Large-signal Analysis Research Articles

Global Modeling of Millimeter-Wave Transistors: Analysis of Electromagnetic-Wave Propagation Effects

In this study, the transmission line concept and the electron transport theory are consolidated in a global modeling approach, the wave-electron-transport (WET) model, to account for the physical phenomena in millimeter-wave devices. No equivalent circuit model is required to represent the innate properties of the device. Hence, the model is reliable for both small- and large-signal analyses. The electrodes of a transistor act as coupled multi-conductor transmission lines at millimeter-wave bands. The WET model consists of a device solver to obtain solutions for carrier-transport equations of the intrinsic device, and an electromagnetic solver (EM solver) to provide solutions for the governing transmission lines equations. As it is crucial to transfer data between these two solvers, an interface scheme is also developed and included in the WET model. The extrinsic parameters of the device are extracted using a novel systematic technique merely based on the physical structure of the transistor. In this paper, the modeling procedure is applied to a fabricated GaN-HEMT device. Power sweep analysis has verified the accuracy of the proposed model under both linear and non-linear operations. Non-uniform voltage distribution caused by traveling waves over the electrodes is elaborately discussed to demonstrate the necessity of incorporating distributed effects.

Large-Signal Stability Analysis and Design of Finite-Time Controller for the Electric Vehicle DC Power System

In the electric vehicle dc power system (EVDCPS), a motor or converter can be regarded as a constant power load (CPL) when tightly controlled. Different from the resistive load, CPL may make the EVDCPS unstable. Thus, in addition to less overshoot and shorter setting time, the controller of the converter applied in EVDCPS should maintain the system stable. In this article, the finite-time controller (FTC) is proposed based on exact feedback linearization (EFL) to stabilize the EVDCPS feeding CPL. First, to handle the nonlinearity caused by the CPL, the affine nonlinear model of EVDCPS is transformed into the Brunovsky canonical form by using EFL. Then, the finite-time control is adopted and a PI compensator is designed to eliminate the steady-state error. Under the proposed control algorithm, rigorous proofs indicate that not only the closed system can be large-signal stable, but also the EVDCPS bus voltage can converge the reference in finite time. Furthermore, to reduce the design difficulty of FTC, the backstepping method is adopted to design a backstepping finite-time controller(BFTC). Finally, simulations and experiments of FTC and BFTC are carried out. Results indicate that both FTC and BFTC have large-signal stability, and although the robustness of BFTC is inferior to FTC, the setting time and overshoot are greatly improved compared with the traditional linear feedback controller.

Large-Signal Stability Analysis of Islanded Dc Microgrids with Multiple Types of Loads

Large-Signal Stability Analysis of Islanded Dc Microgrids with Multiple Types of Loads

Fast and Miniaturized Phase Shifter With Excellent Figure of Merit Based on Liquid Crystal and Nanowire-Filled Membrane Technologies

This paper presents a highly miniaturized tuneable microstrip line phase shifter for 5 GHz to 67 GHz. The design takes advantage of the microstrip topology by substituting the ground plane by a metallic-nanowire-filled porous alumina membrane (NaM). This leads to a slow-wave (SW) effect of the transmission line; thus, the transmission line can be physically compact while maintaining its electric length. By applying a liquid crystal (LC) with its anisotropic permittivity as substrate between the transmission line and the NaM, a tuneable microstrip line phase shifter is realized. Three demonstrators are identically fabricated filled with different types of high-performance microwave LCs from three generations (GT3-23001, GT5-26001 and GT7-29001). The measurement results show good matching in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$50\ \Omega$</tex-math></inline-formula> system with reflection less than −10 dB over a wide frequency range. These demonstrators are able to reach a maximum figure of merit (FoM) of 41 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB, 48 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB, and 70 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB for different LCs (GT3-23001, GT5-26001 and GT7-29001, respectively). In addition, experiments show that all three LCs should be biased with square wave voltage at approximately 1 kHz to achieve maximum tuneability and response speed. The achieved response times with GT3-23001, GT5-26001 and GT7-29001 are 116 ms, 613 ms, and 125 ms, respectively, which are much faster than other reported LC phase shifter implementations. Large-signal analysis shows that these implementations have high linearity with third-order interception (IP3) points of approximately 60 dBm and a power handling capability of 25 dBm.

