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

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

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

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

Scalable haloscopes for axion dark matter detection in the 30 µeV range with RADES

RADES (Relic Axion Detector Exploratory Setup) is a project with the goal of directly searching for axion dark matter above the 30μeV scale employing custom-made microwave filters in magnetic dipole fields. Currently RADES is taking data at the LHC dipole of the CAST experiment. In the long term, the RADES cavities are envisioned to take data in the BabyIAXO magnet. In this article we report on the modelling, building and characterisation of an optimised microwave-filter design with alternating irises that exploits maximal coupling to axions while being scalable in length without suffering from mode-mixing. We develop the mathematical formalism and theoretical study which justifies the performance of the chosen design. We also point towards the applicability of this formalism to optimise the MADMAX dielectric haloscopes.We thank Ciaran O’Hare for his generous and publicly available compilation of axion bounds https://github.com/cajohare /AxionLimits/. This work has been funded by the Spanish Ministerio de Economía, Industria y Competitividad – Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under project FPA-2016-76978, and was supported by the CERN Doctoral Studentship programme. The research leading to these results has received funding from the European Research Council and BD, JG and SAC acknowledge support through the European Research Council under grant ERC-2018-StG-802836 (AxScale project). IGI acknowledges also support from the European Research Council (ERC) under grant ERC-2017-AdG-788781 (IAXO+ project). JR has been supported by the Ramon y Cajal Fellowship 2012-10597, the grant PGC2018-095328-B-I00(FEDER/Agencia estatal de investigaci´on) and FSE-DGA2017-2019-E12/7R (Gobierno de Aragón/FEDER) (MINECO/FEDER), the EU through the ITN “Elusives” H2020-MSCA-ITN-2015/674896 and the Deutsche Forschungsgemeinschaft under grant SFB-1258 as a Mercator Fellow. CPG was supported by PROMETEO II/2014/050 of Generalitat Valenciana, FPA2014-57816-P of MINECO and by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreements 690575 and 674896. AM is supported by the European Research Council under Grant No. 742104. We wish also to thank our colleagues at CAST and at CERN, in particular Marc Thiebert from the coating lab, Sergio Calatroni for many useful discussions, as well as the whole team of the CERN Central Cryogenic Laboratory for their support and advice in specific aspects of the project

Do Air Pollution and Meteorological Variables Have a Bearing on COVID-19 Mortality? Benchmarking of Time Series between the First and Second Waves in Nine Spanish Provinces

