Abstract. A model of a composite material
consisting of a finely dispersed powder of rutile in a polystyrene matrix is
presented. The dielectric properties of the material in the millimeter wave
range are described by formulas that are valid for static electric fields.
Lichtenecker’s empirical formula is applied to the calculation of the complex
dielectric permittivity of the composite. The real and imaginary parts of the permittivity
of the rutile-polystyrene
composite are obtained as a function of the volume concentration of the
components in the millimeter-wave range. The experimental verification of the
model is carried out on rutile-polystyrene samples prepared at the Research and Production
Corporation "Istok," Fryazino, Moscow region. The samples were in the
form of disks with diameter of 100 mm and thickness of 2.3 mm. The measurements
were carried out at frequency of 70 GHz on samples with two values of the
concentration of rutile by the standard method of investigation of dielectric
materials in the millimeter wave range and did not reveal any appreciable
dispersion in the dielectric properties along the plane of the samples, which
is indicative of uniform distribution of the rutile powder in the polystyrene
matrix. The real and imaginary parts of the permittivity calculated within the
model are in good agreement with the results of measurements of the real
composite: the difference between the measured and the model values is less
than 1% for the real part and about 5% for the imaginary part. The model
proposed provides a convenient tool for the design of materials with prescribed
dielectric properties that can be used as matching layers between media with
strongly different dielectric properties in various fields of application of
millimeter waves.
Key words: (dielectric) permittivity,
composite, polystyrene, rutile, Lichtenecker’s formula.
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