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In this paper we focus on the transmission of information signals via chaotic oscillations. To this end, we consider systems which contain generators with additional control loop and could behave chaotically and which dynamics may be controlled using feedback or directional coupling. Below we discuss three schemes of signal transmission and detection using 1) phase or frequency controlled generators,...
The chaotic system is sensitive to the initial value, and this property can be applied in the weak signal detection. There are periodic, critical and chaotic states in a chaotic system. When the system is in the critical state, a small perturbation of system parameter may lead to a qualitative change of the systems state. This paper introduces a method to detect the unknown weak signals by using Hu...
In digital communication systems, application of chaotic signals offers several advantages. One of the most important advantages is increased security which is due to their noise-like and broad spectrum characteristics. In order to find an efficient way for chaotic system synchronization and secure communications this paper combines chaotic masking and chaotic modulation encryptions. The proposed...
This paper briefly analyses the characteristic of the weak Global Positioning System (GPS) signal, elaborates the principle of signal detection with Duffing chaotic oscillator, presents a new method which adopted Duffing chaotic oscillator to detect and capture weak GPS signal. The method utilized the character of Duffing chaotic oscillator system, which is sensitive to the periodic signals whose...
The chaotic oscillator detecting is a new kind of weak signal detecting methods. The present chaotic oscillator detecting system has certain limits. And there is no theoretical foundation to define what kind of chaotic oscillators can constitute weak signal detecting system. This paper analyzes the sensitivity to weak signals and noise immunity of Duffing-Holmes and L-Y chaotic oscillator detecting...
Detecting weak periodic signal by chaotic oscillator is not only a new method, but also practical applications on chaos theory. However, when using this method to detect weak periodic signal, we have to know the frequency of weak periodic signal in advance, which limits applications of the method. This paper studies the relation between the frequency of measured weak periodic signal and max-variance...
Ballistocardiogram (BCG) is a new, noninvasive technique used to record the movement of the body synchronous with the heartbeat due to left ventricular pump activity. However, BCG signal is so weak and easy to be jammed. In this paper, we achieved it through the measure system which is made by our BCG laboratory. Then, attempt to detect useful information from noises by chaotic oscillators. Experimental...
Chaos synchronization between identical or non-identical chaotic systems, via either linear or nonlinear feedback control strategy, had been thoroughly studied during these several decades. Most of existed studies were carried out under the conditions where the control signal affects the interacted system's behavior without noise pollution (or with idea transmitter channel). Unfortunately, the real...
It is an important problem in chaos theory whether an observed irregular signal is deterministic chaotic or stochastic. The detection of chaotic spread spectrum sequences is the prerequisite of molding. This paper proposed a method to detect chaos spread spectrum sequences; even if short data and noise exist the algorithm can detect effectively. Numerical simulations based on Lorenz system verify...
A new signal detection and estimation method based on the intermittency transition between order and chaos is proposed. Using Melnikov function to determine the threshold of the detection system is introduced. The characteristic of Duffing oscillators with the changing of dynamics of the system is analysed. The method of detection of weak signals in strong noise based on Duffing oscillators is studied...
In this paper, we present a new method based on the theory of chaotic oscillator and wavelet transform. Chaotic systems are sensitive to certain signals and immune to noise at the same time, the properties of which demonstrate their potential application in weak signal frequency detection. However, chaotic systems are not suitable for amplitude detection of non-sinusoidal signals. Starting from the...
An audio system which bases on detection theory of chaotic phase transformation is expounded aiming to detect the watermark. It utilizes the characteristic of weak signal detection by chaotic system. Set the format of watermark as a sine wave which has the same frequency of chaotic detection system. Because small movement can make the statement of chaotic system change from the state of critical cycle...
In this paper, the chaotic character of Duffing oscillator is analyzed. It is immune against the noise and the interference signal having larger frequency difference with the intrinsic frequency of chaotic oscillator. This character of chaotic oscillator is used in weak signal diction. Using Melnikov method to determine the threshold value that the system into the chaotic state. The method using Duffing...
Method for secure information transmission based on generalized synchronization in the presence of noise is considered. Characteristics of chaotic systems used in transmitters and receivers are analyzed. Models of generators with delayed feedback, possessing all necessary requirements are revealed.
The method of the weak signal detection using the Duffing oscillator's initial conditions sensitivity was analyzed, and the Melnikov method of determining chaotic threshold of Duffing oscillators is discussed. The principle of weak signal detection based on the change of phase trace is described, and the influence of noise to the system status in the chaos detection process is also studied. Simulation...
The capability of conventional detection method such as power spectral density is limited while detecting periodic signals buried in the noise and deciding accurate frequency, the chaotic oscillator can increase the detection ability of weak periodic signals and improve frequency precision. In this paper, a new method based on duffing oscillator is proposed to detect weak signals. The chaos characteristic...
In this paper we introduced a method to estimate the additive noise in driving signals, this method is grounded on the average deviation rate of response system in a short period. We consider each noise point as a perturbation to initial condition of the chaotic system, and then estimate the evolution of perturbation by seeking the relations between average deviation rate lambda and time T. Lorenz...
Chaos theory is a new method of studying nonlinear system. With the development of society, the theory has been applied in many aspects of radar system and signal processing. In this paper, signal detecting capability of two chaotic oscillator systems is analyzed from detecting sensitivity and stability. It proves that the performance of detecting system with higher power is better but more questions...
Based on the principle of the chaos theory of weak signal detection, a new method is presented for Duffing oscillator used to demodulate 2FSK signal in this paper. The method can demodulate the 2FSK signal under strong noise background in the signal-to-noise rate at -25dB. Finally, the feasibility and the validity of the method were testified by the simulation.
Optoelectronic reduction of intensity noise is presented for solid-state lasers. However the noise suppression feedback loop can make the laser operate in its chaotic regime. The paper shows the way to chaos through bifurcations at different levels of the feedback signal. Additionally a limit for chaos free operation is also given. The bifurcation diagram of the controlled laser is calculated as well.
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