Improvement in dielectric measurement technique of open-ended coaxial line resonator method

An improvement in the dielectric measurement of the open-ended coaxial line resonator method is reported. The usable frequency range has been substantially extended by considering the end radiation effect. Experimental results are given at X-band. The accuracy is much better than in the earlier reported method.     

腐蚀性溶液介电常数测量的探头研究

测量化学反应物的介电常数,必须对测量探头进行保护,采用FDTD方法在圆柱坐标下对一种有保护层的新型同轴线探头进行分析计算,得到了被测物介电常数与反射系数之间的关系。对圆柱中心以及薄层结构进行了特殊处理。计算结果与实验值吻合。     

Comparison of three numerical treatments for the open-ended coaxial line sensor

The open-ended coaxial line sensor is commonly used for non-invasive microwave dielectric measurements. A comparison is made between three mathematical treatments that allow the reflection coefficient of the sensor to be derived from the complex permittivity of the material with which it is in contact. It is shown that the discrepancies between values computed by the three methods are much smaller than the predicted measurement uncertainties. Mappings of permittivity contours onto the complex reflection coefficient plane are shown.<>     

Variational formulation of open-ended coaxial line in contact withlayered biological medium

An open-ended coaxial probe designed to measure layered biological media is analyzed with a new method. The probe is considered as an electrostatic circuit element whose capacitance is solved using a stationary functional. The fundamental transverse electric and magnetic field (TEM)-mode and the series of evanescent wavemodes in the coaxial cable are used as basis functions. The field outside the probe is solved using a Hankel transform. The capacitance is calculated for homogeneous materials and two-layer structures and the results are compared with values measured with a phantom model. The method can be easily extended for structures with an arbitrary number of layers. A practical approximation for two-layer cases, originally developed to take into account the effect of subcutaneous fat in skin measurements, is presented and its validity for different combinations of dielectric constants and the thickness of the first layer is demonstrated. The static approximation limits the frequency range, but it covers biological measurements up to 500 MHz. The developed method is accurate and easy to adopt in practice     

Polynomial characterization of inhomogeneous media and theirreconstruction using an open-ended waveguide

B. Sanadiki and M. Moustafavi (1991) described how an inhomogeneous continuously varying dielectric profile can be inverted using a stepwise successive refinement procedure when an open-ended waveguide is used as the source. Here, an alternative approach based on polynomial characterization of the dielectric medium is discussed. It is shown that this method is more efficient and avoids the convergence difficulties of the previous method for most cases except for discontinuous or stratified profiles     

Linearization of an interferometric modulator at microwavefrequencies by polarization mixing

The polarization-mixing technique is used to reduce the cubic nonlinearity of an integrated-optical interferometric modulator at microwave frequencies. Two-tone intermodulation distortion is reduced by 14 dB at a constant modulation depth of 3% over the frequency range of 3.6-5.6 GHz. The polarization-mixing technique requires no high-speed electronics and can be extended to higher frequencies     

Input impedance of an overmoded coaxial line fed coaxial waveguide

A theoretical formulation for the input impedance of an overmoded coaxial probe fed coaxial waveguide has been derived in terms of the geometrical variables, the modal field solutions, and the probe excitation current distribution. The formulation includes higher order mode propagation, a variable probe length, and general coaxial terminations in the secondary waveguide. The model compares well with experimental data derived from a structure supporting three propagating modes.     

Measurement of complex dielectric permittivity at microwavefrequencies using a cylindrical cavity

A technique is presented for measuring complex dielectric permittivity using a full field analysis of a coaxially driven cylindrical cavity. The analysis of the junction is based on a model which fully considers the coaxial form of the cavity excitation, and which has been shown to produce very accurate results for a wide range of cases. Values of permittivity predicted by this method for two materials of well known permittivity are presented     

Radiation-corrected open-ended coax line technique for dielectricmeasurements of liquids up to 20 GHz

