Physical/electromagnetic analysis of multifinger MOSFETs with SB‐SP combined methods

The frequency‐domain spectral balance technique has been demonstrated to be a viable alternative to the mixed‐domain Harmonic Balance technique. It has already been applied to the space‐domain polynomial expansion of the physical quantities inside the semiconductor, for the solution of steady‐state nonlinear differential equations, for the physical analysis of high‐frequency semiconductor devices. In this article it is coupled to a commercial electromagnetic solver, for the combined physical and electromagnetic analysis of multifinger MOSFET devices in linear and nonlinear regime. This method allows a fast and effective CAD analysis both in DC and RF periodic regime for very high frequencies. A quasi‐2D hydrodynamic formulation is used for a 0.35 μm gate length with a total 30 μm periphery, three finger MOSFET device; results are compared with those of a standard physical time‐domain, a harmonic balance and a spectral balance analysis for comparison of numerical efficiency. Moreover, comparison of S‐parameters with a commercial CAD tool with a compact model for circuit analysis is also given. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

The AB‐C Doherty power amplifier. Part II: Validation

In part I, the complete theoretical (and nonlinear) analysis of a Doherty amplifier employing a Class AB bias condition for the Main Amplifier and a Class C one for the Auxiliary device has been presented. In this article, the experimental validation of the proposed theory is presented, describing the step‐by‐step procedure to be adopted when designing an AB‐C Doherty. The amplifier was realized at 2.14 GHz in hybrid form using two (0.5 μm, 1 mm gate periphery) GaN HEMTs. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Cross‐polarization in dual polarization switching antennas

This paper presents the effect of the interaction between the switch and the antenna parameters on the cross‐polarization of a dual polarization switching antenna. It is shown that the isolated antenna cross‐polarization combines with the isolation of the switch giving place to a degradation of the polarization purity of the combined dual polarization switching antenna. Analytical expressions for the combination of the switch isolation and the antenna cross‐polarization in the switched antenna element are given. Simulations and pattern measurements are presented. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Polarization‐independent modulation for projection displays using small‐period LC polarization gratings

Abstract— Progress in the use of liquid‐crystal polarization grating (LCPG) to modulate unpolarized (and polarized) light with a grating period as small as 6.3 μm is reported. Similar to LCPGs formed at larger periods (11 μm) reported previously, polarization‐independent switching, predominantly three diffraction orders, maximum contrast ratios of ～100:1 for unpolarized broadband light, very low scattering, and diffraction efficiencies >98% continue to be observed. The smaller period led to an expected lower threshold voltage, even though the thickness was greater. Because the smaller grating period enables a brighter result from a Schlieren projection scheme for a microdisplay using the LCPG light valve, the inherent tradeoffs involved with both material and design parameters are discussed, and prospects for a polarization‐independent projection display are commented upon.     

Direct extraction method for stripline packaged field effect transistor small signal equivalent circuit model

A new method for the extraction of the small signal model parameters for packaged field effect transistors (FETs) is proposed in this article. This method differs from previous ones by extracting the packaging model parameters under active bias conditions without global numerical optimization techniques. The main advantage of this method is that a unique and physically meaningful set of extrinsic packaging model parameters are extracted by using a set of closed form expressions based on the coaxial measurement for packaged device and on‐wafer measurement for chip. Good agreement is obtained between simulated and measured results for a gallium arsenide MESFET with 0.5 μm gatelength and 400 μm gatewidth over a wide range of bias points up to 8 GHz. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:306–313, 2014.     

Bayesian inference‐based small‐signal modeling technique for GaN HEMTs

A new modeling methodology for gallium nitride (GaN) high‐electron‐mobility transistors (HEMTs) based on Bayesian inference theory, a core method of machine learning, is presented in this article. Gaussian distribution kernel functions are utilized for the Bayesian‐based modeling technique. A new small‐signal model of a GaN HEMT device is proposed based on combining a machine learning technique with a conventional equivalent circuit model topology. This new modeling approach takes advantage of machine learning methods while retaining the physical interpretation inherent in the equivalent circuit topology. The new small‐signal model is tested and validated in this article, and excellent agreement is obtained between the extracted model and the experimental data in the form of dc I–V curves and S‐parameters. This verification is carried out on an 8 × 125 μm GaN HEMT with a 0.25 μm gate feature size, over a wide range of operating conditions. The dc I–V curves from an artificial neural network (ANN) model are also provided and compared with the proposed new model, with the latter displaying a more accurate prediction benefiting, in particular, from the absence of overfitting that may be observed in the ANN‐derived I–V curves.     

