Saturation Operation Research Articles

Gain-scheduled controllers design for interceptor parameter-varying system with multi-saturated constraint

Based on homogeneous polynomial parameter dependent Lyapunov function (HPPDLF) theory and the algorithm that the nonlinear matrix differential equations converted into convex polyhedron state equations, the robust optimal control system is designed, for the interceptor with time-varying parameters and actuator nonlinear multi-saturated constraint. First, the model of the actuator saturation operator is established, which provides the control system topology. The nonlinear differential equations with time-varying parameters converted into the linear polytopic vertex system by introduced the normalization factors of the amplitude and rate actuator saturation, and then it converted into HPPD matrix differential equations, based on HPPDLF theory and the extension of Pólya’s theorem to the case of matrix-valued polynomials. The dynamic performance of the closed-loop control system is obtained by setting the minimum allowable value of the scaling factor, when solving the minimum of the maximum homothetic set in the iterative processing. Finally the simulations of the interceptor have demonstrated the effectiveness of the approach proposed.

Optimization of Envelope Tracking Power Amplifier for Base-Station Applications

We have proposed two methods of enhancing efficiency of an envelope tracking power amplifier (ET PA) from an interlock operation. The first is the utilization of sinking current. The sinking current is a critical efficiency reduction factor since it is a wasted power. To reduce the sinking current, the gate bias of the power amplifier (PA) is increased so that the sinking current is delivered to the PA and is utilized for amplification. The other one is the RF input shaping method. The input signal of ET PAs is a modulated RF signal, and the signal does not guarantee fully saturated operation of the PA at all power levels due to $g_{ m}$ nonlinearity of a device. To obtain the maximum efficiency for all of the envelope voltage, we have found the optimum RF input conditions and applied it to the input of the PA. To verify the methods, the proposed ET PA is implemented using a Cree CGH40045 GaN HEMT. For a long-term evolution 5-MHz signal with 6.5-dB peak-to-average power ratio, the PA delivers power-added efficiency of 58.76% with 40.14-dBm output power at 889 MHz.

Analytical modeling for drain current of strained Si NMOSFET

Based on the structure of strained Si/SiGe NMOSFET, a unified drain current model is presented in this paper. The model describes current characteristics from subthreshold to strong inversion as well as from the linear to the saturation operating regions with a smoothing function, and guarantees the continuities of the drain current and its derivatives.Furthermore, the model accuracy is enhanced by including carrier velocity saturation and channel length modulation effects. Comparisons between the model and the measured data show that the drain current model can describe the device characteristics well. The proposed model is useful for the design and simulation of digital and analogy circuits made of strained Si.

Asymptotic Stability of Two-Dimensional Discrete Systems With Saturation Nonlinearities

This paper investigates the asymptotic stability of discrete dynamical systems in a class of two-dimensional (2-D) systems whose dynamical parts are described in the Fornasini-Marchesini model along with a standard saturation operator on the state space. Under the assumption that the stability of the nominal system is ensured by the solvability of a linear matrix inequality, two techniques are introduced for checking the tolerance of the system against saturation effects. One is a quadratic method that accounts for the stability margin of a system. Another is a non-quadratic method that uses the asymptotic property of a majorant nonnegative system. These techniques are useful to improve upon previously known results. Two theorems are introduced in this paper in different manners. The first theorem provides a plain interpretation on the stability condition; however, it requires a two-step process to search for a solution. The second theorem is expressed as a linear matrix inequality, which is the dual statement of the first theorem. These results can be naturally modified for 1-D systems, 2-D systems in the Roesser's model, and multidimensional systems. Illustrative examples show that the two techniques adopted in this paper have different effectiveness in enlarging the scope of application.

