Low frequency dielectric loss of metal/insulator/organic semiconductor junctions in ambient conditions

The complex admittance of metal/oxide/pentacene thin film junctions is investigated under ambient conditions. At low frequencies, a contribution attributed to proton diffusion through the oxide is seen. This diffusion is shown to be anomalous and is believed to be also at the origin of the bias stress effect observed in organic field effect transistors. At higher frequencies, two dipolar contributions are evidenced, attributed to defects located one at the organic/oxide interface or within the organic, and the other in the bulk of the oxide. These two dipolar responses show different dynamic properties that manifest themselves in the admittance in the form of a Debye contribution for the defects located in the oxide, and of a Cole–Cole contribution for the defects related to the organic.     

Evaluation of the valence band discontinuity ofSi/Si1-xGex/Si heterostructures by application ofadmittance spectroscopy to MOS capacitors

In this study, admittance spectroscopy is applied for the first time to MOS capacitors fabricated on Si/Si_1-xGe_x/Si double-heterostructures, in order to evaluate the valence band discontinuity ΔE_v at the Si/Si_1-xGe_x interface. The principle of the measurement is presented and verified by the experimental results. A new feature of admittance spectroscopy applied to MOS capacitors is the ability to select the interface whose barrier is measured, by controlling the gate voltage. This fact is confirmed by the measurement of MOS capacitors, which include a SiGe well with different Ge contents at the front and the back interfaces. It is found from this measurement that, while ΔE_v at the back interface of the double-heterostructure is measured under slight depletion conditions for MOS capacitors, ΔE_v averaged between the front and the back interfaces is measured under accumulation conditions. The Ge_x content dependence of the measured ΔE_v is found to be in fairly good agreement with the theoretical values     

Efficient computation for the general solution of a slot loaded by a hemispherical dielectric and/or backing cavity

The problem of a slot loaded by a hemispherical dielectric and/or a hemispherical backing cavity is solved using the method of moments (MoM). A novel recurrence formula is presented for fast calculations of the MoM admittance integrals associated with the spherical homogeneous solutions. The method enables the admittance integrals to be calculated without the need for any numerical integration. Measurements were carried out and good agreement between theory and experiment is obtained.     

Systematic Synthesis of Compressive VDTA-Based T-T Filter with Orthogonal Control of fo and Q

Based on sixteen nullor-mirror models of the voltage differencing transconductance amplifier (VDTA) and port admittance matrices of the tow-Thomas (T-T) filter with orthogonal control between the characteristic frequency (f_o) and figure of merit (Q), two different categories of the voltage-mode and transconductance-mode T-T filters are synthesized by the means of the nodal admittance matrix (NAM) expansion method. The category A filter that employs two compressive VDTAs and two grounded capacitors includes four structures, and the category B filter that uses two compressive VDTAs, two grounded capacitors, and one grounded resistor, also includes four structures. These circuits are suitable for integrated circuit manufacture, and their parameters f_o and Q can be orthogonally adjusted with varying the bias currents of VDTAs. After the paper and pencil test is completed, the computer analyses, including alternating current (AC), parameter sweep, Monte Carlo (MC), and noise analyses, are performed to support the synthesis approach.     

Errors in S/sub 11/ Measurements Due to the Residual Standing-Wave Ratio of the Measuring Equipment

Errors in measurement of S/sub 11/ due to the residual SWR of the slotted line or directional coupler are calculated using admittance considerations. This more complete treatment produces, for some practical conditions, major differences from prior references for phase errors.     

Exact surface impedance/admittance boundary conditions for complexgeometries: theory and applications

A methodology useful to derive exact and higher order surface impedance/admittance boundary conditions (HOI/ABC's) for complex geometries is presented. It is shown that exact surface boundary conditions are always expressed through dyadic integral operators involving the tangential magnetic and electric fields all over the surface of the body. Quasi-local surface boundary conditions that include curvature effects are shown to be computable through an asymptotic approximation of the integral operators. Finally, an example of a surface admittance boundary condition useful to analyze a structure exhibiting discontinuities along its surface boundary is presented. Practical examples to demonstrate the feasibility of the proposed methodology, as well as the accuracy of the resulting surface boundary conditions are also presented     

Admittance of a waveguide radiating into stratified plasma

A slot covered by a stratified plasma is assumed to radiate into a wide waveguide instead of free space. The slot admittance approximates the free space admittance of the slot for waveguide diameters exceeding 6 to10lambda. For thick plasma layers the computed slot admittance checks with earlier admittance calculations for a laterally unbounded plasma. When approximating a plasma profile of a typical hypersonic re-entry, a multilayer plasma model in a wide waveguide appears to provide a more accurate slot admittance than a single-layer approximation in a laterally unbounded geometry.     

