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In this paper, a nonlinear transistor model extraction technique oriented to E-band power amplifier design is discussed. Two models are extracted, based on analytical functions and look-up-tables, respectively. The latter was used for the design of two power amplifiers (PAs) covering the bandwidths 71-76 and 81-86 GHz. The models have been fully validated by comparing their predictions with measurements carried out on the realized MMIC PAs.

Rodlet cells (RCs) are the enigmatic and distinctive pear-shaped cells had found in many tissues of marine and freshwater teleosts. They have a distinctive fibrous capsule or the cell cortex that envelopes conspicuous inclusions called rodlets, basally situated nucleus, and poorly developed mitochondria. The contraction of the cell cortex results in the expulsion of the cell contents through an apical opening. One hundred and thirty years since rodlet cells were first reported, many questions remain about their origin and a function. This review will present new evidence regarding the relationship between RCs and metazoan parasites, and a protozoan infecting organs of different fish species, and update the state of knowledge about the origin, structure and the function of these intriguing fish cells.

Nonlinear modeling of GaN HEMTs is a challenging task especially when accurate predictions are desired under nonlinear dynamic operation. This is mainly due to the dispersion phenomena affecting state-of-the-art devices that must be accurately characterized and correctly accounted for during the development of their nonlinear model. The challenge becomes harder as frequency, power and circuit complexity increase as being demanded by the marketplace for the upcoming 5G-related applications. In this paper, nonlinear measurement techniques are discussed which allow the accurate characterization of microwave GaN HEMTs under actual operating conditions. The paper also discusses how to use these measurements in the extraction phase of nonlinear models highlighting the benefits of their adoption for modeling purposes.

We present a measurement technique for the characterization of the degradation in microwave transistors. The time-domain setup operates in the megahertz range to set a realistic load-line for the device. Data on the degradation of a microwave transistor are reported.

In this paper we investigate the complexity of the characterization of electron devices with microwave load-pull systems when harmonically-tuned classes of amplification are adopted. In particular, we highlight the effects of the transistor dynamic nonlinearities on the load impedances at the transistor current-generator plane.

Dealing with high-power operation (i.e., >100 W) is extremely critical to power-amplifier designers due to the lack of accurate transistor models of multicell (i.e., powerbar) devices. The reason is twofold: from one side, it is extremely difficult to characterize high-power transistors (e.g., device instability, thermal issues, microwave instrumentation costs, and measurement uncertainty that drastically increases with the investigated power level); and from the other side, the scaling proprieties of the model, moving from the unit-cell device to the multicell one, are inherently poor due to the different passive access structures to the active-device area. In this article, for the first time, an accurate modeling technique oriented to multicell devices is described, which allows one to extract a compact model of a multicell transistor showing similar prediction accuracy of the unit-cell one. Our assumptions have been widely demonstrated in the manuscript by a comprehensive characterization campaign from small-to large-signal operations carried out on both the unit-and multicell devices.

In this paper, we apply for the first time the nonlinear embedding technique to the design of power amplifiers (PAs) based on laterally-diffused metal-oxide-semiconductor (LDMOS) field effect transistors. Such a design technique is based on setting the transistor load line at the intrinsic current-generator plane, according to well-known theoretical guidelines. Then, the selected operating condition can be transposed at any design frequency at the extrinsic transistor terminals, by means of a model of the device nonidealities, such as the nonlinear intrinsic capacitances and the linear parasitic effects. A harmonically-tuned high-efficiency class-F and a wideband class-AB PAs operating within the FM broadcasting band 88 ÷ 108 MHz based on a 10-W LDMOS are then designed and realized. To definitely assess the validity of the proposed approach for the LDMOS technology, we compare the measured performance on the fabricated PAs with the expected predictions.

We compared two approaches to use high-frequency transistor load-pull data directly into a circuit simulator. One approach is based on Artificial Neural Networks (ANN), the other on look-up tables (LUT). We discuss some practical aspects, including implementation in the CAD environment and extrapolation capability.

In this paper, a modification of the Angelov DC I/V model is proposed with the aim of improving its accuracy in the back-off condition under Class-B operation yet preserving its excellent prediction capabilities under high output power and saturated operations. Dispersion effects and capacitances are modelled by well-established techniques. As validation, the predictions of the model on S-parameters and load-pull circles at different bias conditions and different input power levels are shown.

In this paper, we discuss the comparison of two GaN HEMT technology processes by means of large-signal low-frequency (LF) measurements. LF load line analysis clarified the increase of output power and drain efficiency resulting from significant improvement of both knee voltage and maximum drain current by a modified technology process. The cross-check on this advantage was carried out by means of commonly adopted high-frequency load-pull measurement setups.

This paper describes the influence of gate-voltage clipping behavior on drain efficiency in case of class-F and inverse class-F $(\mathbf{F}^{-1})$ operations under saturated regime. Numerical analysis using a simplified transistor model was carried out. As a result, we have demonstrated that the limiting factor for $\mathbf{class}-\mathbf{F}^{-1}$ operation is the gate-diode conduction rather than knee voltage. On the other hand, class-F PA is restricted by the knee voltage effects. Furthermore, nonlinear measurements carried out on a GaN HEMT support our analytical results.