[ES] Algunos contaminantes como las PM10, el NO2 o el O3 tienen influencia en la salud de las personas, tal y como apuntan numerosos estudios al relacionarse con la mortalidad tanto a corto como a largo plazo. Se estudió una muestra de 9 de las 52 provincias españolas. Se realizaron modelos lineales generalizados (GLM) con link Poisson en los periodos de la primera y segunda ola entre los valores medios diarios de las variables independientes (PM10, NO2 y O3 como contaminantes atmosféricos y variables meteorológicas (temperatura máxima diaria y humedad absoluta)) y la variable dependiente (tasa de mortalidad por COVID-19, TMC) durante la primera y segunda ola. Entre las variables independientes y la dependiente se establecieron los retardos estadísticamente significativos (lag). A partir de los estimadores obtenidos en los GLM se calcularon los riesgos relativos asociados, por aumentos de 10 μg/m3 para los contaminantes atmosféricos, 1ºC para la temperatura máxima y 1 g/m3 para la humedad absoluta. Los resultados muestran que existe una mayor asociación del NO2 con la TMC que para el resto de los contaminantes atmosféricos. Las variables meteorológicas examinadas no han presentado una asociación robusta entre ambas olas, lo que indica un rol menor en relación a la TMC. En conclusión, la contaminación atmosférica por NO2 y PM10 presentan una asociación estadísticamente significativa con la TMC, aunque limitada y sub[EN] Some pollutants like PM10, NO2 and O3 are detrimental to people’s health, as numerous studies have shown, and they are related to short-term and long-term mortality. A sample of 9 out of the 52 Spanish provinces was studied. Generalized linear models (GLM) with a Poisson link function were developed during the time periods corresponding to the first and second waves of the daily average values of the independent variables (PM10, NO2 and O3, as atmospheric pollutants, and meteorological variables such as the daily maximum temperature and the absolute humidity) versus the dependent variable (COVID-19 mortality rate, or CMR) during said first and second waves. Statistically significant lags between the independent variables and the dependent variable were established. The associated relative risks were calculated from the estimators obtained in the GLMs, with increases of 10 μg/m3 for atmospheric pollutants, 1°C for the maximum temperature and 1 g/m3 for the absolute humidity. The results show that NO2 has a stronger relationship with the CMR than the other air pollutants. The meteorological variables examined did not show a robust relationship between both waves, which indicates that they played a minor role in the CMR. In conclusion, air pollutants such as to NO2 and PM10 had a statistically significant relationship with the CMR, although it is limited and subordinate to other factors such as the public health measures that were taken, the presence of comorbidities and the age of the patient.[PT] Alguns poluentes como as PM10, o NO2 ou o O3 têm influência na saúde das pessoas, como apontam numerosos estudos, pois estão relacionados com a mortalidade tanto a curto como a longo prazo. Foi estudada uma amostra de 9 das 52 províncias espanholas. Realizaram-se modelos lineares generalizados (GLM) com link Poisson nos períodos da primeira e segunda vagas entre os valores médios diários das variáveis independentes (PM10, NO2 e O3 como poluentes atmosféricos e temperatura máxima diária e humidade como condições meteorológicas) e da variável dependente (taxa de mortalidade por Covid-19, TMC) durante a primeira e segunda vagas. Entre as variáveis independentes e a dependente foram estabelecidos atrasos estatisticamente significativos (lag). A partir dos estimadores obtidos nos GLM calcularam-se os riscos relativos associados, para aumentos de 10 μg/m3 para poluentes atmosféricos, 1 °C para temperatura máxima e 1 g/m3 para humidade absoluta. Os resultados mostram que existe uma maior associação do NO2 com a TMC do que para o resto dos poluentes atmosféricos. As variáveis meteorológicas examinadas não apresentaram uma associação robusta entre ambas as vagas, o que indica um papel menor em relação à TMC. Em conclusão, a poluição atmosférica por NO2 e PM10 apresenta associação estatisticamente significativa com a TMC, embora seja limitada e subordinada a outros fatores como as medidas de saúde pública adotadas, a presença de comorbilidades e a idade do paciente

Maximal respiratory pressure reference equations in healthy adults and cut-off points for defining respiratory muscle weakness

[Abstract] Introduction: Maximal inspiratory and expiratory pressures (PImax/PEmax) reference equations obtained in healthy people are needed to correctly interpret respiratory muscle strength. Currently, no clear cut-off points defining respiratory muscle weakness are available. We aimed to establish sex-specific reference equations for PImax/PEmax in a large sample of healthy adults and to objectively determine cut-off points for respiratory muscle weakness. Methods: A multicentre cross-sectional study was conducted across 14 Spanish centres. Healthy non-smoking volunteers aged 18-80 years stratified by sex and age were recruited. PImax/PEmax were assessed using uniform methodology according to international standards. Multiple linear regressions were used to obtain reference equations. Cut-off points for respiratory muscle weakness were established by using T-scores. Results: The final sample consisted of 610 subjects (314 females; 48 [standard deviation, SD: 17] years). Reference equations for PImax/PEmax included body mass index and a squared term of the age as independent variables for both sexes (p<0.01). Cut-off points for respiratory muscle weakness based on T-scores ≥2.5 SD below the peak mean value achieved at a young age were: 62 and 83cmH2O for PImax and 81 and 109cmH2O for PEmax in females and males, respectively. Conclusion: These reference values, based on the largest dataset collected in a European population to date using uniform methodology, help identify cut-off points for respiratory muscle weakness in females and males. These data will help to better identify the presence of respiratory muscle weakness and to determine indications for interventions to improve respiratory muscle function

