Chaotic Signal Generator Research Articles

Generation of polarization-resolved wideband unpredictability-enhanced chaotic signals based on vertical-cavity surface-emitting lasers subject to chaotic optical injection.

A system framework is proposed and analyzed for generating polarization-resolved wideband unpredictability-enhanced chaotic signals based on a slave vertical-cavity surface-emitting laser (S-VCSEL) driven by an injected optical chaos signal from a master VCSEL (M-VCSEL) under optical feedback. After calculating the time series outputs from the M-VCSEL under optical feedback and the S-VCSEL under chaotic optical injection by using the spin-flip model (SFM), the unpredictability degree (UD) is evaluated by permutation entropy (PE), and the bandwidth of the polarization-resolved outputs from the M-VCSEL and S-VCSEL are numerically investigated. The results show that, under suitable parameters, both the bandwidth and UD of two polarization components (PCs) outputs from the S-VCSEL can be enhanced significantly compared with that of the driving chaotic signals output from the M-VCSEL. By simulating the influences of the feedback and injection parameters on the bandwidth and UD of the polarization-resolved outputs from S-VCSEL, related operating parameters can be optimized.

Realization of Digital Chaotic Signal Generation Circuits

To overcome the shortcomings of realizing chaotic system by analog circuits, digital chaotic signal generation circuits based on DSP are designed. Computer simulation of chaotic system is performed firstly, and the discrete equations are obtained using discretization algorithm. On this basis, the design of hardware circuits based on DSP is made, and the corresponding C programs are constructed. Through the debugging of software and hardware, digital design of chaotic system based on DSP is achieved, and chaotic attractor is observed through an oscilloscope by digital-to-analog conversion circuit. The experimental results coincide with the simulation, proving the correctness of the design. The chaotic signal generation circuits can provide rich digital chaotic signals sources for the application of chaotic systems in engineering.

An ultrawideband spin-wave medium-power chaos generator based on field-effect transistors

A prototype of an ultrawideband (UWB) microwave chaos generator based on a nonlinear spin-wave transmission line, a multistage transistor amplifier with an output amplifier based on GaAs field-effect transistors, and a microstrip bandpass filter was constructed. The possibility of autonomous generation of a UWB chaotic microwave signal with a central frequency of 3 GHz and a total power of about 4 W in a frequency band exceeding 30% was demonstrated. The proposed chaos generator is characterized by a fairly high efficiency of about 20%.

Remote Radar Based on Chaos Generation and Radio Over Fiber

Abstract: An ultrawideband (UWB) radar system for remote ranging based onmicrowave-photonic chaotic signal generation and fiber-optic distribution is proposedand demonstrated experimentally. In this system, an optical-feedback semiconductorlaser with optical injection in the central office generates photonic UWB chaos as probingsignal, and two single-mode fibers transport the optical signal to the remote antennamonitoring terminal and return the corresponding echoed signal back to the centraloffice. In the remote antenna terminal, the photonic signal is transformed into microwavechaos by a fast photodetector and then launched to target by a transmitting antenna,and the echoed signal received by another antenna is converted into optical domain bymodulating a laser diode. The target ranging is achieved at the central office by correlat-ing the echoed signal with the reference signal. We experimentally realize a detectionrange of 8 m, for a free-space target, after 24-km remote distance, and achieve a rang-ing resolution of 3 cm for single target and 8 cm for double targets. In another fiber linkbranch with 15-km fiber transmission, we obtained the 2-cm ranging resolution for asingle target.Index Terms: Chaos, remote radar, semiconductor lasers.

Review and Theory of Optical Soliton Generation Used to Improve the Security and High Capacity of MRR and NRR Passive Systems

We review the generation, application and theory of soliton pulses in a nonlinear fiber optic medium to improve the security and capacity of optical passive systems such as add/drop and PANDA ring resonators. The improvement of the ring resonator passive systems depends on the output signals, where the chaotic signal generation within the systems is the critical properties of the output signals which can be used to enhance the security and capacity. The passive ring resonator systems are constructed by a nonlinear Kerr effect fiber optic to produce optical signals in the form of chaotic and multi dark and bright soliton pulses applied in many areas of engineering, biotechnology and communications. In this research, we review the generation and applications of soliton signals and theory of the main ring resonator passive systems as add/drop and PANDA ring resonators, where the easy controlling of the output signals is the benefit of using these systems due to the interferometric roles.