Adaptive Stabilization of a Permanent Magnet Synchronous Generator-Based DC Electrical Power System in More Electric Aircraft

Most loads of electrical power systems on a more electric aircraft (MEA) are regulated power converters. These loads behave as constant power loads (CPLs) that can significantly affect system stability. The system will become unstable and will be unable to operate at the rated power. In this article, a novel adaptive stabilization of a permanent magnet synchronous generator-based dc electrical power system in MEA is presented using a nonlinear feedback approach via loop-cancellation technique with a simple equation of feedback gain, which can be calculated from the power level of the CPL. The equation can be derived from a polynomial curve fitting based on the proposed mathematical model derived using the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> method. The adaptive stabilization results are validated by a small-signal stability analysis using the linearization technique, a large-signal stability analysis using the phase plane analysis, an intensive time-domain simulation using MATLAB, and experimentation. The results indicate that the proposed adaptive stabilization technique can provide the considered aircraft power system always stable for all operating conditions within the rated power, and the dc bus voltage can adhere to the MIL-STD-704F standard.

Modeling, Small-Signal Stability Analyzing and Implementing of an Inverter-based Distributed Generation with Feed-forwarded Model Predictive Controller

Nowadays the control and stability of DG systems are important topics that researchers in both academia and industry. Small and large signal analyses for stability studies on various systems have been done in papers and books. In this paper, first models of an inverter-based Distributed Generation (DG) subsystems are created. After the linearization, if required, the small-signal stability analysis of the DG which is controlled with a voltage and frequency control scheme based on the model predictive control (MPC) that has been used previously, is established. In this control scheme, load currents at the point of common coupling (PCC) of the DG are considered as disturbances and used as feed-forward signals. This technique enhances the performance of the DG control system in transient and steady-state conditions for a wide range of loads. The stability of the DG system under various loads (such as one phase load as imbalanced load, rectifier load as nonlinear load and induction motor load as dynamic load) is demonstrated by the eigenvalues trajectory. The sensitivity analysis and robustness assessment of the control scheme are also conducted and discussed. For more performance consideration, the DG system is simulated with MATLAB/SIMULINK software, implemented in the lab and later the suitable performance of the system is demonstrated by the simulation and experimental studies.

Large signal analysis on intensity‐modulation direct‐detection radio‐over‐fibre dispersive links

This letter proposes a frequency domain closed-form analytical solution for large signal condition in radio-over-fibre systems that employ external intensity-modulation and direct-detection. The received radio frequency signal power was used to evaluate the chromatic dispersion effect in optical links. To the best of knowledge, a comparison between large signal with small signal solutions has been theoretically presented here for the first time. For analogue optical amplitude modulations, the double sideband showed a 30 dB difference between the approaches, a 9 dB for the single sideband, and 17 dB for the suppressed carrier.

A Non-Linear Lumped Model for the Electro-Mechanical Coupling in Capacitive MEMS Microphones

This work provides an analytical non-linear model for the capacitive transduction in MEMS transducers with perforated counter-electrodes, especially applicable to capacitive MEMS microphones. Starting from an electrostatic description of a perforated unit cell of the transducer, analytical formulations of the variable capacitance and electrostatic forces are derived, accounting for the deflection profile of a clamped circular plate. A lumped implementation into conventional circuit simulations tools is enabled via behavioral modeling based on hardware description languages, such as Verilog-A. Therefore, the analytical model is approximated via Taylor series expansions, allowing for a stable and non-linear behavioral implementation. The resulting model finally enables both a small- and large-signal analysis of capacitive MEMS microphones, precisely accounting for non-linearities in the capacitive transduction. This allows to simulate the harmonic distortion of the microphone's output signal and to account for electrostatic spring-softening in simulations of its bias voltage dependent sensitivity.

