Articles de revista
http://hdl.handle.net/2117/653
2024-03-19T13:34:40ZMicrostrip-fed 3D-printed H-sectorial horn phased array
http://hdl.handle.net/2117/373688
Microstrip-fed 3D-printed H-sectorial horn phased array
Zhou, Ivan; Pradell i Cara, Lluís; López Villegas, José María; Vidal Martínez, Neus; Albert Gali, Miquel; Jofre Roca, Lluís; Romeu Robert, Jordi
A 3D-printed phased array consisting of four H-Sectorial horn antennas of 200 g weight with an ultra-wideband rectangular-waveguide-to-microstrip-line transition operating over the whole LMDS and K bands (24.25–29.5 GHz) is presented. The transition is based on exciting three overlapped transversal patches that radiate into the waveguide. The transition provides very low insertion losses, ranging from 0.30 dB to 0.67 dB over the whole band of operation (23.5–30.4 GHz). The measured fractional bandwidth of the phased array including the transition was 20.8% (24.75–30.3 GHz). The antenna was measured for six different scanning angles corresponding to six different progressive phases α, ranging from 0° to 140° at the central frequency band of operation of 26.5 GHz. The maximum gain was found in the broadside direction α = 0°, with 15.2 dB and efficiency η = 78.5%, while the minimum was found for α = 140°, with 13.7 dB and η = 91.2%.
2022-09-29T14:14:21ZZhou, IvanPradell i Cara, LluísLópez Villegas, José MaríaVidal Martínez, NeusAlbert Gali, MiquelJofre Roca, LluísRomeu Robert, JordiA 3D-printed phased array consisting of four H-Sectorial horn antennas of 200 g weight with an ultra-wideband rectangular-waveguide-to-microstrip-line transition operating over the whole LMDS and K bands (24.25–29.5 GHz) is presented. The transition is based on exciting three overlapped transversal patches that radiate into the waveguide. The transition provides very low insertion losses, ranging from 0.30 dB to 0.67 dB over the whole band of operation (23.5–30.4 GHz). The measured fractional bandwidth of the phased array including the transition was 20.8% (24.75–30.3 GHz). The antenna was measured for six different scanning angles corresponding to six different progressive phases α, ranging from 0° to 140° at the central frequency band of operation of 26.5 GHz. The maximum gain was found in the broadside direction α = 0°, with 15.2 dB and efficiency η = 78.5%, while the minimum was found for α = 140°, with 13.7 dB and η = 91.2%.Increasing stratification as observed by satellite sea surface salinity measurements
http://hdl.handle.net/2117/366829
Increasing stratification as observed by satellite sea surface salinity measurements
Olmedo Casal, Estrella; Turiel Martínez, Antonio; González Gambau, Verónica; González Haro, Cristina; García Espriu, Aina; Gabarró Prats, Carolina; Portabella, Marcos; Corbella Sanahuja, Ignasi; Martín Neira, Manuel; Arias Ballesteros, Manuel; Catany, Rafael; Sabia, Roberto; Olivia, Roger; Scipal, Klaus
Changes in the Earth’s water cycle can be estimated by analyzing sea surface salinity. This variable refects the balance between precipitation and evaporation over the ocean, since the upper layers of the ocean are the most sensitive to atmosphere–ocean interactions. In situ measurements lack spatial and temporal synopticity and are typically acquired at few meters below the surface. Satellite measurements, on the contrary, are synoptic, repetitive and acquired at the surface. Here we show that the satellite-derived sea surface salinity measurements evidence an intensifcation of the water cycle (the freshest waters become fresher and vice-versa) which is not observed at the in-situ nearsurface salinity measurements. The largest positive diferences between surface and near-surface salinity trends are located over regions characterized by a decrease in the mixed layer depth and the sea surface wind speed, and an increase in sea surface temperature, which is consistent with an increased stratifcation of the water column due to global warming. These results highlight the crucial importance of using satellites to unveil critical changes on ocean–atmosphere fuxes.
