689 research outputs found

    Inferring the phase response curve from observation of a continuously perturbed oscillator

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    Phase response curves are important for analysis and modeling of oscillatory dynamics in various applications, particularly in neuroscience. Standard experimental technique for determining them requires isolation of the system and application of a specifically designed input. However, isolation is not always feasible and we are compelled to observe the system in its natural environment under free-running conditions. To that end we propose an approach relying only on passive observations of the system and its input. We illustrate it with simulation results of an oscillator driven by a stochastic force.Comment: 11 pages (+6 supplementary), 7 figures (+8 supplementary

    Phase resetting of collective rhythm in ensembles of oscillators

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    Phase resetting curves characterize the way a system with a collective periodic behavior responds to perturbations. We consider globally coupled ensembles of Sakaguchi-Kuramoto oscillators, and use the Ott-Antonsen theory of ensemble evolution to derive the analytical phase resetting equations. We show the final phase reset value to be composed of two parts: an immediate phase reset directly caused by the perturbation, and the dynamical phase reset resulting from the relaxation of the perturbed system back to its dynamical equilibrium. Analytical, semi-analytical and numerical approximations of the final phase resetting curve are constructed. We support our findings with extensive numerical evidence involving identical and non-identical oscillators. The validity of our theory is discussed in the context of large ensembles approximating the thermodynamic limit.Comment: submitted to Phys. Rev.

    Low-Voltage Ultra-Low-Power Current Conveyor Based on Quasi-Floating Gate Transistors

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    The field of low-voltage low-power CMOS technology has grown rapidly in recent years; it is an essential prerequisite particularly for portable electronic equipment and implantable medical devices due to its influence on battery lifetime. Recently, significant improvements in implementing circuits working in the low-voltage low-power area have been achieved, but circuit designers face severe challenges when trying to improve or even maintain the circuit performance with reduced supply voltage. In this paper, a low-voltage ultra-low-power current conveyor second generation CCII based on quasi-floating gate transistors is presented. The proposed circuit operates at a very low supply voltage of only ±0.4 V with rail-to-rail voltage swing capability and a total quiescent power consumption of mere 9.5 ”W. Further, the proposed circuit is not only able to process the AC signal as it's usual at quasi-floating gate transistors but also the DC which extends the applicability of the proposed circuit. In conclusion, an application example of the current-mode quadrature oscillator is presented. PSpice simulation results using the 0.18 ”m TSMC CMOS technology are included to confirm the attractive properties of the proposed circuit

    A LTE MIMO OTA Test System Using Vector Signal Transceivers

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    A 2 × 2 multiple-input-multiple-output over-the-air (MIMO OTA) test system based on four field-programmable Vector-Signal-Transceiver (VST) modules is presented. The system enables 2 x 2 MIMO OTA testing by assembling of a twochannel Evolved Node B (eNodeB) LTE base station emulator, a 2x2 channel emulator, and a two-channel user equipment (UE) simulator. A two-stage MIMO OTA test method has been demonstrated with downlink Long-Term Evolution Time-Division Duplex (LTE-TDD) mode using different modulation and coding schemes (MCSs). Test results and analysis are shown. This system will allow a systematic study of MIMO OTA metrology needs

    Kraus representation of damped harmonic oscillator and its application

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    By definition, the Kraus representation of a harmonic oscillator suffering from the environment effect, modeled as the amplitude damping or the phase damping, is directly given by a simple operator algebra solution. As examples and applications, we first give a Kraus representation of a single qubit whose computational basis states are defined as bosonic vacuum and single particle number states. We further discuss the environment effect on qubits whose computational basis states are defined as the bosonic odd and even coherent states. The environment effects on entangled qubits defined by two different kinds of computational basis are compared with the use of fidelity.Comment: 9 pages, 3 figure
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