Showing papers on "Relative permittivity published in 1969"

Dielectric loss in integrated microwave circuits

Abstract: Dielectric loss is important in integrated microwave and millimeter wave circuits which require small attenuation. Such circuits are usually built with microstrip or suspended microstrip transmission lines. This paper shows that the dielectric loss, the filling factor of the microstrip, and the stored field energy in the dielectric substrate can be computed from the partial derivative ∂U/∂∊ r where U is the total electric field energy and ∊ r the relative dielectric constant of the substrate. It also shows that the effective loss tangent is determined by the partial derivative ∂∊ eff /∂∊ r where ∊ eff is the effective dielectric constant of the microstrip. Useful design formulas for computing the dielectric loss are given for the most important cases.

Surface State and Interface Effects on the Capacitance‐Voltage Relationship in Schottky Barriers

Abstract: In the presence of an interfacial layer and semiconductor surface states, a Schottky barrier height φb decreases with increasing electric field E at the surface of the semiconductor. If the semiconductor doping concentration Nd is uniform throughout the depletion region and if [ (qNd/e) (dφb/dE)−E] [ (d2φb/dE2) (dE/dV) ]≪1, where V is the applied voltage and e is the semiconductor permittivity, the slope of the (capacitance)−2 vs voltage relationship is constant and can be interpreted to give Nd. The voltage intercept of the relationship yields an apparent barrier height φa related to the true barrier φb by φa=φb−E (dφb/dE) + (qNd/2e) (dφb/dE)2, where q is the electron charge. From the measured variation of φa with Nd and one absolute measure of φb at one value of Nd, φb(E), and dφb(E)/dE may be deduced. From dφb(E)/dE the surface state density as a function of energy in the bandgap and the minimum value of interface thickness divided by relative interface permittivity can be obtained. Using the data of Archer and Atalla for vacuum cleaved Au‐Si diodes to illustrate our method, the surface state density is found to peak at a value of ∼2×1014 cm−2·eV−1 at about 0.83 below the conduction band and the minimum value of interface thickness divided by relative dielectric constant is found to be of the order of 5 A. Criteria are given which show how Schottky diode capacitance‐voltage data may be further used, in conjunction with photoelectric barrier measurements, to detect the presence of deep lying impurities or the penetration of surface state charge into the body of the semiconductor.

Molecular Correlation Functions and Dielectric Relaxation

Abstract: A relation between the molecular dipolar autocorrelation function and the complex dielectric permittivity is derived using the Kubo–Kirkwood method.

A differential-capacitance transducer for measuring small displacements

Abstract: Although three-terminal capacitors have been used to measure accurately small displacements in air and vacuum, it is usually impractical to use them in dielectric liquids, due to the strong dependence of the permittivity on purity and temperature. A differential-capacitance transducer in the form of a guarded disk between parallel plates was only slightly affected by variation in temperature over the range 18 to 90?C, and was unaffected by variation in the relative permittivity of air or liquid dielectric from 1 to 49. Displacements up to 2?5 mm could be measured with a precision better than 0?01 ?m.

Dielectric loss in hybrid integrated circuits

Abstract: The dielectric loss is of importance in hybrid integrated circuits which require small attenuation. Such circuits are usually built with microstrip or suspended microstrip transmission lines. It is shown that the dielectric loss can be computed from the loss tangent tan δ of the dielectric substrate and the partial derivate δe eff /δe r where e eff is the effective dielectric constant and e r the relative dielectric constant of the substrate. The effective loss tangent, the unloaded dielectric Q and the attenuation per unit length are given for microstrip and suspended microstrip transmission lines.

Complex permittivity of D2O at 35 GHz over the temperature range 4–62.5°C

Abstract: A microwave bridge operating at a frequency of 34.85 GHz was used to measure the complex permittivity of D2O over a temperature range 4–62.5°C. A precision of 0.12 was achieved in both Iµ′ and Iµ″. The results have been analysed to provide values of the relaxation time τ0 and the real component of the permittivity at high frequencies Iµ∞. The predicted value of this latter parameter is consistent with recent permittivity and absorption measurements carried out in the far infra-red.

Microwave Permittivity of the InSb Lattice at 77°K

Abstract: This paper reports a direct determination of the relative, static permittivity of the atomic lattice of InSb at 77°K. The measurements were performed on relatively pure (ND≤1014 cm−3) n‐type single‐crystal samples at 70.1 GHz by utilizing a strong magnetic field (∼40 kG) to immobilize the charge carriers in a direction parallel to the applied TE01°‐mode electric field. In this manner, the rf losses normally associated with ``drift'' motion of the charge carriers were made negligible, thus permitting the lattice component of the permittivity to be accurately resolved. The measured relative value, es=17.78±0.15, compares favorably with several values previously calculated from measurements of the ir reststrahlen spectrum.

Diffuse component of lunar radar echoes

Abstract: A simple model consisting of volume backscattering from within the lunar regolith can explain the observed diffuse component of lunar radar echoes. At a wavelength of 68 cm, a good match of the model with the data yields a value of 2.5–3 for the relative permittivity of the regolith in good agreement with the quasi-specular backscattering estimates. The fit at 23 cm is poorer but yields a value slightly less than 2. At 3.8 cm, the value is below 1.5, and both that value and the 23 cm value are in good agreement with the radiometrically determined values at their respective wavelengths. These lower values at short wavelengths are probably a result of the rapid density increase with depth just at the surface. A slope-dependent reflectivity can reconcile the values of relative permittivity obtained radiometrically and from the proposed diffuse backscattering model to those obtained from radar cross-section measurements. There is some evidence that the permittivity of the rocks forming the lunar highlands may be lower than that of the rocks underlying the maria.

