An Adaptive Phase Alignment Algorithm for Cartesian Feedback Loops

An adaptive algorithm to correct phase misalignments in Cartesian feedback linearization loops for power amplifiers has been presented. It yields an error smaller than 0.035 rad between forward and feedback loop signals once convergence is reached. Because this algorithm enables a feedback system to process forward and feedback samples belonging to almost the same algorithm iteration, it is suitable to improve the performance not only of power amplifiers but also any other digital feedback system for communications systems and circuits such as all digital phase locked loops. Synchronizing forward and feedback paths of Cartesian feedback loops takes a small period of time after the system starts up. The phase alignment algorithm needs to converge before the feedback Cartesian loop can start its ideal behavior. However, once the steady state is reached, both paths can be considered synchronized, and the Cartesian feedback loop will only depend on the loop parameters (open-loop gain, loop bandwidth, etc.). It means that the linearization process will also depend only on these parameters since the misalignment effect disappears. Therefore, this algorithm relieves the power amplifier linearizer circuit design of any task required for solving phase misalignment effects inherent to Cartesian feedback systems. Furthermore, when a feedback Cartesian loop has to be designed, the designer can consider that forward and feedback paths are synchronized, since the phase alignment algorithm will do this task. This will reduce the simulation complexity. Then, all efforts are applied to determining the suitable loop parameters that will make the linearization process more efficient

Antennas' correlation influence on the GMD-assisted MIMO channels performance

The use of multiple antennas in MIMO (multiple-input multiple-output) systems at both the transmit and receive sides produces the effect known as antennas correlation which impact the overall channel performance, throughput and bit-error rate (BER). The geometric mean decomposition (GMD) is a signal processing technique which can be used to process transmit and receive signals in MIMO channels. The GMD pre- and post-procesing in conjunction with dirty-paper precoding shows some advantages over the popular singular value decomposition (SVD) technique which provides GMD-assisted MIMO systems a superior performance particularly when the channel is affected by antennas correlation. This paper analyses the impact of antennas correlation on the performance of GMD-assisted wireless MIMO channels highlighting the advantages over SVD-assisted ones

Amplificador de Potencia Clase-S para Transmisor EER

A Class-S power amplifier for an EER transmitter is shown in this paper. Simulations and measurements on a circuit prototype are presented showing good agreement. The amplifier is based on MOSFET technology both for the power stage and driver. Pulse Width Modulation driving signal required by the amplifier is generated by means of a in-house designed DSP board. Up to 50W output peak power can be delivered to the RF power amplifier (Class-S amplifier load) at 86 % power-added efficiency while harmonic distortion is below 30 dBc and third order intermodulaction products remain well below 34 dBc

Amplificador de Potencia de Alto Rendimiento para Transmisores EER

Se presenta un amplificador de potencia de alto rendimiento específicamente diseñado para aplicaciones EER (Envelope Elimination Restoration) en transmisores de HF. El amplificador se compone de dos subsistemas: Un amplificador clase-E de banda ancha para HF (B = 40%, POUT = 50W @ 7.5 MHz, ηOV > 90%) excitado por un driver también de banda ancha que amplifica la componente de fase de la señal y un amplificador de envolvente derivado de un amplificador clase-D de audio (o clase-S) que presenta un rendimiento total mejor que el 90% para la mayor parte de su margen de salida y un nivel de intermodulación IMD de -30 dBc (prueba de dos tonos). El amplificador completo es capaz de obtener un rendimiento total ηOV > 80% con una potencia de salida de pico PEP = 50W @ 7.5 MHz en un ancho de banda fraccional B = 40%. Antes de realimentación el amplificador presenta un valor de linealidad para una prueba de dos tonos comprendido entre -28 dBc y -35 dBc

Análisis de un Transmisor Digital de HF Basado en la Técnica de Eliminación y Recuperación de Envolvente