Performance bounds for nonlinear systems with a nonlinear ℒ2-gain property

Nonlinear ℒ2-gain is a finite gain concept that generalises the notion of conventional (linear) finite ℒ2-gain to admit the application of ℒ2-gain analysis tools of a broader class of nonlinear systems. The computation of tight comparison function bounds for this nonlinear ℒ2-gain property is important in applications such as small gain design. This article presents an approximation framework for these comparison function bounds through the formulation and solution of an optimal control problem. Key to the solution of this problem is the lifting of an ℒ2-norm input constraint, which is facilitated via the introduction of an energy saturation operator. This admits the solution of the optimal control problem of interest via dynamic programming and associated numerical methods, leading to the computation of the proposed bounds. Two examples are presented to demonstrate this approach.

Compared deep class-AB and class-B ageing on AlGaN/GaN HEMT in S-Band pulsed-RF operating life

AlGaN/GaN HEMTs are on the way to lead the RF-power amplification field according to their outstanding performances. However, due to its relative youth, reliability studies in several types of operating conditions allow to understand mechanisms peculiar to this technology and responsible for the wearing out of devices. This paper reports the reliability study on two power amplifiers using AlGaN/GaN HEMT. Based on results of a previous study of 1280h in standard operating conditions wherein no evolution of electrical parameters have been observed, two ageing tests in deep class-AB (432h) and class-B (795h) are performed under pulsed-RF operating life at high drain bias voltages and saturated operation. This study shows a drift in RF performances which is linked with the evolution of electrical parameters (RDSON, gm and VP). Similar kinetics and amplitude of degradations are observed revealing quasi-similar contribution of thermal effects in both cases. Degradations are supposed to be related to trapped charges phenomena induced by high voltage operating conditions. Although, several results attest to this hypothesis, a part of the evolutions seems to be linked with structural changes.

Behaviors of Class-F and Class-${\hbox{F}}^{-1}$ Amplifiers

Operational behaviors of the class-F and class-F-1 amplifiers are investigated. For the half-sinusoidal voltage waveform of the class-F-1 amplifier, the amplifier should be operated in the highly saturated region, in which the phase relation between the fundamental and second harmonic currents are out-of-phase. The class-F amplifier can operate at the less saturated region to form a half sinewave current waveform. Therefore, the class-F-1 amplifier has a bifurcated current waveform from the hard saturated operation, but the class-F amplifier operates as a switch at the saturated region for a second harmonic tuned half-sine waveform. To get the hard saturated operation, the fundamental load is very large, more than √2 times larger than that of the tuned load amplifier. The operational behaviors of the amplifiers are explored with the nonlinear output capacitor. Since the capacitor generates a large second harmonic voltage with smaller higher order terms, the class- F-1 amplifier with the nonlinear capacitor can deliver the proper half-sinusoidal voltage waveforms at a lower power, but the effect of the nonlinear capacitor is small for the class-F amplifier. The class-F-1 amplifier delivers the superior performance at the highly saturated operation due to its larger fundamental current and voltage generation at the expense of the larger voltage swing. The simulation results lead to the conclusion that the class-F-1 amplifier with the nonlinear capacitor is suitable topology for high efficiency. However, in the strict sense, the class- F-1 amplifier with the nonlinear capacitor is not the classical class-F-1 amplifier because the voltage-shaping mechanisms and the fundamental load are quite different. We call it the saturated amplifier since the amplifier is the optimized structure of the power amplifier operation at the saturated mode.

Solvent Saturation and Air Operation of Li Air Batteries

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New criterion for stability of discrete-time systems joined with a saturation operator on the state-space

A new criterion for the global asymptotic stability of discrete-time systems in a state-space realization using saturation arithmetic and with the coefficient matrix A fulfilling a certain condition is presented. The criterion possesses a considerable degree of freedom (free parameters) for testing the stability condition. The criterion is compared with some earlier criteria.

