Dielectric Height Research Articles

An efficient design method of LTCC filters with aggressive space mapping technique

AbstractThe aggressive space mapping (ASM) algorithm is applied to the optimization design of LTCC filters. The partial element equivalent circuit (PEEC) method is utilized as a coarse model. Low‐pass and band‐pass LTCC filters are designed with HFSS and IE3D adopted as the fine models, respectively. Conductor thickness is taken into account, since it is fairly large with respect to dielectric height. Only a few instances of fine‐model simulation are needed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 24–28, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20034

Accelerated computation of a spatial domain Green's function for a dielectric layer with a ground plane

The computational load to solve the Green's function for a dielectric layer with a ground plane derived in the spatial domain is mainly determined by the quasi-dynamic term, which is expressed as a sum of an infinite series. A method to accelerate the solution procedure is proposed in which the quasi-dynamic term of the Green's function is simply expressed as a sum of finite terms. Numerical results show that the computation efficiency can be greatly improved using the proposed method, especially in cases where the dielectric constant is large and the ratio between the radial source-field distance and dielectric layer height is small. It is also shown that the proposed method is frequency insensitive over a wide frequency range.

Effect of the Dielectric Anisotropy on the Propagation Properties of Microstrip Tapers with Height Variations

This paper deals with the design and application of nonuniform microstrip transmission lines on anisotropic substrates. A rigorous analysis is based on the use of Hertz vector potentials, moment method and transmission line theory to determine the dispersion characteristics of single and coupled tapered microstrip lines for accurate performance prediction. Results are presented for the main parameters providing the necessary information to design several devices on tapered microstrip, with variation on the strip width and dielectric height, for (M)MIC and antennas applications. A good agreement was observed with the results available in the literature for tapered lines on isotropic substrates.

Modeled tunnel currents for high dielectric constant dielectrics

The effect of dielectric constant and barrier height on the WKB modeled tunnel currents of MOS capacitors with effective oxide thickness of 2.0 nm is described. We first present the WKB numerical model used to determine the tunneling currents. The results of this model indicate that alternative dielectrics with higher dielectric constants show lower tunneling currents than SiO/sub 2/ at expected operating voltages. The results of SiO/sub 2//alternative dielectric stacks indicate currents which are asymmetric with electric field direction. The tunneling current of these stacks at low biases decreases with decreasing SiO/sub 2/ thickness. Furthermore, as the dielectric constant of an insulator increased, the effect of a thin layer of SiO/sub 2/ on the current characteristics of the dielectric stack increases.

Discussion about the nature of polarized microregions in KTaO3

X- and Q-band EPR spectra of rhombic centers Fe3+ in KTaO3 and temperature dependence of dielectric losses have been investigated. Correlation between EPR spectra intensities and dielectric peak height has been found. The models of rhombic Fe3+ centers and origins of polarized microregions are discussed.

Analysis of Signal Distortion On Coupled Microstrip Lines With an Overlay and a Notch- Summary

In this paper, a full wave approach is used to analyze the propagation parameters of two coupled symmetric microstrip transmission line on dielectric multilayer substrate with dielectric overlay and a notch between the strips. The purpose of this analysis is to examine the validity of previously reported quasi-static techniques to higher frequencies for applications in the millimeter wave frequency range. The objective is to reduce the distortion of a transmission line that consists of two parallel microstrip lines on two dielectric substrates with a notch and a dielectric overlay. The distortion in such a transmission line is produced due to the difference in the phase velocities of the even and odd dominant modes. Techniques based on controlling the dielectric constant, height and width of the notch and the overlay are used to reduce distortion. The semi-analytical method of lines (MoL) technique is applied here to solve for the normalized phase velocities of the dominant even and odd modes for this planar microstrip transmission line configuration. The numerical results provide a detailed analysis of the transmission line controlling parameters for frequencies up to 100GHz .

An efficient approach suitable for the analysis and design of nonuniform transmission lines

AbstractA new method of moment‐based formulation for the analysis of nonuniform transmission lines is presented. Subdomain complex basis functions are used to simulate different structures over a wide range of frequencies. The results obtained using the proposed formulation are validated by comparison to those obtained by CAD packages. Strip‐line and microstrip‐line transitions are investigated with an application to the design of a matched microstrip taper with width and dielectric height variations. © 1995 John Wiley & Sons, Inc.

