The so-called 1/Δ f noise

A sinusoidal ac current of frequeencyf _c generates an excess noise in many solidstate conductors. The power spectrum of this noise is calculated starting from the autocorrelation function of the stochastic process. Besides a 1/Δf term the spectrum includes another contribution varying with 1/(f _c+f). In the low frequency range there is white noise.     

1/f noise spectrum of the chaotic motion in a whisker mapping

The power spectrum of the chaotic motion in a whisker mapping is investigated. The 1/f noise spectrum is observed in wide parameter regions. It is shown that the 1/f spectrum is well explained by the framework of the renewal process.     

Quantum percolation tunneling current 1/f~γ noise model for high-κ gate stacks Bi-layer breakdown

Based on the elastic trap-assisted tunneling mechanism in high-κgate stacks,a quantum percolation tunneling current 1/fγ noise model is proposed by incorporating quantum tunneling theory into the quantum percolation model.We conclude that the noise amplitude of the PSD(Power Spectral Density)for three stages,namely the fresh device,one-layer BD(breakdown),and two-layer BD,increases from 10-22→10-14→10-8 A2/Hz.Meanwhile,the noise exponent γ for the three stages,has the 1/f2type(γ→2),1/fγ type(γ→1~2),and 1/f type(γ→1),respectively.The simulation results are in good agreement with the experimental results.This model reasonably interprets the correlation between the bi-layer breakdown and the tunneling 1/fγ noise amplitude dependence and 1/fγ noise exponent dependence.These results provide a theoretical basis for the high-κ gate stacks bi-layer breakdown noise characterization methods.     

Noise spectral power and non-equilibrium dynamics of vortices in the mixed state of Bi2Sr2CaCu2Oy

A model is proposed to explain the observed noise spectral power generated by the moving vortex lattice in Bi₂Sr₂CaCu₂O_y single crystals. The analysis is based on the observations that the noise generated is due to the vortex velocity rather than the thermodynamic phase of the material. The motion of vortices induces a gradual transition of the vortex lattice from the plastic flow to the uniform flow with increasing magnetic field. The influence of the disorder on the dynamics of vortices is such that a uniform distribution in the activation barrier width will exist. This distribution will affect the attempt frequency of the flux line hopping and consequently the spectral shape of the noise generated. The model provides physical basis to the fact that the observed 1/f-noise power corresponds to the smaller velocity of the vortex lattice, while the deviation from the 1/f-spectrum corresponds to the larger velocity region. The results of the simulation are compared to recent experimental measurements where good agreement has been achieved.     

A generalization of the fluctuation-dissipation theorem for the case of excess noise

Electrical fluctuations proportional to the square of the external field are investigated in the case of quasi-equilibrium conditions. The binary correlation function, proportional to the square of the external field, is expressed in terms of the zero-field quaternary correlation function for both quantum and classical cases. This result can be considered as a generalization of the fluctuation-dissipation theorem. The 1/f spectrum is obtained as a consequence of the symmetry properties of the quaternary correlation function without consideration of the physical mechanisms responsible for the noise. The method of investigation of the 1/f spectrum through zero-field quaternary correlation function is discussed.     

Boltzmann power laws

In this paper we propose a model based on the Boltzmann distribution as a mechanism for generating power laws, Boltzmann Power Laws (BPL). Some of these power laws are studied and compared to popular power laws such as ‘1/f’ noise and self-organized criticality (SOC). We will show how, in some cases, these BPLs reproduce behaviors similar to the finite size scaling (FSS) scenario, which is typical of SOC.     

Stochastic resonance in a nonlinear system with a 1/f spectrum

The system of two nonlinear stochastic equations simulating 1/f fluctuations during the interaction of nonequilibrium phase transitions in the presence of an external harmonic force is analyzed using numerical methods. It is shown that the stochastic resonance occurring in the system enhances the output periodic signal under the action of noise. A random process with a 1/f power spectrum corresponds to the Gibbs-Shannon information entropy peak. In stochastic resonance, the information entropy is minimal.     