Saturated Power Amplifier Optimized for Efficiency Using Self-Generated Harmonic Current and Voltage

A saturated power amplifier (PA) optimized for efficiency is described. As a PA is driven into saturated operation, the current source of the device generates a large third harmonic current, which creates a quasi-rectangular current waveform. The large nonlinear output capacitor of the transistor generates a second harmonic voltage with a very small third harmonic component. The second harmonic voltage is in-phase with the fundamental voltage, making a half-sine wave voltage waveform with voltage peaking. These waveforms are similar to those of a class F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The fundamental load at the intrinsic device is resistive with the output capacitance tuned out, which is identical to the class F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> case. However, the required harmonic impedances are just larger than the impedance levels of the output capacitance for both the second and third harmonics. Therefore, the circuit topology is similar to that of a class E amplifier, which is very simple. The PA implemented using a GaN HEMT delivers the expected good performance using the simple circuit topology.

Model for Power SiC Vertical JFET With Unified Description of Linear and Saturation Operating Regimes

A novel SiC junction field-effect transistor (JFET) model that uses a unified description of linear and saturated conduction modes is proposed. Advantages of the proposed model are improved robustness and convergence, inclusion of field-dependent mobility effects, and more physical description of the current saturation phenomenon. The model is validated against a normally off JFET sample over a wide temperature range. Finite-element simulations are used to demonstrate the physics-based nature of the proposed model.

Stability of discrete-time systems joined with a saturation operator on the state-space: Yet another version of Liu–Michel's criterion

A novel criterion for the global asymptotic stability of fixed-point state-space digital filters using saturation arithmetic is presented. The criterion, which is basically a new version of an earlier criterion due to Liu and Michel, is a generalization and improvement over a recently reported criterion. The generalization is due to the fact that the use of even unsymmetric Lyapunov matrix P is permitted. An example illustrating the improvement realized from the present criterion is given.

Cost reduction studies of decorative laminates

Barrier paper, which is made of bleached absorbent kraft pulp, is a significant layer of decorative laminates, since it controls the see-through of brown color of saturating kraft paper and its opacifying effect usually is achieved by a heavy loading of TiO2. The TiO2, due to its very small particle size, passes between the cellulosic fibers and drains into the white water. To overcome this problem, papermakers try to use various retention aids for improving overall retention of TiO2, but agglomeration of TiO2 causes a decrease in light scattering efficiency of TiO2. During the subsequent saturation operation, the air in the voids is replaced by melamine formaldehyde, which has a refractive index close to that of cellulose. As a result, the sheet becomes translucent and poses ‘see through’ problem. Keeping this in view, anhydrous magnesium silicate is used as an extender with TiO2 because it effectively increases the overall filler retention, sheet brightness, opacity. The dispersed aqueous slurry of anhydrous magnesium silicate forms fine gel that entraps TiO2 in the wet web and prevents removal of fines and fillers. The addition of 25% TiO2, 7% micronized soapstone powder, 8% anhydrous magnesium silicate, 1% melamine formaldehyde, and 0.1% sodium hexameta-phosphate was found to improve the overall retention by 65.25% and to cut the manufacturing cost by US$ 546.00 per tonne of pulp without affecting the product quality.

Stability of discrete-time systems joined with a saturation operator on the state–space: Generalized form of Liu-Michel’s criterion

A novel criterion for the global asymptotic stability of discrete-time systems in a state–space realization using saturation arithmetic was previously given by Liu and Michel. In their approach, as in most (or probably all) existing approaches, the matrix P is assumed to be symmetric. In this communique, it is shown that their approach is such as to be extended to allow the use of an unsymmetric matrix P . Taking note of this, a more general form of their criterion is presented. A modified form of the criterion is also presented. Examples show the effectiveness of the generalized approach. To the best of author’s knowledge, this communique is the first report of exploiting an unsymmetric P to obtain a stability condition with reduced conservatism.

Sources and Characteristics of Unbalanced Magnetic Pull in Three-Phase Cage Induction Motors With Axial-Varying Rotor Eccentricity

This paper puts forward a model for assessing unbalanced magnetic pull (UMP) due to rotor eccentricity in cage induction motors that takes into account the axial variation in the eccentricity. It is tested using ten- and four-pole machines with experimental results validating the model. This paper assesses the effects of rotor differential flux, saturation, bar number, and variable-frequency operation on the UMP and highlights the key points for the generation of UMP in cage induction motors. Both dynamic and static eccentricities are studied.