Admittance of rectangular waveguide radiating from a conductingcylinder

Theory and experiment are compared for the admittance presented to a rectangular waveguide which terminates at an arbitrary angle in the surface of a conducting cylinder. Two methods are described for calculating the admittance: a single-mode approximation from the modal solution and an alternative asymptotic solution. Using these methods, the effect of aperture orientation on admittance, and the results obtained are compared with the experiment. The single-mode approximation is in good agreement with experimental results for the case when the input waveguide supports the TE₁₀ mode only. The accuracy of the approximate formula for waveguide admittance was also verified. The admittance is shown to be weakly dependent on aperture orientation for moderately large cylinders     

劈刀和肋环夹持工况对超声键合换能系统电学特性的影响

通过实验分析了肋环夹持松紧度和劈刀存在两个因素对超声键合换能系统电学导纳特性的影响规律。对换能系统在悬挂有无劈刀和夹持8个松紧度等各个情况下进行谐振频率附近的导纳圆测量,确定换能系统等效电路各特征参数的变化情况。由实验结果的分析可知,劈刀的附加质量以及肋环松紧程度对换能系统谐振频率的影响不大,但劈刀的存在改变了换能系统的能量分布和耗散,是影响换能系统各特征参量的主要因素之一。这些结论有助于超声键合换能系统的优化。     

Analysis of coaxial-line/rectangular waveguide junction with dielectrically sheathed probe

The analysis of a coaxial line/rectangular waveguide junction is presented for the case where the centre conductor is sheathed in a dielectric. Expressions for the current distribution and the admittance of the junction are presented. A comparison of theoretical and experimental results show the theory to be very accurate.<>     

The Si3N4/Si ion-sensitive semiconductor electrode

In this paper we investigate the suitability of silicon nitride as a pH-sensitive coating in the EIS (electrolyte-insulator-semiconductor) half cell. The admittance of the EIS capacitor is measured at various pH. The role of the nitride as both gate insulator and ion conducting glass is presented. Hysteresis effects ascribed to changes in the depth of ionic penetration in the Si3N4are found to be significant. We conclude that the dual use of the "gate insulator" as both insulator and ion-conducting material does not appear to be the best route for preparing ion-sensitive semiconductor electrodes.     

Broad-band analysis of VLF/LF aircraft wire antennas

The broad-band response of a VLF/LF dual-wire aircraft antenna is analyzed. The impedance properties and the induced currents on the two wires of different lengths are obtained via a superposition procedure in which the original problem is split into two transmission-line (differential-mode current) problems and two antenna (common-mode current) problems. Results for the input admittance and short-circuit current of a representative VLF/LF dual-wire antenna are presented.     

Design & characterization of a bio-inspired 3-DOF Tactile/Force sensor and implementation on a 3-DOF decoupled parallel mechanism for human-robot interaction purposes

This paper presents the design and implementation of a Tactile/Force sensor which has been used on a 3-DOF decoupled parallel mechanism for Human-Robot Interaction purposes.The sensor, called HexaTactile, is a soft tactile sensor array based on six MEMS barometers, where each of them is covered by a silicone layer in the form of an incomplete pyramid. HexaTactile consists of six soft and highly sensitive tactile modules which are placed on six sides of a cube to allow simultaneous measurement of the force in the positive and negative directions along the x, y and z axes. Some of the advantages of this sensor can be regarded as its high precision, excellent linearity (coefficient of determination r²=0.99), low cost and low noise. The accuracy of the sensor is 0.01 N, within a range of 4 N and therefore HexaTactile can be suitably attached to a robot end-effector for human-robot interaction applications. Then, using the proposed force sensor some control scenarios, including fixed admittance control and active admittance control are applied for human-robot interaction purposes. From the experimental tests, it has been revealed that the active admittance control solved the drawbacks of fixed admittance control, for the considered case studies.     

Spheroidal wave functions of large frequency parametersc = kfand the radiation fields of a metallic prolate spheroid excited by any circumferential slot

Stratton, Chu, Flammer, and others have dealt with spheroidal wave functions and expanded them into series of Legendre or spherical Hankel functions for frequency parametersc = kfless than about ten, wherekis the wavenumber in free space andfis the focal length of the spheroid. However, whencis greater than ten, the series converges very slowly and even diverges. A method is devised by the present authors to calculate the spheroidal wave functions asymptotically for any value ofcgreater than ten using Wentzel-Kramer-Brillouin (WKB) and Langer transformations and the asymptotic characteristics of Airy functions. By means of the functions thus obtained, we calculated the radiation fields and input admittance of a metallic prolate spheroid of any length uniformly excited by any circumferential slot on the spheroid. The radiation patterns and input admittance obtained for some special cases conform very closely with known results.     