A microstrip phase-trim device using a dielectric overlay

A design procedure is given for a microstrip phase-trim device using a dielectric overlay on a conventional microstrip line. The physical operation of the device is based on the change in the effective dielectric constant of the microstrip line caused by the presence of the dielectric layer on top of the microstrip line. The amount of phase trim produced by the device can be selected by the appropriate choice of dielectric constant, height, and length of the dielectric overlay. An approximate expression is given for the effective dielectric constant of the microstrip line as a function of the dielectric constant and height of the overlay. Measured results at 10 GHz are compared with predicted performance. >

A novel technique for the analysis of dielectric height variations in microstrip circuits

This paper presents a technique based on the full-wave, two-dimensional spectral domain method and the distributed transmission line approach to analyze structures with a combination of conductor width and dielectric height variations. The technique is applied to a regular taper and the results are compared with existing models. A matched taper transition is then designed based on simultaneous variation of the conductor width and dielectric height such that their ratio is kept constant. The analysis of such tapers is carried out and compared to measured data. It is shown that significant reduction in the return loss can be achieved with such transitions over fairly wide, tunable frequency ranges.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Enhanced dominant mode operation of a shielded multilayer coplanar waveguide via substrate compensation

The cutoff frequency of the first higher-order even mode in a shielded multilayer coplanar waveguide (CPW) is studied using the spectral domain approach (SDA). The effective dielectric constant for the dominant odd and first higher-order even mode in a shielded multilayer CPW is computed and compared to other published numerical results. Dielectric constant and substrate height are varied with respect to even mode cutoff frequency and plotted for several CPW structures. Different combinations of internal substrates are shown to produce even mode cutoff frequency maximization for increased odd mode operation bandwidth.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Dielectric relaxation of the aluminum-hole center in alpha -quartz: An example of phonon-assisted tunneling.

A detailed study is made of the low-temperature dielectric relaxation peak that develops in crystalline quartz upon irradiation. A wide variety of crystals are employed: from different sources, with different purities, and with the ${\mathrm{Al}}^{3+}$ impurity compensated by a selected alkali-metal ion (${\mathrm{Li}}^{+}$ or ${\mathrm{Na}}^{+}$) or by ${\mathrm{H}}^{+}$ through the use of the technique of ``sweeping.'' A comparison is made between the dielectric peak height and the intensity of the well-known EPR spectrum due to the aluminum-hole (Al-h) center. It shows that the dielectric loss peak is due to the Al-h center, with the hole located on a ``long-bond'' oxygen atom. Analysis of the relaxation rate as a function of temperature shows that, below \ensuremath{\sim}6 K the relaxation takes place by a one-phonon tunneling process, while above this temperature a multiphonon process occurs. While the relaxation time in the one-phonon regime is unique, the relaxation spectrum and the mean relaxation time in the multiphonon regime are sample dependent, due to phonon scattering by crystal defects.

All refractory Nb/Yb-YbOx/Nb Josephson junction

A new all refractory Josephson junction, in which Yb oxide is used as a tunneling barrier, has been fabricated by the self-aligned contact process. The heat formation energy of Yb oxide is higher than that of Al oxide. It is expected that a junction with Yb oxide would be more stable than one with Al oxide. The obtained current-voltage characteristic is Vm=15 mV at the critical current density jJ=1500 A/cm2. Its dielectric constant and barrier height are compared with Al oxide.

The liquid–vapor interface of a binary liquid mixture near the consolute point

The liquid–vapor interface above mixtures of isopropanol (i-C3H7OH) and perfluoromethylcyclohexane (C7F14) has been studied in the vicinity of the consolute point (Tc=363 K). As three-phase coexistence is approached, the excess fluorocarbon adsorbed at this interface increases; the adsorption is expected to diverge at Tc for a mixture of the critical composition. A simple model of the interface which incorporates the adsorption anomaly is compared with our ellipticity measurements. Both the model and our data yield ellipticities which have a finite maximum at 0.1 K above Tc. (In general, the ellipticity is not a monotonic function of the adsorption.) The calculation of the ellipticity uses an exact numerical integration of Maxwell’s equations for a model dielectric constant vs height profile. The model dielectric constant profile for the critical composition is consistent with a short-ranged density vs height profile between the vapor and the liquid mixture as well as a much longer ranged composition vs height profile expected at a boundary of a mixture near its consolute point. The liquid–vapor correlation length (0.6 nm) was estimated from the ellipticity data far from Tc. The correlation length for the composition profile was found by combining our interfacial tension data taken below Tc with a compilation based on two-scale-factor universality. Ellipticity data for noncritical compositions are presented; however, their analysis will be presented elsewhere.

Effect of heat treatment on the dielectric relaxation of polyacrylonitrile. III. Role of duration of heat treatment

Dielectric relaxation of polyacrylonitrile (PAN) heat-treated at 120°C in vacuum for durations varying from 4 to 24 h is studied in order to investigate the effect of the duration of heat treatment. Decrease in dielectric constant increment and loss peak height and an increase in relaxation temperature on heat treatment are observed at all durations of heat treatment. At the studied temperature of heat treatment the observed changes in dielectric relaxation were found to increase with duration of heat treatment showing maxima at a 16 h duration and then a decrease at a higher duration of heat treatment. The results are discussed in terms of the variation of degree of intermolecularly bound nitrile groups with the duration of heat treatment. Glass transition temperature calculated from the dielectric data, through WLF theory, showed a variation, similar to that of the degree of bound nitrile groups, with duration of heat treatment. The observed variation of Tg is attributed to the interlinking effect produced by the bound nitrile group pairs on the segmental mobility.

