Showing papers on "Dielectric loss published in 1978"

High-Speed Computation of Single and Coupled Microstrip Parameters Including Dispersion, High-Order Modes, Loss and Finite Strip Thickness

Abstract: Based on an optimized rigorous hybrid mode solution for covered/open zero thickness microstrip patterns the following frequency dependent single and coupled line data are evaluated with very short CP-times: The characteristic impedances of the even and odd quasi-TEM modes, the propagation/attenuation constants and associated strip current density components of these and the higher order modes, the loss of the dominant modes under consideration of nonuniform strip current, substrate surface roughness and dielectric loss tangent. Finite strip thickness is introduced by a correction of the strip width input values.

Characterisation of dielectric loss in solids and liquids

Abstract: The measured dielectric properties of a range of solids and liquids, as a function of frequency, have been examined and the loss has been shown to fit a generalised empirical relationship. This includes the Cole–Cole, Fuoss–Kirk-wood, Cole–Davidson and Williams–Watts functions as particular cases and implies that a more generalised approach to the dielectric properties of materials is required than that given by the conventional distribution function extension of Debye's method, or by the dipole autocorrelation function of Williams and Watts.

A Combined Total Reflection-Transmission Method in Application to Dielectric Spectroscopy

Abstract: A combined total reflection-transmission method for permittivity measurements at radio and microwave frequencies is described. Analytical expressions for the dielectric constant and the loss factor of a sample, viewed as a two-port in the transmission system, in terms of the measured scattering parameters are given. ne uncertainty of measurements of the dielectric constant and the loss factor is discussed and a method ofselecting an optimum sample length is suggested.

Viscous liquids and the glass transition. VIII. Effect of fictive temperature on dielectric relaxation in the glassy state

Abstract: The influence of fictive temperature Tf (defined as the temperature in the transition range at which the sample was annealed to equilibrium) on dielectric loss tangent in the glassy state has been investigated in six molecular glass systems, of which four have well-defined β-relaxations. The temperature range used extended from a little below the glass transitions temperature Tg to 77 K, and the frequency range was from 300 Hz to 50 kHz. A tendency for some structural relaxation to occur at an appreciable rate below the transformation range, already reported by others, was apparent in our studies, and prevented a quantitative answer to the question of how much the β-relaxation strength depends on Tf. Qualitatively, it was found that in two of the substances the β-relaxation strength decreases as Tf was lowered; in two others the results were ambiguous. In all substances the background dielectric loss, a general feature of the glassy state on which secondary relaxations, when present, are superposed, was significantly dependent on Tf: the percentage change in tan δ per degree change in Tf was about 1–3% in most of the substances, and 5–8% in one of them, although in all cases it tended to decrease as temperature decreased. This is a remarkable sensitivity to Tf, compared to, for example, glass density, which varies by 0.02–0.04% per degree change in Tf. The molecular origin of the background loss is not well understood, but it has been related to anharmonicity, which in turn has been suggested to make a significant contribution to the thermodynamics of the liquid at Tg.

Ferroelectric and antiferroelectric materials with pyrochlore structure

Abstract: Several compounds with the pyrochlore structure have been investigated. Dielectric and structural studies of the compound Cd2NB2O6S show the existence of three phase transitions at 106°C, 184°C and 282°C. The ferroelectric properties have been studied by several methods (x-Ray, DTA, dielectric and dilatometric methods, second harmonic generation). We also discuss some structural hypotheses. Bi2MIIIMvO7, oxides (MIII=Cr, Fe, In, Sc; Mv=Nb, Ta, Sb) with the cubic pyrochlore structure have been prepared. Some compounds exhibit broad maxima in the temperature dependence of the dielectric constant and the tangent of dielectric loss angle.

Low-Loss Rectangular Dielectric Image Line for Millimeter-Wave Integrated Circuits

Abstract: This paper describes some fundamental properties of a low-Ioss E/sub 11//sup x/ mode rectangular dielectric image line where the electric field is parallel to the metal image plane. This image line is characterized by its low transmission loss, compared with the conventional dominant E/sub 11//sup y/ mode rectangular dielectric image line. The transmission loss of this new image line is nearly less than half that of the E/sub 11//sub y/ mode rectangular dielectric image line. As an application example, a bandpass filter is developed using this E/sub 11//sup x/ mode rectangular dielectric image line and the measurement results of its frequency responses in the 50-GHz range are presented. Although the E/sub 11//sup x/ mode is a higher order mode in the rectangular dielectric image line, reasonable bandpass filter characteristics have been realized.