Studies on Dynamics of Driven Bilaterally Coupled Gunn Oscillator

The dynamics of bilaterally coupled Gunn oscillator driven by external periodic signal has been examined through numerical simulation and experimental observation. The coupling factors between the two oscillators in either path as well as the strength and frequency of the external periodic driving signals are key parameters to control the dynamics of Driven Bilaterally Coupled Gunn Oscillator (DBCGO) system. The numerical study explores the possibility of generation of controllable chaotic signals in DBCGO system. The present work also considers this method through a hardware experiment. For different set of coupling factors, driving signal strength and frequencies, chaotic oscillations are observed. Therefore, the DBCGO system with suitable couplings and driving signal conditions can be considered as a potential source of chaotic signals in microwave frequency range.

A New Chaotic Signal Generation of a Series Microring Resonator for Optical Communication

We propose a new method using light pulses tracing in a micro ring resonator, where the randomly digital codes can be performed. The chaotic signals can be generated and formed by the logical pulses by using the signal quantizing method, which can be randomly coded by controlling the specific optical input coupling powers, i.e. coupling coefficient (κ) and ring radii. Simulation results when the ring radius used are between 7-10.0 μm, and the other selected parameters are close to the practical device values that are presented and discussed. The random codes can be generated by the random control of coupling powers, which can be transmitted and retrieved via the design filters by the specific clients. We can be controlled input power used are between 2.0 and 5.0 mW, whereas the quantizing threshold powers and the traveling roundtrips are 0.3–0.4 mW and 8000–10,000, respectively.

Implementation of FPGA-based real time novel chaotic oscillator

Currently, chaotic systems and chaos-based applications are commonly used in the engineering fields. One of the main structures used in these applications is the chaos-based signal generators. Chaotic signal generators have an important role, particularly in chaotic communication and cryptology. In this study, the Pehlivan-Wei chaotic system, which is a recently developed chaotic system, has been implemented with FPGA using three distinct algorithms (the Euler, Heun, and RK4) for the first time in literature. Numerical and HDL approaches are implemented by these three algorithms to compare the performance of each model for use in chaotic generators. In addition, the Lyapunov exponents and phase portraits of the system have been extracted for chaos analysis. RMSE analysis has been conducted on the chaotic generators, which are modeled using the Euler, Heun, and RK4 algorithms in order to observe error rates of each numerical algorithm in a comparative aspect. The performance of new chaotic system with various data sets has been analyzed. The operation frequency of the chaotic oscillators synthesized and tested for the Virtex-6 FPGA chip has been able to reach up to 463.688 MHz and the chaotic system has been able to calculate 300,000 data sets in 0.0284 s. However, PC-based algorithm having highest performance score can calculate 300,000 data sets in a period of 75.363 s. A comparison study has been performed on the performance of the FPGA-based and PC-based solutions to evaluate each approach.

Generation and synchronization of feedback-induced chaos in semiconductor ring lasers by injection-locking

A smart scheme for chaotic signal generation in a semiconductor ring laser (SRL) with optical feedback is proposed and investigated numerically. The chaotic oscillation in the SRL can be generated by the partial reflection of the laser output. Time series, attracter and the power spectrum, as well as the Lyapunov exponent spectrum, are calculated and analyzed. We also study the synchronization scheme of feedback-induced chaos in SRLs by optical injection that consists of a drive SRL with optical feedback and a response SRL with optical injection from the drive laser. High-quality synchronization is achieved with suitable injection strength and detuning frequency between the drive and the response SRLs.

