Flicker Noise in a Locally Nonequilibrium Medium

A model implying that particles of a medium are subjected to external forces with a flicker noise spectrum has been proposed to describe fluctuations in locally nonequilibrium physical media. The Langevin equation with additional integral terms describing the action of the locally nonequilibrium medium has been derived. The spectral density of fluctuations of an electric current flowing in the locally nonequilibrium medium has been calculated. It has been found that this density in the low-frequency spectral range is flicker noise.     

On the anomalous flicker noise intensity in high-temperature superconductors

The problem of anomalously high levels of flicker noise observed in the normal state of the high-temperature superconductors is addressed. It is argued that the anomaly is the result of incorrect normalization of the power spectra according to the Hooge formula. A careful analysis of the available experimental data is given, which shows that the scaling of the spectral power with sample size is essentially different from the inverse proportionality. It is demonstrated that the measured spectra obey the law given by the recently proposed quantum theory of fundamental flicker noise.     

Simulation of flicker noise by fractional integro-differentiation

A relationship is found between the power spectral density of flicker noise and the Riemann-Liouville fractional derivative. It is shown that systems with a flicker-type noise spectrum allow for calculating the fractional derivative of a stationary stochastic process. The results obtained can be used to simulate flicker noise in electronic circuits. The method is implemented with the Pspice code for circuit simulation.     

PSPICE circuit simulation of microbolometer infrared detectors with noise sources

In this paper, we present a method of incorporating various types of noise in circuit simulation of a microbolometer infrared detector to analyze the effect of noise on its performance. This ability of simulating electro-thermal performance of microbolometers in circuit simulation platform along with their noise performance allows designing of its suitable readout integrated circuit (ROIC). Being an electro-thermal device, a microbolometer has both the electrical and thermal components interacting with each other. Therefore, the noise sources existing in standard circuit simulators cannot predict the noise of a microbolometer correctly. Disturbances coming from the background radiation, device temperature fluctuations, flicker noise and the Johnson noise etc. contribute in the total noise of a microbolometer element. All these components of noise can be incorporated using the proposed simulation technique. The technique also allows modifying the frequency response of the noise in simulations as per the user defined noise spectrum, making it suitable for any type of microbolometer.     

短波碲镉汞光伏器件的低频噪声研究

对所研制的短波光伏碲镉汞器件进行了变温电流-电压特性和低频噪声研究，测试温度范围255—293K.实验结果表明随着温度的下降，器件的优值因子R₀A从45×10³Ωcm²增加到7×10⁴Ωcm².器件在低频区的主要噪 声成分是1/f噪声和产生-复合噪声，在高频区主要是散粒噪声.在测试的偏压内，器件的1/f噪声功率谱密度与流过器件的电流的平方成正比，器件的Hooge系数为3×10^-4—7×10^-4.从噪声 功率谱密度曲线分析中得到产生-复合噪声的特征时间常数τ，通过τ的温度特性得到了器件的深能级. 关键词： 碲镉汞 优值因子 低频噪声 深能级     

Rapidly oscillating asymptotic solutions of the Navier-Stokes equations, coherent structures, Fomenko invariants, Kolmogorov spectrum, and flicker noise

Asymptotic solutions of the Navier-Stokes equations describing three-phase coherent structures of the Taylor scale are constructed. These equations are related to topological invariants of the Liouville foliations on the three-dimensional torus into two-dimensional tori. The solutions turn out to be unstable with respect to small-scale perturbations, which finally leads to the appearance of perturbations of Kolmogorov scale. The flicker noise occurs at the corresponding frequencies.     

Low-Frequency Noise in Gate Tunable Topological Insulator Nanowire Field Emission Transistor near the Dirac Point

Low-frequency flicker noise is usually associated with material defects or imperfection of fabrication procedure.Up to now,there is only very limited knowledge about flicker noise of the topological insulator,whose topologically protected conducting surface is theoretically immune to back scattering.To suppress the bulk conductivity we synthesize antimony doped Bi_2Se_3 nanowires and conduct transport measurements at cryogenic temperatures.The low-frequency current noise measurement shows that the noise amplitude at the high-drain current regime can be described by Hooge's empirical relationship,while the noise level is significantly lower than that predicted by Hooge's model near the Dirac point.Furthermore,different frequency responses of noise power spectrum density for specific drain currents at the low drain current regime indicate the complex origin of noise sources of topological insulator.     

Burst noise in non-heated thin film metal-insulator-metal cathodes

In this paper we present the results of experimental and theoretical studies of the noise characteristics of through and emission currents of thin-film metal-insulator-metal systems based on silicon oxynitride in the temperature range from 4.2 to 300 K and at frequencies at 20 Hz–100 kHz. The noise spectrum of the through current consists of burst and shot noise. In the noise spectrum of the emission current flicker noise and shot noise components predominate. The noise of the through current is not correlated with the noise of the emission current over the full range of investigated temperatures and frequencies. A proposed physical model of the origin of the burst noise in an MIM cathode is based on the assumption of the existence of two types of high conductivity channels in the dielectric: pulsating and nonpulsating. Experimental results are found to be in good agreement with the theoretical calculations.Lenin Komsomol Pedagogical Institute, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 89–94, November, 1992.     

