Articles de revista
http://hdl.handle.net/2117/3802
20180217T23:45:48Z

A discretetime technique for the steadystate analysis of nonlinear classE amplifiers
http://hdl.handle.net/2117/106735
A discretetime technique for the steadystate analysis of nonlinear classE amplifiers
Águila López, Francisco del; Palà Schönwälder, Pere; Molina Gaudó, Pilar; Mediano Heredia, Arturo
Switched circuits are widely used, particularly for power electronic applications in which efficiency is important. Of these applications, the classE amplifier has been given particular attention, since it is theoretically a 100%efficient switched circuit that has been successfully demonstrated in applications such as ballasts, converters, frequency multipliers, and communication amplifiers at frequencies as high as 10 GHz. However, with increasing power or frequency, nonlinearities become extremely important, for instance, in order to achieve actual classE operation and even to avoid destruction of the switching device. In this paper, a new method for determining the steadystate response of nonlinear circuits containing ideal switches is proposed. While the method is more general, the description is based on the classE amplifier because of its inherent interest. The method is based on a timedomain Gear discretization of the circuit equations. A technique for determining the initial samples of the discretized equation of each topology is developed, based on the fact that state variables are constant during switching. Finally, assuming a periodic steadystate, a single algebraic system of nonlinear equations is obtained in which the unknowns are the samples of the control variable of the nonlinearity in the whole signal period. To validate the method described, a comparison with PSpice simulations is provided.
20170724T09:58:03Z
Águila López, Francisco del
Palà Schönwälder, Pere
Molina Gaudó, Pilar
Mediano Heredia, Arturo
Switched circuits are widely used, particularly for power electronic applications in which efficiency is important. Of these applications, the classE amplifier has been given particular attention, since it is theoretically a 100%efficient switched circuit that has been successfully demonstrated in applications such as ballasts, converters, frequency multipliers, and communication amplifiers at frequencies as high as 10 GHz. However, with increasing power or frequency, nonlinearities become extremely important, for instance, in order to achieve actual classE operation and even to avoid destruction of the switching device. In this paper, a new method for determining the steadystate response of nonlinear circuits containing ideal switches is proposed. While the method is more general, the description is based on the classE amplifier because of its inherent interest. The method is based on a timedomain Gear discretization of the circuit equations. A technique for determining the initial samples of the discretized equation of each topology is developed, based on the fact that state variables are constant during switching. Finally, assuming a periodic steadystate, a single algebraic system of nonlinear equations is obtained in which the unknowns are the samples of the control variable of the nonlinearity in the whole signal period. To validate the method described, a comparison with PSpice simulations is provided.

Joint symbol and chip synchronization for a burstmodecommunication superregenerative MSK receiver
http://hdl.handle.net/2117/104237
Joint symbol and chip synchronization for a burstmodecommunication superregenerative MSK receiver
López Riera, Alexis; Águila López, Francisco del; Palà Schönwälder, Pere; Bonet Dalmau, Jordi; Giralt Mas, Ma. Rosa; Moncunill Geniz, Francesc Xavier
In this paper we describe a superregenerative (SR)
MSK receiver able to operate in a burstmode framework where
synchronization is required for each packet. The receiver is based
on an SR oscillator which provides samples of the incoming
instantaneous phase trajectories. We develop a simple yet effective
technique to achieve joint chip and symbol synchronization
within the time limits of a suitable preamble. We develop some
general results and focus on the case of the IEEE 802.15.4 MSK
physical layer. We provide details on a VHDL implementation on
an FPGA where the most complex digital processing block is an
accumulator. Simulation and experimental results are provided
to validate the described technique.
20170509T14:46:29Z
López Riera, Alexis
Águila López, Francisco del
Palà Schönwälder, Pere
Bonet Dalmau, Jordi
Giralt Mas, Ma. Rosa
Moncunill Geniz, Francesc Xavier
In this paper we describe a superregenerative (SR)
MSK receiver able to operate in a burstmode framework where
synchronization is required for each packet. The receiver is based
on an SR oscillator which provides samples of the incoming
instantaneous phase trajectories. We develop a simple yet effective
technique to achieve joint chip and symbol synchronization
within the time limits of a suitable preamble. We develop some
general results and focus on the case of the IEEE 802.15.4 MSK
physical layer. We provide details on a VHDL implementation on
an FPGA where the most complex digital processing block is an
accumulator. Simulation and experimental results are provided
to validate the described technique.

