Nonlinear Large Signal Research Articles

A behavioral nonlinear modeling implementation for MEMS capacitive microphones

We are highlighting the behavioral nonlinear system-level modeling approach for MEMS capacitive microphones. The combination of finite element modeling and large signal nonlinear circuit modeling provides a strong capability to predict electroacoustical performance for capacitive transductions. Circuit simulation tools such as Cadence Virtuoso have emerged as powerful aids in designing behavioral models in both linear and nonlinear regimes. Typical small signal lumped element models fail to capture the MEMS behavior which changes over pressure and electrical bias conditions. The models described herein capture diaphragm displacement and capacitance change over large pressure ranges for a simply supported circular plate. This can be coupled with the electrostatic force, due to the applied bias voltage, and converted back to pressure, thereby realizing a feedback loop in the circuit model. The nonlinear model capability is extended to predict capacitance-bias behavior and estimate pull-in of the MEMS device. The microphone sensitivity, signal-to-noise ratio, and harmonic distortions are accurately predicted using the nonlinear large signal model when compared to measured microphone data.

Kronecker Product Based Modeling of Darlington Amplifier and State Estimation using Unscented Kalman Filter

ABSTRACT This paper presents the application of unscented Kalman filter (UKF) for output voltage estimation of the Darlington amplifier (DA). Implementation of UKF requires the state-space model of DA circuit, which has been obtained using Kirchhoff’s voltage law (KVL), Kirchhoff’s current law (KCL) and the Gummel–Poon model of the bipolar junction transistor (BJT). This work uses Kronecker product for vector multiplication. The mathematical representation of nonlinear system in terms of Kronecker product helps to reduce the computational burden involved in the vector multiplication. The proposed method has the advantage that it can be used for the nonlinear region and large amplitude input signal. As the maximal precision of estimation requires modelling in terms of circuit elements and device parameters, the proposed method is able to provide an accurate estimation. We compared the UKF estimation results with the extended Kalman filter (EKF) and iterated extended Kalman filter (IEKF). The UKF presents smaller mean square error (MSE) as compared to EKF and IEKF as UKF is accurate to the third order for any nonlinearity. In addition, IEKF presents smaller MSE as compared to EKF because the linearisation error is taken into account by IEKF.

МОДЕЛЬ ПРИЕМНИКА ОПЕРАТИВНОГО ИЗМЕРЕНИЯ ЧАСТОТЫ С ПРЕДВАРИТЕЛЬНЫМ УМНОЖЕНИЕМ ЧАСТОТЫ И ДОПОЛНИТЕЛЬНЫМ КАНАЛОМ НА ОСНОВЕ НЕЛИНЕЙНЫХ ПАРАМЕТРОВ РАССЕЯНИЯ

The article deals with instantaneous frequency measurement (IFM) receiver model. Proposed receiver exploits preliminary frequency multiplication of input signal and auxiliary microwave detector channel. Article goal is investigation of microwave transfer coefficient irregularity compensation method. Another goal is investigation and reduction of measurement error sources. Research goals are reached by mathematical model construction and it further investigation. Mathematical model is based on the nonlinear large signal scattering parameters. Model demonstrates that preliminary frequency multiplication allows reduction of required group delay time of delay line. It is showed that measurement result affected by transfer coefficient irregularity, transfer coefficient instability of receiver chain elements and multiply reflected from irregularities waves. Auxiliary measurement channel and measurement function in the form of voltage ratio at basic channel detector and auxiliary channel detector provide a way to reduce influence of input signal amplitude, instabilities and irregularities of transfer coefficient on the frequency measurement result. It is showed that full reduction of aforementioned factors prevented by parasitic harmonics and multiply reflected waves. Required suppression level of parasitic harmonic are presented. Obtained results can find applications in sphere of electronic warfare and measurement theory and techniques.