2022-05-04T16:44:54ZOlmedo Casal, EstrellaTuriel Martínez, AntonioGonzález Gambau, VerónicaGonzález Haro, CristinaGarcía Espriu, AinaGabarró Prats, CarolinaPortabella, MarcosCorbella Sanahuja, IgnasiMartín Neira, ManuelArias Ballesteros, ManuelCatany, RafaelSabia, RobertoOlivia, RogerScipal, KlausChanges in the Earth’s water cycle can be estimated by analyzing sea surface salinity. This variable refects the balance between precipitation and evaporation over the ocean, since the upper layers of the ocean are the most sensitive to atmosphere–ocean interactions. In situ measurements lack spatial and temporal synopticity and are typically acquired at few meters below the surface. Satellite measurements, on the contrary, are synoptic, repetitive and acquired at the surface. Here we show that the satellite-derived sea surface salinity measurements evidence an intensifcation of the water cycle (the freshest waters become fresher and vice-versa) which is not observed at the in-situ nearsurface salinity measurements. The largest positive diferences between surface and near-surface salinity trends are located over regions characterized by a decrease in the mixed layer depth and the sea surface wind speed, and an increase in sea surface temperature, which is consistent with an increased stratifcation of the water column due to global warming. These results highlight the crucial importance of using satellites to unveil critical changes on ocean–atmosphere fuxes.Evaluation of the nonlinear surface resistance of REBCO coated conductors for their use in the FCC-hh beam screen
http://hdl.handle.net/2117/359551
Evaluation of the nonlinear surface resistance of REBCO coated conductors for their use in the FCC-hh beam screen
Krkotic, Patrick; Romanov, Artur; Tagdulang, Nikki; Telles, Guilherme; Puig Molina, Teresa; Gutiérrez Royo, Joffre; Granados García, Xavier; Calatroni, Sergio; Pérez, Francis; Pont Montaner, Montserrat; O'Callaghan Castellà, Juan Manuel
To assess the feasibility of using high-temperature superconductors for the beam screens of future circular colliders, we have undertaken a study of the power dependence of the microwave surface resistance in state-of-the-art REBCO coated conductors at about 8GHz and 50K. We have employed a dielectric resonator to produce radio-frequency electromagnetic fields on the surface of the coated conductors having amplitudes similar to those generated by proton bunches circulating in the vacuum chamber of the proposed hadron-hadron Future Circular Collider at CERN. We show that surface resistances in REBCO coated conductors without artificial pinning centers are more affected by a radio-frequency magnetic field than those containing nano-inclusions. Despite that, at 8GHz, 50K, and 9T, most REBCO coated conductors studied outperform copper in terms of surface resistance, with the best sample having a 2.3mO surface resistance while being subject to an RF field 2.5 times stronger than that in the FCC-hh. We also extrapolate the measured data to 16T and 1GHz, the actual FCC-hh dipole magnetic field, and mid beam frequency spectrum, demonstrating the possibility of lowering the surface resistance of the vacuum chamber by up to two orders of magnitude compared to copper. Further, we discuss the correlation between the time structure of the electromagnetic fields provided by vector network analyzers compared to the proton bunches' time structure in the collider and present the effect of low alternating magnetic fields on vortex displacement and the possibility of demagnetization of superconducting samples.
2022-01-13T11:57:25ZKrkotic, PatrickRomanov, ArturTagdulang, NikkiTelles, GuilhermePuig Molina, TeresaGutiérrez Royo, JoffreGranados García, XavierCalatroni, SergioPérez, FrancisPont Montaner, MontserratO'Callaghan Castellà, Juan ManuelTo assess the feasibility of using high-temperature superconductors for the beam screens of future circular colliders, we have undertaken a study of the power dependence of the microwave surface resistance in state-of-the-art REBCO coated conductors at about 8GHz and 50K. We have employed a dielectric resonator to produce radio-frequency electromagnetic fields on the surface of the coated conductors having amplitudes similar to those generated by proton bunches circulating in the vacuum chamber of the proposed hadron-hadron Future Circular Collider at CERN. We show that surface resistances in REBCO coated conductors without artificial pinning centers are more affected by a radio-frequency magnetic field than those containing nano-inclusions. Despite that, at 8GHz, 50K, and 9T, most REBCO coated conductors studied outperform copper in terms of surface resistance, with the best sample having a 2.3mO surface resistance while being subject to an RF field 2.5 times stronger than that in the FCC-hh. We also extrapolate the measured data to 16T and 1GHz, the actual FCC-hh dipole magnetic field, and mid beam frequency spectrum, demonstrating the possibility of lowering the surface resistance of the vacuum chamber by up to two orders of magnitude compared to copper. Further, we discuss the correlation between the time structure of the electromagnetic fields provided by vector network analyzers compared to the proton bunches' time structure in the collider and present the effect of low alternating magnetic fields on vortex displacement and the possibility of demagnetization of superconducting samples.Design of minimum nonlinear distortion reconfigurable antennas for next-generation communication systems
