Nonlinear circuit stability under large‐signal pumping: Three‐port μ stability factor versus conversion matrix system identification—application to a millimeter‐wave band MMIC up‐converter

This article presents and discusses a method to determine stability in nonlinear three‐port circuits based on a generalized three‐port μ stability factor applied to linearized S parameters under large‐signal pumping. A comparison with an extension of the conversion matrix–based, system pole–zero identification used to analyze circuit stability is also presented. The relationship between the two techniques has been verified by means of an ideal two‐port nonlinear circuit, and then, it has been applied in the design of a three‐port millimeter‐wave Monolithic Microwave Integrated Circuit (MMIC) up‐converter. The circuit has been fabricated in a commercial GaAs process. On‐wafer measurements showed an average conversion loss about 3.5 dB in a RF bandwidth between 40.4 and 41.5 GHz with local oscillator (LO) frequency fixed at 42.5 GHz. A RF/LO isolation better than 25 dB was measured in the whole band, also showing outstanding intermodulation performance. With the proposed approach, the appearance of spurious oscillations was prevented. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Modeling power and intermodulation behavior of microwave transistors with unified small‐signal/large‐signal neural network models

This article presents a detailed procedure to learn a nonlinear model and its derivatives to as many orders as desired with multilayer perceptron (MLP) neural networks. A modular neural network modeling a nonlinear function and its derivatives is introduced. The method has been used for the extraction of the large‐signal model of a power MESFET device, modeling the nonlinear relationship of drain‐source current I_ds as well as gate and drain charge Q_g and Q_d with respect to intrinsic voltages V_gs and V_ds over the whole operational bias region. The neural models have been implemented into a user‐defined nonlinear model of a commercial microwave simulator to predict output power performance as well as intermodulation distortion. The accuracy of the device model is verified by harmonic load‐pull measurements. This neural network approach has demonstrated to predict nonlinear behavior with enough accuracy even if based only on first‐order derivative information. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 276–284, 2003.     

Impact of sampling domain and number of samples on the accuracy of large‐signal multisine measurement‐based behavioral model

This article evaluates two alternative ways to execute the sampling of modulated data for large‐signal behavioral modeling. We show that the nonlinear metric domain uniform sampling outperforms the time‐domain uniform approach, and examine how the level of improvement depends on the number of samples used for model generation. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Construction of behavioral models for microwave devices from time domain large‐signal measurements to speed up high‐level design simulations

Behavioral models for microwave devices from time domain large‐signal measurements are developed. For the presented examples, the model is defined by representing the terminal currents as a function of the terminal voltages and their derivatives. When using these models as building blocks of higher level designs, the simulation speed is significantly improved. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 54–61, 2003.     

Microwave frequency small‐signal equivalent circuit parameter extraction for AlInN/GaN MOSHEMT

This article presents an accurate and efficient extraction procedure for microwave frequency small‐signal equivalent circuit parameters of AlInN/GaN metal‐oxide‐semiconductor high electron mobility transistor (MOSHEMT). The parameter extraction technique is based on the combination of conventional and optimization methods using the computer‐aided modeling approach. The S‐, Y‐, and Z‐ parameters of the model are extracted from extensive dynamic AC simulation of the proposed device. From the extracted Y‐ and Z‐ parameters the pad capacitances, parasitic inductances and resistances are extracted by operating the device at low and high frequency pinch‐off condition depending upon requirement. Then, the intrinsic elements are extracted quasi analytically by de‐embedding the extrinsic parameters. S‐parameter simulation of the developed small‐signal equivalent circuit model is carried out and is compared with TCAD device simulation results to validate the model. The gradient based optimization approach is used to optimize the small‐signal parameters to minimize the error between developed SSEC model and device simulation based s‐parameters. The microwave characteristics of optimized SSEC model is carried out (f_T = 169 GHz and f_max = 182 GHz) and compared with experimental data available from literature to validate the model.     