Refined Composite Multi-Scale Reverse Weighted Permutation Entropy and Its Applications in Ship-Radiated Noise

Ship-radiated noise is one of the important signal types under the complex ocean background, which can well reflect physical properties of ships. As one of the valid measures to characterize the complexity of ship-radiated noise, permutation entropy (PE) has the advantages of high efficiency and simple calculation. However, PE has the problems of missing amplitude information and single scale. To address the two drawbacks, refined composite multi-scale reverse weighted PE (RCMRWPE), as a novel measurement technology of describing the signal complexity, is put forward based on refined composite multi-scale processing (RCMP) and reverse weighted PE (RWPE). RCMP is an improved method of coarse-graining, which not only solves the problem of single scale, but also improves the stability of traditional coarse-graining; RWPE has been proposed more recently, and has better inter-class separability and robustness performance to noise than PE, weighted PE (WPE), and reverse PE (RPE). Additionally, a feature extraction scheme of ship-radiated noise is proposed based on RCMRWPE, furthermore, RCMRWPE is combined with discriminant analysis classifier (DAC) to form a new classification method. After that, a large number of comparative experiments of feature extraction schemes and classification methods with two artificial random signals and six ship-radiated noise are carried out, which show that the proposed feature extraction scheme has better performance in distinguishing ability and stability than the other three similar feature extraction schemes based on multi-scale PE (MPE), multi-scale WPE (MWPE), and multi-scale RPE (MRPE), and the proposed classification method also has the highest recognition rate.     

Flicker noise in degenerately doped Si single crystals near the metal-insulator transition

In this paper we report some of the important results of experimental investigations of the flicker noise near the metal-insulator (MI) transition in doped silicon single crystals. This is the first comprehensive work to study low-frequency noise in heavily doped Si over an extensive temperature range (2 K<T<500 K). The measurements of conductance fluctuations (flicker noise) were carried out in the frequency range 10⁻²<f<4 × 10¹ Hz in single crystalline Si across the MI transition by doping with phosphorous and boron. The magnitude of noise in heavily doped Si is much larger than that seen in lightly doped Si over the whole temperature range. The extensive temperature range covered allowed us to detect two distinct noise mechanisms. At low temperatures (T<100 K) universal conductance fluctuations (UCF) dominate and the spectral dependence of the noise is determined by dephasing the electron from defects with two-levels (TLS). At higher temperatures (T>200 K) the noise arises from activated defect dynamics. As the MI transition is approached, the 1/f spectral power, typical of the metallic regime, gets modified by the presence of discrete Lorentzians which arise from generation-recombination process which is the characteristic of a semiconductor.     

Noise analysis of coaxial Schottky barrier carbon nanotube fets using non equilibrium Green’s function formalism

The effect of noise on the performance of Schottky Barrier Carbon Nanotube Field Effect Transistors (SB-CNTFETs) has been investigated under various bias conditions. In order to calculate the noise power spectral density, the Non-Equilibrium Green’s Function formalism (NEGF) is used to obtain the transmission coefficient and the number of carriers inside the channel. Results are presented in two sections: In the first section the Hooge’s empirical rule is used to investigate the flicker noise properties of SB-CNTFETs with defects in the gate oxide region, while in the second section the thermal and shot noise properties of SB-CNTFETs are studied. Finally, the best bias points in the ON and OFF states have been suggested according to the total noise power spectral density and the device signal to noise ratio.      

Low-frequency excess noise characterizations of laser-assisted de-bonded GaN films

Systematic characterization of flicker noise was conducted on GaN-based metal-semiconductor-metal (MSM) interdigitated devices. The devices were fabricated on both the regular GaN-on-sapphire (type A) and laser de-bonded films followed by layer transfer of hydride vapor phase epitaxy-grown GaN films to Si substrates (type B). Experimental results indicated no significant degradation in the I-V characteristics for Schottky MSM devices fabricated on type B films compared to those fabricated on type A films. However, substantial increase in the flicker noise level, particularly in the low-temperature regime, is observed among the ohmic MSM devices fabricated on type B films. The experimental data suggest that material degradation occurs at the vicinity of the GaN-sapphire interface, while in regions close to the GaN film surface there is practically no change in the film quality. This is supported by finite element simulation of the temperature of the film during laser irradiation. The results indicate that the temperature dropped from 1400 K at the GaN-sapphire interface to about 1000 K within 0.5 μm away from the interface stipulating that material degradation occurs only within 0.5 μm from the GaN-sapphire interface.     

