Unknown Permittivity Research Articles

On the Approximation To the Permittivity Profile of an Inhomogeneous Dielectric Slab

Scattering from a time-harmonic wave normally incident upon an inhomogeneous dielectric slab is considered. Based on the use of two Riccati equations derived from two different modeling procedures, an approximation to the unknown permittivity profile is derived. The approximation scheme is based upon constructing the Nth degree interpolation polynomial to approximate the reflection coefficient and the permittivity profile using Legendre-Gauss-Lobatto collocation points. An example is given to demonstrate the accuracy of the developed scheme.

Simultaneous reconstruction of approximate profiles of an inhomogeneous lossy medium through a collocation method

In this paper a one-dimensional inverse-scattering problem is considered. Two approximate inversion formulae are derived. Using these formulae, approximate permittivity and conductivity profiles of an inhomogeneous lossy medium are simultaneously generated from the partial knowledge of the reflection coefficient in the frequency domain. These formulae are deduced through the application of linear transformations to two nonlinear differential equations for the reflection coefficient in the frequency domain. Discrete versions of the inversion formulae are also developed. The transformed equations for the reflection coefficient in the frequency domain are applicable irrespective of whether the derivative of the unknown permittivity profile exists. An example to demonstrate these approximate inversion formulae is given.

Precision microwave testing of dielectric substrates

A new fixture for magnetodielectric substrate measurement, based on the junction "round waveguides-a radial waveguide" has been designed. For creating a cell design theoretical base, a rigorous solution of the eigen axially-symmetrical H/sub ops/ modes of the waveguide junction containing two identical dielectric inserts is obtained. The electrodynamic computation of this structure has been carried out by the rigorous method, based on the representation of the field superposition in the resonance region. This solution analysis approach yields infinite systems of algebraic second-order equations that makes it possible to obtain values of the unknown substrate permittivity from measured resonant frequencies. The general solution for the proposed structure is then evaluated. The principal advantage of this technique is for measuring a large range of substrate permittivities having no thickness limitation.

Dielectric Measurement Of Multi-Layered Medium Using An Open-Ended Waveguide

AbstractThe use of a circular waveguide radiating into a multi-layered media allows the characterization of heterogeneous and fluid subtances. Many microwave measurement devices, based on reflection coefficient measurements, are subjected to air gap problems that introduce some inaccuracy in the determination of the unknown complex permittivity of the materials. Our purpose is to try and take the air gap into account in these measurements.

Dielectric spectroscopy using monopole antennas of general electrical length

A procedure is developed for measuring the complex dielectric permittivity of a material over a broad range of frequencies using a monopole antenna. No restrictions are placed on the electrical size of the antenna. The antenna is calibrated one time by measuring the input admittance in a standard medium with known permittivity, such as air. Next, the admittance is measured with the antenna immersed in a material with unknown permittivity. These two sets of admittances are then used to determine the permittivity of the material. As an application of the procedure, the complex permittivity of the alcohol 1-butanol and saline solutions were measured using a cylindrical monopole antenna. The measured permittivities are in good agreement with those determined by previous investigators.

Imaging of objects in a halfspace with unknown permittivity

A method for the imaging of objects imbedded in a dielectric halfspace of unknown permittivity is presented. For this a synthetic aperture technique with a new ‘focusing condition’ is utilised.