Analysis of nonlinear large signal intrinsic elements for InGaP/GaAs HBT based on Gummel‐Poon model

AbstractA large signal analysis method based on Gummel‐Poon model is proposed to predict nonlinear behavior of InGaP/GaAs HBT. A 2 × 20 μm2 transistor is fabricated with InGaP/GaAs HBT technology. The large signal transconductance Gm, conductance Gbe, and capacitance CBE, CBC are calculated based on the proposed method and measured using a RF testing probe. The calculated and measured results show good consistency up to nonlinear power level. The proposed method is applied to analyze variations of nonlinear large signal intrinsic elements of this transistor with increasing power under different bias conditions, in order to raise benefit of nonlinear consideration for power amplifiers.

Efficiency of capacitive micromachined ultrasound transducers For large signal non-collapsed operation

Although capacitive micromachined ultrasonic transducers (CMUTs) are mostly considered for imaging applications for their broad bandwidth, these devices can also prove useful for high intensity focused ultrasound (HIFU) applications for therapeutics. For these purposes, energy conversion efficiency is especially significant for high intensity and high duty cycle ultrasound applications. The usual small signal coupling coefficient analysis based on capacitance and resonance frequency measurement is not adequate for large signal application when nonlinearity comes to affect device performance. Therefore, an energy conversion ratio (ECR) based on a nonlinear large signal model has been proposed to analyze high power CMUT operation with and without DC bias (AC only). The results on a particular CMUT operating around 5 MHz show that AC only operation at half of device working frequency provides a higher level of pressure (0.8 dB more) as compared to DC biased case and can achieve 90% ECR. Since the input and output frequencies are not the same for AC only operation, Insertion loss (IL) is defined as the ratio of mechanical output power divided by the available electrical power in this case. With that definition, AC only and DC biased operation shows about the same IL in line with the ECR calculations.

Nonlinear Investigation and 3-D Particle Simulation of Second-Harmonic Gyro-TWT With a Mode Selective Circuit

The beam-wave interaction behavior of a second-harmonic Ku-band high-power gyro-TWT comprising a mode selective RF interaction circuit has been investigated using a 3-D particle simulation code. The mode-selective RF circuit has been cut axially into four slices to restrain the electromagnetic modes not having m = 2 symmetry. A self-consistent nonlinear large signal code has been developed to compute the field amplitude, power, energy, and phase of the gyrating beam. The amplifier gives a saturated peak power of ~230 kW at 15.8 GHz for beam parameters of 80 kV and 20 A having a pitch of 1.1. The large signal gain of the device has been calculated as ~16 dB for the beam spread of 14%. Further, the nonlinear findings have been validated against the Particle-in-Cell code that predicts the saturated output power of ~193 kW in a circular TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> mode at the desired operating frequency.

Advanced Methodology for Fast 3-D TCAD Device/Circuit Electrothermal Simulation and Analysis of Power HEMTs

This paper introduces an advanced methodology for fast 3-D Technology Computer Aided Design (TCAD) electrothermal simulation for the analysis of power devices. The proposed methodology is based on coupling finite element method (FEM) thermal and circuit electrical simulation in a mixed-mode setup. A power InAlN/GaN high-electron mobility transistor (HEMT) is used to perform validation of the designed electrothermal simulation. A new equivalent temperature-dependent nonlinear analytical large signal circuit model of HEMT is proposed. The model is implemented to Synopsys TCAD Sentaurus using compact model interface. The designed electrothermal simulation methodology is developed to shorten the simulation time for complex 3-D devices. This approach combines the speed and accuracy, and couples temperature nonuniformity to the active device electrothermal behavior. The simulation results are compared with the measured data and results of 2-D FEM simulations. The features and limitations of the methods are analyzed and presented.

Characteristics of a W-band sixth-harmonic peniotron with a nonideal electron beam

A calculation code for a self-consistent nonlinear large signal of peniotrons has been developed in this study. A PIC simulation of a W-band sixth harmonic peniotron with an ideal electron beam has shown 30 kW output power and conversion efficiency of up to 40%, which agree well with the results obtained under the peniotron self-consistent nonlinear large-signal calculation code. Thus, the code can be used to study peniotron performance when effects such as electron velocity spread and guiding center deviation exist. Calculated results show that a 10 kW microwave output power and a conversion efficiency of 17% can always be obtained if the peniotron guiding center deviation and longitudinal velocity spread are no more than 8%. These results help determine the minimum requirements of the electron beam quality in W-band practical peniotrons.

