies. At the same time, there is a renewed interest to their creation in the form of physical models,based on classical absorption and scattering of electromagnetic waves polar liquid dielectrics. Previous research wasdirected towards physico-chemical investigations of intermolecular interactions in mixtures with classical components,such as water, alcohols, electrolytic solutions, etc.'3Structures, containing liquids are promising physical models of tuneable absorbing structures. Ref showed thatpossibilities ofliquids for variation of electrodynamic parameters in absorbing structures is comparable to ferrites, at thesame time their operating range extends to millimeter wavelengths. This is also confinned in ref.5'6 on polar liquiddielectrics, electrolytic solutions and suspensions offine-sized conducting particles. Refs.7'8 describe antenna design in theform of elongated cavity, filled with suspensions offine-sized conducting particles in liquid dielectric.Present paper proposes the following design ofwide-range tuneable absorbing structure: a layer oflow dielectricconstant polymer (e.g., foamed polymer) with double network of cut channels of different cross sections. Electrodynamicproperties, for example reflection coefficient can be varied by filling channels with liquid or removing it, changingtemperature or composition of liquid, etc.This paper discusses the problem of selecting effective liquid as well as methods of computation of electrodynamicproperties of above structures. Computations are made of reflection coefficients for absorbing structures on metal surface.