Measured Temperature-Dependence of Attenuation Constant and Phase Velocity of a Superconducting PbAu/siO/Pb Microstripline at 10 GHz and 30 GHz

Measured results for the temperature dependence of the attenuation constant and phase velocity of a superconducting microstripline at 10 GHz and 30 GHz are presented here for the first time. At 9.1 GHz the attenuation constant of a PbAu/SiO/Pb microstripline with a dielectric height of 880 nm decreases from 1.6 dB/m to 0.04 dB/m going from 4.2 K to 2.0 K, while at 27.3 GHz a decrease from 2.6 dB/m to 0.09 dB/m going from 3.0 K to 1.7 K was measured. The calculated and measured temperature dependence of the phase velocity are in good agreement. The measured values for the attenuation constant together with the estimate of conductor losses from the Mattis-Bardeen theory, taking radiation losses and surface roughness into account, lead to an ripper limit estimate for the loss factors of SiO.

First measurement of a superconducting microstrip-line attenuation constant at 10 GHz

An Nb/Nb2O5/PbInAu microstrip resonator of 0.4 μm di-electric height at 10 GHz and 4.2 K exhibited an unloaded Q of 257 with a measurement uncertainty of ±5%. This confirms the conductor losses calculated according to the Mattis-Bardeen theory. The dielectric loss factor of Nb2O5 at 10 GHz and 4.2 K is also confirmed by this measurement to be as in the subgigahertz range, namely 2.1 × 10−3.

Use of low dielectric constant substrates for microstrip time-delay triggered TRAPATT oscillators

Our experimentation with microstrip trapatt oscillators of the type described by Davies et al.1 has indicated that the feasibility of such a design is dependent on the ratio of strip width to dielectric height (W/h) for the substrate used for a given microstrip-line impedance. For example, realisation on a polyguide substrate (εr = 2.32) of 1.58 mm height failed to give coherent oscillation due to unexpected transient voltage variations shown up by time-domain-reflectometry tests. However, simple modifications to the microstrip design to remove the transient voltage variations led to considerable improvement in the performance of the oscillator, and coherent behaviour was then obtained.

Transport kinetics of dipicrylamine through lipid bilayer membranes. Effects of membrane structure

Charge-pulse current-relaxation studies have been performed with lipid bilayer membranes in the presence of the hydrophobic ion dipicrylamine. From the analysis of the relaxation times and amplitudes the translocation rate constant k i of dipicrylamine as well as the partition coefficient β between membrane surface and water could be evaluated. In a first series of experiments membranes made from monoolein or dioleoylphosphatidylcholine in a number of different n- alkane solvents were studied, as well as virtually solvent-free bilayer membranes made from monolayers. The thickness d of the hydrocarbon layer of these membranes varied between 5.0 and 2.5 nm. While β was almost insensitive to variations in d, a strong decrease of k i with increasing membrane thickness was found; the observed dependence of k i on d approximately agreed with the theoretically expected influence of membrane thickness on the height of the dielectric barrier. No specific differences between Mueller-Rudin films and solvent-free (Montal-Mueller) membranes other than differences in thickness were found. In a further series of experiments the chemical structure of the lipid was systematically varied (number and position of double bonds in the hydrocarbon chain, nature of the polar head group). The translocation rate constant k i was much larger in phosphatidylethanolamine membranes than in phosphatidylcholine membranes. A strong increase of k i was found when the number of double bonds in the hydrocarbon chain was increased from one to three. These changes were discussed in terms of membrane fluidity and dielectric barrier height. Much higher values of k i were observed in lipids with ester linkage between hydrocarbon chain and glycerol backbone, as compared with the corresponding ether analogs. This finding is qualitatively consistent with determinations of dipolar potentials in monolayers of ester and ether lipids. When cholesterol is added to phosphatidylcholine membranes, the translocation rate constant k i increases up to five-fold, while the partition coefficient β remains virtually constant. The variation of k i in this case can be largely accounted for by a decrease in membrane thickness and a concomitant reduction in dielectric barrier height. In membranes made from the negatively charged lipid phosphatidylserine the partition coefficient of dipicrylamine strongly increased with ionic strength, as expected from the Gouy-Chapman theory of the surface potential.

Hydrostatics and steady dynamics of spatially varying electromechanical flow structures

The hydrostatic and steady laminar hydrodynamic equilibria of spatially varying electromechanical flow structures are investigated. Under certain conditions the relationship between the dielectric height of rise and the applied voltage is found to be double valued. It is found that one of the two equilibrium values is always unstable. This gives rise to the experimentally observed spontaneous rise of the fluid to the top of the structure, once a certain critical voltage is reached. Starting above this critical voltage with the structure completely filled and decreasing the applied voltage toward the critical value results in pinch-in failure at an intermediate point along the structure and trapping of dielectric fluid at the top. The simple mathematical model developed predicts all these phenomena, without recourse to tedious point-by-point surface force equilibrium determination. Experiments are reported which verify the results for the hydrostatic case.