Bill Riddle

A dielectric resonator for measurements of complex permittivity of low loss dielectric materials as a function of temperature

An application of a mode dielectric resonator is described for precise measurements of complex permittivity and the thermal effects on permittivity for isotropic dielectric materials. The Rayleigh-Ritz technique was employed to find a rigorous relationship between permittivity, resonant frequency, and the dimensions of the resonant structure, with relative computational accuracy of less than . The influence of conductor loss and its temperature dependence was taken into account in the dielectric loss tangent evaluation. Complex permittivities of several materials, including cross-linked polystyrene, polytetrafluoroethylene, and alumina, were measured in the temperature range of 300-400 K. Absolute uncertainties of relative permittivity measurements were estimated to be smaller than 0.2%, limited mainly by uncertainty in the sample dimensions. For properly chosen sample dimensions, materials with dielectric loss tangents in the range of to can be measured using the mode dielectric resonator.

Dielectric characterization of low-loss materials a comparison of techniques

Measurements on low-loss materials using closed and open cavity resonators, and dielectric resonator methods are presented. Results indicate that consistent measurement results can be obtained with a number of well-characterized fixtures. Uncertainties associated with each method are addressed. Measurements also were performed on materials used in previous intercomparisons.

Microwave dielectric properties of single-crystal quantum paraelectrics KTaO3 and SrTiO3 at cryogenic temperatures

Microwave dielectric properties of single-crystal incipient quantum ferroelectrics, KTaO3 and SrTiO3, have been measured at cryogenic temperatures. Cylindrical specimens were used as TE0n1-mode and quasi-TE011-mode dielectric resonators at temperatures ranging from 4to300K. Conductive losses of the measurement resonant structures were taken into account, both as a function of frequency and temperature, so that uncertainties in the evaluated dielectric losses were ±5%. The real permittivity was measured with an accuracy of ±0.5%. The evaluated real permittivities of KTaO3 and SrTiO3 exhibit no ferroelectric transition, and remain paraelectric down to 5K, consistent with soft-mode stabilization. Dielectric loss tangent values of KTaO3 at 3GHz were 4.2×10−5 at 5.4K, 8.9×10−5 at 77K, and 1.4×10−4 at 300K, while those of SrTiO3 were 3.4×10−3 at 5.4K, 2.4×10−4 at 77K, and 3.8×10−4 at 300K. Results of the complex permittivity measurements are compared with theoretical predictions from a modified Devonshire pheno...

Ion dynamics near charged electrodes with excluded volume effect

The goal of this paper is to analyze ion relaxation around a charged electrode taking into account finite ion volume and frequency. Time-dependent and electrostatic equations for ion behaviour near an electrode are developed and include the effects of nonequilibrium and steric hindrance. Time-dependent wave equations for the potentials are developed in the Lorentz gauge. The charge density is expressed as a sum of the quasi-steady state solution plus a nonequilibrium term. For slowly changing potentials the ions are in quasi-equilibrium and we show that in this limit the potential satisfies the sinh-Gordon equation. New solutions to this nonlinear time-dependent equation are developed. In the low voltage limit the equation reduces to the Klein-Gordon equation, time-dependent analog of the Debye-Huckel equation. We also present equations for capacitance and surface charge.

Modal cutoff in coaxial transmission lines of conical and cylindrical geometries

We present numerical data on normalized cutoff wavelength versus cone half-angle for the first three higher-order TE/sub m1/ modes, as well as four other modes of interest, in conical coaxial transmission lines (the co-conical line). These are given as a function of the ratio of outer-to-inner cone half-angles (proportional to line impedance) for outer cone half-angles of 10 and 22.5 degrees. Results were compared to those for the coaxial transmission line of cylindrical geometry and found to be qualitatively similar.

Microwave characterization of semiconductors with a split-cylinder cavity

In this paper we demonstrate the use of a split-cylinder cavity for characterizing semiconductors of low to medium loss over a temperature range of 173 K (−100 °C) to 373 K (+100 °C) at microwave frequencies (9–30 GHz). Complex permittivity measurements of silicon (Si) and gallium arsenide (GaAs) wafers are presented in order to evaluate the cavitys performance with this type of material.

W-band dual channel AM/PM noise measurement system - an update

We discuss the performance of a W-band (92-96) GHz amplitude modulated (AM) and phase modulated (PM) noise measurement system. The system uses two nearly identical channels to measure the residual noise in amplifiers in pulsed mode with a duty cycle of 10 % to 100 % (CW) at a given pulse repetition frequency (PRF). We describe details of the dual-channel measurement test set system and several design considerations that are essential for accurately extracting the device noise from measurement-system noise. We also discuss the modifications made to the synthesis scheme of the (92-96) GHz signal compared to the previous scheme. Finally, we present updated results for the source noise and the noise floor of the measurement system

Permittvity and permeability and the basis of effective parameters

The concepts of effective permittivity and permeability are used throughout the literature to describe heterogeneous materials, inhomogeneous materials, and small collections of molecules. In this paper we study definitions of the permittivity and permeability based on the microscopic Maxwells equations and then discuss the ramifications of the common usage of the term effective.

Corrections to "Complex Permittivity Measurements of Common Plastics Over Variable Temperatures"

Despite our best efforts to present error-free measurements to the IEEE Microwave Theory and Techniques Society (IEEE MTT-S), one of the figures in the above paper [1] contains an incorrect scaling factor. In [1, Fig. 11], the loss tangent data for polycarbonate is low by a factor of ten. The correct data is shown in Fig. 1 in this paper. We apologize for any confusion this error may have caused.

Behavior of έ(ω) and tan δ for a class of low-loss materials

We report a study on the relaxation behavior of the real part of the permittivity. We also discuss the loss tangent of a class of materials in the microwave to millimeter band of frequencies. For relaxation response we show that the permittivity is a monotonic decreasing function of frequency. Also, for many low-loss ceramics, glasses, crystals, and solid polymers we found that the loss tangent increases nearly linearly with frequency. This linearity is explained in terms of the pulse-response function and the Sparks-King-Mills model. We show that the linearity may be used to extrapolate the loss tangent beyond the measurement band.