Regime Of Chaotic Oscillations Research Articles

Chaotic signal generation in a CW K-band gyro-TWT with strong output reflections

We experimentally study the dynamics of a K-band continuous wave gyro-resonant traveling wave tube (gyro-TWT) with strong output reflections. By varying system parameters, we have obtained transitions from periodic self-modulation regimes with line spectra to more complex oscillation regimes. We present the analysis of experimental data verifying the experimental observation of chaotic oscillation regimes. We have shown that chaotic oscillation regimes emerge in a fairly narrow parameter area, about 0.5% of magnetic field strength and about 10% of reflectivity. Maximum oscillation power reaches 0.5 kW at about 2% efficiency. For a gyro-TWT with output reflections operating in the CW mode, the chaotic oscillations are being experimentally observed and systematically analyzed for the first time.

High-Power Tunable Source of Chaotic Radiation Based on a Ka-Band Helical Gyro-BWO

We present results of experiments where Ka-band chaotic oscillation regimes with a bandwidth of about 1 GHz have been obtained in a pulsed gyrotron backward wave oscillator (gyro-BWO) using a helically corrugated waveguide. The averaged radiated power reached 40 kW with a pulse duration of about 120 μs and a repetition rate of up to 10 Hz. The variation of magnetic field allows for tuning of the central frequency of the radiation in the 32.5-35.5 GHz range.

Control for statistical characteristics of chaotic oscillation regimes by noise exposure

The possibility to control for statistical characteristics of chaotic oscillation regimes by use of noise is studied. For synchronous oscillation regimes in the dynamics of coupled oscillatory systems, it is shown that noise leads to significant changes in the mean Holder exponent. The presence of a monotonic dependence of this quantity on the intensity of the external noise makes it possible to generate a chaotic signal with given correlation characteristics.

Regular and chaotic dynamics of the dipole moment of square dipole arrays

Dipole lattices, which represent square dipole arrays, are investigated. Various types of equilibrium configurations of arrays are obtained, and conditions are shown under which these configurations are established. On the basis of parametric bifurcation diagrams, the main types of regular and chaotic oscillation regimes of the total dipole moment of a system are considered and their dependence on the amplitude, frequency, and polarization of an alternating field, as well as on the initial equilibrium configuration of arrays, is analyzed. Scenarios of the onset of chaotic regimes are demonstrated, including those that occur via the establishment and variation of quasiperiodic oscillations of the dipole moment of a system. The dynamic bistability state is revealed in which a stochastic resonance—an increase in the response of a system to a harmonic signal in the presence of noise—can be implemented.

Spectral characteristics of noisy Josephson flux flow oscillator

The current-voltage and spectral characteristics of a flux flow oscillator (FFO) based on a long Josephson junction are studied. The investigations are performed in the range of small bias currents and magnetic fields where the FFO radiates a quasi-chaotic signal with extremely large radiation linewidth, and the displaced linear slope (DLS) is observed at the current-voltage characteristic. Using direct numerical simulation of the sine-Gordon equation, it is shown that for large lengths of the Josephson junction or in the case of partial matching of the FFO with external waveguide system, the DLS with extremely large linewidth is transformed into Fiske steps with very narrow linewidth. As for Fiske steps, the appearance of regime of chaotic oscillations can be explained by multiple reflections of the traveling waves from junction ends rather than simply by excitation of the internal oscillation modes in the “soft” fluxon chain at weak magnetic fields.

Models of seismotectonic systems with dry friction

Several models of a seismic regime and block dynamics that are based on frictional self-oscillations in systems with nonlinear dry friction are considered. The set of Burridge-Knopoff models is presented to describe the generation of earthquakes with the relative movement of the fault sides. The disk model, which describes rotary dynamics of the crustal blocks, and the model of the block dynamics in the foredeeps, are examined. It is established that a regime of chaotic oscillations exists in a certain range of parameters (frictional force, the velocity of leading blocks, etc.) in the considered systems. This limits the predictability of these systems.