Surrogate modeling for expedited two‐objective geometry scaling of miniaturized microwave passives

Geometry scaling of compact microwave structures is a challenging problem because of complex relationships between the physical dimensions of the circuit and its electrical characteristics, which is mostly caused by considerable cross‐couplings in densely arranged layouts. Yet, possibility of rapid redesign of a structure for various sets of design specification is important from practical point of view. In this article, we develop a procedure for expedited dimension scaling of compact microwave couplers with respect to two independent criteria. Our approach exploits inverse surrogates constructed at the level of equivalent circuit model and correction techniques that permits low‐cost re‐design of the coupler structure (at the level of EM‐simulation model) for a required operating frequency and power split ratio. The procedure is demonstrated using a folded microstrip rat‐race coupler. The scaling range for the considered example is from 0.5 to 2.0 GHz for the operating frequency, and from ?6 dB to 0 dB for the power split ratio. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:531–537, 2016.     

An improved empirical large‐signal model for the GaAs‐ and GaN‐based HEMTs

A complete empirical large‐signal model for the GaAs‐ and GaN‐based HEMTs is presented. Three generalized drain current I–V models characterized by the multi‐bias Pulsed I–V measurements are presented along with their dependence on temperature and quiescent bias state. The new I–V equations dedicated for different modeling cases are kept accurate enough to the higher‐order derivatives of drain‐current. Besides, an improved charge‐conservative gate charge Q–V formulation is proposed to extract and model the nonlinear gate capacitances. The composite nonlinear model is shown to accurately predict the S‐parameters, large‐signal power performances as well as the two‐tone intermodulation distortion products for various types of GaAs and GaN HEMTs. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2011.     

A HEMT large‐signal model for use in the design of microwave switching circuits

The nonlinear sources of switch‐HEMTs have been well analyzed by using the measured data. The small signal intrinsic capacitances (under both positive and negative V _ds operation) have been extracted by an extended small signal model. one‐dimension capacitance model has been effectively applied to model the small signal incremental capacitances directly extracted from the key operation region, which has also automatically taken into account the surface trapping effects. A new capacitance model has been effectively proposed to well fit the key nonlinear source (the deep subthreshold capacitance) of switch‐HEMTs. Simple switching function and additional voltage dependence have been applied to model the wide linear‐region (from high‐ V _gs region to deep subthreshold region) of channel current. On/off state small signal insertion loss, small signal isolation, weak harmonics, and power carrying capabilities are accurately predicted by the large signal model. The model shows very good convergence of circuit simulation. Meanwhile, the simple equations and distinguishing among the capacitances accurately make the scaling rules simple and accurate.     

Viewing‐angle characterization of reflective‐type liquid‐crystal displays by using an ellipsoidal mirror and a two‐dimensional CCD camera

A new photometry to perform the viewing‐angle characterization for reflective‐type LCDs has been developed. The optics consists of a rotating ellipsoidal mirror and a 2‐D CCD camera. The information obtained by this photometry includes the viewing‐angle characteristics of reflectance, contrast ratio, and chromaticity coordinates, which are comparable to gonioscopic photometry in terms of accuracy. Both the illuminating polar angle and azimuth angle can be scanned. The measurement time for this method is as short as that for conoscopic photometry when using a 2‐D CCD camera. An instrument equipped with light‐polarizing devices is already available. If analytic software was available, viewing‐angle characterization could be determined by a polarization analysis.     

Effects of low‐frequency drain termination and injection on nonlinear amplifier performances

Low‐frequency parameters have important effects on the nonlinear performances of power amplifiers. Injection at the output of a low‐frequency‐voltage device, following the signal envelope, is proposed. Two‐tone simulations, measurements using the principle of a low‐frequency active load‐pull system, and implementation of the technique are presented. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Computation of the 1‐dB compression point in radio frequency amplifier circuits using moments analysis

Nonlinear distortion analysis is one of the most computationally challenging aspects in the simulation of radio frequency circuits. Recently, an efficient moments‐based approach to determine the third‐order intercept point from the general harmonic balance equations, without the need to perform a harmonic balance simulation, was presented. In this article, the efficient computation of another important performance figure of merit, that of the 1‐dB compression point, using moments analysis is presented. In addition, the computations of the second‐ and fifth‐order intercept points are also presented. As a result, moments analysis becomes a comprehensive approach for quantifying nonlinear distortion using several key distortion figures of merit with a significant speed‐up over traditional harmonic balance methods. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:10–20, 2015.     