Region of Attraction Estimation for DC Microgrids With Constant Power Loads Using Potential Theory

The stability issues of DC power grids are attracting researchers' attention, especially with the increasing adoption of power electronic devices and nonlinear loads. Large-signal stability analysis is required to detect and avoid large disturbance and destabilization, which can cause detrimental effects on DC power grids. However, the issue is still unsolved due to the complicated dynamics of large-scale power grids. This paper develops a novel method for estimation of the region of attraction (ROA) with less conservativeness using the Brayton-Moser mixed potential theory. This reliable and robust ROA estimation method provides useful insights into the stable operation of DC power grids. Moreover, this paper reveals the weak correlation between the state variables <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> of branch currents and system stability. It makes it possible to reduce computational cost and lessen the curse of dimensionality by separating these state variables. The case study shows that the proposed approach can obtain a much less conservative ROA compared to traditional methods such as Lyapunov's method.

Oscillation Amplitude Analysis of MOS Hartley Oscillator Using a General Model

New analytical equations for amplitude analysis of MOS Hartley oscillator are presented. Using exact large-signal circuit analysis, analytical equations for estimating the amplitude of Hartley oscillator are derived that considers all operation regions of transistor; including saturation, triode and cutoff. The analysis is based on a reasonable estimation for the output waveform. The estimated waveform should satisfy the nonlinear differential equations describing the circuit. Using this novel point, we can simply find the unknown parameters of the waveform, especially amplitude. The validity of the resulted equations is verified through simulations using TSMC 0.18 μm CMOS process. The amplitude calculated from this approach has a very good agreement with simulation for a large range of circuit parameters.

Design of the interaction cavity extending to the nonlinear taper for a 10 kw, W-band gyrotron

ABSTRACT In this paper, the design of an interaction structure for a 10-kW, W-band gyrotron is presented. The beam voltage and beam current are chosen as 30 kV and 1 A, respectively. The mode of interaction was chosen as TE6,2. A parametric design code and a gyro large-signal analysis (LSA) code were developed. The computational steps are discussed in brief. The LSA was done using the in-house developed code and the Gyro-K code. The results of these two codes were found to be in good agreement. The design of the nonlinear taper (NLT) was also carried out. Based on Ohmic loss, the power dissipated in the cavity was estimated. A novel cooling arrangement was proposed with two concentric cylindrical jackets around the cavity. The computational fluid dynamics (CFD) analysis was done using the software FloEFD. Steady-state analysis for the CW mode of operation and the transient analysis for the pulsed mode of operation were carried out for various flow-rates of the coolant.

Two-Level Stability Analysis of Complex Circuits

A new methodology is proposed for the small- and large-signal stability analysis of complex microwave systems, containing multiple active blocks. It is based on a calculation of the system characteristic determinant that ensures that this determinant does not exhibit any poles on the right-hand side (RHS) of the complex plane. This is achieved by partitioning the structure into simpler blocks that must be stable under either open-circuit (OC) or short-circuit (SC) terminations. Thus, the system stability is evaluated using a two-level procedure. The first level is the use of pole-zero identification to define the OC- or SC-stable blocks, which, due to the limited block size, can be applied reliably. In large-signal operation, the OC- or SC-stable blocks are described in terms of their outer-tier conversion matrices. The second level is the calculation and analysis of the characteristic determinant of the complete system at the ports defined in the partition. The roots of the characteristic determinant define the stability properties. The Nyquist criterion can be applied since, by construction, the determinant cannot exhibit any poles in the RHS. In addition, one can use pole-zero identification to obtain the values of the determinant zeroes. Because the determinant is calculated at a limited number of ports, the analysis complexity is greatly reduced.

Coupled-Cavity VCSEL with an Integrated Electro-Absorption Modulator: Small- and Large-Signal Modulation Analysis

We consider an integrated electro-absorption modulator within a coupled-cavity VCSEL structure (EAM-VCSEL). We derive expressions for the modulation transfer function (MTF) of the EAM-VCSEL for small-signal modulation of either VCSEL injection current or EAM losses. For current modulation, the cut-off frequency remains limited by relaxation oscillation frequency. For EAM loss modulation, the MTF curve is much flatter and its shape around the relaxation oscillation frequency displays either a well-pronounced maximum, both a maximum and a minimum or a sharp minimum only depending on the bias point of the EAM losses. Such features have been found experimentally in Marigo-Lombart et al., J. Physiscs: Photonics, 1, 2019, but remained unexplained hitherto. Furthermore, the cut-off frequency remains beyond 100 GHz for moderate and week coupling between the VCSEL and EAM cavities. Such ultrahigh bandwidth modulation is due to the fact that the changes of EAM impact much less the optical power distribution along the EAM-VCSEL and, consequently, the confinement factor and photon density in the VCSEL cavity. The three cases of strong, intermediate and weak coupling are also considered when carrying out the large-signal modulation response of the EAM-VCSEL and a clear open-eye diagram is demonstrated at 100 Gbs for an optimal EAM cavity length.