An HF EER (Envelope Elimination and Restoration) Digital Transmitter simulation is presented in this paper. Effects that increase the IMD (Intermodulation Distortion) levels in an EER system are described and simulated. Basically, the main effects are the limitation of the envelope bandwidth, AMAM distortion and AM-PM distortion at the power amplifier stage, and the delay between the envelope and phase branches. These effects deteriorate the EER Digital Transmitter linearity. By means of this simulation, it is shown the contribution of every effect to the global IMD. The system was tested with a DSB (Double Side Band) signal. As a result, with an envelope bandwidth of 2kHz and a delay between branches smaller than 5 μs, more than 60 dB of intermodulation product rejection was achieved. It has also been developed an algorithm which determines the delay between branches with an error smaller than 0.035o when the signal is a non-modulated tone

Nueva técnica de modulación de excitación para sistemas EER

This paper shows a novel drive modulation technique applied to a high power, high efficiency, linear Envelope Elimination and Restoration (EER) amplifier for L-Band. It comprises a mixed-mode suboptimum Class-E / Class-A wideband RF amplifier based on a dual GaN HEMT for RF carrier amplification and a high efficiency, high switching frequency, multi-phase, buck power converter based on Silicon LDMOS transistors to work as a modulator (or envelope amplifier). The linearity and power gain for this EER amplifier is improved by means of a new digital drive modulation technique and digital predistortion (DPD) to achieve linearity performances equivalent or better than Class-AB amplifiers of similar output power level and frequency band but exhibiting much higher efficiency. This EER amplifier provides 120W peak output power at the L-band without any adjustment. In a two tone test, measured third and fifth-order intermodulation products were -45 dBc and -49 dBc, respectively, reaching 67.5 % maximum PAE

Adaptación de la asignatura “tecnología de computadores” al espacio europeo de educación superior.

Este artículo describe la experiencia práctica en la adaptación de la asignatura de Tecnología de Computadores a las nuevas exigencias del EEES (Espacio Europeo de Educación Superior). Esta adaptación se ha realizado dentro del contexto de las acciones emprendidas por la ACSUG (Agencia para la Calidad del Sistema Universitario de Galicia) y la UDC (Universidad de A Coruña) como parte del proceso de convergencia hacia el EEES. La asignatura objeto de la adaptación es una asignatura troncal que se imparte en el primer curso de la titulación de Ingeniería Técnica en Informática de Gestión de la Facultad de Informática de la UDC. Los contenidos de la asignatura se desarrollaban tradicionalmente utilizando fundamentalmente la clase magistral, apoyada por clases de problemas y algunas sesiones prácticas de montaje de circuitos digitales en el laboratorio. La adaptación de la docencia se ha realizado con el objetivo de centrarla más en el alumno, definiendo de forma clara las competencias que estos desarrollarán al cursarla y proponiendo actividades que faciliten su desarrollo. El objetivo de este trabajo es describir como se realizó la adaptación de dicha asignatura, qué materiales y actividades se prepararon, qué dificultades se encontraron, cuáles fueron los objetivos conseguidos y cuál fue la respuesta de alumnos y profesores ante tales cambios.Este artigo descreve a experiência prática na adaptação da disciplina de Tecnologia dos Computadores com as novas exigências do EEES (Espaço Europeu de Ensino Superior). Esta adaptação foi feita no contexto das UDC (Universidade da Corunha) no processo de implementação do EEES. A disciplina objecto da adaptação é uma disciplina obrigatória ministrada no primeiro curso do plano de estudos da Engenharia Técnica em Informática de Gestão da Faculdade de Informática da U circuitos digitais no laboratório. A adaptação foi feita com o objectivo de centrar mais o ensino nos estudantes, definindo claramente as competências que eles vam adquirir e propondo actividades que facilitem o seu desenvolvimento. O objectivo deste artigo é descrever a adaptação realizada na cadeira, que materiais e actividades foram propostas, que dificuldades foram resolvidas, quais os objectivos obtidos e qual a resposta dos estudantes e professores diante de tais mudanças.This article describes the practical experience in the adaptation of the subject of Computer Technology to the new requirements of the EHEA (European Higher Education Area). This adaptation has been conducted within the context of the actions undertaken by the ACSUG (Agency for the quality of the University System of Galicia) and the UDC (University of A Coruña) as part of the process of convergence toward the EHEA. The course's subject of adaptation is a core subject that is taught in the first course of the degree in technical engineering degree in Computer Management from the Faculty of Informatics of the UDC. The content of the subject is traditionally developed using primarily the masterclass, supported by classes of problems and some practical sessions of mounting of digital circuits in the laboratory. The adaptation of teaching has been done with the aim to focus more on the student, by defining clear competencies that they develop the desirable and proposing activities that facilitate their development. The objective of this paper is to describe how you conducted the adaptation of this subject, materials and activities that were prepared, that difficulties were found, what were the goals achieved and what was the response of students and teachers before such changes

