Revival of an abandoned telescope: the Boller and Chivens Bochum 0.61-metre telescope of Universidad de Valparaiso

In 2015 the Institute of Physics and Astronomy of the Universidad de Valpara\'iso in Chile received as a donation the Bochum 0.61-meter telescope. Here we preset the ongoing project to convert this senior member of La Silla Observatory to modern standards aiming at performing state-of-art science, as well as teaching and outreach. Firstly, the site characterization was performed in order to verify the observing conditions. The preliminary results were auspicious in relation to the nights available for observation. In early 2016 began the transfer work form La Silla Observatory to the new site of operations. The actual status of the telescope was analyzed and an upgrade plan was proposed to make it usable remotely using a web-based telescope control system developed in Chile by ObsTech SpA. Future upgrade and scientific collaboration will be discussed based on the site characterization and technical studies regarding the potential for new instrumentation.Comment: 8 pages, SPIE Proceedings Volume 10700, Ground-based and Airborne Telescopes VII; 107002X (2018). Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United State

Buck derived converters based on gallium nitride devices for Envelope Tracking applications

Envelope tracking (ET) is a technique designed to enhance the efficiency of radio frequency power amplifiers (RF PA). It is based on providing the voltage to the RF PA with variations that mimic the shape of the envelope of the communication signal that the RF PA is processing. As the bandwidth of these signals can be around several megahertz, the switching frequency of the switching mode power supply designed for ET applications has to be very high. The good switching characteristics of Gallium Nitride devices makes them suitable for this application. This paper presents two multiphase converters to be used as envelope modulators in envelope tracking application

Reproducing single-carrier digital modulation schemes for VLC by controlling the first switching harmonic of the dc-dc power converter output voltage ripple

A DC-DC power converter based on a two-phase synchronous buck converter that reproduces single-carrier digital modulation schemes by controlling the first switching harmonic of the output voltage ripple is presented in this work. The DC-DC power converter carries out both the lighting and the transmission functionalities of Visible Light Communication (VLC) transmitters. Control of both the amplitude and the phase of sinusoidal currents injected towards High-Brightness LEDs (HB-LEDs) enables the use of efficient modulation schemes such as Quadrature Amplitude Modulation (QAM), Carrier-less Amplitude and Phase modulation (CAP), Amplitude-Shift Keying (ASK) and Phase-Shift Keying (PSK). These modulation schemes achieve higher spectral efficiency (i.e. more data can be transmitted using the same bandwidth) than previously proposed modulation schemes performed by VLC transmitters based on the use of DC-DC power converters. To the author's knowledge, the ratio between the bit rate achieved and the switching frequency of the DC-DC power converter presented in this paper is the highest that can be found in literatur

Hybrid Quantum/Classical simulations of the vibrational relaxation of the Amide I mode of N-methylacetamide in D2O solution

Hybrid quantum/classical molecular dynamics (MD) is applied to simulate the vibrational relaxation (VR) of the amide I mode of deuterated N-methylacetamide (NMAD) in aqueous (D2O) solution. A novel version of the vibrational molecular dynamics with quantum transitions (MDQT) treatment is developed in which the amide I mode is treated quantum mechanically while the remaining degrees of freedom are treated classically. The instantaneous normal modes of the initially excited NMAD molecule (INM0) are used as internal coordinates since they provide a proper initial partition of the system in quantum and classical subsystems. The evolution in time of the energy stored in each individual normal mode is subsequently quantified using the hybrid quantum-classical instantaneous normal modes (INMt). The identities of both the INM0s and the INMts are tracked using the equilibrium normal modes (ENMs) as templates. The results extracted from the hybrid MDQT simulations show that the quantum treatment of the amide I mode accelerates the whole VR process versus pure classical simulations and gives better agreement with experiments. The relaxation of the amide I mode is found to be essentially an intramolecular vibrational redistribution (IVR) process with little contribution from the solvent, in agreement with previous theoretical and experimental studies. Two well-defined relaxation mechanisms are identified. The faster one accounts for ≈40% of the total vibrational energy that flows through the NMAD molecule and involves the participation of the lowest frequency vibrations as short-life intermediate modes. The second and slower mechanism accounts for the remaining ≈60% of the energy released and is associated to the energy flow through specific mid-range and high-frequency modes.Fil: Bastida, Adolfo. Universidad de Murcia; EspañaFil: Soler, Miguel A.. Universidad de Murcia; EspañaFil: Zúñiga, José. Universidad de Murcia; EspañaFil: Requena, Alberto. Universidad de Murcia; EspañaFil: Kalstein, Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Fernández Alberti, Sebastián. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