System-Level Large-Signal Stability Analysis of Droop-Controlled DC Microgrids

In the literature, many studies on stability analysis of dc microgrids have been conducted. However, most of them mainly focus on small-signal stability. On the other hand, few works analyze large-signal stability, but the major part of these works is based on a single unit or a simple cascaded system as a case study. Different from those, this article aims to address the large-signal stability analysis of a dc microgrid from a system-level perspective. First, the equivalent model of a droop-controlled dc microgrid is developed. Subsequently, the Lyapunov-based large-signal stability analysis and the stability criterion are derived, and mixed potential theory is used to make comparisons to verify the effectiveness of the derived criterion. The equilibrium point stability for different operation stages was obtained by means of theoretical calculation. Furthermore, the instabilities principle as well as their physical interpretation is revealed. In this article, the bus voltage is used as the only index to assess the microgrid power balance. Hence, the power load limit can be obtained by taking into consideration the stability and voltage deviation constraints. Finally, simulation and experimental results from a four-converter dc microgrid system verify the feasibility of the proposed theoretical analysis.

Multi-terminal Medium Voltage DC Distribution Network Large-signal Stability Analysis

The Brayton-Moser’s mixed potential theory is a popular approach for large-signal stability analysis of DC-based systems with constant power load (CPL). The criterion from the conventional mixed potential theory contains multiple time-varying parameters which are complicated for convenient stability analysis hence the need for simplification. On the other hand, stability analysis of droop-controlled multiple source converter-based DC systems are scarce. Thus, the large-signal stability criterion of a scaled-down droop-controlled multi-terminal MVDC distribution network with CPL using Brayton-Moser’s mixed potential theory was simplified and derived to show that CPL power rating, PI control parameters, droop and damping coefficients have profound effects on the system’s large-signal stability. By way of MATLAB/Simulink simulations, the large-signal stability of the MVDC distribution system was observed to reduce with increase in CPL power rating and source converter droop coefficients as well as increase with increase in proportionate coefficient values and use of optimized unlike non-optimized damping coefficients. Therefore, the droop-controlled MVDC distribution network with optimized PI control parameters, droop and damping coefficients have enhanced dynamic response and large-signal stability margin proving the accuracy and validity of the simplified large-signal stability criterion.

Carrier to Intermodulation (C/I ratio) Calculations of a GaN 10W Class AB Power Amplifier

This article presents the analysis and design of a circuit to generate 3rd- order intermodulation (IM3) products for a GaN 10W Class AB power amplifiers (PA), The intermodulation products can’t be eliminated by filters. So, it’s a critical problem to resolve in RF systems. The circuit has been studied using a two-tone signal at a center frequency of 3.7 GHz. The two tones test is applied to make a large signal analysis of the RF power amplifier. For this paper, the two frequencies are at (3.7 0.005) GHz. The (C/I) ratio, is chosen to investigate the power amplifier non-linearity, and due to various causes, upper_C/I and lower_C/I, can be distinct.

A Robust Local Positive Feedback Based Performance Enhancement Strategy for Non-Recycling Folded Cascode OTA

In this study, a local positive feedback technique is proposed to enhance the performance of the folded cascode (FC) operational transconductance amplifier (OTA) when working in its saturation region. The enhanced FC-OTA has a higher gain bandwidth (GBW), higher DC gain and higher slew rate (SR) over its conventional counterparts and popular recycling FC-OTAs. The proposed enhanced FC-OTA is implemented by reusing the current generated by the input transistors through the proposed local positive feedback loop to provide additional transconductance and negative resistance. It is then fabricated with SMIC 180nm process. To verify the effectiveness of the proposed FC-OTA performance enhancement strategy, extensive mathematical analysis, small-/large-signal stability analysis, simulation and experimentation are thoroughly investigated in this study. Simulation and experimental results agree well with the theoretical analysis and the expected performances, which corroborates the control design.

