Complex Permittivity Of Dielectric Materials Research Articles

Wide-band measurement of the complex permittivity of dielectric materials using a wide-band cavity

A technique is presented for the characterization of dielectric materials over a wide band of frequencies (RF to millimeter wave region). The cavity structure offers a well-defined reference plane for precision measurements of dielectric characteristics. The dielectric sample completely fills a cylindrical cavity adapted to a precision air line(s). Two configurations are considered: the terminating cavity configuration, in which the cavity is adapted to the end of a precision air line; and the through-cavity configuration where the cavity is placed between two precision air lines. The measured scattering parameters, the reflection and/or the transmission coefficients, are used to determine the complex permittivity of the dielectric sample. >

Broad-Band Analysis of a Coaxial Discontinuity Used for Dielectric Measurements

A coaxial line terminated by a gap is considered, the gap being filled with an unknown material. This cell enables measurements of complex permittivity of dielectric materials to be made. The relationship linking the measured admittance to the dielectric properties is obtained from a theoretical analysis of the electromagnetic field in the tine. The equivalent-circuit parameters of a coaxial line terminated by a gap are obtained all higher order waves excited at the discontinuity are taken into account. The measurements show good agreement between measured and calculated data from dc to 12.4 GHz.

A microwave bridge method for measuring the complex permittivity of liquids

A microwave bridge method is discussed for measuring the complex permittivity of dielectric materials. The underlying principle of the technique along with the experimental results is presented. The complex permittivities of benzene, carbon tetrachloride, petrol, and kerosene are illustrated at a few frequencies in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band. The variation of the dielectric properties of petrol-kerosene mixture is also studied.

Noninvasive beam-wave reflectometric instrumentation for measuring complex permittivity of dielectric materials at microwave frequencies

A noncontact and nondestructive method of measuring at microwave frequencies the complex permittivity of a selected region in a dielectric slab is described. For this purpose the test dielectric sample is irradiated with a focused (gaussian) microwave beam by means of a suitable applicator. From the characteristics of the reflected beam wave measured at a reflectometric bridge arrangement, the complex permittivity of the exposed region is determined. Some theoretical and experimental results analysing the test conditions are presented. Application of this method to biological in vivo (or in vitro) measurements of dielectric properties of bones and tissues, with selective partial-body microwave irradiation, is discussed.

Comments on "A Nondestructive Method for Measuring the Complex Permittivity of Dielectric Materials at Microwave Frequencies Using an Open Transmission Line Resonator"

Comments on "A Nondestructive Method for Measuring the Complex Permittivity of Dielectric Materials at Microwave Frequencies Using an Open Transmission Line Resonator"

A Two Coupler Method for Measurement of Complex Permittivity of Dielectric Materials at Microwave Frequencies

This paper describes two coupler method for measurement of dielectric properties of materials, at microwave frequencies. Two waveguide sections, fed from a common source, are coupling power into a waveguide filled with dielectric. The phase and attenuation constants are computed from the values of phase and attenuation adjustment required for cancellation of the signal in the dielectric filled waveguide. The two coupler method is particularly applicable for measurements of dielectric properties of aerosols and gases.

A nondestructive method for measuring the complex permittivity of dielectric materials at microwave frequencies using an open transmission line resonator

The method is based on perturbing the fringing field at the open end of the transmission line by an unknown dielectric material, and is applicable not only for solid dielectric materials but also for liquids and gases. Forming or shaping of solid dielectrics is not required, but there should be a small area available for contact. Thickness of the dielectric material terminating the line does not affect the measurement unless the material is thinner than twice the spacing between conductors of the coaxial line. The experimental results obtained for some solid dielectric materials, liquids, and biological tissue shows that the method has sufficient accuracy for most applications up to about 4 GHz.