Self-organization and 1/f noise in granular superconductors

The interplay between the widespread phenomena such as 1/f noise and self-organization of the critical state is studied both theoretically and by computer simulation using a model of multijunction SQUID exposed to an external magnetic field. It is demonstrated that the spectra of the average current in the systems of different size exhibit a broad region of 1/f noise limited only by the system size. However, the coexistence of 1/f noise and self-organization of the critical state was observed only in one two-dimensional system.     

基于小波变换和维纳滤波的半导体器件1/f噪声滤波

针对半导体器件中普遍存在的1/f噪声提出了一种结合了提升小波变换和维纳滤波器的处理方法.首先利用重新加权迭代最小二乘法拟合1/f噪声的功率谱曲线得到噪声参数的估计,从而选择恰当的小波.其次,对包含了1/f噪声的信号进行提升小波变换.考虑到小波变换对1/f噪声的白化作用,利用维纳滤波器对每一层小波系数进行处理.设计了最优全通滤波器以校正维纳滤波器的相频特性,使得小波系数经滤波后相位不变.最后利用提升小波逆变换获得被1/f噪声淹没的信号.利用实验检验了提出方法的有效性,实验数据采自用于微创外科手术机器人的力传感器.结果表明提出的方法能够有效抑制1/f噪声,并使传感器的分辨力提高了25%. 关键词： 半导体器件 f噪声')" href="#">1/f噪声 提升小波变换 维纳滤波     

The effect of forward flight on the noise and flow field of inverted profile jets

Noise and flow field measurements are reported for an inverted profile coannular jet (where the annular jet speed exceeds the center jet speed) under simulated flight conditions. The annular and center jets were cold and both were operated subsonically. Forward flight was simulated by placing the coannular jet inside a larger open jet. Acoustic measurements show the effects of inverted profile shape and simulated flight on far field directivity, total radiated power, and spectral content. Measurements of total acoustic power demonstrate that the acoustic efficiency of inverted profile jets is about 3 dB less than the efficiency of “top hat” profile jets, and that the noise decreases as the seventh power of the relative jet velocity in the limit of small flight velocity, U_f. Flow measurements demonstrate that the jet spreading parameter λ = (U_j ? U_f)/(U_j + U_f) scales the thickness of the outer shear layer and the passage frequencies of the large turbulence scales. Comparisons between the turbulence time scales and the noise spectra suggest that coherent noise sources may become more important in forward flight.     

On low frequency and 1/f noise from diffusion like processes

The noise spectrum resulting from diffusion like processes is calculated in two and three dimensions for two different forms of free energy fluctuation. For example it is shown that in a three dimensional system with ideal non-interacting particles the noise is almost white up to a certain frequency. In a two dimensional system where the free energy fluctuations are proportional to the gradient of a parameter modulating the electrical conductivity a 1/f noise power spectrum is expected in a certain frequency interval.     

基于辐照前1/f噪声的金属-氧化物-半导体场效应晶体管辐照退化模型

基于金属-氧化物-半导体场效应晶体管(MOSFET)噪声的载流子数涨落和迁移率涨落理论,建立了MOSFET辐照前1/f噪声参量与辐照后分别由氧化层陷阱和界面陷阱诱使阈值电压漂移之间的定量数学模型,并通过实验予以验证.研究结果表明,辐照诱生的氧化层陷阱通过俘获和发射过程与沟道交换载流子,在引起载流子数涨落的同时也通过库仑散射导致沟道迁移率的涨落,因此辐照前的1/f噪声幅值正比于辐照诱生的氧化层陷阱数.利用该模型对MOSFET辐照前1/f噪声与辐照退化的相关性从理论上 关键词： f噪声')" href="#">1/f噪声 辐照 金属-氧化物-半导体场效应晶体管 陷阱     

Calculating the 1/<Emphasis Type="Italic">f</Emphasis><Superscript>α</Superscript> noise exponent in metals

Mechanisms responsible for an increase in the 1/f ^α noise exponent up to α = 3/2 are considered. The exponent has been calculated using the renormalization-group technique and ?-expansion in the space of d = 6-ε dimension. It is shown that the 1/f ^α noise exponent in pure metals varies within 1 ≤ α < 3/2 and exhibits a small maximum in the temperature dependence. Possible conditions for the disappearance of this maximum are discussed.     

