Raymond Quéré

An Electrothermal Model for AlGaN/GaN Power HEMTs Including Trapping Effects to Improve Large-Signal Simulation Results on High VSWR

A large-signal electrothermal model for AlGaN/GaN HEMTs including gate and drain related trapping effects is proposed here. This nonlinear model is well formulated to preserve convergence capabilities and simulation times. Extensive measurements have demonstrated the impact of trapping effects on the shapes of I(V) characteristics, as well as load cycles. It is shown that accurate modeling of gate-and drain-lag effects dramatically improves the large-signal simulation results. This is particularly true when the output loads deviate from the optimum matching conditions corresponding to real-world simulations. This new model and its modeling approach are presented here. Large-signal simulation results are then reported and compared to load-pull and large-signal network analyzer measurements for several load impedances at high voltage standing wave ratio and at two frequencies.

New design method of uniform and nonuniform distributed power amplifiers

A new design methodology of uniform and nonuniform distributed power amplifiers is reported in this paper. This method is based on analytical expressions of the optimum input and output artificial lines making up the uniform and nonuniform distributed architectures. These relationships are derived from the load-line requirement of each transistor size for optimum power operation. Furthermore, specific design criteria are presented to enable an efficient choice between uniform and nonuniform distributed architectures. To validate this new design methodology, a nonuniform distributed power amplifier has been manufactured at the TriQuint Semiconductor Foundry, Richardson, TX, using a 0.25-/spl mu/m power pseudomorphic high electron-mobility process. This single-stage monolithic-microwave integrated-circuit amplifier is made of six nonuniform cells and demonstrates 1-W output power with 7-dB associated gain and 20% power-added efficiency over a multioctave bandwidth.

A unified approach for the linear and nonlinear stability analysis of microwave circuits using commercially available tools

For the first time, an exhaustive linear and nonlinear stability analysis of multi-transistor MMIC circuits is presented. A key point of the proposed stability analysis lies in that it can be easily implemented on any CAD package. Our straightforward and powerful approach allows both linear and nonlinear stability analysis of any complex circuit submitted or not to large RF signals. Following our novel approach, a MMIC HBT power amplifier was analyzed. Division frequency phenomena and spurious oscillations were detected by simulations and confirmed by measurements.

Synchronization analysis of autonomous microwave circuits using new global-stability analysis tools

A new spectral-balance technique for the global-stability analysis of autonomous circuits is presented in this paper. This technique relies on the introduction of measuring probes into the circuit and it allows a simple determination of both bifurcation diagrams and bifurcation loci as a function of any suitable parameter. Through the proposed algorithms, this kind of analysis can be easily added to any existing software, since it is performed externally to the harmonic-balance (HB) calculation. Due to its local nature, it also allows an easy selection of the bifurcation parameters, which spreads the simulation possibilities. Both periodic and quasi-periodic regime simulations are possible, and bifurcations are detected in both operating modes. The synchronization phenomenon in injected oscillators and frequency dividers is also analyzed in detail for an accurate prediction of the operating bands. The simulation techniques are illustrated by means of their application to a cubic nonlinearity oscillator. They are then used for the stability analysis of a monolithic microwave integrated circuit (MMIC) divider by two operating in the millimetric range. A very good agreement has been obtained with the experimental results.

A pulsed-measurement based electrothermal model of HBT with thermal stability prediction capabilities

In this paper, a new electrothermal non linear model of HBT suitable for CAD purposes is presented. This model is fully determined by pulsed measurement techniques and for the first time, it is shown that the prediction of thermal instabilities (collapse of current gain) is obtained from the CAD model. The model has been validated both by DC and RF load-pull measurements.

Fully integrated nonlinear modeling and characterization system of microwave transistors with on-wafer pulsed measurements

A novel approach for nonlinear characterization and modeling of microwave transistors has been developed. The whole process is organized as a set of methods contained in the transistor database. This implies that characterization and modeling are performed in an integrated manner. I(V) and S-parameters are measured on wafer under pulsed conditions, suitable for MESFETs, HEMTs or HBTs as illustrated by the proposed models.<<ETX>>

A 60-GHz HEMT-MMIC analog frequency divider by two

This paper describes an analog frequency divider by two working in the millimeter wave frequency range around 60 GHz. This circuit is analyzed with a new method that allows one to determine the steady-state regime of any synchronized circuits with standard CAD commercial software. The method proposed relies upon the concept of open loop systems and is applicable to any feedback transistor circuits. The designed circuit was processed using a standard 0.25-/spl mu/m HEMT technology. Four transistors were used for realizing the frequency division function as well as the input and output amplification. More than 10% frequency lock-in bandwidth was achieved, and conversion gain was obtained using input and output buffers. Measured results were found to be in good agreement with simulated ones. >

A new nonlinear I(V) model for FET devices including breakdown effects

The nonlinear FET I(V) behavior, including gate conduction and breakdown, has been investigated using a pulse measurement setup. An excessive current source has been observed in addition to the usual gate breakdown current. From these measurements, a nonlinear model including the conduction, breakdown, and excessive current phenomenon is proposed for the nonlinear simulation of high-power circuits. This I(V) model presents an improvement in terms of load line prediction and limits for the high-power nonlinear circuit design.<<ETX>>

A pulsed S-parameters measurement setup for the non-linear characterization of FETs and bipolar power transistors

A pulsed I(V) and S-parameters setup for the RF modeling of semi-conductor devices is described. The management of the whole setup as well as the database is made by an object-oriented software, which provides a large amount of modularity and reusability of the different tools developed. Measurements capability on power devices is demonstrated as well as the S-parameters measurements capabilities in critical regions of FET devices. I(V) and RF measures are presented. These measurements provide a nonlinear small-signal equivalent circuit function of the command voltages.

A Drain-Lag Model for AlGaN/GaN Power HEMTs

A circuit modeling drain-lag effects has been added in a non-linear electrothermal model for AlGaN/GaN HEMTs. Modeling these trapping effects allows a better description of the I-V characteristics of measured devices as well as their large-signal characteristics. This drain-lag model is well suited to preserve the convergence capabilities and the simulation times of the non linear models of these devices. This paper presents our drain-lag modeling approach, the implementation of the model in CAD software, its operating mode, and also the parameters extraction from measurements. Then, significant comparison results will be reported on pulsed IV and large signal measurements with an AlGaN/GaN HEMT transistor.