Channel Dropping Filter for Millimeter-Wave Integrated Circuits

Abstract: The dielectric waveguide structure finds various applications in integrated circuits for the millimeter-optical-frequency range. Many passive and active devices, using dielectric waveguide, have been developed. From the viewpoint of Iow-loss property, the dielectric rectangular waveguide seems to be more suitable for integrated circuits. This paper describes the design method and experimental results for channel dropping filter using dielectric rectangular waveguide. Some experimental investigations of the dielectric rectangular waveguide properties are also presented. The channel dropping loss of the filter is 1.5 dB at a channel center frequency of 52 GHz with a 180-MHz 3-dB bandwidth. Experimental results agree fairly well with the theoretical calculations.

Attenuation Characteristics of Circular Dielectric Waveguide at Millimeter Wavelengths

Abstract: Experiments were done to determine the practicality of using circular dielectric waveguide for a low-loss transmission line at millimeter wavelengths. The lowest order mode on a circular dielectric guide will propagate regardless of how small the guide diameter is. Thus it is possible to make the attenuation factor of a circular dielectric guide arbitrarily small by reducing its diameter. Loss measurements for several different diameters of polystyrene and Teflon rods were made at 72.70 GHz. The measurements were made by directly probing long sections of dielectric guide and plotting the average power as a function of length on an X-Y plotter. Dielectric constants were measured from the standing wave patterns of polystyrene Teflon, and fused quartz rods at 71.0 GHz. Teflon rods exhibited attenuation factors from 0.8 dB/m to 2.2 dB/m depending on the diameter. This is an improvement over silver waveguide at this frequency. Polystyrene rods were found to have attenuation factors ranging from 3.9 dB/m to 12.5 dB/m, again depending on the diameter of the rod. The measured dielectric constants are consistent with previously published data. The various attenuation factors are related to the intrinsic loss tangent of the dielectric using the theory of the HE/sub 11/ mode. Values of tan delta derived from measurements of different rods are consistent indicating that the experimental results are valid. The problem of radiation from dielectric rods is discussed. The experimental results are not conclusive but it appears likely that radiation loss is negligible.

Absolute Measurement of Loss Angle Using a Toroidal Cross Capacitor

Abstract: An absolute measurement of loss angle has recently been completed at NBS. The measurement utilized a special toroidal cross capacitor in which the effects of dielectric films are greatly attenuated. The resulting unit of loss angle has an estimated uncertainty of 0.02 ?rad at an optimum frequency of 1592 Hz.

Anomalous dielectric losses in manganese doped lead-titanate-zirconate-ceramics

Abstract: Lead-titanate-zirconate ceramics doped with a Mn mole fraction of about 0.5 to 2% show anomalous dielectric losses. For samples with high dielectric losses an anomalous behavior of loss tangent measured during cycling a hysteresis loop is also found. These effects can be understood in terms of local conductivity near grain boundaries which is correlated to manganese doping.

Dielectric properties of moist cellulose

Abstract: The dielectric constant ϵ′ and the dielectric loss ϵ″ for cellulose fiber were measured over a frequency band 0.2 to 10 Mc/sec and a temperature range from −20 to 80°C. Also, the variation of the dielectric behavior with relative humidity was measured at 25°C. From these data, both the specific resistivity Rs and the dissociation energy U0 were calculated. The results showed that the dielectric constant increased with frequency and temperature. This may be due to the increase in the rotation and the polarization of the flexible part in the fiber. The variation of the dielectric loss with temperature showed a maximum absorption corresponding to the β-relaxation. For the moist fiber, it is found that as the relative humidity increases, the dielectric constant and the dielectric loss increase. This increase may be due to the presence of polar water molecules, to the freeing of the polar groups, and to the freeing of the ions in the fiber molecule as well as to the increase in the number of OH− and H+ ions resulting from the ionization of water. A relation between the dielectric constant and resistivity at different humidities is represented graphically. From this relation, it is found that the dissociation energy is equal to 0.318 × 10−12 and 5.46 × 10−12 erg below and above 52% RH, respectively.

Dielectric Properties of Styrene-Sodium Methacrylate Copolymers in the Glass Transition Region

Abstract: Dielectric loss measurements have been conducted on high molecular weight copolymers containing 2.0, 3.9. 5.1. 6.5, 8.1, and 9.0 mol % of sodium methacrylate over a temperature range of Ca. 100-200 °C at frequencies from 10 1 to 10 4 Hz. After subtraction of the large conductivity loss, two overlapping loss tangent peaks are observed whose relative heights depend on composition and measurement frequency and whose positions are in agreement with torsion pendulum data. The dielectric data indicate that although clustering of multiplets occurs at all composi- tions, it is not clearly manifested until the number of ions in clustered multiplets exceeds the number of ions in isolat- ed multiplets in the surrounding matrix, which occurs at compositions containing more than ca. 5% salt, There is evi- dence for cluster dissociation at higher temperatures, and it is shown that this may account for the unusually high values of the WLF parameters C I and C2 and other theological anomalies.