Laser frequency modulation noise measurement by recirculating delayed self-heterodyne method

I propose and demonstrate the use of the recirculating delayed self-heterodyne (DSH) method for measuring FM noise power spectral densities (PSDs), which are the most fundamental measure characterizing the spectral purity of laser sources. By analyzing the DSH beat signals with 1, 10, and 160?km delays, the FM noise PSD of a narrow-linewidth fiber laser is evaluated for Fourier frequency range between 10?Hz and 100?kHz, which exhibits flicker noise as the dominant contribution.     

Field emission fluctuation phenomena of potassium microcrystals on tungsten: I. Spectral density functions and flip-flop

The field emission flicker noise technique has been applied to study dynamical properties of epitaxial potassium microcrystals on tungsten. Spectral density functions of the (111) region for temperatures between 78 and about 230 K were obtained. Some preliminary observations of flip-flop behaviour of potassium crystals are presented and discussed.     

Frequency noise of free-running 4.6 μm distributed feedback quantum cascade lasers near room temperature

The frequency noise properties of commercial distributed feedback quantum cascade lasers emitting in the 4.6 μm range and operated in cw mode near room temperature (277 K) are presented. The measured frequency noise power spectral density reveals a flicker noise dropping down to the very low level of <100 Hz(2)/Hz at 10 MHz Fourier frequency and is globally a factor of 100 lower than data recently reported for a similar laser operated at cryogenic temperature. This makes our laser a good candidate for the realization of a mid-IR ultranarrow linewidth reference.     

Coverage dependence of fe flicker noise: Spectral density functions due to potassium on W(112) and W(111)

Field emission flicker noise spectral density functions W(?) have been determined for potassium on W(112) and W(111) single planes. The coverage dependence of the spectral densities W(?_j) shows pronounced maxima and minima, whereas the slopes ? obtained from double logarithmic plots of W(?) ~ ?^?? vary considerably. Minima and maxima of W(?_j) are assumed to be due to coherent and disordered adlayers, respectively, and the behaviour of the exponents ? supports further the proposed observation of order-disorder transitions of the potassium adsorbate. LEED results for W(112)K and W(111)K are in fair agreement with the corresponding coverages from noise measurements.     

基于流形模糊双支持向量机的恒星光谱分类方法

支持向量机(support vector machine, SVM)具有良好的学习性能和泛化能力,因而被广泛应用于恒星光谱分类中。然而实际应用面临的数据规模往往很大,SVM便暴露出计算量大、分类速度慢等问题。为了解决上述问题,Jayadeva等提出双支持向量机(twin support vector machine, TWSVM),将计算时间减少至SVM的1/4。然后上述方法仅关注数据的全局特征,对每类数据的局部特征并未关注。鉴于此,提出基于流形模糊双支持向量机(manifold fuzzy twin support vector machine, MF-TSVM)的恒星光谱分类方法。利用流形判别分析获得数据的全局特征和局部特征,模糊隶属度函数的引入将各类数据区别对待,尽可能减少噪声点和奇异点对分类结果的影响。与C-SVM,KNN等传统分类方法在SDSS恒星光谱数据集上的比较实验表明了该方法的有效性。     

Rapidly fluctuating fields as a source of low-frequency conductivity fluctuations and the size effects in quantum kinetics

Tunneling contact was taken as an example to demonstrate that the interaction of electron quantum transitions can serve as a source of low-frequency flicker fluctuations of conductivity. Estimates are made for the fluctuations of tunnel conductance. The theory explains the effect of flicker noise sensitivity to the discreteness of the electronic spectrum, as it was observed in nanocomposites.     

合成孔径雷达图像的Contourlet域空间选择滤波降斑算法

合成孔径雷达(SAR)图像的相干斑噪声降低了影像分割和分类的效果,会导致影像判识困难。结合Con-tourlet系数的结构特点和SAR图像相干斑乘性噪声模型,提出了一种新的基于Contourlet变换的降斑算法。该算法利用信号与噪声在Contourlet域尺度间相关性的不同,通过空间选择滤波对系数进行分类,采用混合分布模型,实现了SAR图像的降斑处理。实验结果表明,该算法不仅能有效地抑制相干斑,而且还能有效地保护图像的细节特征。     

非晶铟锌氧化物薄膜晶体管的低频噪声特性与分析

本文针对底栅结构非晶铟锌氧化物薄膜晶体管的低频噪声特性开展实验与理论研究.由实验结果可知:受铟锌氧化物与二氧化硅界面处缺陷态俘获与释放载流子效应的影响,器件沟道电流噪声功率谱密度随频率的变化遵循1/fγ(γ≈0.75)的变化规律;此外,器件沟道电流归一化噪声功率谱密度随沟道长度与沟道宽度的增加而减小,证明器件低频噪声来源于沟道的闪烁噪声,可忽略源漏结接触及寄生电阻对器件低频噪声的影响.最后,基于载流子数涨落及迁移率涨落模型,提取γ因子与平均Hooge因子,为评价材料及器件特性奠定基础.