Robust control of a family of uncertain nonminimum‐phase systems via continuous‐time and sampled‐data output feedback

The problem of global robust stabilization is studied by both continuous‐time and sampled‐data output feedback for a family of nonminimum‐phase nonlinear systems with uncertainty. The uncertain nonlinear system considered in this paper has an interconnect structure consisting of a driving system and a possibly unstable zero dynamics with uncertainty, ie, the uncertain driven system. Under a linear growth condition on the uncertain zero dynamics and a Lipschitz condition on the driving system, we show that it is possible to globally robustly stabilize the family of uncertain nonminimum‐phase systems by a single continuous‐time or a sampled‐data output feedback controller. The sampled‐data output feedback controller is designed by using the emulated versions of a continuous‐time observer and a state feedback controller, ie, by holding the input/output signals constant over each sampling interval. The design of either continuous‐time or sampled‐data output compensator uses only the information of the nominal system of the uncertain controlled plant. In the case of sampled‐data control, global robust stability of the hybrid closed‐loop system with uncertainty is established by means of a feedback domination method together with the robustness of the nominal closed‐loop system if the sampling time is small enough.     

The AM‐PM conversion model as a phase statement of compression and desensitization in highly linear multicarrier power amplifiers

In this article, a novel AM‐PM conversion model is compared to the classical behavioral quadrature one. The proposed model can be seen as a phase statement of compression and desensitization. These two models are closely related. However, the proposed method does not have the limitations considered in the classical model, which can be seen in the investigation of the AM‐PM conversion introduced in a given carrier due to the presence of several signals, as is the case in multicarrier amplifiers. The method allows us to find the design conditions to reduce the AM‐PM conversion introduced by nonlinear circuits. To show the dependence of the AM‐PM conversion as a function of several input tones and frequency spacing, which is not considered in the classical model, the performance of medium power BJT and GaAsFET operating at 900 and 1900 MHz, is investigated when one, two, and three tones are simultaneously fed at the input. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

In‐field evaluation of the modulation transfer function and the signal‐to‐noise ratio of electronic‐display devices

Abstract— This paper describes a charged‐coupled device (CCD) camera, which was developed for in‐field evaluation of the image quality of electronic‐display devices [such as cathode‐ray tubes (CRTs) and liquid‐crystal displays (LCDs)] used for medical applications. Contrary to traditional cameras for display‐image‐quality evaluation, this CCD camera does not require a sophisticated x‐y‐z translation stage for mounting and adjustment. Instead, it is handheld and pressed by gentle pressure against the display screen. It is controlled by a software package which was originally developed for display calibration according to the DICOM 14 gray‐scale standard display function (GSDF). This software package controls the camera gain when measurements are made at different display luminance, display test patterns, performs image analysis and displays the results of the measurements and calculations. The work concentrated on the measurement of modulation transfer function (MTF) and of signal‐to‐noise ratio (SNR) per display pixel. The MTF is derived from the Fourier transform of the line spread function (LSF). The single‐display‐pixel SNR is derived from the integration of the noise power spectrum (NPS) of a camera image taken of a display with a uniform luminance. It is demonstrated that the device can produce repeatable results in terms of MTF and SNR. MTFs were measured on three monochrome CRTs and five monochrome LCDs in order to study repeatability and similar quantities. The MTF was measured on a 5‐Mpixel LCD yielding values that lie within 3.5% of the average MTF at the Nyquist frequency and 4.0% of the maximum total sharpness (∫ MTF² df). The MTF was also measured on a 9‐Mpixel LCD, yielding values that lie within 9.0% of the average MTF at the Nyquist frequency and 8.0% of the maximum total sharpness. The SNR was measured eight times on a 3‐Mpixel monochrome LCD at nine digital driving levels (DDLs). At a DDL of 185, the mean SNR was 15.694 and the standard deviation (Stdv) was 0.587. At a DDL of 65, the mean SNR was 5.675 and Stdv was 0.120.     