Digital Chaotic Signal Generator Using Robust Chaos in Compound Sinusoidal Maps

SUMMARY This paper presents an implementation of a digital chaoticsignal generator based on compound one-dimensional sinusoidal maps.The proposed chaotic map not only offers high chaoticity measured from apositive lyapunov exponent but also provides diverse bifurcation structureswith robust chaos over most regions of parameter spaces. Implementationon FPGA realizes small number of components and offers a highly randomchaotic sequence with no autocorrelation. The proposed chaotic signal gen-erator offers a potential alternative in random test pattern generation or insecured data communication applications. key words: sinusoidal chaotic map, digital chaotic signal generator 1. Introduction A digital chaotic signal generator provides a random digitalsequence for various applications such as in automatic testpattern generation [1], in data encryption [2], or in securecommunications [3]. A search for effective chaotic mapswith hardware implementations for use as a core buildingblock in such digital chaotic signal generators have there-fore been made continuously, involving logistics map [4],tent map [5] and Rossler chaotic model [6]. However, most¨one-dimensional chaotic maps that employ simple nonlin-earity may not provide sufficient complexity. This lettertherefore focuses on a chaotic map using a sinusoidal func-tion with an inherent multi-modal polynomial function de-scribed by Maclaurin series. The compound topology of si-nusoidal maps is proposed for the enhancement of dynami-cal behaviors in terms of a positive lyapunov exponent, bi-furcation structure, and hence randomness entropy of a dig-ital sequence output.

전압 제어형 카오스회로의 온도특성 해석

This paper presents a temperature analysis of the chaotic behavior in the voltage controlled CMOS chaotic circuit. The circuit is based on a simple nonlinear function block which is needed for chaotic signal generation. It consists of a NFB (nonlinear function block), a level shifter and non-overlapping two-phase clock for sample and hold. By SPICE simulation, chaotic dynamics such as frequency spectra and bifurcations according to the temperature variations were analyzed. And, it was showed that the circuit can generate discrete chaotic signals within control voltage in the range from 1.2 V to 2.3 V in a specific temperature condition of .

Subharmonics and chaos generation in all-fiber phase modulator: experimental and theoretical analyses with simulation

We report the results of experimental observation and theoretical analysis of the generation of subharmonic and chaotic signals in a harmonically driven all-fiber phase modulator (PM). When a PM constructed with optical fiber wrapped around a piezoelectric cylinder is driven at high amplitude, we identified that the fiber itself moves with subharmonic frequencies while the piezoelectric cylinder maintains harmonic motion. A theoretical model is presented that is a modification of the model for a bouncing ball on an oscillating table. Some key physical parameters for the model are identified. Potential origins for the discrepancy between the experimental and theoretical analyses are discussed. Ways to suppress the nonlinear effect are also discussed.

Synaptic Variability in a Cortical Neuromorphic Circuit

Variable behavior has been observed in several mechanisms found in biological neurons, resulting in changes in neural behavior that might be useful to capture in neuromorphic circuits. This paper presents a neuromorphic cortical neuron with synaptic neurotransmitter-release variability, which is designed to be used in neural networks as part of the Biomimetic Real-Time Cortex project. This neuron has been designed and simulated using carbon nanotube (CNT) transistors, which is one of several nanotechnologies under consideration to meet the challenges of scale presented by the cortex. Some research results suggest that some instances of variability are stochastic, while others indicate that some instances of variability are chaotic. In this paper, both possible sources of variability are considered by embedding either Gaussian noise or a chaotic signal into the neuromorphic or synaptic circuit and observing the simulation results. In order to embed chaotic behavior into the neuromorphic circuit, a chaotic signal generator circuit is presented, implemented with CNT transistors that could be embedded in the electronic neural circuit, and simulated using CNT SPICE models. The circuit uses a chaotic piecewise linear 1-D map implemented by switched-current circuits. The simulation results presented in this paper illustrate that neurotransmitter-release variability plays a beneficial role in the reliability of spike generation. In an examination of this reliability, the precision of spike timing in the CNT circuit simulations is found to be dependent on stimulus (postsynaptic potential) transients. Postsynaptic potentials with low neurotransmitter release variability or without neurotransmitter release variability produce imprecise spike trains, whereas postsynaptic potentials with high neurotransmitter-release variability produce spike trains with reproducible timing.

Chaos Based Optical Communication

 Abstract—Chaos based communication has been a very attractive research field from last couple of decades due to its potential of providing secure communication. In this paper, we reviewed principles and theory governing the field of chaos. We studied governing principles and different methods for chaotic signal generation and schemes used to modulate message signal with chaotic signal in optical fiber communication systems. We also reviewed the principal concepts governing chaos synchronization, types of chaos synchronization and some proposed techniques used for the synchronization of transmitter and receiver in optical fiber communication systems.

Generation of Feedback-induced Chaos in a Semiconductor Ring Laser

A scheme for chaotic signal generation in a semiconductor ring laser (SRL) with optical feedback is presented. Part of the output is returned to the SRL, resulting in chaotic oscillation.

