Design and development of a technological demonstrator for the study of high dynamics GNSS receivers

[ES] En el marco de esta tesis se van a estudiar, principalmente, los efectos del movimiento de alta dinámica en receptores de Sistemas Globales de Navegación por Satélite (GNSS). El término alta dinámica es un término utilizado para referirse al movimiento de los vehículos en los que van embarcados receptores GNSS, los cuales se mueven lo suficientemente rápido como para causar un gran desplazamiento en frecuencia de la portadora debido al efecto Doppler. Se identificarán los problemas inherentes a este tipo de entornos y se estudiarán y propondrán soluciones. Para poder efectuar el estudio de estos fenómenos, se diseñará un demostrador tecnológico (conjunto de hardware y software para prueba y prototipado de tecnologías) en el que desarrollar el estudio de los casos de interés. Con el fin de trabajar en un entorno repetible, se utilizará un generador de señal GNSS. La señal generada se traslada a un receptor de radiofrecuencia definido por software, Software Defined Radio (SDR). Este tipo de receptor únicamente se encarga de digitalizar la señal de entrada y de llevar las muestras digitales a un ordenador, de modo que todo el procesado de señal se implementa en dicho ordenador. Este esquema de trabajo es ideal habida cuenta de su simplicidad y flexibilidad. Dicha flexibilidad conlleva la posibilidad de sintonizar el demostrador para poder estudiar una amplia gama de arquitecturas de receptor GNSS. Una vez se haya ensamblado el demostrador, se comprobará su correcto funcionamiento en escenarios conocidos usando los algoritmos más utilizados a día de hoy en receptores GNSS. Asegurado el correcto funcionamiento, se comparará el rendimiento de algoritmos de referencia con los algoritmos a estudiar y se extraerán conclusiones.[CA] En aquest treball s'estudiaran, principalment, els efectes del moviment d'alta dinámica en receptors de Navegació per Satèl.lit GNSS (Global Navigation Satellite System). La denominació alta dinámica, s'utilitza per a descriure el moviment dels vehicles dins dels quals hi han receptors GNSS. El moviment d'aquests vehicles és suficientment ràpid com per a causar un gran desplaçament en freqüència de la freqüència portadora. Aquest desplaçament és consqüència de l'efecte Doppler. S'identificaran els problemes inherents d'aquest tipus de entorns GNSS i es propsararàn solucions. Per a estudiar l'efecte de l'alta dinàmica, es dissenyarà un demostrador tecnològic (conjunt de maquinari i software per a proves i prototipat de tecnologies) en que es pot desenvolupar l'estudi dels casos d'interès. Amb l'objectiu d'aconseguir treballar en un entorn repetible s'utilitzarà un generador de senyal GNSS. El senyal es processarà mitjançant un receptor SDR (Software Defined Radio). Aquest tipus de receptor s'encarrega del processat que fa un receptor GNSS en un PC. Aquesta filosofia de treball és idónia per la seua flexibilitat i simplicitat. Quan s'haja ensamblat el demostrador, és comprovarà el seu correct funcionament en escenaris de prova utilitzant els algoritmes implementats en receptors GNSS comercials. En aquest moment, el demostrador estarà preparat per a estudiar el casos d'alta dinàmica, que és l'objectiu fonamental d'aquest treball.[EN] The study of the effects of the high dynamics on Global Navigation Satellite System (GNSS) receivers constitute the main matter of study in this work. The term high dynamics refers to the movement of vehicles that carry GNSS embedded receivers, which move fast enough to generate a large carrier frequency drift caused by the Doppler effect. The problems linked to these environments will be characterized and solutions to counteract possible signal impairments will be discussed. In order to correctly characterize these problems, a technological demonstrator (set of hardware components interacting with software tools enabling fast prototyping) will be designed and constructed. Using this technological demonstrator, different case studies will be developed. With the aim of achieving experimental repeatability, a GNSS signal generator will be used. The generated GNSS signal is fed to a Software Defined Radio (SDR) GNSS receiver. This receiver type is in charge of digitizing the analog RF signal and carrying the resulting samples to a computer in which signal processing tasks implementing the functions of GNSS receivers, take place. The main advantage linked to the usage of this work scheme is that by changing the software part, different receiver architectures can be implemented in a simple manner. Furthermore, by taking advantage of the flexible architecture it is possible to tune the detector in such a manner that it is possible to implement many different architecture types. Once the technological demonstrator is assembled, tests to assure its correct operation will be conducted by performing comparisons with the behaviour of well-known GNSS receivers in known scenarios. Later on, comparative tests using signals from high dynamics scenarios will take place. Insight and analysis of comparative performance will be given.Alcaide Guillén, C. (2019). Design and development of a technological demonstrator for the study of high dynamics GNSS receivers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/131697TESI

A New Reference Sample for High-Frequency Multipactor Testing

[EN] Multipactor (MP) is a high-power effect severely limiting the performance of satellite communication links. A reference sample is normally used in the experimental setups for MP testing in order to verify its correct operation. However, the low gaps required for high frequencies jeopardize the manufacturability of the devices traditionally used for this purpose. A new reference sample, based on a stepped-impedance resonator (SIR), is proposed in this letter. The key design considerations are also outlined. A prototype operating between 17 and 18 GHz has been manufactured and tested, proving the novel structure allows higher gaps, and is, thus, suitable for higher frequency bands.This work was supported in part by the Ministerio de Ciencia e Innovacion (Spanish Government) under Research and Development Project PID2019-103982RB-C41, in part by the European Space Agency(ESA) through several research and development activities, and in part by the ESA-VSC European High Power RF and Space Materials Laboratories for contributing with its installations through the European Regional Development Fund. The work of Pablo Gonzalez was supported by the FPU Fellowship ofthe Ministerio de Educacion, Cultura y Deporte under Grant FPU17/02901.González-Santatecla, P.; Smacchia, D.; Alcaide-Guillén, C.; Soto Pacheco, P.; Rodríguez Pérez, AM.; Morro, JV.; Mata-Sanz, R.... (2023). A New Reference Sample for High-Frequency Multipactor Testing. IEEE Microwave and Wireless Technology Letters. 33(6):675-678. https://doi.org/10.1109/LMWT.2023.323941967567833