© 2001-2012 IEEE. GaN FETs have achieved superior performance in the design of microwave power circuits. Nevertheless, the amount of dispersion related to this technology poses severe issues for the correct modeling and characterization of these devices. In this letter, the effects of GaN FET dispersion on the design of power amplifiers (PAs) with dynamic power supply, largely adopted in state-of-the-art high-efficiency pulsed radar transmitters, are discussed. In particular, we propose a technique for evaluating GaN device performance degradation in new-generation PAs that represents an effective alternative to pulsed-RF multiharmonic source/load-pull microwave setups. ispartof: IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS vol:28 issue:11 pages:1035-1037 status: published

Starting from the mathematical bases of waveform engineering, this contribution demonstrates the effectiveness of class-F power amplifier design in different bias conditions, provided the correct harmonic content is presented at the input. To validate the theoretical assumptions, low-frequency multi-harmonic load-pull measurements are carried out on a 1-mm gate periphery GaN HEMT, giving an experimental proof of the validity of the extended harmonic manipulation approach.

The term waveform engineering denotes all those circuit design techniques that are based on shaping the transistor voltage and current waveforms. From a general perspective, these design techniques can be grouped in two main categories according to the adopted design tool: measurement- and model-based. In the last two decades, thanks to the proliferation of setups enabling calibrated waveform acquisition at microwave frequencies, waveform engineering has attracted continuously increasing interest in the microwave engineering community. In this article, a comprehensive analysis of the waveform-engineering based design techniques is reported, paying particular attention to the advantages and drawbacks associated to each approach.

In this paper an automated measurement system for the investigation of degradation phenomena in GaN FETs is presented. The system is able to perform both static and dynamic stress cycles under actual device operation, gathering useful information strictly related to the “health” of the device. As case study a 75-VDC GaN HEMT was used for a 19-hours stress test, putting in evidence how the device performance slightly degrades during the stress experiment.

In this paper, we present a measurement setup for characterizing high-voltage high-power microwave transistors in terms of their reliability under actual operating conditions. By operating in the megahertz range, one exploits important advantages as the use of low-cost instrumentation and the possibility of handling high voltages and high powers. Finally, the gathered data, which are consistent with RF operation, are used to evaluate the reliability of the technology-under-test. An example of stress measurements is provided for a 100-VDC GaN HEMT delivering an output power of 10 W.

This paper presents an innovative extraction technique for the modelling of transistor I/V characteristics. Starting from few continuous wave measurements carried out at 10 MHz by a vector load-pull measurement system, it is demonstrated how the extracted I/V model shows good predictions in harmonically tuned operations. As a case study, a 0.5-μm GaN HEMT with 1-mm of periphery is considered. The extracted model has been validated through comparisons with vector nonlinear measurements carried out in condition very different from the ones exploited in the identification phase.

Date of Conference: 3-4 Oct. 2016 In this paper, we introduce the use of the low-frequency characterization of electron devices as an accurate and economical way to fast gather consistent data about the electron device performance at microwaves in the evaluation phase of new components, technologies and processes. © 2016 European Microwave Association.

This contribution aims at the experimental confirmation of the advantages of the harmonic manipulation theory, using a low-frequency low-cost characterization setup. A 0.5-μm 10x100-μm (1-mm gate periphery) GaN HEMT has been characterized synthesizing at the current-generator plane different load conditions, realizing tuned-load and Class-F operation. The measurements clearly demonstrate the importance of by synthesizing the required loads at the correct reference plane, giving an experimental proof of the performance predicted by theoretical analysis. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

A nonlinear multi-bias model oriented to accurately predict the effects of charge-trapping in Gallium Nitride (GaN) HEMTs is proposed. As a case study, we considered a 0.25-µm 8×75-µm GaN HEMT. The model is identified by using CW low-frequency time-domain data and validated through high-frequency vector nonlinear measurements.

Gallium Nitride (GaN) transistors are increasingly attracting the attention of the microwave research community due to their performance in terms of power density and frequency capabilities. As a matter of fact, GaN is considered as the leading technology for future telecom and space applications. Nevertheless, nonlinear modelling of GaN transistors is still an open issue that continuously poses new challenges. In this paper, the comparison between two models, based on behavioural and analytical approaches, will be deeply discussed with the aim of pointing out advantages and disadvantages of each modelling technique.

In this work, the design of a C-band class-AB power amplifier based on the waveform engineering approach is presented. The design leverages the low-frequency characterization of the transistor to obtain the prediction of its optimum operating condition. An exhaustive validation of the realized amplifier fully validates the proposed design technique.

In this paper, an empirical characterization technique of charge-trapping effects in GaN FETs based on low-frequency measurements is proposed. It is applied on a 0.25 × 600 μm2GaN HEMT. Experimental results confirm theoretical assumptions reported in literature.