http://hdl.handle.net/2117/355790
Design of minimum nonlinear distortion reconfigurable antennas for next-generation communication systems
Ramírez Arroyave, Germán Augusto; Barlabe Dalmau, Antoni; Pradell i Cara, Lluís; Araque Araque, Javier Leonardo; Cetiner, Bedri Artug; Jofre Roca, Lluís
Nonlinear effects in the radio front-end can degrade communication quality and system performance. In this paper we present a new design technique for reconfigurable antennas that minimizes the nonlinear distortion and maximizes power efficiency through the minimization of the coupling between the internal switching ports and the external feeding ports. As a nonlinear design and validation instance, we present the nonlinear characterization up to 50 GHz of a PIN diode commonly used as a switch for reconfigurable devices in the microwave band. Nonlinear models are extracted through X-parameter measurements supported by accurate calibration and de-embedding procedures. Nonlinear switch models are validated by S-parameter measurements in the low power signal regime and by harmonic measurements in the large-signal regime and are further used to predict the measured nonlinearities of a reconfigurable antenna. These models have the desired particularity of being integrated straightforwardly in the internal multi-port method formulation, which is used and extended to account for the power induced on the switching elements. A new figure of merit for the design of reconfigurable antennas is introduced—the power margin, that is, the power difference between the fed port and the switching elements, which combined with the nonlinear load models directly translates into nonlinearities and power-efficiency-related metrics. Therefore, beyond traditional antenna aspects such as port match, gain, and beam orientation, switch power criteria are included in the design methodology. Guidelines for the design of reconfigurable antennas and parasitic layers of minimum nonlinearity are provided as well as the inherent trade-offs. A particular antenna design suitable for 5G communications in the 3.5 GHz band is presented according to these guidelines, in which the specific switching states for a set of target performance metrics are obtained via a balancing of the available figures of merit with multi-objective separation criteria, which enables good control of the various design trade-offs. Average Error Vector Magnitude (EVM) and power efficiency improvement of 12 and 6 dB, respectively, are obtained with the application of this design approach. In summary, this paper introduces a new framework for the nonlinear modeling and design of reconfigurable antennas and provides a set of general-purpose tools applicable in cases beyond those used as examples and validation in this work. Additionally, the use of these models and guidelines is presented, demonstrating one of the most appealing advantages of the reconfigurable parasitic layer approach, their low nonlinearity
2021-11-08T17:27:46ZRamírez Arroyave, Germán AugustoBarlabe Dalmau, AntoniPradell i Cara, LluísAraque Araque, Javier LeonardoCetiner, Bedri ArtugJofre Roca, LluísNonlinear effects in the radio front-end can degrade communication quality and system performance. In this paper we present a new design technique for reconfigurable antennas that minimizes the nonlinear distortion and maximizes power efficiency through the minimization of the coupling between the internal switching ports and the external feeding ports. As a nonlinear design and validation instance, we present the nonlinear characterization up to 50 GHz of a PIN diode commonly used as a switch for reconfigurable devices in the microwave band. Nonlinear models are extracted through X-parameter measurements supported by accurate calibration and de-embedding procedures. Nonlinear switch models are validated by S-parameter measurements in the low power signal regime and by harmonic measurements in the large-signal regime and are further used to predict the measured nonlinearities of a reconfigurable antenna. These models have the desired particularity of being integrated straightforwardly in the internal multi-port method formulation, which is used and extended to account for the power induced on the switching elements. A new figure of merit for the design of reconfigurable antennas is introduced—the power margin, that is, the power difference between the fed port and the switching elements, which combined with the nonlinear load models directly translates into nonlinearities and power-efficiency-related