Performance analysis of HfO2/InAlN/AlN/GaN HEMT with AlN buffer layer for high power microwave applications

We present a performance enhancement evaluation of n + doped graded InGaN drain/source region-based HfO 2 /InAlN/AlN/GaN/AlN on SiC metal-oxide-semiconductor high electron mobility transistor (MOS-HEMTs) with a T-shaped gate. Impact on the device characteristics with the inclusion of a HfO 2 surface passivation layer and an AlN buffer layer in the MOS-HEMT structure as a performance booster has been analyzed for the HEMT device with 30 nm gate length using Silvaco ATLAS TCAD. The proposed MOS-HEMT exhibits an outstanding performance, with an enhanced power gain cut-off frequency (f max ) of 366 GHz, a current gain cut-off frequency (f t ) of 426 GHz, and a off-state breakdown voltage (V br ) of 81 V. The high -k (high permittivity) HfO 2 based metal oxide semiconductor HEMT device experiences a low off-state gate leakage current (I g ~ 10 −11 A/mm) and a high I on /I off ratio of 10 9 . The InAlN/GaN/AlN heterostructures demonstrate improved two-dimensional electron gas (2DEG ~ 5.3 × 10 13 cm −2 ), carrier mobility (μ) of 1256 Cm 2 /V-s and drain current density of (I ds ) 2.7 A/mm. A large signal analysis performed at 30 GHz yielded a maximum of 28% power-added efficiency. The high JFoM of 34.506 THz V (Johnson Figure of Merit = f t × V br ) and (f t .f max ) 1/2 of 394.86 GHz indicate the potential applicability of the HfO 2 /InAlN/GaN MOS-HEMTs in high-frequency and high-power applications.

High-performance combined ring oscillators

PurposeThe purpose of this paper is to investigate a more robust ring oscillator. Less sensitivity to power supply variations is a target. This is important since low-quality ring oscillators could be exploited in numerous systems to reduce die costs.Design/methodology/approachThe method in this work is large signal analysis. Delay time as the large signal parameter is calculated symbolically to explore dependency on a power supply voltage. Then simulations are performed to make a comparison. In this work, mathematical justifications are verified via HSPICE circuit simulator outputs, while 0.18 µm TSMC CMOS technology is exploited.FindingsAt least two combined configurations are presented with higher robustness. These circuits are more appropriate in noisy conditions. Both theoretical calculations and simulation results verify less sensitive oscillation against supply voltage ripples and temperature variations.Originality/valueIntroducing a band-switched inverter in combined configurations is contribution. In this way, three structures are presented which both show higher stability in oscillation frequency. The band switched delay time calculations are quite new and also the validity of the symbolical delay time approach is verified by circuit simulations.

Large signal analysis of multiple quantum well transistor laser: Investigation of imbalanced carrier and photon density distribution

In this paper, we present a large-signal and switching analysis for the Heterojunction Bipolar Transistor Laser (HBTL) to reveal its optical and electrical behavior under high current injection conditions. Utilizing appropriate models for carrier transport, nonlinear optical gain, and optical confinement factor, we have simulated the large-signal response of the HBTL in relatively low and high modulation frequencies. Our results predict that for multiple quantum well (MQW) structures at low frequencies, there should not be a difference in either the carrier density or the photon density. However, the carrier concentration can be differently distributed between subsequent wells in the case of a high speed yet large-signal input. This leads to increased linewidth instead as it depends on ΔNqw. We show the effect of different structural parameters on the switching behavior by performing a switching analysis of the single quantum well and MQW structures using computationally efficient numerical methods. A set of coupled rate equations are solved to investigate the large-signal and switching behavior of MQW-HBTL. Finally, to have a comprehensive judgment about this optoelectronic device, we introduce a relative performance factor taking into account all the optoelectronic characteristics such as the output power, ac current gain, modulation bandwidth, and base threshold current, as well as turn-on time in order to design a suitable TL for optoelectronic integrated circuits.