An experimental technique and associated analysis are described for the measurement of the dielectric constants of liquids at microwave frequencies using an open-ended coax probe. The analysis includes radiative corrections to the probe-liquid interface impedance. The technique is applicable to liquid and liquid-like (e.g., biological) samples, having dielectric constants comparable to water, at frequencies up to 20 GHz and possibly as high as 40 GHz     

Nondestructive determination of the steel fiber content in concrete slabs with an open-ended coaxial probe

A microwave nondestructive testing technique to measure the steel fiber content in hardened concrete slabs is presented. The technique is based on an open-ended coaxial probe reflectometry method for measuring the effective permittivity of the steel fiber reinforced concrete and on a classical homogenization approach for determining the fiber content. Two different full-wave models for the probe-aperture admittance as a function of the permittivity are applied: a spectral domain model for the forward problem and a rational function approximation for the inverse problem. A Maxwell-Garnett type of mixing rule is derived for randomly oriented conducting prolate spheroids in a dielectric host medium. A coaxial probe has been constructed, calibration aspects are discussed, and experimental results are presented for concrete slabs with various fiber contents. It can be concluded that the presented technique is a promising one.     

Precision open-ended coaxial probes for in vivo and ex vivo dielectric spectroscopy of biological tissues at microwave frequencies

Hermetic stainless-steel open-ended coaxial probes have been designed for precision dielectric spectroscopy of biological tissue, such as breast tissue, over the 0.5-20-GHz frequency range. Robust data-processing techniques have also been developed for extracting the unknown permittivity of the tissue under test from the reflection coefficient measured with the precision probe and a vector network analyzer. The first technique, referred to as a reflection-coefficient deembedding method, converts the reflection coefficient measured at the probe's calibration plane to the desired aperture-plane reflection coefficient. The second technique uses a rational function model to solve the inverse problem, i.e., to convert the aperture-plane reflection coefficient to the tissue permittivity. The results of the characterization and validation studies demonstrate that these precision probes, used with the prescribed measurement protocols and data-processing techniques, provide highly accurate and reliable in vivo and ex vivo biological tissue measurements, including breast tissue spectroscopy.     

Determination of dielectric permittivity of materials by an isolated coaxial probe

The paper investigates the possibility of measuring complex dielectric permittivity of various media by a probe in the form of open-ended coaxial line isolated from the medium probed by a thin dielectric layer. Suitable-for-calculations full-wave admittance model of such probe has been developed in the form of a series with the number of terms corresponding to the number of higher modes excited in its aperture. The presented numerical estimates indicate that despite a certain loss of sensitivity as compared with the conventional technique, this isolated probe can have an application due to a higher stability of its parameters.     

Rigorous evaluation of the vertex effects on thefrequency-dependent circuit parameters of an open-ended microstrip line

This study presents the original inclusion of right singular vertex conditions in integral equations solved by the method of moments for accurate evaluation of the frequency-dependent microstrip discontinuity models required in microwave integrated circuits (MIC) and monolithic microwave integrated circuits (MMIC) design. The 90° wedges singularity function for the current density, weighted with a novel sampling function for “corner cells,” and the harmonic Green's function for shielded structures, is accurately and efficiently integrated in the conical geometry of the 90° sector. The frequency-dependent effective length and excess equivalent capacitance of a shielded open-ended microstrip line are calculated to a higher accuracy with respect to previous two-dimensional and three-dimensional “full wave analyses”     

Focus characterization using end of line metrology

A new method is introduced to measure relative focus using conventional optical overlay instruments. Optical end of line metrology (OELM), is based on patterning a wide frame in which adjacent sides are constructed of submicron sized lines that run perpendicular to the center opening. Because truncation is size dependent, line and space features exhibit significantly more line shortening effects than the solid sections. When measured with a conventional optical overlay tool, the difference in line shortening between the solid and line and space sections are measured as an alignment offset, which is a relative measure of actual line shortening. Reproducibility for measuring the apparent misalignment of these modified box-in-box structures was 3 nm (3σ^est), which is similar to the repeatability for measuring conventional resist box in box alignment boxes. Truncation is sensitive to focus and the utility for using OELM toward characterizing focus-dependent lens parameters was investigated. Estimated 3σ for calculating best focus and astigmatism were 0.04 μm and 0.01 μm, respectively. Focus corrections were accurate to 0.05 μm within ±0.3 μm of best focus. Additionally, a general method is presented to estimate the error in the calculated best focus     