A linear assisted switching envelope amplifier for a UHF polar transmitter

Spectrally efficient wireless communication standards impose stringent linearity specifications, which would require traditional IQ transmitters to operate with back-offed and power inefficient linear RF power amplifiers (PAs). In order to overcome such a significant limitation, alternative architectures have been proposed, as those based on the envelope elimination and restoration technique. An example of the application of this technique is the polar transmitter. In this paper, a UHF polar transmitter is presented, combining switching and linear stages in the envelope amplifier as to achieve both wide bandwidth and high efficiency, when drain modulating a GaN HEMT Class E RF PA. Several tests, using EDGE, TETRA, and WCDMA standards have been performed with good results.This work was supported by the Spanish Ministries MICINN and MINECO through the FEDER cofunded Project TEC2011-29126-C03-01, Consolider Project CSD2008-00068, Consolider Project RUECSD2009-00046, and Project DPI2010-21110-C02-01

Power Efficient VLC Transmitter Based on Pulse-Width Modulated DC-DC Converters and the Split of the Power

Visible Light Communication (VLC) has gained relevance during the last years. It consists in using High-Brightness LEDs (HB-LEDs) both for lighting and for transmitting information changing the light intensity rapidly. However, there are some bottlenecks that are slowing down the deployment of this technology. One of the most important problems is that the HB-LED drivers proposed for addressing high data rates in VLC achieve poor power efficiency. Since these HB-LED drivers must be able to reproduce fast current waveforms, the use of Linear Power Amplifiers (LPAs) has been adopted, which clearly damages the power efficiency of HB-LED lighting. In order to alleviate this problem, a HB-LED driver made up of two DC-DC power converters is presented in this work. One of them is responsible for performing the communication functionality by operating at high switching frequency (10 MHz), whereas the second converter fulfills the illumination functionality by ensuring a certain biasing point. The split of the power allows us to minimize the power delivered by the fast-response DC-DC power converter, which suffers from high switching losses. Thus, the overall efficiency can be maximized for each particular communication scenario and for scenarios with changing condition

Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMCdc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMCdc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMCdc-dc are presented: increasing the order of the SMCdc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10Wand power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lightin

On the Role of Power Electronics in Visible Light Communication

The continuous demand of increasing data rates provided by wireless communication systems is contributing to saturating the RF spectrum. Visible Light Communication (VLC) systems aim to alleviate this congestion by using the visible light spectrum. These systems have been proposed to make use of High-Brightness LEDs (HB-LEDs) not only for lighting, but also for transmitting information by rapidly changing the intensity of the emitted light. A critical issue is that VLC requires a fast HB-LED driver in order to reproduce the target light intensity waveforms, which can include components of several MHz. Consequently, the HB-LED drivers proposed to date are based on the use of an RF Power Amplifier (RFPA). These devices provide the required speed, but suffer from very high power losses. To overcome this drawback, different solutions based on the use of fast-response DC/DC converters are presented in this paper. Several DC/DC converters, either to be used instead of an RFPA or to help an RFPA to achieve high efficiency, are thus analysed. The proposed HB-LED drivers enable the implementation of VLC transmitters without sacrificing one of the most important advantages of HB-LED lighting, namely its high power efficienc

Power-Efficient VLC Transmitter Able to Reproduce Multi-Carrier Modulation Schemes by Using the Output Voltage Ripple of the HB-LED Driver

2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL), 25-28 junio, Padua (Italia)Visible Light Communication (VLC) consists in using High-Brightness LEDs (HB-LEDs) not only for lighting, but also for transmitting information by changing the light intensity rapidly. One of the most important problems of VLC is that the HB-LED drivers that have been proposed for achieving the highest bit rates offer low power efficiency. The reason is that since these HB-LED drivers must be able to reproduce fast current waveforms, the use of Linear Power Amplifiers (LPAs) has been adopted, which damages the power efficiency of HB-LED lighting. To the author’s knowledge, there is only one approach reported in the literature that is able to reproduce the most recommended modulation schemes by using a power efficient HB-LED driver. However, since it is based on the use of pulse-width modulated dc-dc power converters, the required switching frequency is between 3 and 6 times higher than the maximum frequency of the communication signal. As a result, the approach suffers from high switching losses when the highest bandwidths are addressed. A method for reproducing the most recommended modulation schemes by modulating both the amplitude and the phase of the output voltage ripple is presented in this work. The major benefits are the high efficiency, the simplicity and the lower switching frequency required for the implementatio

Designing single-stage power factor correctors and LC passive filters to comply with the new version of the IEC 1000-3-2 regulations

The design of low-cost power supplies is influenced by the regulations on the low-frequency harmonic content in the line. As IEC 1000-3-2 regulations have just been modified, the design procedure of low-cost power supplies should also be modified. According to the new version of the above-mentioned regulations, many power supplies classified as Class D in the past are classified as Class A now. This fact allows a remarkable saving in the sue of the reactive elements used to reduce the line harmonics if they have been properly designed. The minimum values of the magnetic elements used in two well-known PFC solutions (one is an S2PFC and the other is a passive fdter) have been obtained in this paper for equipment classified in both the new Class A and the new Class D and for any power level between 75W and 600W