Global decentralized sampled‐data output feedback stabilization for a class of large‐scale nonlinear systems with sensor and actuator failures

In this paper, we investigate global decentralized sampled‐data output feedback stabilization problem for a class of large‐scale nonlinear systems with time‐varying sensor and actuator failures. The considered systems include unknown time‐varying control coefficients and inherently nonlinear terms. Firstly, coordinate transformations are introduced with suitable scaling gains. Next, a reduced‐order observer is designed to estimate unmeasured states. Then, a decentralized sampled‐data fault‐tolerant control scheme is developed with an allowable sampling period. By constructing an appropriate Lyapunov function, it can be shown that all states of the resulting closed‐loop system are globally uniformly ultimately bounded. Finally, the validity of the proposed control approach is verified by using two examples.     

Frequency‐dependent behavioral‐model‐based nonlinear analysis and design of a low‐profile transmit active phased array antenna

Design and behavioral‐model‐based nonlinear analysis of a 3‐GHz active‐phased array antenna (APAA) are presented. Four nonlinear power amplifiers are employed in the output ports of the feeding network (FN) and analyzed based on a 5‐order polynomial model with frequency‐dependent coefficients. The FN is based on 4‐port new Gysel power dividers and combiners arranged in such a way to feed the array with Gaussian‐like amplitude and in‐phase distributions. Beam steering capability is obtained in 2 directions by a new technique including a phase shifter and an amplitude controller (AC). The features result in a low‐profile APAA whose design and fabrication complexity and cost are reduced. Single and 2‐tone power tests are performed to develop analytical expressions in nonlinear region for array factor as a function of the model, FN and the phase and ACs. A similar system with frequency‐independent model is also analyzed for comparison in terms of scan loss, beamwidth, side‐lobe level, beam position, and gain. A microstrip array antenna including the power amplifiers, pre‐amplifiers, AC, delay‐line‐based phase shifters and Gysels is fabricated and measured. The simulation results at the single and dual tones and the intermodulation products are presented which have a good agreement with the measurements.     

Hybrid small‐signal model parameter extraction of GaN HEMTs on Si and SiC substrates based on global optimization

This article presents efficient parameters extraction procedure applied to GaN High electron mobility transistor (HEMT) on Si and SiC substrates. The method depends on combined technique of direct and optimization‐based to extract the elements of small‐signal equivalent circuit model (SSECM) for GaN‐on‐Si HEMT. The same model has been also applied to GaN‐on‐SiC substrate to evaluate the effect of the substrates on the model parameters. The quality of extraction was evaluated by means of S‐parameter fitting at pinch‐off and active bias conditions.     

Effect of guard‐ring on the DC and high‐frequency performance of deep‐submicrometer metal oxide semiconductor field effect transistor

The influence of guard‐ring (GR) on the direct current (DC) and high‐frequency performance of deep‐submicrometer metal oxide semiconductor field effect transistors (MOSFETs) is investigated in this study. MOSFETs with four different GRs are fabricated using 90 nm complementary metal oxide semiconductor (CMOS) process, and a detailed comparative study on their device performances is performed. A united DC and small signal equivalent circuit model that takes into the effect of GR is developed. A set of simple, but efficient formulas provide a bidirectional bridge for the S parameters transformation between devices with different GRs. The corresponding model parameters for MOSFETs with different GRs are determined from S parameter on‐wafer measurement up to 40 GHz. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:259–267, 2014.     

Performance evaluation of a two‐echelon supply chain with stochastic demand,lost sales,and Coxian‐2 phase replenishment times

This paper deals with a two‐echelon supply chain comprising a retailer and manufacturer. The retailer faces Poisson demand and follows a (S, s) continuous review inventory policy. The manufacturer produces and ships the retailer's orders with random delay that follows the Coxian‐2 distribution. Assuming lost sales at the retailer and infinite capacity at the manufacturer, we try to explore the performance of the supply chain system. The system is modeled as a continuous‐time Markov process with discrete space. The structure of the transition matrices of these specific systems is categorized as block‐partitioned, and a computational algorithm generates the matrices for different values of system characteristics. The proposed algorithm allows the calculation of performance measures—fill rate, cycle times, average inventory (work in progress [WIP])—from the derivation of the steady‐state probabilities. Moreover, expressions for the holding costs and shortage costs are derived.