Photonic Generation of Wideband Time-Delay-Signature-Eliminated Chaotic Signals Utilizing an Optically Injected Semiconductor Laser

Photonic generation of wideband chaotic signals with time delay signature elimination is investigated experimentally and numerically based on a semiconductor laser (slave laser) with chaotic optical injection from a master laser. The master laser is subject to moderate optical feedback where the feedback strength and external-cavity length are fixed, while the slave laser stands alone. The experimental results show that wideband chaotic signals with successful time delay concealment can be generated in the slave laser by simply adjusting the coupling strength and frequency detuning between the two lasers. Furthermore, the numerical results are in accordance with the experimental observations. Finally, we propose a simple method for simultaneously generating multiple streams of high-quality chaotic signals using multichaotic lasers, where the time delay is effectively concealed in the autocorrelation function and delayed mutual information calculated from the chaotic time series.

Chaotic dynamics of a three-phase clock-driven oscillator with dual voltage controllability

In this work, we study a novel dual-voltage-controlled chaotic oscillator by using a three-phase clock. The chaotic oscillator is based on two nonlinear functions, which are needed for chaotic signal generation. The proposed chaotic circuit consists of three non-overlapping clock-driven MOS (metal oxide semiconductor) switches for S/H (sample and hold), a level shifter, and two nonlinear functions for nonlinearity in the feedback. After nonlinear functions for chaotic signal generation had been optimized, the proposed circuit was simulated with SPICE (Simulation Program with Integrated Circuit Emphasis) program using a 0.6 µm CMOS (complementary metal oxide semiconductor) process parameter. For various control voltages, its chaotic dynamics, such as time waveform, bifurcation diagram and state transition diagram were analyzed. We confirmed that the circuit could generate discrete chaotic signals in specific control voltages. This circuit is expected to be utilized for various chaos applications.

광감지 제어성을 갖는 카오스 신호 생성회로

A chaotic oscillator with light controllability was designed. The proposed chaotic oscillator consists of a photo sensor, two phase clock driven MOS switches, nonlinear function blocks for chaotic signal generation. SPICE circuit analysis using a 0.35 um CMOS process parameters was performed for its chaotic dynamics. And we confirmed that chaotic behaviors of the circuit can be controlled according to light intensity. By SPICE simulation, chaotic dynamics by time waveforms, frequency analysis was analyzed. SPICE results showed that proposed circuit can make various light-controlled chaotic signals.

Photonic generation and transmission of chaotic ultra wideband signals

We propose and experimentally demonstrate a chaotic ultra wideband (UWB) over fiber link based on optical feedback laser diode, in which UWB signals are generated and transmitted at three different bit rates of 360, 720 Mbit/s, and 1.44 Gbit/s respectively. Without utilizing any dispersion compensation module, the signal at a bit rate of 1.44 Gbit/s is detected using a digital signal processing receiver after 10 km fiber and 0.6 m wireless channel transmission. The power spectrum does not have any discrete spectral line because of the random output of the chaotic pulses, which means that the harmful effects of discrete spectral lines could be avoided with this method.

ELECTROMAGNETIC INTERFERENCE IMPACT ON FRONT-END RECEIVERS OUTSIDE THE ANTENNA BANDWIDTH

Impact of electromagnetic interference on front-end receiver behaviour is theoretically and experimentally studied outside the bandwidth of the antennas. Microwave chaotic generation is observed. Under certain conditions, re∞ected waves combined to the non linearity of the front-end receiver leads to a chaotic signal generation between the antenna and the front-end receiver. Difierent antennas, such as patch, loop, monopole and horn, are tested. Theoretical and experimental results are presented for each antenna. When an intentional or an unintentional electromagnetic interference is applied outside of the bandwidth of an antenna, re∞ection waves are generated between the antenna radiation impedance which is in the case of a few ohms and the nonlinear impedance of the front-end circuit of the receiver which is interconnected to the antenna via a transmission line. Under certain conditions, the efiects of the re∞ected waves due to antenna mismatch combined to those of the nonlinear impedance of the front-end circuits lead to chaos generation. This can have an impact on the electrical behaviour of the receiver particularly for high speed receiver systems and short electromagnetic interference wave lengths. The chaotic behaviour has already been observed in a microwave limiter circuit (1), in 'R-L-diode' circuits (2{7) and also in VHF microstrip oscillator (8). The doubling period has been observed