Fluctuations and waves in a spatially distributed system with the 1/<Emphasis Type="Italic">f</Emphasis> spectrum

A spatially distributed system with the 1/ _f spectrum of fluctuation power is modeled by two nonlinear stochastic equations. The numerical methods show the formation of 1/ _f and 1/ _k spectra of extreme fluctuations against the background of the formation and motion of waves under the effect of white noise. The distribution of extreme fluctuations corresponds to the maximum of entropy, which testifies to their stability. Under an external periodic perturbation in the system, it is possible to observe space?time stochastic resonance.     

Clusterization of light interstitial impurities and the 1/f noise in metals

The effect of clusterization of light interstitial impurities on the 1/f noise spectrum in metals has been studied by numerical simulation. It is shown that an increase in the intensity of the 1/f noise may serve as an indication of clusterization, and that the shape of the activation energy spectrum can provide information on the character of impurity ordering in the clusters formed.     

Room-temperature relaxation of the electrical resistance and electrical 1/fα noise observed at very low frequency in the remanent state of glass-ceramics containing magnetite nanoparticles

Slow fluctuations of the electrical resistance R have been systematically observed in three glass-ceramics containing aggregates of magnetite nanoparticles, in measurements where R was studied as a function of time at the magnetic remanence. These fluctuations are shown to be an intrinsic (i.e., not instrumental or spurious) feature of these materials. The associated electrical noise has been obtained by performing a numerical FFT transform of different segments of the R(t) curves after proper baseline subtraction. In this way, the spectral density has been investigated in the very low-frequency region (1×10^?3<f<0.2 Hz), usually not covered in standard noise measurements. The spectral density shows a 1/f^α behaviour (with α?1.6) in all cases. The results are discussed in terms of the existing models about conductance fluctuations in half-metallic oxides in the hopping regime. It is suggested that electron trapping–detrapping mechanisms (thought to be the source of electrical noise) play a relevant role in the hopping processes between adjacent nanoparticle aggregates of magnetite, which dominate the material's resistivity.     

A consistent model for 1/f-noise in thin-film devices such as bolometers,Josephson junctions and squids

The 1/f noise power spectrum is calculated consistently for thin-film devices such as bolometers, Josephson junctions and SQUIDs, using a model based on spontaneous temperature fluctuations and heat exchange between the device and the surrounding medium. Numerical results agree closely with existing experimental data.     

Oscillations and Waves in a Nonlinear System with the 1/<Emphasis Type="Italic">f</Emphasis> Spectrum

Numerical methods are used to study a spatially distributed system of two nonlinear stochastic equations that simulate interacting phase transitions. Conditions for self-oscillations and waves are determined. The 1/f and 1/k spectra of extreme fluctuations are formed when waves emerge and move under the action of white noise. The distribution of the extreme fluctuations corresponds to the maximum entropy, which is proven by the stability of the 1/f and 1/k spectra. The formation and motion of waves under external periodic perturbation are accompanied by spatiotemporal chaotic resonance in which the domain of periodic pulsations is extended under the action of white noise.     

Noise behavior of amorphous GexSi1−xOy for microbolometer applications

High resistivity sputtered a-Ge_xSi_1−xO_y compound was investigated for application to microbolometer fabrication for thermal imaging. Noise behavior of the fabricated bolometers was measured, showing no evidence of random telegraph switching (RTS) noise. 1/f noise was measured at several measuring currents, resulting in a 1/f noise factor of 2.9 × 10⁻¹¹ that can be used for further design and modeling.