metrics. Therefore, beyond traditional antenna aspects such as port match, gain, and beam orientation, switch power criteria are included in the design methodology. Guidelines for the design of reconfigurable antennas and parasitic layers of minimum nonlinearity are provided as well as the inherent trade-offs. A particular antenna design suitable for 5G communications in the 3.5 GHz band is presented according to these guidelines, in which the specific switching states for a set of target performance metrics are obtained via a balancing of the available figures of merit with multi-objective separation criteria, which enables good control of the various design trade-offs. Average Error Vector Magnitude (EVM) and power efficiency improvement of 12 and 6 dB, respectively, are obtained with the application of this design approach. In summary, this paper introduces a new framework for the nonlinear modeling and design of reconfigurable antennas and provides a set of general-purpose tools applicable in cases beyond those used as examples and validation in this work. Additionally, the use of these models and guidelines is presented, demonstrating one of the most appealing advantages of the reconfigurable parasitic layer approach, their low nonlinearityA simple low-cost electrocardiogram synchronizer
http://hdl.handle.net/2117/355780
A simple low-cost electrocardiogram synchronizer
Amorós García de Valdecasas, Susana; Galvez Monton, Carolina; Rodríguez Leor, Oriol; O'Callaghan Castellà, Juan Manuel
Electrocardiogram (ECG) synchronization is useful to avoid the effects of cardiac motion in medical measurements, and is widely used in standard medical imaging. A number of medical equipment include embedded commercial synchronizers. However, the use of independent synchronization modules is sometimes needed when several non-integrated instruments are used, or in the development of new medical instruments and procedures. We present a simple low-cost ECG synchronizer module based on an Arduino controller board that converts the ECG signal into a transistor-transistor-logic (TTL) one, allowing real-time medical measurements triggered at specific phases of the cardiac cycle. The device and conversion algorithm developed is optimized in vitro using synthetic and human ECG signals, and tested in vivo on three swine specimens. Error rates during the in vivo testing stage remain below the 2% of the cycles in all animals and critical false positives are less than 1%, which is sufficient for most applications. Possible algorithm updates are discussed if its performance needs to be improved.
2021-11-08T16:29:47ZAmorós García de Valdecasas, SusanaGalvez Monton, CarolinaRodríguez Leor, OriolO'Callaghan Castellà, Juan ManuelElectrocardiogram (ECG) synchronization is useful to avoid the effects of cardiac motion in medical measurements, and is widely used in standard medical imaging. A number of medical equipment include embedded commercial synchronizers. However, the use of independent synchronization modules is sometimes needed when several non-integrated instruments are used, or in the development of new medical instruments and procedures. We present a simple low-cost ECG synchronizer module based on an Arduino controller board that converts the ECG signal into a transistor-transistor-logic (TTL) one, allowing real-time medical measurements triggered at specific phases of the cardiac cycle. The device and conversion algorithm developed is optimized in vitro using synthetic and human ECG signals, and tested in vivo on three swine specimens. Error rates during the in vivo testing stage remain below the 2% of the cycles in all animals and critical false positives are less than 1%, which is sufficient for most applications. Possible algorithm updates are discussed if its performance needs to be improved.Rayleigh backscattering rejection in single-laser homodyne transceiver for UD-WDM using λ-Shifting
http://hdl.handle.net/2117/355113
Rayleigh backscattering rejection in single-laser homodyne transceiver for UD-WDM using λ-Shifting
Masanas Jiménez, Miquel; Santos Blanco, M. Concepción; Tabares Giraldo, Jeison; Polo Querol, Víctor; Prat Gomà, Josep Joan
With the aim of using a single laser per transceiver in single fiber splitter-based passive optical networks (PON) with coherent homodyne receivers, we apply wavelength shifting in an ultra-dense wavelength division multiplexing (UD-WDM) scheme. The studied architecture is based on a dual-parallel Mach-Zehnder Modulator (DP-MZM) operating in carrier-suppressed single-sideband (CS-SSB). In this configuration, a single laser feeds both the coherent homodyne receiver, and the transmitter, simplifying the wavelength management in the PON. The modulator carries out both data modulation and wavelength shifting. In this study, a bit rate of 4 Gb/s in QPSK is used to test several roll-off factors and channel spacing configurations. The results show that power budget gains of 18 dB are achievable with a channel spacing equal to only the symbol rate.