On the convergence of common FDTD feed models for antennas

The finite-difference time-domain (FDTD) method is routinely used to calculate the input admittance/impedance of simple antennas. The value of the input admittance/impedance depends on the level of discretization used in the method, and should converge to a final value as the discretization becomes finer. In this paper, the level of discretization necessary for convergence is studied using two common feed models: the hard-source feed and the transmission-line feed. First, the simplest and most naive methods for introducing the voltage and the current in these models are considered, and the results for the admittance are shown not to converge. Next, improved methods for introducing the voltage and current in these models are constructed. The results for the admittance are then shown to converge, and guidelines are offered for the level of discretization needed for convergence. In addition, two general problems associated with the computation of the admittance are discussed: the agreement between admittances computed with different simple feed models, and the agreement between these admittances and measurements.     

IF Amplifier using C/SUB c/ compensated transistors

An integrated bridge network of four transistors is used as a self-neutralized active element in tuned RLC amplifier designs. The bridge network compensates for the transistor collector-base junction capacitance (C/SUB c/), yielding a 95-percent reduction in the common-emitter reverse transmission admittance. IF amplifier stages that achieve the maximum unilateral power gain of a common-emitter transistor while maintaining excellent alignability are realized using the C/SUB c/ compensated transistor structure. Variations of the relative bias current levels of the transistors in the bridge network provides gain control by way of signal cancellation. This technique produces minimal frequency response variations of the amplifier stage being controlled. A noise analysis shows output signal to noise ratio at maximum attenuation can be a performance limitation.     

360/spl deg/ Varactor Linear Phase Modulator

Theory is presented which 1) derives the circuit impedance requirements to match the nonlinearity of the varactor reactance-versus-voltage curve to the tangent /spl theta/ curve to obtain 180/spl deg/ linear phase modulation from one diode; 2) gives the value and position of a resistor to make insertion loss invariant with phase; and 3) derives the circuit requirements for combining two 180/spl deg/ diode phase moduIators in an admittance adding network to obtain 360/spl deg/ phase modulation. Experiments are disclosed rising series tuning at 1 GHz providing 360/spl deg/ phase modulation within /spl plusmn/ 3.0 percent of linearity, and using shunt tuning at 5 GHz providing 360/spl deg/ phase modulation within /spl plusmn/ 3.3 percent of linearity. A discussion is given of the application of the modulators to the serrodyne function.     

Admittance spectroscopy of ring diode InGaAs/InAlAs/InP quantum-well structures

The admittance of ring planar diode Au/InGaAs/InP and Au/InGaAs/InAlAs heteronanostructures on i-InP has been studied. The structures are constituted by a silicon ??-doped layer and an InGaAs quantum well (QW) in InP or InAlAs epitaxial layers. An analysis of the capacitance-voltage and conductance-voltage characteristics yielded distribution profiles of the electron concentration and mobility in the vicinity of the QW and ??-doped layer. It is shown that lowering the temperature leads to an increase in the electron concentration and mobility in the QW.     

Analysis of a general coaxial-line/radial-line region junction

A general analysis of a coaxial-line/radial-line region junction is presented for the case in which the center conductor is sheathed in a dielectric and extends the full width between two parallel metal plates. Expressions for the current distribution and the admittance of the junction are presented. Two example environments are considered, a rectangular waveguide and a base entrant cylindrical cavity, although the technique can be used for other environments. Comparison of theoretical and experimental results for these two cases shows the theory to be very accurate     

Human Intention-Oriented Variable Admittance Control with Power Envelope Regulation in Physical Human-Robot Interaction

Human intention adaptation is usually realized by changing impedance/admittance parameters according to human interaction in physical human-robot interaction (pHRI). However, determining which admittance parameters need to be updated and how to update depends on the context of pHRI and system stability. This paper aims to provide a systematic study for all three admittance parameters considering human intention adaptation and system passivity for ensuring an intuitive and safe pHRI. For intuitiveness, a general human intention framework based on the robot's roles is summarized as a premise for designing human intention-oriented updating rules for admittance parameters. For the changing trends of these parameters (i.e., increasing or decreasing), only those impacting system passivity are studied. A power envelope regulation (PER) concept is then proposed to impose constraints on variable admittance parameters inferred from human intention for maintaining safe interaction. Our initial results suggest that the passivity condition is not a sufficient condition for system stability in pHRI, whereas preserving the power envelope inferred from the passivity condition can maintain passivity as well as avoid mismatch of admittance parameters arising from unpredicted human interaction. As a result, drastic changes in admittance controller dynamics, which usually result in instability, are restrained. The effectiveness of our approaches not only to maintain intuitive interaction but also to preserve passivity is validated via numerical simulation and experiments.