大参数周期信号随机共振解析

通过调节双稳系统参数实现大参数频率范围内周期信号的随机共振, 在工程上具有重要意义. 推导了双稳系统参数的归一化变换, 利用归一化变换原理对大参数周期信号的随机共振进行了数值仿真, 阐明该原理适用于任意频率周期信号. 对大参数随机共振用电路模拟进行了实验验证, 揭示了通过调节双稳系统参数可以实现大参数频率范围内的随机共振. 分析了二次采样实现大参数周期信号随机共振的机理, 通过数值仿真与参数归一化变换方法进行了比较. 仿真结果表明, 在输入信号幅度变化的情况下, 二次采样方法易出现发散现象, 而归一化变换具有更好的稳定性与适应性.     

非高斯噪声驱动下一维双稳系统的逻辑操作

本文以成功率作为逻辑随机共振的测度, 主要研究了非高斯噪声激励下一维双稳系统的逻辑随机共振现象, 并用平均首次通过时间的方法对此现象的机理进行了解释. 研究结果表明: 只有在适当的噪声强度带或关联时间带上, 成功率才会达到共振峰值. 通过对系统参数进行优化, 提高了系统实现逻辑操作的可靠性. 关键词： 逻辑随机共振 一维双稳系统 非高斯噪声 平均首次通过时间     

Time-varying coupling-induced logical stochastic resonance in a periodically driven coupled bistable system

Coupling-induced logical stochastic resonance(LSR) can be observed in a noise-driven coupled bistable system where the behaviors of system can be interpreted consistently as a specific logic gate in an appropriate noise level. Here constant coupling is extended to time-varying coupling, and then we investigate the effect of time-varying coupling on LSR in a periodically driven coupled bistable system. When coupling intensity oscillates periodically with the same frequency with periodic force or relatively high frequency, the system successfully yields the desired logic output. When coupling intensity oscillates irregularly with phase disturbance, large phase disturbance reduces the area of optimal parameter region of coupling intensity and response speed of logic devices. Although the system behaves as a desired logic gate when the frequency of time-periodic coupling intensity is precisely equal to that of periodic force, the desired logic gate is not robust against tiny frequency difference and phase disturbance. Therefore, periodic coupling intensity with high frequency ratio is an optimal option to obtain a reliable and robust logic operation.     

The Availability of Logical Operation Induced by Dichotomous Noise for a Nonlinear Bistable System

Instead of a continuous system driven by Gaussian white noise, logical stochastic resonance will be investigated in a nonlinear bistable system with two thresholds driven by dichotomous noise, which shows a phenomenon different from Gaussian white noise. We can realize two parallel logical operations by simply adjusting the values of these two thresholds. Besides, to quantify the reliability of obtaining the correct logic output, we numerically calculate the success probability, and effects of dichotomous noise on the success probability are observed, these observations show that the reliability of realizing logical operation in the bistable system can be improved through optimizing parameters of dichotomous noise.     

双稳动力学系统中耦合效应对逻辑随机共振现象的增强作用

研究了电路耦合作用对逻辑随机共振现象以及逻辑门器件稳定性的影响．相对于单个的逻辑门电路,耦合的逻辑门器件可以在更宽的噪声范围内都保持逻辑运算的准确性,即耦合作用可以增强逻辑随机共振现象．此外,这种增强效应随着耦合体系尺度的增大而增大,但是当体系尺度达到一定程度时,这种增强作用达到一个稳定值．最后还考察了耦合强度的影响,发现随着耦合强度的增加,逻辑门器件可以保持逻辑运算准确性所对应的噪声区间非单调地改变,表现出一种共振的行为.     

Realizing reliable logic and memory function with noise-assisted Schmitt trigger circuits

Schmitt trigger is a comparator circuit with hysteresis, implemented by applying positive feedback to a noninverting input. Recently, it has been verified that noise under certain condition can help nonlinear circuit to realize reliable logical stochastic resonance (LSR). In this letter, we demonstrate that, without any modifications, Schmitt trigger can operate flexibly both as logic operation and latch operation in an optimal noise range. In traditional Schmitt trigger, the hysteresis is designed for resisting noise. In the new design, the hysteresis tends to enhance the LSR effect in Schmitt trigger with the help of noise and helps the system to perform better at higher noise levels. Thus, our results extend the application scope and generality of the traditional Schmitt trigger.     

