Advanced design features of Doherty power amplifiers

A Doherty power amplifier (DPA) is an effective structure born in 1936 which, after a scarce revival around year 2000), had been strengthened from 2005 because its capability to combine linear amplification with power efficiency. Despite the conceptual simplicity of its basic operation, a lot of practical drawbacks shrink the theoretical behavior, thus leading a significant number of research works to overcome them. The main objective in DPA research is to increase efficiency while maintaining linearity and filling the specified bandwidth. This paper presents a survey of the state of the art of DPA advanced design aspects. After a short review of the DPA operation principles, aspects regarding improvements for linearity, power efficiency and amplification bandwidth are introduced. Besides, some alternative structures and technologies, as well as practical design aspects and some trade-offs which the designer usually has to face are also presented.Peer ReviewedPostprint (published version

Majors i mitjans de comunicació: ¿una assignatura pendent?

La realidad demográfica del envejecimiento de la población ha promovido cambios socioeconómicos y culturales que están modificando el papel y la imagen pública de las personas mayores en nuestra sociedad. Para conocer cómo se transmite esta imagen a través de los medios de comunicación, nace en el año 2007, dentro de la Universidad Permanente de la UA, el Observatorio Mayores y Medios de Comunicación. Somos un seminario de investigación de carácter permanente con investigadores y expertos, del ámbito de la comunicación, y un grupo de alumnos de la Universidad Permanente. Así, los componentes del observatorio se convierten en investigadores

El análisis comparativo entre razas de gallinas mediterráneas en base a sus características morfológicas no refleja relaciones de origen ni aptitud

The aim of this study was to carry out the systematic classification in related groups and based on morphological similarities of 19 breeds of hens of the Mediterranean group. These breeds were 15 Spanish (Alicantina, Andaluza Azul, Cara Blanca, Castellana Negra, Empordanesa, Flor d'Ametller, Mallorquina, Menorquina, Murciana, Pairal, Penedesenca, Prat, Sobrarbe, Utrerana and Valenciana de Chulilla) and four Italians (Italiana, Livorno, Mericanel della Brianza and Paduana). The analysis included the evaluation of 17 qualitative morphological characteristics and was based on the principle of parsimony using Fitch method. The resulting phylogram should be interpreted as a group tree oncerning the morphological relationships between breeds and not as a phylogenetic tree because does not allow a clear clustering of breeds according to their origin of purpose. This, together with the rates obtained for synapomorphy -shared homologous characters- and homoplasia - independently acquired parallel changes- higher in the former, allows to suppose that, although in the process of breed diversification, there may have been phenomena of convergence of morphological characters, the conservation phenomena of existing morphological characters have been greater. That is, there have been changes in the morphological models in the process of formation of the breeds, independent of their origin and aptitude.El objetivo del estudio fue realizar la clasificación sistemática de grupos afines y con base a semejanzas morfológicas de 19 razas de gallinas del grupo mediterráneo. Estas fueron 15 españolas (Alicantina, Andaluza Azul, Cara Blanca, Castellana Negra, Empordanesa, Flor d’Ametller, Mallorquina, Menorquina, Murciana, Pairal, Penedesenca, Prat, Sobrarbe, Utrerana y Valenciana de Chulilla) y cuatro italianas (Italiana, Livorno, Mericanel della Brianza y Paduana) a partir de 17 características morfológicas cualitativas. Se evaluaron con base al principio de parsimonia usando el método de Fitch. El filograma resultante, interpretado como un árbol de grupos concernientes a las relaciones morfológicas entre las razas estudiadas y no como un árbol filogenético, ya que no permite la agrupación de las razas en función de su origen o aptitud. Ello, junto con los índices obtenidos de sinapomorfia –caracteres homólogos compartidos– y homoplasia –cambios paralelos adquiridos independientemente–, más elevado en el primero, permite suponer que, aunque en el proceso de diversificación de la gallina se hayan podido dar fenómenos de convergencia de caracteres morfológicos, han sido mayores los fenómenos de conservación de caracteres morfológicos ya existentes. Es decir, que se han dado cambios en los modelos morfológicos en el proceso de formación de las razas, independientes de su origen y aptitud

A method for real-time generation of slew-rate limited envelopes in envelope tracking transmitters

Postprint (published version

Reconfigurable DPD based on ANNs for wideband load modulated balanced amplifiers under dynamic operation from 1.8 to 2.4 GHz

This article proposes a methodology to ensure linear amplification of a load modulated balanced amplifier (LMBA) while keeping the power efficiency as high as possible over a frequency band ranging from 1.8 to 2.4 GHz and where the transmitted signals can present different bandwidth (BW) configurations. The proposed reconfigurable linearization methodology consists of, in a first step, tuning some free parameters (with dependence on the signal BW and frequency of operation) of the LMBA to trade-off linearity and power efficiency. In a second step, two multipurpose adaptive digital predistortion (DPD) linearizers are considered, properly combined with crest factor reduction (CFR) techniques, to meet the required linearity specifications. Either a DPD based on artificial neural networks or a DPD based on polynomials can be selected taking into account the compromise between computational complexity and linearization performance. Experimental results will validate the proposed methodology to guarantee the linearity levels (ACPR < -45 dBc and EVM < 1%) with high power efficiency in an LMBA under dynamic transmission, where both the signal BW (from 20 and up to 200-MHz instantaneous BW) and frequency of operation (in the range of 1.8-2.4 GHz) change.This work was supported in part by the Spanish Government (Ministerio de Ciencia, Innovación y Universidades) and FEDER (Fondo Europeo de Desarrollo Regional) under Grant TEC2017-83343-C4-2-R and in part by the Generalitat de Catalunya under Grant 2017 SGR 813. This paper is an expanded version from the International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC), Cardiff, United Kingdom, July 2020.Peer ReviewedPostprint (author's final draft

Improvement of Up-converters linearity for Ka-band operation

The application of a digital predistorter to the linearisation of a Ka-band mixer is presented herein. The general objective in the TX design is to get the best trade-off between linearity and costs. This require the most of the simplicity and possibly to take advantage from already existing device without perturbing its other functionalities. After a presentation of the problem and its constraints, we present the digital predistorter, which has been tested and debugged by means of IEEE-488 bus (GPIB) controllable instrumentation (EMA, electronic measuring automation) in order to finally consider its implementation on a fast newgeneration FPGA device. Results show an increment of the linear zone in the up-converter AM-AM curve, of about 15 dB