Добірка наукової літератури з теми "Active load pull"

In this thesis, an investigation of the use of the poly-harmonic distortion model and related techniques is conducted, and applied to model fundamental and harmonic load-pull. Contained within the thesis is a detailed review of the development of the poly-harmonic distortion model and related methods. This thesis shows that although the poly-harmonic distortion model improves on the prediction of fundamental load-pull, over Hot-S-Parameters it still has a limited range of application. To address this observation, higher order models have been investigated along with Fourier methods allowing rapid extraction of the behavioral models. These methods allow conclusions to be drawn on the accuracy of the extracted models, by the direct observation of the magnitudes of the model coefficients. The thesis is concluded with the presentation of the results from third party, using a model extracted using the methods discussed in this thesis. The Model is of a 0.5W GaAs pHEMT at 9 GHz and is used within the design of a Class-J MMIC amplifier.

The advent of fourth generation (4G) wireless communication with available modulation bandwidth ranging from 1 MHz to 20 MHz is starting to emerge. The linear modulation technique being employed means that the power amplifiers that support the standards need to have high degree of linearity. By nature, however, all power amplifiers are non-linear. Load-pull measurement system provides anindispensable non-linear tool for the characterization of power amplifier and transistor for linearity enhancement. Conventional passive or active load-pull has delay problem that get worse as the modulation frequency is increased beyond few MHz. Furthermore in order to provide robust non-linear measurement, load-pull system needs to provide bandwidth at least five times the modulation bandwidth by including the fifth-order inter-modulation (IMD5). This thesis presents, for the first time, delay compensation on the unique active envelope load-pull architecture providing constant impedance for bandwidth up to 20 MHz. In doing so, it provides a superior load-pull measurement and also the ability to directly control in-band impedances. Artificial variations imposed on the in-band impedances offer further insight on power amplifier and transistor behaviours under wideband multi-tone stimulus.

Mestrado em Engenharia Electrónica e Telecomunicações
Por razões de potência, linearidade e e ciência o ampli cador é um componente limitador de performance em qualquer tipo de aplicações relacionadas com estações base de voz e dados, motivando a indústria das telecomunica ções a investir em sistemas capazes de ajudar o projetista de Ampli cador de Potência (AP) a obter o máximo deste elemento ativo. O sistema de 'load-pull' é uma ferramenta essencial para auxiliar o projeto de ampli cadores de potência, permitindo determinar as condições ideais de impedância que maximizam a sua performance. Esta dissertação insere-se na área de caracterização e projeto de AP, em rádio frequência e visa a concepção, implementação e validação de um sitema automático de 'load-pull' passivo. Neste trabalho, realizou-se um estudo sobre os mais diversos tipos de sistemas de 'load-pull' utilizados na caracterização de transistores de alta potência. De modo a cumprir a nalidade desta dissertação, construí-se um sistema passivo automatizado de 'load-pull' capaz de lidar com potência 250W forma de onda contínua (CW) e 2.5 kWde potência de pico em relação a envolvente de modulação (PEP), onde a repetibilidade da malha de saída deste sistema é -60dB a uma frequência correspondente de 1.8GHz, garantindo uma boa precisão das impedâncias apresentadas ao transístor de microondas.
Due to power, linearity and e ciency reasons the PA is the performance limiting component in any state-of-the-art mobile voice and data base station, motivating the telecommunications industry to invest in systems capable of helping the designer of PA to get the most of the active devices. The load-pull system is an essential tool to assist the design of PA, allowing to determine the optimum matching conditions that maximizes the PA performance parameters. This dissertation ts in the area of radio frequency characterization and PA design, aiming the artful conception, implementation and validation of an automated passive load-pull system. In this work a study was also performed on the most diverse types of load-pull systems that are used in the characterization of high power transistors. In order to ful ll the purpose of this dissertation, an automated load-pull system was built, being capable to handle 250W of power in continuous wave (CW) and 2.5kW in peak-to-envelope (PEP), where the system repeatability of its output network is -60dB at a frequency of 1.8GHz, granting a good accuracy of impedances presented to the microwave transistor.