Some Properties of Solid-Liquid Composite Dielectric Systems

Abstract: The phenomenological aspects of the electrical properties of Solid-liquid dielectrics are discussed with special relevance to the utilization of such systems at high electric stresses. The implications of conduction, dielectric loss and breakdown in the separate phases have been related to the performance of the solid-liquid system as a whole. The effects of solid dielectric structure and thickness have been developed and associated with possible breakdown processes for the impregnated dielectric in practical situations. The use of plastic films, with or without paper, in impregnated capacitors is treated at some length as a useful device for developing the criteria which are important in all highly stressed solid-liquid systems. Considerable attention is given to aging phenomena and the way in which they may lead to various forms of failure in impregnated systems. Comprehensive data are provided from a summary of the literature relating to effects of temperature and electric stress applied singly and in combination. The effects of life-prolonging additives have been discussed briefly.

The effect of polar groups on the dielectric loss of polyethylene

Abstract: The dielectric loss tangent for polyethylene with low dielectric loss was approximated by tan δ = Cf Σ(nμ2), where n and μ are the number and dipole moment of polar groups, respectively, and Cf is a parameter. The type and number of polar groups in the polyethylenes were mainly determined from infrared spectra obtained with a Fourier transform spectrometer. It was found that the contribution of hydroxyl and carbonyl groups to tan δ was significantly large, but the contribution of double bond groups was less significant. The tan δ was observed to decrease with a decrease of methyl group density although the overall contribution of methyl groups to tan δ was small. This suggests that tan δ is closely related to the secondary structure of polyethylenes, thus indicating the methyl groups seem to play an important role in the secondary structure.

Anorthite glass-ceramics

Abstract: The instant invention is related to the production of highly refractory glass-ceramic articles having moderate coefficients of thermal expansion in the CaO-Al 2 O 3 -SiO 2 -TiO 2 field wherein anorthite comprises the predominant crystal phase with a minor amount of rutile also being present. The articles demonstrate very high D.C. volume resistivities and high dielectric constants with exceptionally low loss tangents and dielectric loss factors. Their refractoriness and moderate expansion suggests an application such as kiln furniture where high temperatures, but not severe temperature changes, are encountered. Their high D.C. resistivities and low A.C. dielectric losses suggest their utility as insulators and electronic substrate materials.

Precise Dielectric Measurement Techniques for the Frequency Range 10 GHz to 150 GHz

Abstract: Systems have been developed for the measurement of permittivity ?' and loss angle ? for low and medium loss liquids and solids. Closed cavities constructed from helix waveguide have been used at 10 GHz and 35 GHz. Open resonators using one plane and one concave mirror in the near hemispherical configuration have been used at 35 GHz, 72 GHz and 144 GHz. In general the accuracy obtainable with these systems is ± 0.1% for ?' and ± (1% + 1?rad) form ?. The accuracy tends to vary a little with operating frequency and technique of measurement.

A Review Of Pyroelectric Detector Technology

Abstract: Pyroelectric detectors offer the advantages of room temperature operation and wide spectral response. High performance requires good thermal design of the detector and its mounting structure to maximize low frequency responsivity and to minimize temperature noise. The intrinsic detector noise is caused by dielectric losses. In the crystalline ferroelectrics, such as Sr 0.5 Ba 0.5 Nb2O6 (SBN) and LiTaO3, dielectric loss tangents on the order of 0.0003 have been obtained and a intrinsic detector noise may be limited by material impurities. A low frequency D* of 2 x 109 cm Hz /W has been measured for these materials. At these loss tangent values, temperature noise and preamplifier noise for both JFET and CCD amplifiers presently limit performance. Despite its lower pyroelectric coefficient, the polymer PVF2 is a competitive pyroelectric material for detector arrays using CCD signal processors.© (1978) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Electrical and mechanical loss in iron-phosphate glasses

Abstract: The mechanical and dielectric loss and the DC conductivity in iron-phosphate glasses were investigated. The similarity of activation energy suggests that the same mechanism associated with the hopping of the charge carriers between ions in different valency states is responsible for both loss processes as well as for the DC conductivity.

Comparison of dynamic mechanical and dielectric loss data on the β relaxation process in poly(ethylene terephthalate)

Abstract: The dynamic mechanical and dielectric β loss peaks in poly(ethylene tereph-thalate) are shown not to be comparable. Only the dielectric data are internally consistent, and these are used to infer which conformational changes occur during commercial processing.