基于振动共振的随机共振控制

分析了非线性双稳系统在高、低两种不同频率信号作用下的动力学特性，给出了高频信号参数与双稳系统输出信号的信噪比和功率谱放大率关系的解析表达式，提出了基于振动共振的随机共振控制方法.理论分析和数值仿真结果表明，通过调节高频信号的幅值或频率大小，能有效地控制双稳系统输出信号的信噪比和功率谱放大率.     

Effects of potential functions on stochastic resonance

In this paper, the effects of a bistable potential function U(x)=-ax²/2+b|x|^2γ/(2γ) on stochastic resonance (SR) is discussed. We investigate the effects of index γ on the performance of the SR system with fixed parameters a and b, and with fixed potential barriers, respectively. To measure the performance of the SR system in the presence of an aperiodic input, the bit error rate is employed, as is commonly used in binary communications. The numerical simulations strongly support the theoretical results. The goal of this investigation is to explore the effects of the shape of potential functions on SR and give a guidance of nonlinear systems in the application of information processing.     

Stochastic resonance in multi-scale bistable array

This Letter explores a new mechanism of stochastic resonance (SR) that is induced by the multi-scale noise decomposed from the input signal, which is promising in signal detection and processing under heavy background noise. The input signal is firstly decomposed to multi-scale signals by orthogonal wavelet transform. Then, the approximate signal, which contains the driving signal, is processed by an uncoupled parallel bistable array with the detailed signal of each scale as the internal noise. At last, a SR mechanism combining the effects of colored noise and array SR is proposed. The simulation results show that a high quality output signal can be obtained by the new mechanism. The proposed model is more adaptive to input signal with high noise intensity than single bistable SR system, which can be seen from the signal-to-noise ratio curves and average noise intensity curves.     

Ultrafast all-optical XOR logic gate based on a symmetrical Mach-Zehnder interferometer employing SOI waveguides

We present an integrated Silicon-on-Insulator (SOI) based Mach-Zehnder interferometer (MZI) in order to perform ultrafast all-optical XOR logic gate operation with a bit rate of ∼ 0.33 Tb/s. A numerical simulation is carried out in order to study various parameters such as extinction ratio and eye-opening parameters, characterizing the performance of the XOR logic gate. The output XOR logic gate signal can have improved extinction and eye margin if the initial powers of primary signals and the probe continuous-wave (CW), and SOI waveguide length are judiciously adjusted.     

Implentation of optical encoder and multiplexer using Mach-Zehnder inferometer

In this paper a simple all-optical logic device, called Mach-Zhender Interferometer is composed by using a semiconductor optical amplifier (SOA) and an optical coupler. This device is used for generating the logical functions (AND, XOR) and a multiplexer and an Encoder are obtained using this device in Optical Tree Architecture. The simulation of Encoder and Multiplexer is done at a rate of 10 Gb/s and both are simulated for different input logical combinations. Simulations indicate that the device is suitable to operate at much higher bit rate and also for different logical entities.     

基于光纤中交叉相位调制的波长转换器研究

波长转换器在未来的全光网络中将起到重要的作用.通过大量的数值仿真,研究了利用色散位移光纤中的自相位调制效应的波长转换器,首次对各参量,包括输入光信号脉冲的峰值功率,连续波的功率,两束光信号的频率间隔,光纤的色散,光纤的长度以及输入信号的比特率对此波长转换器的性能影响进行了数值研究.结果表明,光纤的色散和输入光信号脉冲的功率在这种波长转换器中起重要作用,而且这种波长转换器可以对高达200Gb/s的信号进行转换.     

Schemes of effective magnetic AND and XOR logic elements

Schemes and calculated characteristics of effective logic elements with two inputs for classical ground-state computations are reported. These elements have a high threshold (0.48) and perform a desired logical operation in a wide range of input signals.     