The objective of this work was to advance the design of Active Harmonic Load-Pull systems to facilitate accurate modelling of RF semiconductors, with specific regard to time dependant behaviours. Pulse capability is added, to extend the thermally safe operating region, investigate thermal behaviour, and reduce the thermal loading on the system components. The safe operation region extension is demonstrated with a GaAs die, the thermal aspects of behaviour are illustrated with GaN on SiC, GaN on Si and GaN on diamond die. A violet laser is added, which releases some types of trapped charge, helping to reveal the full potential of the device. The thermal transient response of the device is thereby exposed, and the trap filling times may be studied. The application of this to GaN die with and without Source Coupled Field Plates is described. The relevance of the light wavelength is briefly investigated. A novel wafer probe station is described, providing access to the backside of the wafer for photonic trap release and the measurement of hot electron electroluminescence, as RF measurements are conducted on the front side. Replacing the drain RF and DC circuits with a fixed resistor, and stepping the gate voltage allows the device to be held at any point on the load-line and then moved to another, here this demonstrates that the residual “knee-walkout” on a GaN on SiC part with an optimised source coupled field plate is not a thermal effect, and must therefore be due to trapped charge, despite the field plate. A low loss diplexer/ bias tee combination with very good DC supply memory properties is described, demonstrated with a InAlN/GaN die at Ka band. Accurate measurement of harmonics is vital to waveform engineering. Here a novel method of increasing the effective dynamic range of the system is presented.

