CIRCUIT - Grup de Recerca en Circuits i Sistemes de Comunicació
http://hdl.handle.net/2117/3801
2017-08-20T02:34:48ZA discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
http://hdl.handle.net/2117/106912
A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
Bonet Dalmau, Jordi; Palà Schönwälder, Pere; Miró Sans, Joan Maria
We present a direct method for the steady-state and stability analysis of autonomous circuits with transmission lines and generic nonlinear 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 build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is described. Without any modification 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.
2017-07-27T09:00:31ZBonet Dalmau, JordiPalà Schönwälder, PereMiró Sans, Joan MariaWe present a direct method for the steady-state and stability analysis of autonomous circuits with transmission lines and generic nonlinear 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 build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is described. Without any modification 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.A discrete-time technique for the steady-state analysis of nonlinear class-E amplifiers
http://hdl.handle.net/2117/106735
A discrete-time technique for the steady-state analysis of nonlinear class-E 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 class-E 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 class-E operation and even to avoid destruction of the switching device. In this paper, a new method for determining the steady-state response of nonlinear circuits containing ideal switches is proposed. While the method is more general, the description is based on the class-E amplifier because of its inherent interest. The method is based on a time-domain 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 steady-state, 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.
2017-07-24T09:58:03ZÁguila López, Francisco delPalà Schönwälder, PereMolina Gaudó, PilarMediano Heredia, ArturoSwitched circuits are widely used, particularly for power electronic applications in which efficiency is important. Of these applications, the class-E 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 class-E operation and even to avoid destruction of the switching device. In this paper, a new method for determining the steady-state response of nonlinear circuits containing ideal switches is proposed. While the method is more general, the description is based on the class-E amplifier because of its inherent interest. The method is based on a time-domain 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 steady-state, 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.Análisis de circuitos autónomos no lineales con parámetros distribuidos mediante técnicas temporales discretas
http://hdl.handle.net/2117/106645
Análisis de circuitos autónomos no lineales con parámetros distribuidos mediante técnicas temporales discretas
Bonet Dalmau, Jordi; Palà Schönwälder, Pere; Miró Sans, Joan Maria
2017-07-20T10:18:16ZBonet Dalmau, JordiPalà Schönwälder, PereMiró Sans, Joan MariaReceptor superregenerativo para comunicaciones opticas no guiadas
http://hdl.handle.net/2117/105963
Receptor superregenerativo para comunicaciones opticas no guiadas
Miguel López, José María; Moncunill Geniz, Francesc Xavier; Puerta Notario, Antonio
2017-06-28T16:03:59ZMiguel López, José MaríaMoncunill Geniz, Francesc XavierPuerta Notario, AntonioConsideraciones sobre el diseño de los sistemas para comunicaciones opticas no guiadas
http://hdl.handle.net/2117/105955
Consideraciones sobre el diseño de los sistemas para comunicaciones opticas no guiadas
Puerta Notario, Antonio; Miguel López, José María; Miró Sans, Joan Maria; Sanz Postils, Margarita
2017-06-28T14:52:03ZPuerta Notario, AntonioMiguel López, José MaríaMiró Sans, Joan MariaSanz Postils, MargaritaJoint symbol and chip synchronization for a burst-mode-communication superregenerative MSK receiver
http://hdl.handle.net/2117/104237
Joint symbol and chip synchronization for a burst-mode-communication 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 burst-mode 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.
2017-05-09T14:46:29ZLópez Riera, AlexisÁguila López, Francisco delPalà Schönwälder, PereBonet Dalmau, JordiGiralt Mas, Ma. RosaMoncunill Geniz, Francesc XavierIn this paper we describe a superregenerative (SR)
MSK receiver able to operate in a burst-mode 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 direct-sequence spread-spectrum super-regenerative receiver
http://hdl.handle.net/2117/104130
A direct-sequence spread-spectrum super-regenerative receiver
Moncunill Geniz, Francesc Xavier; Mas Casals, Orestes Miquel; Palà Schönwälder, Pere
Current applications of the super-regenerative receiver use narrowband modulations. In this paper a new architecture that allows incoherent detection of spread-spectrum signals is presented. A pseudorandom code generator has been added to the original circuit. It is clocked by the quench oscillator and takes advantage of the characteristic broad reception bandwidth. CDMA can be achieved via ASK and FSK modulated signals with high simplicity in the RF stage as well as low power consumption.
2017-05-05T13:34:53ZMoncunill Geniz, Francesc XavierMas Casals, Orestes MiquelPalà Schönwälder, PereCurrent applications of the super-regenerative receiver use narrowband modulations. In this paper a new architecture that allows incoherent detection of spread-spectrum signals is presented. A pseudorandom code generator has been added to the original circuit. It is clocked by the quench oscillator and takes advantage of the characteristic broad reception bandwidth. CDMA can be achieved via ASK and FSK modulated signals with high simplicity in the RF stage as well as low power consumption.Steady 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.