Efficiency Enhancement of Doherty Amplifier Through Mitigation of the Knee Voltage Effect

This paper presents an approach to maximize the efficiency of a Doherty power amplifier (PA) with the knee voltage effect. Since the carrier PA with , which is the usual matching impedance for a carrier PA at a low power region, does not reach to the saturated operation at the 6-dB back-off power level, the maximum efficiency could not be achieved. However, the carrier amplifier can be driven into the saturation using the load impedance larger than and can deliver the maximum efficiency even under the knee voltage effect. The optimized design for the maximum efficiency at the back-off level is derived. The optimized amplifier is analyzed and simulated in terms of its load modulation behavior, efficiency, and output power, then compared with the conventional Doherty PA. The enhanced performance is demonstrated by the Doherty PA built using CREE's GaN HEMT CGH40045 devices at 2.655 GHz. For worldwide interoperability for microwave access applications with a 7.8-dB peak-to-average power ratio, the proposed PA delivers an efficiency of 49.3% at an output power of 42 dBm with an acceptable linearity of 23.1 dBc. The linearity is improved to 43 dBc by employing a digital feedback predistortion technique, satisfying the system linearity specification.

A unified short-channel compact model for cylindrical surrounding-gate MOSFET

For the first time, a continuous and explicit model valid in all operating regions, for undoped short-channel cylindrical gate-all-around (GAA) MOSFETs, is presented in this study. From a two-dimensional analysis, the threshold voltage roll-off, the drain-induced barrier lowering (DIBL) and the subthreshold swing are explicitly modeled. Short-channel effects are then implemented into a continuous drain-current model based on an effective surface potential approach using the gradual channel approximation. Improving the model behavior in the saturation operating region by accounting the channel pinch-off displacement, channel length modulation is studied and implemented as well. Analytical results are compared to TCAD-Atlas numerical simulations and validate the short-channel model in all operating modes making it suitable for circuit design simulations.

A New Algorithm to Identify Magnetizing Inrush Conditions Based on Instantaneous Frequency of Differential Power Signal

This paper presents a novel algorithm to recognize magnetizing inrush condition in power transformers by analyzing average differential power signal. The algorithm is independent of the value of transformer parameters and consumed power and relies only on the waveshape properties of the average power signal. These distinctive properties are obtained from the power signal by determining its instantaneous frequency. Extensive simulation studies presented in this paper demonstrate the merits of the proposed technique in discriminating between fault and inrush cases accurately in less than a quarter cycle. The accuracy and speed of the method is unaffected by changing parameters of the transformer or for different operating conditions of the power system, since it is based on a fundamental difference between iron-core saturation and other operating conditions. Since the employed signatures are extracted from the low-frequency spectrum of the power signal, the algorithm is robust against high-frequency noise.

Improved Analytical Model for ZTC Bias Point for Strained Tri-gates FinFETs

The zero temperature coefficient (ZTC) is investigated experimentally in standard and biaxially strained Tri-gate nFinFETs fabricated on SOI wafers. In this work an improved model to analyze the behavior of the gate-source voltage (VGS) at Zero Temperature Coefficient point (VZTC) is proposed in the linear and saturation operation regions. The analysis takes into account the temperature variations of the threshold voltage and the transconductance degradation factor. Although simple, the model predictions present a good agreement with the experimental results.

Stability of Discrete-Time Systems Joined With a Saturation Operator on the State-Space $ $

This note studies the stability of discrete-time dynamical systems acted upon by a saturation process in the state-space. A finite procedure is proposed to focus on the asymptotic behavior of systems, which produces linear constraints imposed on Lyapunov-Stein matrix inequalities to be solved. A little linear algebra broadens the scope of stability test from that of the earlier Liu-Michel's criterion.