A discretetime approach to the steadystate and stability analysis of distributed nonlinear autonomous circuits
http://hdl.handle.net/2117/98495
A discretetime approach to the steadystate and stability analysis of distributed nonlinear autonomous circuits
Bonet Dalmau, Jordi; Palà Schönwälder, Pere
We present a direct method for the steadystate and stability
analysis of autonomous circuits with transmission lines and generic non
linear elements. With the discretization of the equations that describe the
circuit in the time domain, we obtain a nonlinear algebraic formulation
where the unknowns to determine are the samples of the variables directly
in the steady state, along with the oscillation period, the main unknown in
autonomous circuits.An efficient scheme to buildtheJacobian matrix with
exact partial derivatives with respect to the oscillation period and with re
spect to the samples of the unknowns is described. Without any modifica
tion in the analysis method, the stability of the solution can be computed a
posteriori constructing an implicit map, where the last sample is viewed as
a function of the previous samples. The application of this technique to the
timedelayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the perioddoubling bifurcations.
20161216T16:30:04Z
Bonet Dalmau, Jordi
Palà Schönwälder, Pere
We present a direct method for the steadystate and stability
analysis of autonomous circuits with transmission lines and generic non
linear elements. With the discretization of the equations that describe the
circuit in the time domain, we obtain a nonlinear algebraic formulation
where the unknowns to determine are the samples of the variables directly
in the steady state, along with the oscillation period, the main unknown in
autonomous circuits.An efficient scheme to buildtheJacobian matrix with
exact partial derivatives with respect to the oscillation period and with re
spect to the samples of the unknowns is described. Without any modifica
tion in the analysis method, the stability of the solution can be computed a
posteriori constructing an implicit map, where the last sample is viewed as
a function of the previous samples. The application of this technique to the
timedelayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the perioddoubling bifurcations.

Stability analysis of periodic solutions in nonlinear autonomous circuits: a discrete time approach
http://hdl.handle.net/2117/97804
Stability analysis of periodic solutions in nonlinear autonomous circuits: a discrete time approach
Miró Sans, Joan Maria; Palà Schönwälder, Pere; Mas Casals, Orestes Miquel
Steadystate methods have been devised to compute periodic waveforms without having to integrate the
autonomous circuit equations until the transients die out. Stability analysis of the computed solutions is the
next topic to be addressed by a steady state circuit simulator. Shooting methods based on Newton's iteration
are expensive in terms of computing time, because each iteration step requires integration of the variational
equation, but directly provide information on the stability of the final On the other hand, when
making use of harmonic balance methods, the stability of the computed solutions is typically investigated
from a continuation point of view.4 Recently a discrete time approach (DTA) was proposed for the analysis
and optimization of nonlinear autonomous circuits.' This letter describes how the stability of the
computed periodic waveforms may be easily determined (I posteriori with no modification to the DTA
solution method.
20161205T16:39:28Z
Miró Sans, Joan Maria
Palà Schönwälder, Pere
Mas Casals, Orestes Miquel
Steadystate methods have been devised to compute periodic waveforms without having to integrate the
autonomous circuit equations until the transients die out. Stability analysis of the computed solutions is the
next topic to be addressed by a steady state circuit simulator. Shooting methods based on Newton's iteration
are expensive in terms of computing time, because each iteration step requires integration of the variational
equation, but directly provide information on the stability of the final On the other hand, when
making use of harmonic balance methods, the stability of the computed solutions is typically investigated
from a continuation point of view.4 Recently a discrete time approach (DTA) was proposed for the analysis
and optimization of nonlinear autonomous circuits.' This letter describes how the stability of the
computed periodic waveforms may be easily determined (I posteriori with no modification to the DTA
solution method.

The MendeleevMeyer force project
http://hdl.handle.net/2117/96683
The MendeleevMeyer force project
Santos Hernández, Sergio; Lai, ChiaYun; Amadei, Carlo Alberto; Gadelrab, Karim Raafat; Tang, TzuChieh; Verdaguer Prats, Albert; Barcons Xixons, Víctor; Font Teixidó, Josep; Colchero, Jaimer; Chiesa, Matteo
Here we present the Mendeleev–Meyer Force Project which aims at tabulating all materials and substances in a fashion similar to the periodic table. The goal is to group and tabulate substances using nanoscale force footprints rather than atomic number or electronic configuration as in the periodic table. The process is divided into: (1) acquiring nanoscale force data from materials, (2) parameterizing the raw data into standardized input features to generate a library, (3) feeding the standardized library into an algorithm to generate, enhance or exploit a model to identify a material or property. We propose producing databases mimicking the Materials Genome Initiative, the Medical Literature Analysis and Retrieval System Online (MEDLARS) or the PRoteomics IDEntifications database (PRIDE) and making these searchable online via search engines mimicking Pubmed or the PRIDE web interface. A prototype exploiting deep learning algorithms, i.e. multilayer neural networks, is presented.
20161115T16:04:39Z
Santos Hernández, Sergio
Lai, ChiaYun
Amadei, Carlo Alberto
Gadelrab, Karim Raafat
Tang, TzuChieh
Verdaguer Prats, Albert
Barcons Xixons, Víctor
Font Teixidó, Josep
Colchero, Jaimer
Chiesa, Matteo
Here we present the Mendeleev–Meyer Force Project which aims at tabulating all materials and substances in a fashion similar to the periodic table. The goal is to group and tabulate substances using nanoscale force footprints rather than atomic number or electronic configuration as in the periodic table. The process is divided into: (1) acquiring nanoscale force data from materials, (2) parameterizing the raw data into standardized input features to generate a library, (3) feeding the standardized library into an algorithm to generate, enhance or exploit a model to identify a material or property. We propose producing databases mimicking the Materials Genome Initiative, the Medical Literature Analysis and Retrieval System Online (MEDLARS) or the PRoteomics IDEntifications database (PRIDE) and making these searchable online via search engines mimicking Pubmed or the PRIDE web interface. A prototype exploiting deep learning algorithms, i.e. multilayer neural networks, is presented.

Circuitos de capacidades conmutadas. Análisis frecuencial por ordenador
http://hdl.handle.net/2117/87859
Circuitos de capacidades conmutadas. Análisis frecuencial por ordenador
Puerta Notario, Antonio; Miró Sans, Joan M.; Sanz Postils, Margarita
El interés fundamental de los circuitos de condensadores conmutados radica en su aplicación a la realización de filtros monolíticos y de otros bloques funcionales para su tratamiento analógico de la señal. Resulta del máximo interés disponer de métodos de análisis y programas de simulación que permitan evaluar los resultados de las diferentes técnicas de síntesis.
En este artículo se presenta un programa de simulación, basado en los métodos de análisis desarrollados por los autores, que permite la obtención de las funciones de transferencia y de la respuesta frecuencial de circuitos SC. Para su realización se requiere un soporte informático reducido, lo que, junto con la facilidad de utilización, son sus características más sobresalientes.
20160609T15:57:23Z
Puerta Notario, Antonio
Miró Sans, Joan M.
Sanz Postils, Margarita
El interés fundamental de los circuitos de condensadores conmutados radica en su aplicación a la realización de filtros monolíticos y de otros bloques funcionales para su tratamiento analógico de la señal. Resulta del máximo interés disponer de métodos de análisis y programas de simulación que permitan evaluar los resultados de las diferentes técnicas de síntesis.
En este artículo se presenta un programa de simulación, basado en los métodos de análisis desarrollados por los autores, que permite la obtención de las funciones de transferencia y de la respuesta frecuencial de circuitos SC. Para su realización se requiere un soporte informático reducido, lo que, junto con la facilidad de utilización, son sus características más sobresalientes.

Formalism for a multiresolution time series database model
http://hdl.handle.net/2117/87125
Formalism for a multiresolution time series database model
Llusa Serra, Aleix; Vila Marta, Sebastià; Escobet Canal, Teresa
We formalise a specialised database management system model for time series using a multiresolution approach. These special purpose database systems store time series lossy compressed in a spacebounded storage. Time series can be stored at multiple resolutions, using distinct attribute aggregations and keeping its temporal attribute managed in a consistent way.
The model exhibits a generic approach that facilitates its customisation to suit better the actual application requirements in a given context. The elements, the meaning of which depends on a real application, are of generic nature.
Furthermore, we consider some specific time series properties that are a challenge in the multiresolution approach. We also describe a reference implementation of the model and introduce a use case based on real data.
20160517T15:17:06Z
Llusa Serra, Aleix
Vila Marta, Sebastià
Escobet Canal, Teresa
We formalise a specialised database management system model for time series using a multiresolution approach. These special purpose database systems store time series lossy compressed in a spacebounded storage. Time series can be stored at multiple resolutions, using distinct attribute aggregations and keeping its temporal attribute managed in a consistent way.
The model exhibits a generic approach that facilitates its customisation to suit better the actual application requirements in a given context. The elements, the meaning of which depends on a real application, are of generic nature.
Furthermore, we consider some specific time series properties that are a challenge in the multiresolution approach. We also describe a reference implementation of the model and introduce a use case based on real data.

Single cycle and transient force measurements in dynamic atomic force microscopy
http://hdl.handle.net/2117/78946
Single cycle and transient force measurements in dynamic atomic force microscopy
Gadelrab, Karim Raafat; Santos, Sergio; Font Teixidó, Josep; Chiesa, Matteo
The monitoring of the deflection of a microcantilever, as the end of a sharp probe mounted at its end, i.e. the tip, interacts with a surface, forms the foundation of atomic force microscopy AFM. In a nutshell, developments in the field are driven by the requirement of obtaining ever increasing throughput and sensitivity, and enhancing the versatility of the instrument to simultaneously map the topography and quantify nanoscale processes and properties. In the most common dynamic mode of operation, the motion of the driven cantilever is monitored at a single point on its longitudinal axis. Here, we show that from this single point a waveform is obtained that contains all the details about conservative and dissipative interactions. Then a formalism that accounts for multiple arbitrary flexural modes is developed for an indirectly driven cantilever. The formalism is shown to allow recovery of the details of the interaction even in the presence of complex and relevant hysteretic forces when the cantilever oscillates in the steady state. In a different approach, we develop a formalism that monitors the wave profile of the cantilever, i.e. the waveform at five different points on its longitudinal axis. With this formalism the interaction can be reconstructed during a single oscillation cycle even in the transient state of oscillation. Finally, we discuss the potential and advantages of the proposed methods and future technical challenges. Other standard and state of the art techniques and methods are also discussed and compared with the ones presented here. This work should also provide insight into the current high throughputhigh sensitivity developments dealing with multifrequency dynamic AFM where information is recovered from multiple eigenmodes. © 2013 The Royal Society of Chemistry.
20151109T17:31:13Z
Gadelrab, Karim Raafat
Santos, Sergio
Font Teixidó, Josep
Chiesa, Matteo
The monitoring of the deflection of a microcantilever, as the end of a sharp probe mounted at its end, i.e. the tip, interacts with a surface, forms the foundation of atomic force microscopy AFM. In a nutshell, developments in the field are driven by the requirement of obtaining ever increasing throughput and sensitivity, and enhancing the versatility of the instrument to simultaneously map the topography and quantify nanoscale processes and properties. In the most common dynamic mode of operation, the motion of the driven cantilever is monitored at a single point on its longitudinal axis. Here, we show that from this single point a waveform is obtained that contains all the details about conservative and dissipative interactions. Then a formalism that accounts for multiple arbitrary flexural modes is developed for an indirectly driven cantilever. The formalism is shown to allow recovery of the details of the interaction even in the presence of complex and relevant hysteretic forces when the cantilever oscillates in the steady state. In a different approach, we develop a formalism that monitors the wave profile of the cantilever, i.e. the waveform at five different points on its longitudinal axis. With this formalism the interaction can be reconstructed during a single oscillation cycle even in the transient state of oscillation. Finally, we discuss the potential and advantages of the proposed methods and future technical challenges. Other standard and state of the art techniques and methods are also discussed and compared with the ones presented here. This work should also provide insight into the current high throughputhigh sensitivity developments dealing with multifrequency dynamic AFM where information is recovered from multiple eigenmodes. © 2013 The Royal Society of Chemistry.