High-frequency and large amplitude current is a driving requirement for applications such as induction heating, wireless power transfer, power amplifier for magnetic resonant imaging, electronic ballasts, and ozone generators. Voltage-fed resonant inverters are normally employed, however, current-fed (CF) resonant inverters are a competitive alternative when the quality factor of the load is significantly high. The input current of a CF resonant inverter is considerably smaller than the output current, which benefits efficiency. A simple, parallel resonant tank is sufficient to create a high-power sinusoidal signal at the output. Additionally, input current is limited at the no-load condition, providing safe operation of the system. Drawbacks of the CF resonant inverter are associated with the implementation of the equivalent current source. A large input inductor is required to create an equivalent dc current source, to reduce power density and the bandwidth of the system. For safety, a switching stage is implemented using bidirectional voltage-blocking switches, which consist of a series connection of a diode and a transistor. The series diode experiences significant conduction loss because of large on-state voltage. The control of the output current amplitude for constant-frequency inverters requires a pre-regulation stage, typically implemented as a cascaded hard-switched dc/dc buck converter. The pre-regulation also reduces the efficiency. In this dissertation, a variety of CF resonant inverters with two input inductors and two grounded switches are investigated for an inductive-load driver with loaded quality factor larger than ten, constant and high-frequency (~500 kHz) operation, high reactive output power (~14 kVA), high bandwidth (~100 kHz), and high efficiency (over 95 %). The implementation of such system required to question the fundamental operation of the CF resonant inverter. The input inductance is reduced by around an order of magnitude, ensuring sufficient bandwidth, and allowing rich harmonic content in the input current. Of particular importance are fundamental and second harmonic components since they influence synchronization of the zero-crossing of the output voltage and the turn-on of the switches. The synchronization occurs at a particular frequency, termed synchronous frequency, and it allows for zero switching loss in the switches, which greatly boosts efficiency. The synchronous conditions were not know prior this work, and the dependence among circuit parameters, input current harmonics, and synchronous frequency are derived for the first time. The series diode of the bidirectional switch can reduce the efficiency of the system to below 90 %, and has to be removed from the system. The detrimental current-spikes can occur if the inverter is not operated in synchronous condition, such as in transients, or during parametric variations of the load coil. The resistance of the load coil has a wide variance, five times or more, while the inductance changes as well by a few percent. To accommodate for non-synchronous conditions, a low-loss current snubber is proposed as a safety measure to replace lossy diodes. The center-piece of the dissertation is the proposal of a two-phase zero-voltage switching buck pre-regulator, as it enables fixed frequency and synchronous operation of the inverter under wide parametric variations of the load. The synchronous operation is controlled by phase-shifting the switching functions of the pre-regulator and inverter. The pre-regulator reduces the dc current in the input inductors, which is a main contributor to current stress and conduction losses in the inverter switches. Total loss of the inverter switches is minimized since no switching loss is present and minimal conduction losses are allowed. The dc current in the input inductors, once seen as a means to transfer power to load, is now contradictory perceived as parasitic, and the power is transferred to the load using a fundamental frequency harmonic! The input current to the resonant tank, previously designed to be a square-wave, now resembles a sine-wave with very rich harmonic content. Additionally, the efficiency of the pre-regulator at heavy-load condition is improved by ensuring ZVS for with an additional inductive tank. The dissertation includes five chapters. The first chapter is an introduction to current-fed resonant inverters, applications, and state-of-the-art means to ensure constant frequency operation under load's parametric variations. The second chapter is dedicated to the optimization of the CF resonant inverter topology with a dc input voltage, two input inductors, and two MOSFETs. The topology is termed as a boost amplifier. If the amplifier operates away from the synchronous frequency, detrimental current spikes will flow though the switches since the series diodes are eliminated. Current spikes reduce the efficiency up to few percent and can create false functioning of the system. Operation at the synchronous frequency is achieved with large, bulky, input inductors, typically around 1-2 mH or higher, when the synchronous frequency follows the resonant frequency of the tank at 500 kHz. The input inductance cannot be reduced arbitrarily to meet the system bandwidth requirement, since the synchronous frequency is increased based on the inductance value. The relationship between the two (input inductance and the synchronous frequency) was unknown prior this work. The synchronous frequency is determined to be a complicated mathematical function of harmonic currents through the input inductors, and it is found using the harmonic decomposition method. As a safety feature, a current snubber is implemented in series with the resonant tank. Snubber utilizes a series inductance of cable connection between the tank and the switching stage, and it is more efficient than the previously employed series diodes. Topology optimization and detailed design procedure are provided with respect to efficiency and system dynamics. The mathematics is verified by a prototype rated at 14 kVA and 1.25 kW. The input inductance is reduced by around an order of magnitude, with the synchronous frequency increase of 2 %. The efficiency of the power amplifier reached 98.5 % and might be improved further with additional optimization. Silicon carbide MOSFETs are employed for their capability to operate efficiently at high frequency, and high temperature. The third chapter is dedicated to the development of the boost amplifier's large signal model using the Generalized State-space Averaging (GSSA) method. The model accurately predicts amplifier's transient and steady-state operation for any type of input voltage source (dc, dc with sinusoidal ripple, pulse-width modulated), and for either synchronous or non-synchronous operating frequency. It overcomes the limitation of the low-frequency model, which works well only for dc voltage-source input and at synchronous frequency. As the measure of accuracy, the zero-crossing of the resonant voltage is predicted with an error less than 2° over a period of synchronous operation, and for a range of interest for input inductance (25 μH – 1000 μH) and loaded-quality factor (10 – 50). The model is validated both in simulation and hardware for start-up transient and steady-state operation. It is then used in the synthesis of modulated output waveforms, including Hann-function and trapezoidal-function envelopes of the output voltage/current. In the fourth chapter, the GSSA model is employed in development of the PWM compensation method that ensures synchronous operation at constant frequency for the wide variation of the load. The boost amplifier is extended with a cascaded pre-regulator whose main purpose is to control the output resonant voltage. The pre-regulator is implemented as two switching half-bridges with same duty-cycle and phase-shift of 180°. The behavior of the cascaded structure is the same as of the buck converter, so the half-bridges are named buck pre-regulators. ZVS operation is ensured by putting an inductive tank between the half-bridges. Each output of half-bridges is connected to each of input inductors of the boost to provide the PWM excitation. Using the GSSA model, the synchronous condition and control laws are derived for the amplifier. Properties of the current harmonics in the input inductors are well examined. It is discovered that the dc harmonic, once used to transfer power, is unwanted (parasitic) since it increases conduction loss in switches of the boost. A better idea is to use the fundamental harmonic for power transfer, since it does not create loss in the switches. Complete elimination of the dc current is not feasible for constant frequency operation of the amplifier since the dc current depends on the load coil's resistance. However, significant mitigation of around 55 % is easily achievable. The proposed method improves significantly the efficiency of both the buck pre-regulator and the boost. Synchronous operation is demonstrated in hardware for fixed switching frequency of 480 kHz, power level up to 750 W, input voltage change from 300 V to 600 V, load coil's resistance change of three times, and load coil's inductance change of 3.5 %. Measured efficiency is around 95 %, with a great room for improvements. Chapter five summarizes key contributions and concludes the dissertation.
Ph. D.