Improved circuit for impedance measurement at very high frequency and its application in testing dielectric properties of insulating materials

Abstract: This paper describes improvements on an impedance measuring circuit for the measurement of very small conductance at very high frequency and one of its applications, viz., the accurate measurement of dielectric constant and loss angle of very low loss materials. In this circuit, a feedback loop for the stabilization of the output level of the high‐frequency oscillator unit also provides compensation for the changes of the series resistance of resonance coil and the transfer characteristic of the detector that occur with their temperature drifts. This circuit has the sensitivity and stability to detect a 0.002 μmho change in a 16‐pF specimen at 100, 150, or 200 MHz. It is capable of measuring a loss angle of several μrad with the electrode system developed for the varying gap immersion method. The warming‐up time is also shortened to about 10 min even for measurements requiring the highest sensitivity.

Permittivity Measurements in a Resonator Terminated by an Infinite Sample

Abstract: A method of measuring the permittivity of dielectric materials using a resonator terminated by an infinite sample is described. The method is based on measurements of the changes of the resonant frequency and the Q factor produced by the test sample. The method is particularly suitable for lossy materials with a high dielectric constant, namely, biological substances and tissues. Analytical and graphical solutions, which lead to material permittivity from experimental data, and a discussion of the measurement uncertainty are presented. The experimental results obtained for water are given.

High field dielectric loss of PVF2 and the electromechanical conversion efficiency ofa PVF2 fan

Abstract: The input admittance of a PVF2 multilayer bimorph fan was measured using relatively high electric fields, e.g., 200 kV/cm. The tanΔ expression for the loss term showed background dielectric loss with a peak at the mechanical vibrational resonance frequency of ∼5 Hz. The peak disappeared when fan vibration was blocked. From the height of the peak and the background loss, the electromechanical conversion efficiency was determined. This is 25-50% depending upon the applied voltage. The motional admittance of a PVF2 multilayer bimorph fan was calculated and expressed as a function of the vibrational amplitude. The observed peak was explained by the conductive term in the motional admittance.

Dielectric loss of high‐density polyethylene below 4.2°K

Abstract: Drawing of oxidized high-density polyethylene (HDPE) and subsequent annealing greatly reduce the low-temperature dielectric loss when the electric field is applied perpendicular to the draw direction. This supports our model (J. Polym. Sci. Polym. Phys. Ed., 15, 43 (1977)) of the proton moving parallel to the c axis of the PE crystal. A particular antioxidant (Ionox 330) in unoxidized HDPE induces a dielectric loss with a frequency and temperature dependence which differs from that for the loss in oxidized HDPE. The antioxidant loss seems to be an overlapping of tunneling and a thermal activation process. The possibility that the hydroperoxide group in the PE crystal is the origin of the loss in oxidized HDPE was theoretically examined in a manner similar to that used for the hydroxyl group in the previous paper. Results suggest that the hydroperoxide group is less probable than hydroxyl as the origin of the low-frequency loss in HDPE.

Electronic system for investigation of the electrical hysteresis of ferroelectric thin films with high dielectric losses.

Abstract: A description is given of operating principles and technical data of an electronic system to investigate an electric hysteresis phenomenon of ferroelectric thin films with high dielectric losses. Two hysteresis loops, the compensated and the noncompensated, can be observed simultaneously on the dual‐trace oscilloscope screen.

Groove- and H-Waveguide Design and Characteristics at Short Millimetric Wavelengths

Abstract: The design of the H guide and groove guide for use in the short millimetric range with relatively low-loss, Iow-dispersion, and single-mode operation is considered. Measurements at 40 and 100 GHz show encouraging characteristics. It is considered feasible to construct components to form complete systems in these guides.

Porcelain dielectric composite for temperature compensation

Abstract: PURPOSE:To provide a good workability of processing with dielectric loss of magnetic composite made small as well, by means of adding a rare earths element oxide and other metal oxide to the basic constituent including SrTiO3, CaTiO3.

Dielectric loss of colloidal particles in electrolyte solution at microwave frequencies

Abstract: The dielectric loss of aqueous colloidal suspensions of polystyrene particles have been measured for various KCl and LiCl concentrations at a frequency of 10.0 GHz in the temperature range of 0 to 60°C. The dielectric behavior is characterized by the presence of a remarkable thermal anomaly, strongly affected by the ionic species and their concentrations. The results are analyzed in terms of some “mixture equations” and there are suggestions that the water in the double layer exhibits a dielectric constant different from that of the bulk medium.