State observer for stochastic resonance in bistable system

We investigate numerically stochastic resonance variation in bistable system. Putting signals with different intensities into a bistable system, or adjusting system structural parameters for an input, will produce different motion trajectories. These trajectories contain both chaos and non-chaos parts. We classify these states according to the state of resonance and chaos, and propose a state observer. In this way, bistable system becomes an observable nonlinear system. State observer can provide us with a new perspective that is not available through conventional observation methods. These investigations contribute to nonlinear system optimization, and can also be applied to other interesting noise-induced phenomena.     

Improved optical performance of the Radon-Wigner display for one-dimensional signals

An improved optical implementation of the Radon-Wigner display for one-dimensional signals based on fractional Fourier transform is proposed. All of the fractional Fourier transform orders with the correct magnification can be achieved simultaneously by the suggested new setup with high precision, which consists of only two optical elements, a cemented linear varifocal lenses and a curvy image plane. This setup can offer practical applications for analyzing and processing of stationary or non-stationary signals.     

Fractional optical Hilbert transform using phase shifted fiber Bragg gratings

In this paper, we demonstrate that an arbitrary order (including both integer and fractional orders) Hilbert transform (HT) of an input optical waveform can be implemented by a simple and practical phase-shifted fiber Bragg grating (PSFBG) operated in reflection mode. The PSFBG consists of two concatenated identical uniform FBGs with a proper phase shift between them. It is proved that both the phase shift of the FBGs and the apodizing profile of the refractive index modulation determine the order of the transform. The simulation results show that the device can perform arbitrary fractional Hilbert transform (FHT) with excellent accuracy for input signals with up to hundreds of GHz bandwidth using feasible FBG structures.     

Demonstration of a directed optical encoder using microring-resonator-based optical switches

We propose and demonstrate a directed optical logic circuit that performs the encoding function from a 4 bit electrical signal to a 2 bit optical signal based on cascaded microring switches. The four logic input signals control the states of the switches, while the two logic outputs are given by the optical power at the output waveguides. For proof of concept, a thermo-optic switching effect is used with an operation speed of 10 kbps.     

A mixed scrambling operation for hiding image

A mixed scrambling operation is defined by the use of Arnold transform and Baker mapping. Following a designed sequence, the combined scrambling operation is utilized for changing the pixel position of secret image under the control of a random matrix. At the same time, the pixel value is altered by random bit shift for obtaining an encrypted image encoded in N-bit data. The operations mentioned above are employed for all pixels of original secret image. Finally an encrypted image is obtained and encoded into N-bit data being from the input image. Some numerical simulations have been achieved for checking the performance of the image hiding scheme.     

并行帧同步扰码器的扩充比特设计法

在递推公式并行扰码处理方法的基础上,提出了一种使用扩充比特进行帧同步扰码器设计的新方法.利用扰码序列的周期性原理,从理论上证明了并行扰码复杂度与扰码生成多项式的具体形式无关.无需计算并行扰码递推公式,简化了解扰码器的设计过程,只须用深度与生成多项式阶数相关的存储器和少量的读写控制逻辑就可以实现对任意字宽解扰码处理.该方法在FPGA设计与实现中得到了验证,实现了高效和低复杂度.采用该方法的处理模块已在光通信传输网前端处理系统中得到了应用.     

Adaptive bistable stochastic resonance and its application in mechanical fault feature extraction

Stochastic resonance (SR) is an important approach to detect weak vibration signals from heavy background noise. In order to increase the calculation speed and improve the weak feature detection performance, a new bistable model has been built. With this model, an adaptive and fast SR method based on dyadic wavelet transform and least square system parameters solving is proposed in this paper. By adding the second-order differential item into the traditional bistable model, noise utilization can be increased and the quality of SR output signal can be improved. The iteration algorithm for implementing the adaptive SR is given. Compared with the traditional adaptive SR method, this algorithm does not need to set up the searching range and searching step size of the system parameters, but only requires a few iterations. The proposed method, discrete wavelet transform and the traditional adaptive SR method are applied to analyzing simulated vibration signals and extracting the fault feature of a rotor system. The contrastive results verify the superiority of the proposed method, and it can be effectively applied to weak mechanical fault feature extraction.