Le développement technologique du transistor à effet de champ à grille submicronique, l'évolution croissante de sa montée en fréquence et ses capacités actuelles en puissance nécessitent de mettre en œuvre des méthodes de caractérisation adéquates. Ce travail concerne d'une part, la réalisation, entre 45 MHz et 40 GHz, des mesures de paramètres S petit signal des transistors à effet de champ et d'autre part, la réalisation des mesures de leurs performances optimales en puissance et en impédances dans la bande 26,5-40 GHz. Dans la première partie, nous développons la méthode de mesure des paramètres S à l'analyseur de réseau HP 8510 des transistors à effet de champ millimétriques jusqu'à 40 GHz et nous déterminons leurs performances potentielles petit signal ainsi que leurs schémas équivalents optimums. Dans la deuxième partie, nous développons pour ces transistors, en premier lieu, les mesures de puissance au banc classique et en second lieu, les mesures de puissance et d'impédance de charge au banc «load-pull à charge active» dans la bande 26,5-40 GHz. Parallèlement, nous étudions les problèmes posés par la réalisation de ces bancs de mesure. Des comparaisons sont effectuées en permanence entre les résultats obtenus par les trois systèmes de mesure: analyseur de réseau, banc classique et banc «load-pull à charge active». Cette étude nous a amené à définir les conditions permettant des mesures précises et «in situ» des performances en puissance du transistor dans la bande 26,5-40 GHz et à envisager, pour un développement ultérieur le couplage du banc «load-pull à charge active» avec un analyseur de réseau performant du type HP 8510 (ou Wiltron 360) assisté par une méthode d'étalonnage automatique équivalente à la méthode TRL

Le travail présenté dans ce mémoire propose une contribution à la conception optimisée d'amplificateurs de puissance par l'utilisation de plusieurs caractérisations fonctionnelles. Celles ci sont réalisées aux premiers stades de la conception, au niveau du transistor en environnement source et load pull. Il est ainsi montré qu'un banc load pull fonctionnant en mode pulsé permet de participer à la validation des technologies utilisées pour la génération de fortes puissances aux fréquences microondes (Bande S). Cette étape permet également de valider fortement les modèles non linéaires électrothermiques des transistors développés à cet effet. Dans le domaine millimétrique, l'amplification de puissance sous contrainte de rendement et de linéarité est à l'heure actuelle un des points critiques du fait des faibles réserves de gain proposées. Dans ce contexte, le développement d'un banc source et load pull actif fonctionnant en bande K et permettant de déterminer les conditions optimales de polarisation et d'adaptation pour l'obtention du meilleur compromis rendement/linéarité se révèle être de première importance pour la conception optimisée d'amplificateur. Enfin, une nouvelle technique de caractérisation dédiée à l'extraction des quatre paramètres S à chaud en environnement load pull est proposée. Une application de cette nouvelle caractérisation a ainsi permis de prédire les oscillations paramétriques hors bande pouvant apparaître en fonction des conditions opératoires lorsque le transistor fonctionne en régime fort signal
Advanced functional characterizations of power transistors for the validation of nonlinear models of SC devices used in CAD packages. This work deals with different functional characterization methods for the design of optimized power amplifiers. These characterizations are carried out on transistors at the first stages of the design, in a source and load-pull environment. Thus, it is shown that a pulsed load-pull set up is very useful to validate the technologies used for the generation of high power at RF and microwave frequencies. It also enables to deeply validate the thermoelectric nonlinear models of transistors developed for this purpose. For the design of amplifiers which operate up to millimetric frequencies (Ku / K Band), reaching high power under constraint of efficiency and linearity is one of the most critical point because of the weak reserves of power gain proposed. In this context, the development of an active source and load-pull setup is of prime importance. It enables to primarily determine the transistor optimum operating conditions (Matching and DC bias) to reach the best trade off between efficiency and linearity. Finally, a new method to perform Hot Small-Signal S-Parameter measurements of power transistors operating under large signal conditions is proposed. An application to the prediction of parametric oscillations when the transistor is driven by a pump signal is demonstrated

