153 research outputs found
Phase noise in distributed oscillators
The phase noise of a distributed oscillator is evaluated very simply by identifying an effective capacitance equal to the total capacitance distributed along the transmission lines. The contributions of the various passive and active noise sources to the total phase noise are calculated revealing several guidelines for improved distributed oscillator designs
Persistent chimera states in nonlocally coupled phase oscillators
Chimera states in the systems of nonlocally coupled phase oscillators are
considered stable in the continuous limit of spatially distributed oscillators.
However, it is reported that in the numerical simulations without taking such
limit, chimera states are chaotic transient and finally collapse into the
completely synchronous solution. In this paper, we numerically study chimera
states by using the coupling function different from the previous studies and
obtain the result that chimera states can be stable even without taking the
continuous limit, which we call the persistent chimera state.Comment: To be published in Physical Review E (Rapid Communication), 5 pages,
7 figure
Silicon-based distributed voltage-controlled oscillators
Distributed voltage-controlled oscillators (DVCOs) are presented as a new approach to the design of silicon VCOs at microwave frequencies. In this paper, the operation of distributed oscillators is analyzed and the general oscillation condition is derived, resulting in analytical expressions for the frequency and amplitude. Two tuning techniques for DVCOs are demonstrated, namely, the inherent-varactor tuning and delay-balanced current-steering tuning. A complete analysis of the tuning techniques is presented. CMOS and bipolar DVCOs have been designed and fabricated in a 0.35-μm BiCMOS process. A 10-GHz CMOS DVCO achieves a tuning range of 12% (9.3-10.5 GHz) and a phase noise of -103 dBc/Hz at 600 kHz offset from the carrier. The oscillator provides an output power of -4.5 dBm without any buffering, drawing 14 mA of dc current from a 2.5-V power supply. A 12-GHz bipolar DVCO consuming 6 mA from a 2.5-V power supply is also demonstrated. It has a tuning range of 26% with a phase noise of -99 dBc/Hz at 600 kHz offset from the carrier
A novel tuning technique for distributed voltage controlled oscillators
A novel current-steering delay-balanced tuning technique for distributed voltage controlled oscillators (DVCO) is demonstrated. This tuning technique is used to design a DVCO operating at 10 GHz in a 0.35 μm CMOS technology. The DVCO is continuously tunable between 9.9 and 10.3 GHz. Special attention is paid to the layout issues for the high frequency design
Plasticity and learning in a network of coupled phase oscillators
A generalized Kuramoto model of coupled phase oscillators with slowly varying
coupling matrix is studied. The dynamics of the coupling coefficients is driven
by the phase difference of pairs of oscillators in such a way that the coupling
strengthens for synchronized oscillators and weakens for non-synchronized
pairs. The system possesses a family of stable solutions corresponding to
synchronized clusters of different sizes. A particular cluster can be formed by
applying external driving at a given frequency to a group of oscillators. Once
established, the synchronized state is robust against noise and small
variations in natural frequencies. The phase differences between oscillators
within the synchronized cluster can be used for information storage and
retrieval.Comment: 10 page
Analysis of 2D THz-Raman spectroscopy using a non-Markovian Brownian oscillator model with nonlinear system-bath interactions
We explore and describe the roles of inter-molecular vibrations employing a
Brownian oscillator (BO) model with linear-linear (LL) and square-linear (SL)
system-bath interactions, which we use to analyze two-dimensional (2D)
THz-Raman spectra obtained by means of molecular dynamics (MD) simulations. In
addition to linear absorption (1D IR), we calculated 2D Raman-THz-THz,
THz-Raman-THz, and THz-THz-Raman signals for liquid formamide, water, and
methanol using an equilibrium non-equilibrium hybrid MD simulation. The
calculated 1D IR and 2D THz-Raman signals are compared with results obtained
from the LL+SL BO model applied through use of hierarchal Fokker-Planck
equations with non-perturbative and non-Markovian noise. We find that all of
the qualitative features of the 2D profiles of the signals obtained from the MD
simulations are reproduced with the LL+SL BO model, indicating that this model
captures the essential features of the inter-molecular motion. We analyze the
fitted 2D profiles in terms of anharmonicity, nonlinear polarizability, and
dephasing time. The origins of the echo peaks of the librational motion and the
elongated peaks parallel to the probe direction are elucidated using optical
Liouville paths.Comment: 37 pages with 14 figures and 3 table
Enhanced squeezing with parity kicks
Using exponential quadratic operators, we present a general framework for
studying the exact dynamics of system-bath interaction in which the Hamiltonian
is described by the quadratic form of bosonic operators. To demonstrate the
versatility of the approach, we study how the environment affects the squeezing
of quadrature components of the system. We further propose that the squeezing
can be enhanced when parity kicks are applied to the system.Comment: 4 pages, 2 figure
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