Digital Control of a Buck Converter Based on a Non-linear Switching Surface Technique

This paper proposes analysis and implementation of a digital control of a buck converter based on a non-linear switching surface technique. The on and off time intervals of a switching power device are evaluated by the novel switching criteria design. As a result, the output voltage can be completely preserved. The nonlinear-large signal performance for both continuous and discontinuous conduction modes of operation can be achieved with fast transient response and constant switching frequency. In order to verify the correctness of the mathematical approach, the simulation results are compared with the experimental ones. It is found that experimental results of a prototype well agree with the theoretical predictions.

140-GHz V-Shaped Microstrip Meander-Line Traveling Wave Tube

A study on a miniature, low voltage, wide bandwidth, and high RF efficiency V-shaped microstrip meander-line slow-wave structure is carried out in this paper. The fabrication of this structure is very convenient by utilizing the 2-D micro-fabrication techniques. Radio-frequency characteristics including dispersion properties, interaction impedance and S-parameters are analyzed. Based on these results, nonlinear large signal performances of the V-shaped microstrip meander-line traveling-wave tube are calculated by 3-D particle-in-cell code. This study shows that this miniature millimeter-wave power amplifier is capable of delivering several tens of watts output power ranging from 127 GHz to 145 GHz.

A Tapered Ridge-loaded Folded Waveguide Slow-wave Structure for Millimeter-wave Traveling-wave Tube

This paper presents a tapered ridge-loaded folded waveguide (FWG) slow-wave structure (SWS) for broadband and high power millimeter wave traveling wave tube (TWT). The radio-frequency characteristics including dispersion properties, interaction impedance, S-parameters are analyzed. And based upon these results, the nonlinear large signal performance of the tapered ridge-loaded folded waveguide TWT working in W-band is simulated by 3-D particle-in-cell code. In the same ridge length, the tapered FWG has lower reflection and radio-frequency loss than the normal ridge-loaded FWG. Besides, the tapered ridge-loaded FWG TWT also has higher electron efficiency and larger bandwidth, which is more suitable for millimeter-wave TWT.

Modelling of heterojunction bipolar transistors (HBTs) based on gallium arsenide (GaAs)

This work describes an approach for small signal modelling of GaAs-based heterojunction bipolar transistors (HBTs) for low-voltage/high-power application (i.e., Vce=3 V, Jc=3×104 A/cm2). The parameter extraction procedure is discussed in detail. Furthermore, it is demonstrated that the model is fully scalable with respect to emitter area by comparison of simulated and measured S-parameters in the frequency range from DC to 20 GHz. Based on the small signal model, a nonlinear large signal model with the same Π-type topology is proposed. It has a small number of parameters and considers self-heating, which is particularly important for HBTs. Parameter extraction is discussed and it is demonstrated by comparison of simulation and measurement that the model can accurately predict the DC characteristics of a HBT for ambient temperatures ranging from 20 to 100°C. ©2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 33–42, 2000.

A frequency-domain mixer model for diffusion-cooled hot-electron bolometers

A new frequency domain hot-electron bolometer (HEB) mixer model is described, which takes into account the non-uniform temperature distribution found in superconducting diffusion-cooled devices. In this model the bolometer is discretized into a finite number of segments, and the non-linear large signal response to local oscillator and DC heating is found by an iterative algorithm. A frequency-domain coupling matrix is introduced to represent small-signal modulations around the large-signal values of temperatures and heat flows inside the device. The coupling matrix and a Norton representation of the mixer DC and intermediate frequency (IF) circuit allows the mixer conversion to be calculated.

Nonlinear large signal admittance in n-GaAs diodes at terahertz frequencies based upon transport analysis

Previous simulations of the transport in a n-GaAs n+nn+ diode structure using both moments of the Boltzmann equation and a Monte Carlo particle-field self-consistent approach suggest that submillimeter-wave generation may be possible only at cryogenic temperatures. These simulations employed only modest ac signal levels compared to the dc value. Here the terminal admittance behavior is examined for truly large signal levels, up to 100% of the dc value. It seems that such large signal conditions suppress the appearance of negative conductance in the submicron diode.