Gustavo Avolio

Nonlinear Dispersive Modeling of Electron Devices Oriented to GaN Power Amplifier Design

This paper presents a new modeling approach accounting for the nonlinear description of low-frequency dispersive effects (due to thermal phenomena and traps) affecting electron devices. The theoretical formulation is quite general and includes as particular cases different models proposed in the literature. A large set of experimental results, oriented to microwave GaN power amplifier design, is provided to give an exhaustive validation under realistic device operation.

An Extensive Experimental Analysis of the Kink Effects in

This paper, for the first time, analyzes in detail the kink phenomenon in S22 as observed in GaN HEMT technology. To gain a comprehensive understanding, the kink effect (KE) is studied with respect to temperature and bias conditions. The achieved results clearly show that the dependence of the KE on the operating condition should be mainly ascribed to the transconductance, which plays a determinant role in the appearance of this effect. Furthermore, the analysis is extended to investigate the peak in the magnitude of h21 showing its disappearance at low drain-source voltage, due to the increase of the intrinsic output conductance. The importance of this investigation originates from the fact that an accurate and complete characterization of these anomalous phenomena enables microwave engineers to properly take them into account during the modeling and design phases.enables microwave engineers to properly take them into account during the modeling and design phases.

{ S}_{22}

In recent years, wireless systems have rapidly evolved due to the increasing demands of different services, functionalities, and applications. In order to provide high-speed connectivity while using the available spectrum in an efficient manner, wideband digitally modulated signals are increasingly used to transmit information.

and

A novel nonlinear de-embedding procedure based on only the use of low- and high-frequency vector large-signal measurements is proposed. The nonlinear Q-V characteristics, along with the parasitic network, are here determined by combining vector measurements with numerical optimization. Consequently, the knowledge of their contributions allows one to retrieve the actual waveform at the current generator plane starting from any high-frequency load line.

{ h}_{21}

A novel extraction methodology is proposed to distinguish between the extrinsic and intrinsic capacitances of wide GaN HEMTs. This approach is based on the experimental observation that the real parts of the impedance parameters of such devices increase at high-frequency. The mathematical analysis clearly shows that this so far uninvestigated behavior can be attributed to the extrinsic capacitances.

for a GaN HEMT

We evaluate the uncertainty in on-wafer vector-calibrated nonlinear measurements with the National Institute of Standards and Technology (NIST) Microwave Uncertainty Framework. We include in our analysis uncertainties in the passive calibration standards, power meter, NIST-traceable phase calibration reference, cable bending, and probe alignment. These uncertainties are propagated first to the electrical quantities across the terminals of the device-under-test, which was an on-wafer microwave transistor. Next, we propagate uncertainties to the transistor current-generator plane, whose temporal voltage/current waveforms and impedances are of interest for the design of power amplifiers.

Large-Signal Network Analysis Including the Baseband

Process variations influence the accuracy of designs and yield in production. This paper addresses the implementation of these variations in large signal FET models, with particular attention on the organization of measurements as to speed up the direct extraction of the model parameters.

Waveforms-Only Based Nonlinear De-Embedding in Active Devices

We propose a three-port nonlinear dynamic behavioral model for supply-modulated power amplifiers (PAs). The proposed model not only accounts for the radio frequency (RF) input-output relationship, but also for the interaction between a modulated voltage supply, the RF output power and the supply current. The model is based on a modified Volterra formulation which accounts for the dynamic deviations with respect to a quasi-static model. The frequency-domain kernels of the proposed model are directly extracted from measurements performed with a low-frequency-extended large-signal network analyzer on an RF hand-set PA. The model is validated under random multitone modulated RF input and supply. The presented technique allows for the independent control of the RF and the supply ports. As such, it allows a separate description of both the dynamic contribution of the RF modulated input and of the dynamic supply voltage. The proposed model shows an improvement with respect to a quasi-static approach in predicting the RF output, the supply current, as well as the power-added efficiency.

High-Frequency Extraction of the Extrinsic Capacitances for GaN HEMT Technology

In this work we describe a novel technique for the extraction of nonlinear model for microwave transistors from nonlinear measurements obtained by simultaneously driving the device under test with low- and high-frequency excitations. Specifically, the large-signal operating point of the device is set by large-signal low-frequency excitations. On top of these a tickle tone at high-frequency is applied. In this way, one can separate the contributions of the IDS current source and the charge sources by a single measurement. The nonlinear model, based on equations available in commercial CAD tools, is extracted for a 0.15 μm GaAs pHEMT. Good agreement is obtained between model predictions and experimental data.

Evaluation of Uncertainty in Temporal Waveforms of Microwave Transistors

A non-linear model suitable for mixer applications is developed for advanced 0.15 μm GaAs HEMTs. The proposed model is based on a look-up table approach. The validity of the described modeling technique is confirmed by the good agreement between model simulations and measurements.