A multi reference point based index to assess and monitor European water policies from a sustainability approach

The scarcity of water resources is a serious problem that concerns governments and international institutions. The importance of water resources and the expectations of billions of people with serious water shortages and subsequent food shortages have made European water policy makers focus all their attention on the sustainability of water as a resource. In this paper we propose a new Water Sustainability Indicator based on a MultiReference methodology (WSI-MR) which permits modeling compensation between the analyzed criteria and provides a participative approach. The WSI-MR provides results based on 19 variables grouped into 5 dimensions: availability, access, resilience, good governance and economic capacity. The indicator was applied to assess water sustainability in 27 European countries. The results showed that Finland, the Netherlands, Sweden and the United Kingdom obtained the best global results in terms of weak water (compensatory) sustainability. Using a non-compensatory approach, no country gained acceptable results in terms of strong sustainability. Some subdimensions related to climate change and the state of freshwater resources were detected as especially vulnerable in all the analyzed countries. Finally, the study identified some eastern European countries with low GDP and good performance of availability and cost of water, where bad results in terms of governance and water productivity could jeopardize water sustainability in the event of a potential economic development, if these limitations are not addressed. In a context of economic and political instability, due to the current armed conflict in nearby countries such as Ukraine, it is especially important to pay attention to these countries, whose good governance indicators could worsen even more. The proposed indicator is useful to identify warning signs and can contribute to the improvement in decision-making processes and to monitoring international water policies

Multi-Tubular Reactor for Hydrogen Production: CFD Thermal Design and Experimental Testing

This study presents the Computational Fluid Dynamics (CFD) thermal design and experimental tests results for a multi-tubular solar reactor for hydrogen production based on the ferrite thermochemical cycle in a pilot plant in the Plataforma Solar de Almería (PSA). The methodology followed for the solar reactor design is described, as well as the experimental tests carried out during the testing campaign and characterization of the reactor. The CFD model developed for the thermal design of the solar reactor has been validated against the experimental measurements, with a temperature error ranging from 1% to around 10% depending on the location within the reactor. The thermal balance in the reactor (cavity and tubes) has been also solved by the CFD model, showing a 7.9% thermal efficiency of the reactor. CFD results also show the percentage of reacting media inside the tubes which achieve the required temperature for the endothermic reaction process, with 90% of the ferrite pellets inside the tubes above the required temperature of 900 C. The multi-tubular solar reactor designed with aid of CFD modelling and simulations has been built and operated successfullyFondo Europeo de Desarrollo Regional (FEDER) IPT- 2011-1323-920000Programa Operativo FEDER para Andalucía 2007–2013 RNM-612

High Efficiency Power Amplifier Based on Envelope Elimination and Restoration Technique

Due to complex envelope and phase modulation employed in modern transmitters it is necessary to use power amplifiers that have high linearity. Linear power amplifiers (classes A, B and AB) are commonly used, but they suffer from low efficiency especially if the transmitted signal has high peak to average power ratio (PAPR). Kahn's technique based on envelope elimination and restoration (EER) is based on idea that high efficiency power supply (envelope amplifier) could be used to modulate the envelope of high efficient non linear power amplifiers (classes D or E). This paper presents solutions for power amplifier that performs envelope modulation and class E amplifier that is used as a non linear amplifier. The envelope amplifier is implemented as a multilevel converter in series with linear regulator and can provide up to 100 W of instantaneous power and reproduce 2 MHz sine wave. The implemented Class E amplifier can operate at 120 MHz with efficiency near to 85%. The envelope amplifier and class E amplifier have been integrated and efficiency and linearity of the implemented transmitter has been measured and presente