Les télécommunications mobiles, afin de subvenir à leurs insatiables besoins, trouvent des moyens d’améliorer leurs capacités depuis maintenant plus de trente ans. En 2019 la cinquième génération (5G) est à l’épreuve afin de garantir une connexion non seulement au marché des téléphones mobiles toujours croissant, mais aussi au vaste univers de l’internet des objets (IoT). Afin de pouvoir remplir ses objectifs, la 5G marque une expansion sans précédent en matière de bandes de fréquences utilisées. En effet, des bandes jusqu’à 60 GHz et plus font partie des ambitions du réseau et cela implique de radicaux changements technologiques qui impactent toute l’électronique dédiée. Nouvelles fréquences plus élevées, pertes de propagation dans l’air plus élevées et niveau d’exigences relevé, les réseaux phasés d’antenne sont introduits pour pallier à toutes ces contraintes et imposent une toute nouvelle architecture système et une interface inédite pour les front-end RF des communications mobiles.Dans ce travail, nous proposons donc une analyse de ces réseaux d’antennes phasés et des contraintes qu’ils représentent en particulier pour les amplificateurs de puissance (PA), tel que la variation de charge parasite et le comportement des composantes générées par le comportement non-linéraire de ces derniers. Une évaluation de la variation de charge active due aux différents couplages existants dans les réseaux d’antennes est proposée ainsi que de son impact sur la performance des amplificateurs notamment en termes d’efficacité (PAE). Le comportement des non-linéarités telles que les produits d’intermodulation du troisième ordre (IMD3) est montré dans les réseaux d’antennes. Un concept utilisant le principe de génération et d’orientation de faisceau des réseaux d’antennes est proposé, permettant de relâcher les contraintes de linéarité des amplificateurs 5G et ainsi de permettre une réduction de leur consommation d’énergie. Une implémentation d’un PA utilisant ce principe est démontrée en technologie ST CMOS 65 nm PD-SOI à 28 GHz
Mobile telecommunications, in order to support its insatiable needs, has been finding ways to improve its capabilities for over thirty years now. In 2019 the fifth generation (5G) is on trial to ensure connection not only to the ever-growing cell phone market, but also to the vast world of the Internet of Things (IoT). In order to meet its goals, 5G marks an unprecedented expansion in the frequency bands used. Indeed, bands up to 60 GHz and beyond are part of the network's ambitions and this implies radical technological changes that impact all dedicated electronics. New higher frequencies, higher propagation losses in the air, and higher requirements, antenna phased arrays are introduced to overcome all these constraints and impose a completely new system architecture and interface for the RF front-end of mobile communications.In this work, we propose an analysis of these phased antenna arrays and the constraints they represent particularly for power amplifiers (PA), such as the parasitic load variation and the behavior of the components generated by the non-linear behavior of the latter. An evaluation of the active load variation due to the different coupling existing in the antenna networks is proposed as well as its impact on the performance of the amplifiers, particularly in terms of power added efficiency (PAE). The behavior of nonlinearities such as third-order intermodulation products (IMD3) is shown in antenna arrays. A concept using the principle of beam generation and steering of antenna arrays is proposed, allowing for relaxing the linearity constraints of 5G amplifiers and thus allowing a reduction of their power consumption. An implementation of an AP using this principle is demonstrated in ST CMOS 65 nm PD-SOI technology at 28 GHz