A quick‐response liquid‐powder display (QR‐LPD®) with plastic substrate

Abstract— Paper‐like displays as thin as 290 μm have been developed using QR‐LPD technology. We fabricated two types of displays. One is a dot‐matrix type with a 160 × 160 array of pixels and a 3.1‐in.‐diagonal viewable image size. The other is a segmented type for clock use. Each display has a paper‐like appearance and exhibits high contrast. Plastic substrates with a thickness of 120 μm were used, resulting in flexible displays that can be bent up to a radius of curvature of 20 mm.     

Analysis of scalable two‐π equivalent‐circuit model for on‐chip spiral inductors

High‐accuracy inductor model is vital for the success of RF/mm‐wave circuit design. In this article, the development of two‐π scalable model with four ladder skin effect structure has been described in detail. For the scalable compact circuit modeling, a set of formulas by which all of the compact circuit elements can be calculated according to the components geometric dimensions and process parameters will be given. The proposed modeling method is regarded as full scalable as all the component parameters are calculated by physical equations or revise equations. A series of spiral inductors with various geometries have been fabricated with 0.13 μm SiGe BiCMOS aluminum process to verify the model. Excellent agreements are obtained between the measured data and calculation form the proposed model up to frequencies above self‐resonant. This scalable 28‐element two‐π model enables to accurately characterize RF behaviors of on‐chip spiral inductors and optimize the inductor performance. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:93–100, 2015.     

Triple‐band polarization‐insensitive metamaterial absorber with low profile

In this article, a triple‐band metamaterial low‐profile absorber with polarization independence is proposed. The proposed metamaterial unit cell is composed of two modified rings with square patch at corners. In addition, the proposed absorber is consists of 10 × 10 periodic unit cells with size of 100 mm × 100 mm. To explain the mechanism, the electric field, the surface current distribution, and equivalent circuit model are present. The structure exhibiting three absorption peaks of 99.01%, 97.18%, and 99.53% under normal incidence at 8.92‐9.11 GHz, 13.78‐14.05 GHz and 14.92‐15.21 GHz which cover X and Ku‐band, respectively. In addition, the proposed structure is insensitive for the transverse magnetic/transverse electric field polarization of incident waves and also the angle of incidence. Furthermore, the three operating bands of the absorber can be adjusted independently and offers low profile which makes the design suitable for different curved surface applications. The proposed structure is fabricated and experiments are carried out to validate the design principle. Good agreements are observed between the measured and the corresponding simulated results.     

Silicon‐based integrated millimeter‐wave CPW‐to‐dielectric image‐guide transition

In this article, a novel mm‐wave dielectric image‐guide (DIG) to CPW transition is proposed, fabricated, and successfully tested in the silicon technology. A DIG is implemented on high resistivity Silicon‐On‐Insulator (SOI) wafer. The image‐guide height and handle layer thickness are 500 μm and 130 μm, respectively. An Aluminum coplanar waveguide is patterned over the DIG. The measured transmission characteristics of the transition are in acceptable agreement with the simulation results. A transition (coupling) loss of about 1 dB has been achieved at 60 GHz. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:490–497, 2014.     

Implications of microcavity plasma devices for new plasma‐display‐panel cell structures with improved luminosity

