Permittivity measurement of disk and annular dielectric samples using coaxial transmission line fixtures. part II: experimentation and accuracy analyses

Abstract

An improved permittivity measurement technique for dielectric disks involving S-parameter measurement of a two-port coaxial transmission line fixture is presented. The previous form of the method suffers from variation of the retrieved permittivity with frequency, which leads to inaccuracies that may be severe at some frequencies. An extension of the method that reduces these errors is devised. In addition, an independently developed new technique for measuring the permittivity of annular samples via quadratic curve fitting is presented. This technique also involves S-parameter measurement of a coaxial fixture and requires measurement of only three known materials (one of them may be free space, in which case the requirement is reduced to only two solid dielectrics). The permittivity of any unknown dielectric may subsequently be determined with high accuracy over a wide frequency range. The method is based on the premise that the variation of the reflection characteristics of the two-port coaxial transmission line fixture with the permittivity of the sample displays a strongly quadratic behaviour. This paper constitutes the second of two parts of this work. Part I, also appearing in this issue, presents the theoretical formulation for the moment method mode-matching treatment of the coaxial fixture for treating annular samples. In the present paper, the measurement techniques are described, and numerical simulations of the experimental procedure based on the theory of Part I are presented. In addition, comparative results of accuracy for these two approaches are given. Sensitivity analyses are also presented, along with preliminary experimental results.Une technique améliorée de mesure de la permittivité de disques diélectriques impliquant la mesure des paramètres S d'un gabarit de deux ports d'une ligne de transport coaxiale est présentée. La précédente forme de la méthode souffre de la variation de la permittivité en fonction de la fréquence, ce qui conduità des inexactitudes qui peuventêtre importantesà certaines fréquences. Une extension de la méthode qui permet de réduire ces erreurs est conçue. En outre, une nouvelle technique développée indépendamment de la mesure de la perméabilité deséchantillons annulaires en utilisant l'ajustement quadratique des courbes est présentée. Cette technique impliqueégalement la mesure des paramètres S de l'installation coaxiale, mais exige la mesure de seulement trois matériaux connus (l'un d'eux peutêtre l'espace libre, réduisant ainsi la conditionà deux solides diélectriques). La permittivité d'un diélectrique quelconque peutêtre ainsi déterminée avec une grande précision sur une large gamme de fréquences. La méthode est basée sur l'hypothèse que la variation des caractéristiques de réflexion du gabarit de deux ports de transmission coaxiale en ligne avec la permittivité de l'échantillon affiche un comportement fortement quadratique. Cet article constitue la seconde partie de ce travail. Partie I, qui figureégalement dans ce numéro, présente la formulation théorique du tra...

Complex permittivity and permeability estimation by reflection measurements of open and short coaxial transmission line

“…The measurement of dielectric properties of materials has been subject of extensive research . Several different techniques have been developed allowing for lossy or low‐loss, solid or liquid dielectric material measurements.…”

Development of test fixture for measurement of dielectric properties and its verification using animal tissues

“…Within intermediate frequency bands, permittivity and conductivity can be computed from measurements of the amplitude and phase of a wave transmitted through a coaxial tube containing the measuring sample (Kehn et al 2009). Typically, such measurements are performed on a liquid medium in a single-conductor, unicameral test fixture (Kamei et al 2002).…”