Experimental Studies of Internal Field Effects on the Dielectric Properties of Anisole–Benzene and Other Mixtures

Abstract: An equation derived by Cole, which relates the frequency‐dependent complex dielectric permittivity to the molecular dipolar autocorrelation function, is compared to dielectric measurements reported in the literature. The dielectric behavior of binary polar mixtures agrees with that predicted by Cole's equation provided specific short‐range interactions are absent. Measurements of the complex dielectric permittivity of anisole–benzene mixtures as a function of composition, wavelength, and temperature are reported. The anomalous dielectric behavior exhibited by this system is not due to internal field effects. Possible causes of the anomalies are discussed.

Dielectric Permittivity Measurements at Centimeter Wavelengths

Abstract: Improved apparatus for dielectric permittivity measurements at centimeter wavelengths is described. A method of data reduction which minimizes the effect of systematic errors, helps to average out random errors, and is free from significant mathematical approximations is presented. This method is compared to data reduction techniques common in the literature.

High q microwave cavity

Abstract: A low loss microwave transmission structure composed of a section of waveguide within which is concentrically placed an array (one or more) of cylindrical sections of dielectric material with relative dielectric constant greater than four, spaced away from the walls by a significant fraction of the radius (at least of the order of 10 percent) and possessing appreciable discontinuities. In the dielectric loaded sections electromagnetic radiation is propagated primarily within the dielectric so that the losses observed are mainly a function of the dielectric material and are, to first order, insensitive to the wall composition or condition. In this most general form the structure can by synthesized as a low loss filter or equalizer. When operated at frequencies at which the unloaded waveguide is below cutoff a high-Q cavity can be formed. A single section cavity of this type has been used to measure the Q of the low loss high dielectric constant dielectrics. A particularly simple and easily adjustable coaxial input and output structure is available which couples strongly to the cylindrically symmetric TM01 mode, all other propagating modes being greatly disfavored.

Microwave Measurement of Permittivity and Electrical Conductivity in Shock Compressed Liquids

Abstract: A microwave technique for measuring the permittivity and electrical conductivity of shock compressed fluids is described. The results of experiments on carbon tetrachloride are presented and compared with previous work. The technique has a range of 1 to 104 in relative dielectric constant and 4×10−5 to 4×102 Ω·cm−1 in conductivity.

Approximate method for deducing a.c. permittivity from d.c. measurements

Abstract: A simple procedure is developed for deducing the a.c. permittivity of a material from measurements of anomalous conductivity. This procedure is similar to the Hamon method for calculating the loss factor. The range of applications, as well as the accuracy of the method, is discussed. Two examples of the applications of this procedure are given, namely for a nonpolar and for a polar dielectric.

Dielectric Constant and Loss Tangent Measurement of High-Temperature Electromagnetic Window Materials.

Abstract: : The research performed in the development of a new technique for measuring the complex permittivity of electromagnetic window materials from ambient temperatures to 4500F is described in this report The measurement technique employs a focused, free-space microwave bridge and a rotating disk sample heated on one side by oxy-acetylene flames Provisions were made for eliminating flame from the microwave measurement area Data are included to substantiate the feasibility of the measuring technique Surface temperatures of the sample were measured by optical pyrometers, and internal temperatures were determined by embedded thermocouples Dynamic measurements were made of the sample insertion phase and insertion loss A transient heat conduction analysis was used to determine temperature profiles within the sample, and the electrical transmission data were correlated with the temperature profiles to give dielectric constant and loss tangent as functions of temperature The relative dielectric constant versus temperature function of high purity slip-cast fused silica (85 percent density) is a segmented straight line (Author)

Calculation of the complex permittivity of lossy dielectric materials using the Roberts-von Hippel standing-wave method

Abstract: A program has been written for calculating the complex permittivity e1 – je2 of lossy dielectric materials using the Roberts-von Hippel method

Measurement of complex permittivity of liquids at microwave frequencies

Abstract: The effect of lossy short-circuiting plungers in permittivity measurements involving variable line lengths is discussed. It is shown that, in some cases, neglecting the resistive component of such plungers can lead to errors as high as 20% for the dielectric loss. Tables are given which allow the rapid calculation of the complex permittivity by measuring the plunger resistance and the real input impedance or admittance. Error curves drawn for a special case allow the correction of measurements already made providing the plunger resistance is known.

Reflection from subrefractive layers

Abstract: Total reflection of electromagnetic waves from an inhomogeneous region is considered. The transition region has a linearly varying relative permittivity. The phase shift on reflection is π/2 + Φ radians, where Φ is a correction given graphically in the letter.

Cylindrical capacitor and its application to measurements on cylindrical gas discharges.

Abstract: The measurement of high electron densities within a plasma is often conveniently performed using microwave techniques, requiring a probing-signal frequency of the same order as the electron-plasma frequency. If the electron density is high, considerable cost and expertise are associated with this form of measurement.The device described is able to evaluate the electron density at a probing frequency much lower than the plasma frequency, and thus eases the measurement considerably. For example, a tube of 10 cm bore, whose wall is 2 mm thick and is composed of material whose relative permittivity is 6, will enable electron densities at plasma frequencies of 12.5 GHz to be checked using a probing signal of only 1 GHz.

Measurement of ferrite parameters at microwave frequencies

Abstract: A method for determining, at microwave or millimetre-wave frequencies, the relative permittivity and the saturation magnetisation of a ferrite is described. The method is based on the measurement of the guide wavelength in a rectangular guide completely filled with the ferrite and magnetised transversely. Tentative results are presented.