Correction of errors due to airgaps for microwave complexpermittivity measurement using a coaxial line

Microwave complex permittivity of PTFE (Teflon) was measured using a transmission/reflection (TR) method and a coaxial sample fixture. A range of sample dimensions were prepared in order to examine the effect of airgaps on the measured permittivities. The measurements were compared with calculated values using a formula derived by considering the total capacitance     

Broad-band simultaneous measurement of the complex permittivitytensor for uniaxial materials using a coaxial discontinuity

A technique is presented for simultaneously measuring the complex values of the permittivity tensor of uniaxial materials. A gap in a coaxial line is filled with the material under test. Complex elements of the permittivity tensor are computed from measurements of the S-parameters (S₁₁ and S₂₁ ) made on the gap taking into account higher order modes excited at the discontinuity. The authors demonstrate that this problem is reduced to two systems, each containing three equations with three unknowns. Computer time is therefore reasonable without affecting accuracy. Measured complex permittivity data from 45 MHz to 18 GHz are presented. Good agreement between calculated and generally accepted values is obtained     

Measurement of the electrical constitutive parameters of materials using antennas

A general technique is presented for measuring the electrical constitutive parameters of a material using a monopole (dipole) antenna. A normalized impedance that is only a function of the dimensionless parameterkh(wavenumber length) is defined for the antenna. The normalized impedance is expressed as a rational function, and the coefficients in this function are determined from a measurement of the impedance in a standard medium. The impedance measured in a material with unknown constitutive parameters is used with the rational function to form a polynomial inkh. The constitutive parameters of the medium are determined from a root of this polynomial. The measurement technique is implemented for a rational function of order three. The constitutive parameters of the alcohol 1-butanol and saline solutions were measured over a range of frequencies using the technique with cylindrical and conical monopole antennas. The measured constitutive parameters are in good agreement with those determined by previous investigators.     

Structural and electrical investigation of BLT films deposited at different times using electron beam evaporation technique

Thin films Bi4Ti3O12 (BLT) were deposited using electron beam evaporation on silicon substrate at several times, also on AlN/Si and SiO2/Si substrates. Thin films morphology and thickness were measured via scanning electron microscopy (SEM). The crystallography was studied using X-ray diffraction (XRD) technique for films which have a (0010) preferred orientation in all substrate types. The capacitance values were contingent on frequency value in C-V measurement. The ferroelectric characterization was investigated for BLT film deposited on isolator layer (SiO2 or AlN) for Al/Bi4Ti3O12/SiO2/Si devices. Memory effect value varied from 1 V to 3 V depending on the thin films isolator on substrate.     

Extensive electrical and thermal characterization of an MCM-Dtechnology

In this paper, it is shown the work carried out on thermal characterization of the main materials employed in the deposited-type multichip module (MCM-D) technology. In this technology, silicon chips are mounted onto a silicon substrate by a flipchip technique. The substrates can be either passive with interconnection lines, Rs, Cs, and Ls or active with complementary metal oxide semiconductor (CMOS) technology cells. The metals used in this technology are aluminum for interconnection purposes, tantalum silicide for making resistors and a multilayer of wettable metal for solder connection. Measurements of sheet resistance and contact resistance versus temperature in the range of -28°C to 100°C of the metals used in the technology are shown. A set of classic test structures such as Kelvin contacts, cross bridge resistors (CBR), and Van der Pauw structures have been used for this purpose as well as a new Kelvin-like structure to test the contact resistance of the Flip Chip connection through the ball. This structure has been proven to be very sensitive allowing the measurement of changes in ball resistance in the range of mΩ. A thermal model of the MCM package has been obtained, taking into account all the thermal resistances added by this kind of package