High Power RF Discharge Detection Technique Based on the In-Phase and Quadrature Signals

[EN] High power radio frequency (RF) breakdown testing is a subject of great relevance in the space industry, due to the increasing need of higher transmission power and smaller devices. This work presents a novel RF breakdown detection system, which monitors the same parameters as the microwave nulling system but with several advantages. Where microwave nulling-a de facto standard in RF breakdown testing-is narrowband and requires continuous tuning to keep its sensitivity, the proposed technique is broadband and maintains its performance for any RF signal. On top of that, defining the detection threshold is cumbersome due to the lack of an international standardized criterion. Small responses may appear in the detection system during the test and, sometimes, it is not possible to determine if these are an actual RF breakdown or random noise. This new detection system uses a larger analysis bandwidth, thus reducing the cases in which a small response is difficult to be classified. The proposed detection method represents a major step forward in high power testing as it runs without human intervention, warning the operator or decreasing the RF power automatically much faster than any human operator.This work was supported in part by the "Ministerio de Ciencia e Innovacion," Spanish Government, under Project PID2019-103982RB-C41, and in part by the European High RF Power Space Laboratory of the European Space Agency and Val Space Consortium for contributing with its installations, Laboratory co-funded by the European Regional Development Fund-A way of making Europe.Monerris-Belda, O.; Cervera Marín, R.; Rodríguez Jodar, M.; Diaz-Caballero, E.; Alcaide Guillén, C.; Petit, J.; Boria Esbert, VE.... (2021). High Power RF Discharge Detection Technique Based on the In-Phase and Quadrature Signals. IEEE Transactions on Microwave Theory and Techniques. 69(12):5429-5438. https://doi.org/10.1109/TMTT.2021.312065754295438691

Genetic diversity and population structure of Pepino mosaic virus in tomato crops of Spain and Morocco

Pepino mosaic virus (PepMV, genus Potexvirus) is an emergent and highly infectious pathogen responsible for economically important diseases in tomato crops. An extensive survey of tomato plants showing PepMV-like symptoms was carried out in 2017 to study the PepMV genetic diversity and populations structure in different tomato-producing areas of Spain and Morocco. Molecular dot-blot hybridization analysis showed that virus populations from Spain and Morocco were mainly composed of isolates belonging to the Chilean 2 (CH2) strain, although isolates of the European (EU) strain were detected in significant proportions in Spanish populations, mainly in mixed infections. A few isolates of the American (US1) strain were also detected in Tenerife (Canary Islands, Spain) crops. Eighty-five isolates were randomly selected and sequenced in the genomic region that encodes the triple gene block and capsid protein genes. Our phylogenetic and population genetics analyses confirmed the presence of the CH2, EU and US1 PepMV strains. Despite the high genetic similarity observed within populations, variants were maintained at low frequency under purifying selection, and differentiation among more geographically distant locations was identified, with potential gene flow contributing to the shaping of the PepMV populations structur

Alterations of perineuronal nets in the dorsolateral prefrontal cortex of neuropsychiatric patients

Background: Alterations in the structure and physiology of interneurons in the prefrontal cortex (PFC) are important factors in the etiopathology of different psychiatric disorders. Among the interneuronal subpopulations, parvalbumin (PV) expressing cells appear to be specially affected. Interestingly, during development and adulthood the connectivity of these interneurons is regulated by the presence of perineuronal nets (PNNs), specialized regions of the extracellular matrix, which are frequently surrounding PV expressing neurons. Previous reports have found anomalies in the density of PNNs in the PFC of schizophrenic patients. However, although some studies have described alterations in PNNs in some extracortical regions of bipolar disorder patients, there are no studies focusing on the prefrontocortical PNNs of bipolar or major depression patients. For this reason, we have analyzed the density of PNNs in post-mortem sections of the dorsolateral PFC (DLPFC) from the Stanley Neuropathology Consortium, which includes controls, schizophrenia, bipolar and major depression patients. Results: We have not observed differences in the distribution of PV+ cells or PNNs, or in the percentage of PV+ interneurons surrounded by PNNs. The density of PV+ interneurons was similar in all the experimental groups, but there was a significantly lower density of PNNs in the DLPFC of bipolar disorder patients and a tendency towards a decrease in schizophrenic patients. No differences were found when evaluating the density of PV+ cells surrounded by PNNs. Interestingly, when assessing the influence of demographic data, we found an inverse correlation between the density of PNNs and the presence of psychosis. Conclusions: The present results point to prefrontocortical PNNs and their role in the regulation of neuronal plasticity as putative players in the etiopathology of bipolar disorder and schizophrenia. Our findings also suggest a link between these specialized regions of the extracellular matrix and the presence of psychosis

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AimThe SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery.MethodsThis was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin.ResultsOverall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P ConclusionOne in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease