CIRCUIT - Grup de Recerca en Circuits i Sistemes de Comunicació
http://hdl.handle.net/2117/3801
2017-05-01T06:36:07ZSteady state analysis of class-E amplifier with non-linear capacitor by means of discrete-time techniques
http://hdl.handle.net/2117/103862
Steady state analysis of class-E amplifier with non-linear capacitor by means of discrete-time techniques
Águila López, Francisco del; Palà Schönwälder, Pere; Bonet Dalmau, Jordi; Giralt Mas, Ma. Rosa
A new method to determine the steady state response of switched nonlinear circuits is proposed. The method is based on a Gear discretization of the circuit equations. Additional samples of the waveform are used to describe the circuit when switching from one topology to another. Results are presented for a class-E resonant inverter.
2017-04-28T16:48:48ZÁguila López, Francisco delPalà Schönwälder, PereBonet Dalmau, JordiGiralt Mas, Ma. RosaA new method to determine the steady state response of switched nonlinear circuits is proposed. The method is based on a Gear discretization of the circuit equations. Additional samples of the waveform are used to describe the circuit when switching from one topology to another. Results are presented for a class-E resonant inverter.Steady state analysis of Chua's circuit with RLCG transmission line
http://hdl.handle.net/2117/103803
Steady state analysis of Chua's circuit with RLCG transmission line
Bonet Dalmau, Jordi; Palà Schönwälder, Pere; Águila López, Francisco del
In this paper we present a new technique to compute the steady state response of nonlinear autonomous circuits with RLCG transmission lines. Using multipoint Pade approximants, instead of the commonly used expansions around s=0 or s/spl rarr//spl infin/ accurate, low-order lumped equivalent circuits of the characteristic impedance and the exponential propagation function are obtained in an explicit way. Then, with the temporal discretization of the equations that describe the transformed circuit, we obtain a nonlinear algebraic formulation where the unknowns to be determined 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 build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is obtained. Steady state solutions of the Chua's circuit with RLCG transmission line are computed for selected circuit parameters.
2017-04-27T16:23:14ZBonet Dalmau, JordiPalà Schönwälder, PereÁguila López, Francisco delIn this paper we present a new technique to compute the steady state response of nonlinear autonomous circuits with RLCG transmission lines. Using multipoint Pade approximants, instead of the commonly used expansions around s=0 or s/spl rarr//spl infin/ accurate, low-order lumped equivalent circuits of the characteristic impedance and the exponential propagation function are obtained in an explicit way. Then, with the temporal discretization of the equations that describe the transformed circuit, we obtain a nonlinear algebraic formulation where the unknowns to be determined 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 build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is obtained. Steady state solutions of the Chua's circuit with RLCG transmission line are computed for selected circuit parameters.Anharmonicity in multifrequency atomic force microscopy
http://hdl.handle.net/2117/102988
Anharmonicity in multifrequency atomic force microscopy
Santos Hernandez, Sergio; Barcons Xixons, Víctor
In multifrequency atomic force microscopy higher eigenmodes are externally excited to enhance resolution and contrast while simultaneously increasing the number of experimental
observables with the use of gentle forces. Here, the implications of externally exciting multiple frequencies are discussed in terms of cantilever anharmonicity, fundamental period and the onset of subharmonic and superharmonic components. Cantilever anharmonicity is shown to affect and control both the observables, that is, the monitored amplitudes and phases, and the main expressions quantified via these observables, that is, the virial and energy transfer expressions which form the basis of the theory.
2017-03-28T15:50:13ZSantos Hernandez, SergioBarcons Xixons, VíctorIn multifrequency atomic force microscopy higher eigenmodes are externally excited to enhance resolution and contrast while simultaneously increasing the number of experimental
observables with the use of gentle forces. Here, the implications of externally exciting multiple frequencies are discussed in terms of cantilever anharmonicity, fundamental period and the onset of subharmonic and superharmonic components. Cantilever anharmonicity is shown to affect and control both the observables, that is, the monitored amplitudes and phases, and the main expressions quantified via these observables, that is, the virial and energy transfer expressions which form the basis of the theory.Deconstructing the governing dissipative phenomena in the nanoscale
http://hdl.handle.net/2117/102982
Deconstructing the governing dissipative phenomena in the nanoscale
Santos Hernandez, Sergio; Amadei, Carlo Alberto; Tang, Tzu-Chieh; Barcons Xixons, Víctor; Chiesa, Matteo
An expression describing the controlling parameters involved in short range nanoscale dissipation is proposed and supported by simulations and experimental findings. The expression is deconstructed into the geometrical, dynamic, chemical and mechanical properties of the system. In atomic force microscopy these are translated into 1) tip radius and tip-sample deformation, 2) resonant frequency and oscillation amplitude and 3) hysteretic and viscous dissipation. The latter are characteristic parameters defining the chemical and mechanical properties of the tip-sample system. Long range
processes are also discussed and footprints are identified in experiments conducted on mica and silicon samples. The present methodology can be exploited to validate or invalidate nanoscale dissipative models by comparing predictions with experimental observables.
2017-03-28T15:04:11ZSantos Hernandez, SergioAmadei, Carlo AlbertoTang, Tzu-ChiehBarcons Xixons, VíctorChiesa, MatteoAn expression describing the controlling parameters involved in short range nanoscale dissipation is proposed and supported by simulations and experimental findings. The expression is deconstructed into the geometrical, dynamic, chemical and mechanical properties of the system. In atomic force microscopy these are translated into 1) tip radius and tip-sample deformation, 2) resonant frequency and oscillation amplitude and 3) hysteretic and viscous dissipation. The latter are characteristic parameters defining the chemical and mechanical properties of the tip-sample system. Long range
processes are also discussed and footprints are identified in experiments conducted on mica and silicon samples. The present methodology can be exploited to validate or invalidate nanoscale dissipative models by comparing predictions with experimental observables.Wearing a single DNA molecule with an AFM tip
http://hdl.handle.net/2117/102976
Wearing a single DNA molecule with an AFM tip
Santos Hernandez, Sergio; Barcons Xixons, Víctor; Font Teixidó, Josep; Thomson, Neil H.
While the fundamental limit on the resolution achieved in an atomic force microscope (AFM) is clearly related to the tip radius, the fact that the tip can creep and/or wear during an experiment is often ignored. This is mainly due to the difficulty in characterizing the tip, and in particular a lack of reliable methods that can achieve this in situ. Here, we provide an in situ method to characterize the tip radius and monitor tip creep and/or wear and biomolecular sample wear in ambient dynamic AFM. This is achieved by monitoring the dynamics of the cantilever and the critical free amplitude to observe a switch from the attractive to the repulsive regime. The method is exemplified on the mechanically heterogeneous sample of single DNA molecules bound to mica mineral surfaces. Simultaneous monitoring of apparent height and width of single DNA molecules while detecting variations in the tip radius R as small as one nanometer are demonstrated. The yield stress can be readily exceeded for sharp tips (R<10 nm) at typical operating amplitudes (A>10nm). The ability to know the AFM tip radius in situ and in real-time opens up the future for quantitative nanoscale materials properties determination at the highest possible spatial resolution.
2017-03-28T14:10:14ZSantos Hernandez, SergioBarcons Xixons, VíctorFont Teixidó, JosepThomson, Neil H.While the fundamental limit on the resolution achieved in an atomic force microscope (AFM) is clearly related to the tip radius, the fact that the tip can creep and/or wear during an experiment is often ignored. This is mainly due to the difficulty in characterizing the tip, and in particular a lack of reliable methods that can achieve this in situ. Here, we provide an in situ method to characterize the tip radius and monitor tip creep and/or wear and biomolecular sample wear in ambient dynamic AFM. This is achieved by monitoring the dynamics of the cantilever and the critical free amplitude to observe a switch from the attractive to the repulsive regime. The method is exemplified on the mechanically heterogeneous sample of single DNA molecules bound to mica mineral surfaces. Simultaneous monitoring of apparent height and width of single DNA molecules while detecting variations in the tip radius R as small as one nanometer are demonstrated. The yield stress can be readily exceeded for sharp tips (R<10 nm) at typical operating amplitudes (A>10nm). The ability to know the AFM tip radius in situ and in real-time opens up the future for quantitative nanoscale materials properties determination at the highest possible spatial resolution.A discrete-time equivalent system approach to the periodic response of nonlinear autonomous circuits
http://hdl.handle.net/2117/101717
A discrete-time equivalent system approach to the periodic response of nonlinear autonomous circuits
Palà Schönwälder, Pere; Miró Sans, Joan Maria
The problem of computing the steady state response of nonlinear autonomous circuits is solved making use of a discrete-time equivalent system approach. With the application of an s-plane to z-plane mapping, the circuit equations are discretized and written in vector form. Using this technique, it is not necessary to repeatedly compute transforms between the time and the frequency domain. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknown variables is described. Application examples on two widely studied circuits are provided to validate the proposed technique.
2017-02-28T15:34:46ZPalà Schönwälder, PereMiró Sans, Joan MariaThe problem of computing the steady state response of nonlinear autonomous circuits is solved making use of a discrete-time equivalent system approach. With the application of an s-plane to z-plane mapping, the circuit equations are discretized and written in vector form. Using this technique, it is not necessary to repeatedly compute transforms between the time and the frequency domain. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknown variables is described. Application examples on two widely studied circuits are provided to validate the proposed technique.An explicit method for modeling lossy and dispersive transmission lines
http://hdl.handle.net/2117/100927
An explicit method for modeling lossy and dispersive transmission lines
Palà Schönwälder, Pere; Miró Sans, Joan Maria
In this paper, an explicit -non iterative- method for modeling lossy and dispersive transmission lines, allowing the inclusion of skin-effect parameters is described. This method, based on multipoint Padé approximation, allows direct implementation to obtain models for existing simulation program -such as SPICE-without the need of making use of optimization algorithms at any stage. Examples are given to show that the described procedure yields the same accuracy as other existing techniques that do require this iterative approach.
2017-02-13T14:26:09ZPalà Schönwälder, PereMiró Sans, Joan MariaIn this paper, an explicit -non iterative- method for modeling lossy and dispersive transmission lines, allowing the inclusion of skin-effect parameters is described. This method, based on multipoint Padé approximation, allows direct implementation to obtain models for existing simulation program -such as SPICE-without the need of making use of optimization algorithms at any stage. Examples are given to show that the described procedure yields the same accuracy as other existing techniques that do require this iterative approach.A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
http://hdl.handle.net/2117/98495
A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
Bonet Dalmau, Jordi; Palà Schönwälder, Pere
We present a direct method for the steady-state 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
time-delayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the period-doubling bifurcations.
2016-12-16T16:30:04ZBonet Dalmau, JordiPalà Schönwälder, PereWe present a direct method for the steady-state 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
time-delayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the period-doubling bifurcations.Stability analysis of periodic solutions in non-linear autonomous circuits: a discrete time approach
http://hdl.handle.net/2117/97804
Stability analysis of periodic solutions in non-linear autonomous circuits: a discrete time approach
Miró Sans, Joan Maria; Palà Schönwälder, Pere; Mas Casals, Orestes Miquel
Steady-state methods have been devised to compute periodic wave-forms 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 non-linear autonomous circuits.' This letter describes how the stability of the
computed periodic wave-forms may be easily determined (I posteriori with no modification to the DTA
solution method.
2016-12-05T16:39:28ZMiró Sans, Joan MariaPalà Schönwälder, PereMas Casals, Orestes MiquelSteady-state methods have been devised to compute periodic wave-forms 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 non-linear autonomous circuits.' This letter describes how the stability of the
computed periodic wave-forms may be easily determined (I posteriori with no modification to the DTA
solution method.The Mendeleev-Meyer force project
http://hdl.handle.net/2117/96683
The Mendeleev-Meyer force project
Santos Hernández, Sergio; Lai, Chia-Yun; Amadei, Carlo Alberto; Gadelrab, Karim Raafat; Tang, Tzu-Chieh; 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.
2016-11-15T16:04:39ZSantos Hernández, SergioLai, Chia-YunAmadei, Carlo AlbertoGadelrab, Karim RaafatTang, Tzu-ChiehVerdaguer Prats, AlbertBarcons Xixons, VíctorFont Teixidó, JosepColchero, JaimerChiesa, MatteoHere 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.