2021-11-02T09:39:58ZMasanas Jiménez, MiquelSantos Blanco, M. ConcepciónTabares Giraldo, JeisonPolo Querol, VíctorPrat Gomà, Josep JoanWith the aim of using a single laser per transceiver in single fiber splitter-based passive optical networks (PON) with coherent homodyne receivers, we apply wavelength shifting in an ultra-dense wavelength division multiplexing (UD-WDM) scheme. The studied architecture is based on a dual-parallel Mach-Zehnder Modulator (DP-MZM) operating in carrier-suppressed single-sideband (CS-SSB). In this configuration, a single laser feeds both the coherent homodyne receiver, and the transmitter, simplifying the wavelength management in the PON. The modulator carries out both data modulation and wavelength shifting. In this study, a bit rate of 4 Gb/s in QPSK is used to test several roll-off factors and channel spacing configurations. The results show that power budget gains of 18 dB are achievable with a channel spacing equal to only the symbol rate.A novel digital IQ demodulation for interferometric radiometers
http://hdl.handle.net/2117/353304
A novel digital IQ demodulation for interferometric radiometers
Corbella Sanahuja, Ignasi; Martín Neira, Manuel; Vilaseca, Roger; Catalán Artigas, Albert; Torres Torres, Francisco; Suess, Martin
In the frame of an SMOS follow-on operational mission, a new instrument design is being developed based on the lessons learned from MIRAS, the SMOS payload. To reduce hardware complexity and mass, digital In-phase Quadrature (IQ) demodulation is considered. In this schema, Q components are obtained by delaying one clock of the digitized IF signals instead of using phase quadrature analog mixers. The purpose of this article is to formulate this concept for application to interferometric radiometry, establish the required data processing methods, and provide experimental results.
2021-10-07T12:23:53ZCorbella Sanahuja, IgnasiMartín Neira, ManuelVilaseca, RogerCatalán Artigas, AlbertTorres Torres, FranciscoSuess, MartinIn the frame of an SMOS follow-on operational mission, a new instrument design is being developed based on the lessons learned from MIRAS, the SMOS payload. To reduce hardware complexity and mass, digital In-phase Quadrature (IQ) demodulation is considered. In this schema, Q components are obtained by delaying one clock of the digitized IF signals instead of using phase quadrature analog mixers. The purpose of this article is to formulate this concept for application to interferometric radiometry, establish the required data processing methods, and provide experimental results.Characterisation of copper and stainless steel surfaces treated with laser ablation surface engineering
http://hdl.handle.net/2117/350134
Characterisation of copper and stainless steel surfaces treated with laser ablation surface engineering
Hannah, Adrian N.; Krkotic, Patrick; Valizadeh, Reza; Malyshev, Oleg; Mutch, J.; Whitehead, David J.; Pont, Montse; O'Callaghan Castellà, Juan Manuel; Dhanak, Vinod R.
In the past few years, it has been established that Laser Ablation Surface Engineering (LASE) is a very effective way of producing surfaces which have Secondary Electron Yields (SEY)¿<¿1. This can be achieved with a variety of laser pulse durations from nano-to picoseconds. However, the features (i.e. moderately deep grooves and nano-particulates) that help to reduce the SEY can produce undesirable effects such as an increase in the RF surface resistance. In this paper we discuss the methods employed utilising the dielectric resonator technique to quantify the surface resistance of laser treated copper and stainless steel samples. The quantification is based on a non-destructive measurement of high-frequency losses on the conducting surface. It has been demonstrated that the LASE surface can be produced with SEY<1 and an RF surface resistance of only ~6% higher than that on untreated surfaces. Furthermore, a comparative study of electron stimulated desorption (ESD) between the LASE treated and untreated samples of copper and stainless steel is reported for H2, CH4, CO and CO2. It has been shown that there are negligible differences in ESD between LASE treated and untreated stainless steel. It has been demonstrated that LASE-treated copper samples have a considerable reduction in ESD as compared with untreated sample.
