Microwave class-E power amplifiers: a brief review of essential concepts in high-frequency class-E PAs and related circuits

Since Nathan Sokal's invention of the class-E power amplifier (PA), the vast majority of class-E results have been reported at kilohertz and millihertz frequencies, but the concept is increasingly applied in the ultrahigh-frequency (UHF) [1]-[13], microwave [14]-[20], and even millimeter-wave range [21]. The goal of this article is to briefly review some interesting concepts concerning high-frequency class-E PAs and related circuits. (The article on page 26 of this issue, "A History of Switching-Mode Class-E Techniques" by Andrei Grebennikov and Frederick H. Raab, provides a historical overview of class-E amplifier development.)We acknowledge support, in part, by a Lockheed Martin Endowed Chair at the University of Colorado and in part by the Spanish Ministry of Economy, Industry, and Competitiveness (MINECO) through TEC2014-58341-C4-1-R and TEC2017-83343-C4-1-R projects, cofunded with FEDER

Class-E rectifiers and power converters

This paper reviews the use of the class-E topology for RF-to-DC and DC-to-DC power conversion. After covering its early history, the class-E rectifier is introduced in the context of the time-reversal duality principle, to be then integrated with an inverter in a class-E2 DC/DC converter. Recent examples and applications at UHF and microwave bands are finally presented. A review of RF rectifiers based on Schottky diodes or FET transistors, is followed by a discussion of synchronous and self-synchronous implementations of the double class-E DC/DC converter, using advanced GaN HEMT transistors.This work was supported in part by the Spanish Ministry of Economy and Competitiveness (MINECO) under project TEC2014-58341-C4-1-R, co-funded with FEDER, and in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DEAR0000216 and the DARPA MPC program, ONR award N00014-11-1-0931

Class-E rectifiers and power converters: the operation of the class-E topology as a power amplifier and a rectifier with very high conversion efficiencies

In the late 70’s, the interest in reducing the value and size of reactive components moved power supply specialists to operate dc-to-dc converters at hundreds of kHz or even MHz frequencies. Passive energy storage (mainly magnetics) dominates the size of power electronics, limiting also its cost, reliability and dynamic response. Motivated by miniaturization and improved control bandwidth, they had to face the frequency-dependent turn-on and turn-off losses associated with the use of rectangular waveforms in the hard-switched topologies of that time. Similar to approaches for RF/microwave power amplifiers (PAs), the introduction of resonant circuits allowed shaping either a sinusoidal voltage or current, with parasitic reactive elements absorbed by the topology in the neighborhood of the switching frequency. The resulting resonant power converters, obtained by cascading a dc-to-ac resonant inverter with a high-frequency ac-to-dc rectifier, first transform the dc input power into controlled ac power, and then convert it back into the desired dc output [1]. This paper provides some historic notes on the operation of the class-E topology, introduced worldwide to the RF/microwave community by Nathan O. Sokal [2], as a power inverter and as a rectifier, with very high conversion efficiencies up to microwave frequencies. Recent research advances and implementations of class-E rectifiers and dc-to-dc converters at UHF and beyond are included. Offering competitive performance in terms of efficiency for RF power recovery, together with a wide bandwidth for low-loss power conversion, their potential for some modern applications is highlighted.The authors would like to acknowledge support in part by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) through TEC2014-58341-C4-1-R and TEC2017-83343-C4-1-R projects, co-funded with FEDER, and in part by Lockheed Martin Endowed Chair at the University of Colorado

Microwave class-E power amplifiers

This paper reviews circuit architectures and demonstrated class-E power amplifiers in the UHF and microwave frequency range. Scaling class-E soft-switching operation to high frequencies presents a number of challenges, particularly in the control of parasitic reactances of the device and the circuit. Different approaches have been taken, from using parasitics of lumped elements to provide the correct fundamental and harmonic impedances in the UHF range, to transmission-line implementations at frequencies above 10GHz

Vivir es el ser de la persona: una interpretación de la sustancia aristotélica

El personalismo rechaza la clásica definición de persona por considerar la noción de sustancia como un lastre de la filosofía aristotélica porque se considera la sustancia como substrato inalterado detrás de las variaciones accidentales. Esta interpretación “cosista” proviene de la fenomenología que niega la condición sustancial de la persona: la persona es una realidad abierta, dinámica, que continuamente reobra sobre sí misma. Pero la interpretación cosista de la sustancia no se halla en la metafísica de Aristóteles, para quien la sustancia es principalmente el ser vivo. Además, para obtener la noción de sustancia Aristóteles no acude al mundo exterior (como afirma el personalismo) sino a la interioridad propia de un ser vivo libre. Desde esta perspectiva “vitalista” es posible llegar a una visión compatible con el personalismo. Personalism rejects the classical definition of person and considers its notion of substance as a drag of Aristotelian philosophy because it regards substance as an unchanged principle behind variations in the accidents.  This interpretation comes from phenomenology which denies the person´s substantial condition: the person is an open and dynamic reality which continuously operates on himself.  But such explanation of the substance is not found in the metaphysics of Aristotle, who identifies substance as mainly the living being. Moreover, in his notion of substance, Aristotle does not turn to the external world (as claimed by personalism) but to the proper interiority of a free living being.  From this approach it is possible to achieve a view compatible with personalism. al and the historical, points to a new (not limited by time) conception of (the history of) philosophy

Recent literary theory and criticism in Spanish Anglistics : some observations on its institutional context and practices

This paper addresses the institutional context and academic practices related to the production and use of literary theory and criticism in the Spanish universities, with a special focus on the role of theory in Spanish Anglistics in recent years. The paper assesses interdisciplinary communication, the impact of new theoretical paradigms (feminism, postcolonial Studies, etc.) in a specifically Spanish setting, and the disciplinary transformations and new publishing opportunities associated to the new media ecology. Close attention is paid to issues of cultural colonization, disciplinary marginality and the contextual roots of academic praxis