Recently there has been significant attention given to imaging biological tissues using microwave radiation. In order to verify microwave imaging algorithms, realistic body models are needed to measure and simulate the penetration of microwave energy into the tissue and to reconstruct the image. We have created a phantom which has dielectric properties that are close to the properties of the real breast tissue. The phantom includes materials that accurately simulate the dielectric properties of skin, fat, gland and tumor tissues while providing good contrast of conductivity. The phantom is fabricated from materials that are widely available and is easy to make. In addition the elasticity of the materials enables the phantom to be shaped into two dimensional (2D) or three dimensional (3D) forms.
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...
In this paper, Finite Element Method (FEM) in Ansoft HFSS is compared to summation of the Fourier Transform of the tangential reflected electric field on each element, for the simulation of the reflect-array antenna. Reflect-array antenna elements are square patches which are designed using Finite Element Method (FEM) in Ansoft HFSS, including the effect of incident angles.
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