First results of the CAST-RADES haloscope search for axions at 34.67 μeV

We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67μeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaγ & 4 × 10−13 GeV−1 over a mass range of 34.6738μeV < ma < 34.6771μeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25μeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavitiesWe wish to thank our colleagues at CERN, in particular Marc Thiebert from the coating lab, as well as the whole team of the CERN Central Cryogenic Laboratory for their support and advice in speci c aspects of the project. We thank Arefe Abghari for her contributions as the project's summer student during 2018. This work has been funded by the Spanish Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under project FPA-2016-76978-C3-2-P and PID2019-108122GB-C33, and was supported by the CERN Doctoral Studentship programme. The research leading to these results has received funding from the European Research Council and BD, JG and SAC acknowledge support through the European Research Council under grant ERC-2018-StG-802836 (AxScale project). BD also acknowledges fruitful discussions at MIAPP supported by DFG under EXC-2094 { 390783311. IGI acknowledges also support from the European Research Council (ERC) under grant ERC-2017-AdG-788781 (IAXO+ project). JR has been supported by the Ramon y Cajal Fellowship 2012-10597, the grant PGC2018-095328-B-I00(FEDER/Agencia estatal de investigaci on) and FSE-GA2017-2019-E12/7R (Gobierno de Aragón/FEDER) (MINECO/FEDER), the EU through the ITN \Elusives" H2020-MSCA-ITN-2015/674896 and the Deutsche Forschungsgemeinschaft under grant SFB-1258 as a Mercator Fellow. CPG was supported by PROMETEO II/2014/050 of Generalitat Valenciana, FPA2014-57816-P of MINECO and by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreements 690575 and 674896. AM is supported by the European Research Council under Grant No. 742104. Part of this work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344

Psychometric characteristics of the Spanish version of instruments to measure neck pain disability

Background: The NDI, COM and NPQ are evaluation instruments for disability due to NP. There was no Spanish version of NDI or COM for which psychometric characteristics were known. The objectives of this study were to translate and culturally adapt the Spanish version of the Neck Disability Index Questionnaire (NDI), and the Core Outcome Measure (COM), to validate its use in Spanish speaking patients with non-specific neck pain (NP), and to compare their psychometric characteristics with those of the Spanish version of the Northwick Pain Questionnaire (NPQ). Methods: Translation/re-translation of the English versions of the NDI and the COM was done blindly and independently by a multidisciplinary team. The study was done in 9 primary care Centers and 12 specialty services from 9 regions in Spain, with 221 acute, subacute and chronic patients who visited their physician for NP: 54 in the pilot phase and 167 in the validation phase. Neck pain (VAS), referred pain (VAS), disability (NDI, COM and NPQ), catastrophizing (CSQ) and quality of life (SF-12) were measured on their first visit and 14 days later. Patients' self-assessment was used as the external criterion for pain and disability. In the pilot phase, patients' understanding of each item in the NDI and COM was assessed, and on day 1 test-retest reliability was estimated by giving a second NDI and COM in which the name of the questionnaires and the order of the items had been changed. Results: Comprehensibility of NDI and COM were good. Minutes needed to fill out the questionnaires [median, (P25, P75)]: NDI. 4 (2.2, 10.0), COM: 2.1 (1.0, 4.9). Reliability: [ICC, (95%CI)]: NDI: 0.88 (0.80, 0.93). COM: 0.85 (0.75,0.91). Sensitivity to change: Effect size for patients having worsened, not changed and improved between days 1 and 15, according to the external criterion for disability: NDI: -0.24, 0.15, 0.66; NPQ: -0.14, 0.06, 0.67; COM: 0.05, 0.19, 0.92. Validity: Results of NDI, NPQ and COM were consistent with the external criterion for disability, whereas only those from NDI were consistent with the one for pain. Correlations with VAS, CSQ and SF-12 were similar for NDI and NPQ (absolute values between 0.36 and 0.50 on day 1, between 0.38 and 0.70 on day 15), and slightly lower for COM (between 0.36 and 0.48 on day 1, and between 0.33 and 0.61 on day 15). Correlation between NDI and NPQ: r = 0.84 on day 1, r = 0.91 on day 15. Correlation between COM and NPQ: r = 0.63 on day 1, r = 0.71 on day 15. Conclusion: Although most psychometric characteristics of NDI, NPQ and COM are similar, those from the latter one are worse and its use may lead to patients' evolution seeming more positive than it actually is. NDI seems to be the best instrument for measuring NP-related disability, since its results are the most consistent with patient's assessment of their own clinical status and evolution. It takes two more minutes to answer the NDI than to answer the COM, but it can be reliably filled out by the patient without assistance