Il est aujourd’hui admis que les semi-conducteurs à large bande interdite vont permettre de repousser les frontières atteintes à ce jour dans le domaine de la génération de puissance hyperfréquence. L’analyse des principaux critères technologiques (physiques et électriques) des matériaux grands gap, et plus précisément du GaN montre que ce dernier est un candidat sérieux pour les applications de télécommunications et radar. Un modèle électrothermique de ces transistors hyperfréquences à FET sur GaN a été utilisé dans ces travaux pour analyser les comportements transitoires lents dus aux effets thermiques et aux effets de pièges. Une comparaison des performances en puissance, rendement et linéarité a été faite entre les résultats de simulation et ceux de mesure pour des signaux de deux types : CW impulsionnels et Bi porteuses impulsionnels. L’utilisation de signaux CW impulsionnels a permis une validation pratique des modèles électrothermiques de transistors HBT et une expertise de différentes filières technologiques de ces transistors. L’utilisation de signaux bi porteuses impulsionnels a permis d’observer des tendances sur les compromis rendement/linéarité en fonction des effets de pièges de transistors FET GaN. Des mesures réalisées sur une configuration originale d’un banc de caractérisation de type « load-pull » pour une mesure d’intermodulation en mode pulsé ont permis de montrer les limitations actuelles des modèles de ces transistors dans le cadre de simulations de fonctionnement dynamique
It is admitted today that wide band-gap materials will make it possible to push back the borders reached to date in the field of RF power generation. The analysis of the properties of wide band-gap materials, and especially the GaN material, highlights that it is a serious candidate for telecommunication and radar applications. RF field effect transistors on GaN are prone to show dispersive behaviors due to heating and trapping effects. A non linear electrothermal model of these high frequency FETs transistors on GaN used in this work makes possible the analysis of dispersive behaviors due to heating and trapping effects. A comparison of performances in terms of output power, power added efficiency and linearity has been made between simulation and measurement results for two type of excitation: one tone pulsed signal and two tones pulsed signal. The use of a one tone pulsed excitation permitted the validation of an HBT electrothermal model and the expertise of different technological process of these transistors. The use of a two tone pulsed excitation has permitted to observe the trade-offs between power added efficiency and linearity versus trapping effects. The measurements carried out on an original configuration of the load pull set up for intermodulation measurements under pulsed conditions had shown the actual limitations of the transistor model

Les antennes réseaux actives en cours de développement ont pour particularité de posséder, à l'émission, des amplificateurs en régime saturé placés à proximité immédiate des éléments rayonnants. Les couplages du réseau peuvent induire des variations de charge susceptibles de perturber les amplificateurs et de modifier les performances globales de l'antenne. Afin de prédire cet effet, un outil de simulation associant la description des éléments passifs et actifs de l'antenne a été développé. Plusieurs modèles d'amplificateurs, dont le modèle de distorsion polyharmonique (PHD), ont été obtenus à partir de mesures et évalués. D'autre part, le calcul électromagnétique du réseau d'éléments rayonnants a fait l'objet d'une approche originale couplant la technique par changement d'échelle (SCT) et la méthode de décomposition de domaine (DDM). Finalement, la simulation d'un réseau actif d'une centaine éléments a révélé des phénomènes inédits tels que le rayonnement d'un lobe parasite dû aux non-linéarités.

This textbook has covered the common causes of broken down teeth: dental caries, tooth wear, and trauma. In addition, long-term failure of parts, or all, of the existing tooth–restoration complex can be significant and may require further operative intervention for its successful management (see Chapter 9). Many intra-coronal defects can be repaired with direct adhesive restorations, as discussed in Chapters 5 and 9. However, the situation can be complicated by the loss of significant portions of existing restoration or tooth structure (e.g. cusps, buccal/lingual walls), which influence the restorative procedures used in an attempt to maintain the tooth longevity, as well as pulp viability, for as long as possible. For direct restorations to succeed clinically, they require healthy dental tissues to aid support, retention, and ideally provide an element of protection from excessive occlusal loads. With diminishing amounts of tooth structure to work with, greater thought and care are required to manage and prepare the remaining viable hard tissues to support and retain the larger restoration. The core restoration describes the often large direct plastic restoration used to build up the clinically broken down crown. It is retained and supported by remaining tooth structure wherever possible (sometimes including the pulp chamber and posts in root canals of endodontically treated teeth). These large restorations often benefit from further overlying protection to secure their clinical longevity, by means of indirect onlays, and partial or full coverage crowns. Before carrying out a detailed clinical examination of the individual tooth and the related oral cavity, it is always important to justify your clinical decisions, for both operative and non-operative preventive interventions. The five key reasons for minimally invasive (MI) operative intervention are:… • to repair hard tissue damage/cavitation caused by the active, progressing caries/tooth-wear process (where non-operative prevention has failed repeatedly) • to remove plaque stagnation areas within cavities/defects which will increase the risk of caries activity due to the lack of effective plaque removal by the patient • to help to manage acute pulpitic pain caused by active caries by removing the bacterial biomass and sealing the defect, thereby protecting the pulp • to restore the tooth to maintain structure and function in the dental arch • aesthetics.