Establishing nanoscale heterogeneity with nanoscale force measurements
http://hdl.handle.net/2117/78535
Establishing nanoscale heterogeneity with nanoscale force measurements
Chang, YunHsiang, YunHsiang; Olukan, Tuza; Lai, ChiaYun; Santos, Sergio; Lin, TzeYu; Apostoleris, Harry; Font Teixidó, Josep; Barcons Xixons, Víctor; Chiesa, Matteo
Establishing the presence or absence of nanoscale compositional heterogeneity with nanoscale resolution is becoming instrumental for the development of many fields of science. Force versus distance measurements and parameters directly or indirectly derived from these profiles can be potentially employed for this purpose with sophisticated instruments such as the atomic force microscope (AFM). On the other hand, standards are necessary to reproducibly and conclusively support hypothesis from experimental data and these standards are still emerging. Here, we define a set of standards for providing data originating from atomic force measurements to be employed to compare between sample properties, parameters, or, more generally, compositional heterogeneity. We show that reporting the mean and standard deviation only might lead to inconsistent conclusions. The fundamental principle behind our investigation deals with the very definition of reproducibility and repeatability in terms of accuracy and precision, and we establish general criteria to ensure that these hold without the need of restricting assumptions.
20151029T19:05:50Z
Chang, YunHsiang, YunHsiang
Olukan, Tuza
Lai, ChiaYun
Santos, Sergio
Lin, TzeYu
Apostoleris, Harry
Font Teixidó, Josep
Barcons Xixons, Víctor
Chiesa, Matteo
Establishing the presence or absence of nanoscale compositional heterogeneity with nanoscale resolution is becoming instrumental for the development of many fields of science. Force versus distance measurements and parameters directly or indirectly derived from these profiles can be potentially employed for this purpose with sophisticated instruments such as the atomic force microscope (AFM). On the other hand, standards are necessary to reproducibly and conclusively support hypothesis from experimental data and these standards are still emerging. Here, we define a set of standards for providing data originating from atomic force measurements to be employed to compare between sample properties, parameters, or, more generally, compositional heterogeneity. We show that reporting the mean and standard deviation only might lead to inconsistent conclusions. The fundamental principle behind our investigation deals with the very definition of reproducibility and repeatability in terms of accuracy and precision, and we establish general criteria to ensure that these hold without the need of restricting assumptions.

Periodicity in bimodal atomic force microscopy
http://hdl.handle.net/2117/76907
Periodicity in bimodal atomic force microscopy
Lai, ChiaYun; Barcons Xixons, Víctor; Santos, Sergio; Chiesa, Matteo
Periodicity is fundamental for quantification and the application of conservation principles of many important systems. Here, we discuss periodicity in the context of bimodal atomic force microscopy (AFM). The relationship between the excited frequencies is shown to affect and control both experimental observables and the main expressions quantified via these observables, i.e., virial and energy transfer expressions, which form the basis of the bimodal AFM theory. The presence of a fundamental frequency further simplifies the theory and leads to close form solutions. Predictions are verified via numerical integration of the equation of motion and experimentally on a mica surface.
20150917T14:41:26Z
Lai, ChiaYun
Barcons Xixons, Víctor
Santos, Sergio
Chiesa, Matteo
Periodicity is fundamental for quantification and the application of conservation principles of many important systems. Here, we discuss periodicity in the context of bimodal atomic force microscopy (AFM). The relationship between the excited frequencies is shown to affect and control both experimental observables and the main expressions quantified via these observables, i.e., virial and energy transfer expressions, which form the basis of the bimodal AFM theory. The presence of a fundamental frequency further simplifies the theory and leads to close form solutions. Predictions are verified via numerical integration of the equation of motion and experimentally on a mica surface.