2021-07-27T08:30:54ZHannah, Adrian N.Krkotic, PatrickValizadeh, RezaMalyshev, OlegMutch, J.Whitehead, David J.Pont, MontseO'Callaghan Castellà, Juan ManuelDhanak, Vinod R.In the past few years, it has been established that Laser Ablation Surface Engineering (LASE) is a very effective way of producing surfaces which have Secondary Electron Yields (SEY)¿<¿1. This can be achieved with a variety of laser pulse durations from nano-to picoseconds. However, the features (i.e. moderately deep grooves and nano-particulates) that help to reduce the SEY can produce undesirable effects such as an increase in the RF surface resistance. In this paper we discuss the methods employed utilising the dielectric resonator technique to quantify the surface resistance of laser treated copper and stainless steel samples. The quantification is based on a non-destructive measurement of high-frequency losses on the conducting surface. It has been demonstrated that the LASE surface can be produced with SEY<1 and an RF surface resistance of only ~6% higher than that on untreated surfaces. Furthermore, a comparative study of electron stimulated desorption (ESD) between the LASE treated and untreated samples of copper and stainless steel is reported for H2, CH4, CO and CO2. It has been shown that there are negligible differences in ESD between LASE treated and untreated stainless steel. It has been demonstrated that LASE-treated copper samples have a considerable reduction in ESD as compared with untreated sample.Optical phase effects in reconfigurable microwave photonic filters with multiple wavelength input
http://hdl.handle.net/2117/348085
Optical phase effects in reconfigurable microwave photonic filters with multiple wavelength input
Nuño Gómez, Daniel-Juan; Santos Blanco, M. Concepción
Microwave photonic filters with a multiple wavelength input are analyzed. A comprehensive model assessing the impact of the phase characteristic of the optical stage is presented from which optimized design rules have been derived. Examples with one, 2 and 3 lasers are provided along with experimental results supporting our findings.
2021-06-29T13:49:34ZNuño Gómez, Daniel-JuanSantos Blanco, M. ConcepciónMicrowave photonic filters with a multiple wavelength input are analyzed. A comprehensive model assessing the impact of the phase characteristic of the optical stage is presented from which optimized design rules have been derived. Examples with one, 2 and 3 lasers are provided along with experimental results supporting our findings.Algorithm for resonator parameter extraction from symmetrical and asymmetrical transmission responses
http://hdl.handle.net/2117/347020
Algorithm for resonator parameter extraction from symmetrical and asymmetrical transmission responses
Krkotic, Patrick; Gallardo Moix, Queralt; Tagdulang, Nikki; Pont Montaner, Montserrat; O'Callaghan Castellà, Juan Manuel
We describe an algorithm capable of extracting the unloaded quality factor and the resonant frequency of microwave resonators from vector S-parameters. Both symmetrical (Lorentzian) and asymmetrical (Fano) transmission responses are supported. The algorithm performs an adaptive outlier removal to discard measurement points affected by noise or distortion. It removes the effects caused by imperfections in the device (such as modes with close resonance frequencies or stray coupling between the resonator ports) or the experimental setup (such as lack of isolation or dispersion in the test set and cables). We present an extensive assessment of the algorithm performance based on a numerical perturbation analysis and the evaluation of S-parameter fitting results obtained from network analyzer measurements and resonator equivalent circuits. Our results suggest that uncertainty is mainly caused by factors that distort the frequency dependence of the S-parameters, such as cabling and coupling networks, and is highly dependent on the device measured. Our perturbation analysis shows improved results with respect to those of previous publications. Our source code is written in Python using open-source packages and is publicly available under a freeware license.
2021-06-10T09:05:30ZKrkotic, PatrickGallardo Moix, QueraltTagdulang, NikkiPont Montaner, MontserratO'Callaghan Castellà, Juan ManuelWe describe an algorithm capable of extracting the unloaded quality factor and the resonant frequency of microwave resonators from vector S-parameters. Both symmetrical (Lorentzian) and asymmetrical (Fano) transmission responses are supported. The algorithm performs an adaptive outlier removal to discard measurement points affected by noise or distortion. It removes the effects caused by imperfections in the device (such as modes with close resonance frequencies or stray coupling between the resonator ports) or the experimental setup (such as lack of isolation or dispersion in the test set and cables). We present an extensive assessment of the algorithm performance based on a numerical perturbation analysis and the evaluation of S-parameter fitting results obtained from network analyzer measurements and resonator equivalent circuits. Our results suggest that uncertainty is mainly caused by factors that distort the frequency dependence of the S-parameters, such as cabling and coupling networks, and is highly dependent on the device measured. Our perturbation analysis shows improved results with respect to those of previous publications. Our source code is written in Python using open-source packages and is publicly available under a freeware license.