Abstract— The unique properties of microcavity plasma devices, and their potential to provide the basis for alternative PDP cell structures of improved luminosity, are described. Arrays as large as 500 × 500 (250,000) inverted pyramid microcavity devices, each with an emitting aperture of 50 × 50 μm² and designed for AC or bipolar excitation, have been fabricated in Si and operated in the rare gases and Ar/N₂ mixtures at pressures up to and beyond 1 atm. For a device pitch of 100 μm, the array filling factor is 25% and the device packing density is 10⁴ cm^?2. Measurements of the unoptimized radiant output of 500 × 500 arrays of Si microplasma devices, operating in Ne/(5–50)% Xe mixtures and photoexciting (in transmission mode) a 20‐μm‐thick film of green phosphor, yield values of the luminous efficacy up to 7.2 ± 0.6 lm/W for a Ne/50% Xe mixture (total pressure of 800 Torr) excited by a 20‐kHz sinusoidal voltage waveform. Sustaining voltages ranging from ～250 to 340 V (RMS) yield luminance values up to ～2000 cd/m² for Ne/50% Xe mixtures but the incorporation of field emitters or MgO into the microcavity is expected to significantly reduce the required operating voltage. Also, the fabrication of microplasma devices in ceramic multilayer structures or glass for scaling the display area is discussed briefly. Recent laser spectroscopic measurements of Xe(a ³Σ_u⁺) absorption in the visible and near‐infrared suggest steps to be taken in PDP cell design, particularly as the Xe content in Ne/Xe mixtures is increased.     

Analysis and design of a stacked power amplifier with 196% fractional bandwidth using equivalent circuit model

Stacked structure is a good solution to overcome the low output voltage swing provided by a single device. When several devices are stacked, the bandwidth and output power are multiple times higher. This article analyzes the small‐signal voltage gain of the stacked structure, deriving the gain expression of the high‐frequency model and simplified model. Based on the specific device parameter, the different small‐signal voltage gains between the two models are compared and the designed stacked structure is proved to obtain a flat gain at low frequencies below about 3 GHz. To our best knowledge, this is the first article to analyze the gain flatness of stacked structure with two equivalent circuit models. To verify the stacked theory, a pseudomorphic high‐electron‐mobility transistor（PHEMT） power amplifier (PA) is implemented using 0.25 μm Gallium arsenide (GaAs) technology. The PA achieves an ultra‐high bandwidth of 30 MHz to 3 GHz and a linear gain of 21 dB ± 1.5 dB. At a 16‐V drain bias voltage, a saturated output power of higher than 2 W and a peak power‐added efficiency (PAE) of 44.1% are attained.     

Neural‐space mapping‐based large‐signal modeling for MOSFET

In this article, a large‐signal modeling approach based on the combination of equivalent circuit and neuro‐space mapping modeling techniques is proposed for MOSFET. In order to account for the dispersion effects, two neuro‐space (S) mapping based models are used to model the drain current at DC and RF conditions, respectively. Corresponding training process in our approach is also presented. Good agreement is obtained between the model and data of the DC, S parameter, and harmonic performance for a 0.13 μm channel length, 5 μm channel width per finger and 20 fingers MOSFET over a wide range of bias points, demonstrating the proposed model is valid for DC, small‐signal and nonlinear operation. Comparison of DC, S‐parameter, and harmonic performance between proposed model and empirical model further reveals the better accuracy of the proposed model. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2011.     

Design and optimization of RF ICs with embedded linear macromodels of multiport MEMS devices

In this paper, we demonstrate efficient modeling approach for simulation, analysis, design, and optimization of multiport radio frequency microelectromechanical systems (RF MEMS) resonating structures embedded in RF circuits. An in‐house finite element method (FEM) solver is utilized to develop accurate and efficient macromodels that capture all the essential characteristics of the device. Using the datasets generated from the FEM simulations, the artificial neural network models are trained for two‐way mapping between the physical input and electrical output parameters. Realized model is implemented in a circuit simulator, enabling a simple yet accurate circuit simulator compatible modeling and optimization procedure instead of memory and time demanding FEM analysis. The derivation of dynamic macromodels with preserved electromechanical behavior of the multiport resonating structures is also presented. Capabilities of the proposed approach are demonstrated with several examples featuring capacitively actuated MEMS resonating structures: a clamped–clamped beam, a free–free beam, and a coupled clamped–clamped beam. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Digital lithographic processing for large‐area electronics

Abstract— A non‐contact jet‐printed mask‐patterning process is described. By combining digital imaging with jet printing, digital lithography was used to pattern a‐Si:H‐based electronics on glass and plastic substrates in place of conventional photolithography. This digital lithographic process is capable of layer‐to‐layer registration of ±5 μm using electronic mask files that are directly jet printed onto a surface. Aminimum feature size of 50 μm was used to create 180 × 180 element backplanes having 75‐dpi resolution for display and image‐sensor applications. By using a secondary mask process, the minimum feature size can be reduced down to ～15 μm for fabrication of short‐channel thin‐film transistors. The same process was also used to pattern black‐matrix wells in fabricating color‐filter top plates in LCD panels.     

