1,720,965 research outputs found
Non-instantaneous synaptic transmission in spiking neuron networks and equivalence with delay distribution
No full textEfficient Transient Noise Analysis of Non-Periodic Mixed Analog/Digital Circuits
No full textThis paper proposes a numerical method for accurate time-domain noise simulation of mixed analog/digital electrical circuits that in principle do not admit a periodic steady-state working condition, such as fractional PLL. By means of a tool known as saltation matrix, which allows dealing with non-smooth vector fields, a variational approach is adopted.
The power spectral density of a noisy electrical variable is computed by applying the Thomson's MTM to the numerical solution of the stochastic variational model of the circuit. This allows to resort to a single transient simulation run, thus avoiding cpu time consuming Monte-Carlo-like approaches. The effectiveness of the proposed method is shown by comparing simulation results related to a commercial fractional PLL with experimental data
Transient dynamics of an adiabatic NEMS
No full textThis paper is focused on the transient dynamics of an adiabatic nano-electromechanical system (NEMS), consisting of a nano-mechanical oscillator coupled to a quantum dot. By numerically solving the nonlinear stochastic differential equation governing the oscillator, the time evolution of the oscillator position, of the dot occupation number and of the current are studied. Different parameter settings are studied where the system exhibits bi-stable, tri-stable or mono-stable behavior on a finite-time horizon. It is shown that, after a typically long transient, the system under investigation exhibits no hysteretic behavior and that a unique steady state is reached, independently of the initial conditions. The transient dynamics is marked out by one or two well separated characteristic times, depending on the considered case (i.e., mono- or multi-stable). These times are evaluated for a dot on-resonance or off-resonance. It turns out that the characteristic time scales are long in comparison to the period of the uncoupled oscillator, particularly at low bias, suggesting that the predicted transient dynamics may be observed in state-of-the-art experimental setups
A circuit model of hysteresis and creep
No full textA circuit architecture that models hysteretic phenomena is proposed. The model is flexible enough to reproduce both rate-independent hysteresis and thermal relaxation effects (creep), commonly observed in many real-world physical systems such as piezoelectric actuators. By suitably tuning the nonlinear characteristics of the resistive elements of the network, the well-known log(t) time dependence of the creep relaxation dynamics can be accurately reproduced. An identification procedure is proposed, and two test cases are discussed
Memory characteristics of hysteresis and creep in multi-layer piezoelectric actuators: An experimental analysis
No full textIn this paper we provide an experimental characterization of creep and hysteresis in a multi layer piezoelectric actuator (PEA), taking into account their relationships in terms of memory structure. We fit the well-known log-t model to the response of the PEA when driven by piecewise-constant signals, and find that both the instantaneous and the delayed response of the PEA display hysteretic dependence on the voltage level. We investigate experimentally the dependence of the creep coefficient on the input history, by driving the PEA along first order reversal curves and congruent minor loops, and find that it displays peculiar features like strict congruence of the minor loops and discontinuities. We finally explain the observed experimental behaviors in terms of a slow relaxation of the staircase interface line in the Preisach plane
A low-complexity circuit model of hysteresis
No full textA circuit architecture modelling rate-independenthysteretic phenomena is presented and discussed. The core ofthe circuit is a ladder structure with longitudinal nonlinearresistors and transverse linear capacitors. In a separate loop, alinear combination of input and capacitor voltages provides thedriving voltage for a resistor with monotonic, piecewise-lineardriving-point characteristic. The resistor current represents theoutput variable. The circuit parameters can be found fromexperimental data through a standard quadratic programmingoptimization procedure. The model fitting features are tested byusing two experimental data sets. One is theB(H)function of amagnetic material; the other is the deformation of a piezoelectricactuator as a function of the applied voltage. In this last case,an accurate comparison with the predictions of the well-knownPreisach model evidences that the circuit model achieves the sameaccuracy with a much smaller number of parameters. All thecircuit simulations are performed by using PSPICE
Reliable and efficient phase noise simulation of mixed-mode integer-N Phase-Locked Loops
No full textAccurate and efficient PSD computation in mixed-signal circuits: A time-domain approach
Full text linkThe aim of this brief is twofold. On one side, the time-domain technique presented by Vasudevan to obtain the average and instantaneous power-spectral density of electrical variables in analog circuits characterized by (non)stationary noise sources is rigorously extended to the wide class of analog mixed-signal circuits modeled as hybrid dynamical systems. On the other side, an efficient numerical implementation is proposed to overcome the computational effort required by the original approach. The reliability of the method is first tested through the analog ring oscillator analyzed by Vasudevan. A fractional delta-sigma phase-locked loop with dithering is then simulated and the obtained results are partially validated through experimental measurements. © 2004-2012 IEEE
Coulomb blockade microscopy of spin-density oscillations and fractional charge in quantum spin Hall dots
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