Spontaneous voltage oscillations and response dynamics of a Hodgkin-Huxley type model of sensory hair cells

We employ a Hodgkin-Huxley-type model of basolateral ionic currents in bullfrog saccular hair cells for studying the genesis of spontaneous voltage oscillations and their role in shaping the response of the hair cell to external mechanical stimuli. Consistent with recent experimental reports, we find that the spontaneous dynamics of the model can be categorized using conductance parameters of calcium-activated potassium, inward rectifier potassium, and mechano-electrical transduction (MET) ionic currents. The model is demonstrated for exhibiting a broad spectrum of autonomous rhythmic activity, including periodic and quasi-periodic oscillations with two independent frequencies as well as various regular and chaotic bursting patterns. Complex patterns of spontaneous oscillations in the model emerge at small values of the conductance of Ca2+-activated potassium currents. These patterns are significantly affected by thermal fluctuations of the MET current. We show that self-sustained regular voltage oscillations lead to enhanced and sharply tuned sensitivity of the hair cell to weak mechanical periodic stimuli. While regimes of chaotic oscillations are argued to result in poor tuning to sinusoidal driving, chaotically oscillating cells do provide a high sensitivity to low-frequency variations of external stimuli.

Evolution of transient oscillation regimes in monolithic ring lasers

The evolution of the regions of existence and stability of quasi-periodic and chaotic oscillation regimes in a monolithic ring Nd:YAG laser caused by changing the pump power is studied experimentally. It is shown that the dynamic chaos regime appearing upon modulation of the pump power is alternated by windows in which different quasi-periodic lasing regimes take place. A scenario of the passage from the self-modulation lasing regime to dynamic chaos is considered.

Effect of a permanent magnetic field on quasi-periodic and chaotic oscillation regimes in solid-state ring lasers

Features of nonlinear dynamics of solid-state ring lasers in quasi-periodic and chaotic oscillation regimes in a magnetic field are studied experimentally. Windows of periodic and quasi-periodic regimes within the region of dynamic chaos in a monolithic ring laser with periodically modulated pumping are observed experimentally for the first time. It is shown that an applied magnetic field changes the boundaries of the existence of various nonstationary regimes. It is established that, under certain conditions, lasing regimes can be switched in magnetic fields with strengths of ∼1 Oe.

Chaotic Negative-Resistance Oscillators with a Multibranch Piecewise-Linear Current–Voltage Characteristic

Chaotic oscillators with a negative-differential-resistance (NDR) subsystem having a multibranch piecewise-linear i–v characteristic (IVC) are considered. The problem of switching between chaotic oscillation regimes by changing the IVC electronically is addressed. New circuit realizations of the NDR subsystem are described in detail. It is shown that they provide highly stable IVCs.

A method for determining the transient process duration in dynamic systems in the regime of chaotic oscillations

We describe a method for determining the transient process duration in a standard two-dimensionaldynamic system with discrete time (Henon map), occurring in the regime of chaotic oscillations

COMMUNICATIONS USING CASCADE COUPLED PHASE-LOCKED LOOP CHAOS

It has been shown that chaotic signal can be obtained from cascade coupled phase-locked loop systems in a broad region of parameter variation. In this paper we demonstrate by computer simulation that the cascade coupled PLLs may be a useful tool for the solution of the problem of synchronization of two PLL systems in the regime of chaotic oscillations (with stabilized average frequency). We give an example of using cascade coupled PLLs for data communication by means of the chaotic signal.

Images of synchronized chaos: Experiments with circuits.

Synchronization of oscillations underlies organized dynamical behavior of many physical, biological and other systems. Recent studies of the dynamics of coupled systems with complex behavior indicate that synchronization can occur not only in case of periodic oscillations, but also in regimes of chaotic oscillations. Using experimental observations of chaotic oscillations in coupled nonlinear circuits we discuss a few forms of cooperative behavior that are related to the regimes of synchronized chaos. This paper is prepared under the request of the editors of the special focus issue of Chaos and contains the materials for the lecture at the International School in Nonlinear Science, "Nonlinear Waves: Synchronization and Patterns," Nizhniy Novgorod, Russia, 1995. The main goal of the paper is to outline the collection of examples that illustrate the state of the art of chaos synchronization. (c) 1996 American Institute of Physics.

Sources of intensive noise signals of millimeter wave band

The new method of the CW intensive noise signals excitation in millimeter wave band has been studied. With this aim in mind the O-type Backward Wave Oscillators, operating in chaotic oscillation regime, are proposed to use. The noise sources, based onBWO, have a high efficiency, universal power spectrums and feasibility of electronic tuning of the noise signal frequency in the relative range of 4–10%. Low voltage noise sources, operating in the bands needed over the range from 30to 60GHz, make possible output power of 8 − 25W and 4W respectively and 3 −dB power spectrum width more than 300M H z. Application of the suitableBWO offers to excite the noise signals in decimeter and centimeter ranges too.