Flexible electronic‐paper active‐matrix displays

Abstract— A100‐μm‐thick 320 × 240‐pixel active‐matrix display integrated into a functional‐device prototype is presented. The active matrix is composed of alternating layers of organic materials and gold. A six‐mask photolithographic process is used. An electrophoretic electronic imaging film is laminated on top of the active matrix. The display is bendable to a radius of 7.5 mm for more than 30,000 repetitions.     

Signal‐noise support vector model of a microwave transistor

In this work, a support vector machines (SVM) model for the small‐signal and noise behaviors of a microwave transistor is presented and compared with its artificial neural network (ANN) model. Convex optimization and generalization properties of SVM are applied to the black‐box modeling of a microwave transistor. It has been shown that SVM has a high potential of accurate and efficient device modeling. This is verified by giving a worked example as compared with ANN which is another commonly used modeling technique. It can be concluded that hereafter SVM modeling is a strongly competitive approach against ANN modeling. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Passively addressed FLC display possessing an inherent gray scale and memory

Abstract— A passively addressed 64 × 64 ferroelectric liquid‐crystal display (FLCD) has been developed. The display matrix has a 33 × 33 mm² aperture, and the FLC layer thickness is 5.2 ± 0.2 μm. The display device operates with a frame frequency of 30 Hz (at V_row = ±18 V, V_col = ±9 V, T = 23°C), generating a continuous gray scale which can be memorized for more than 10 days after the driving voltage is switched off. A new approach for multiplex electronic addressing of the FLCD gray scale is proposed. The conditions of the hysteresis‐free gray‐scale generation for multiplex addressing and the gray‐scale memorization after the voltage is switched off, as well as the time steadiness of memorized images, are considered.     

Enhancement of Johnson figure of merit in III‐V HEMT combined with discrete field plate and AlGaN blocking layer

The performance of AlGaN/GaN HEMT is enhanced by using discrete field plate (DFP) and AlGaN blocking layer. The AlGaN blocking layer provides an excellent confinement of electrons toward the GaN channel, resulting very low subthreshold drain current of 10^?8 A/mm. It reveals very high off state breakdown voltage (BV) of 342 V for 250 nm gate technology HEMT. The breakdown voltage achieved for the proposed HEMT is 23% higher when compared to the breakdown voltage of conventional field plate HEMT device. In addition, the DFP reduces the gate capacitance (C_G) from 12.04 × 10^?13 to 10.48 × 10^?13 F/mm. Furthermore, the drain current and transconductance (g_m) reported for the proposed HEMT device are 0.82 A/mm and 314 mS/mm, respectively. Besides, the cut‐off frequency (f_T) exhibited for the proposed HEMT is 28 GHz. Moreover, the proposed HEMT records the highest Johnson figure of merit (JFOM) of 9.57 THz‐V for 250 nm gate technology without incorporating T‐gate.     

Study on parasitic and channel resistance of poly‐Si thin‐film transistors by metal‐induced crystallization

Abstract— The channel‐length‐dependent transfer characteristics of TFTs using poly‐Si by metal‐induced crystallization through a cap (MICC) of a‐Si to evaluate the parasitic and channel resistances have been studied. The MICC p‐channel TFTs studied in the present work showed a maximum field‐effect mobility, threshold voltage, and gate swing of 53 cm²/V‐sec, −4.4 V, and 0.8 V/dec for W/L = 12 μm/6 μm, 71 cm²/V‐sec, −5.3 V, and 0.9 V/dec for W/L = 12 μm/12 μm, and 113 cm²/V‐sec, −7 V, and 1 V/dec for W/L = 12 μm/24 μm, respectively. It is found that the parasitic resistance is higher than the channel resistance, and both decrease with increasing temperature.