什么是1/f噪声?

在以往的工作的基础上,发现1/f噪声是一个新的相.它有一个酝酿、发育的过程,最终能否成形,取决于能否满足可信度M#的最低要求,即M#>500.这也是判别是否是1/f噪声的依据.往后还可得知,1/f噪声的熵S#值为S#=A×10-20尔格/度.S#极小,是所有1/f噪声的共性.A不同则表现了1/f的个性.     

什么是1/ƒ噪声?

在以往的工作的基础上,发现1／f噪声是一个新的相。它有一个酝酿、发育的过程,最终能否成形,取决于能否满足可信度M^#的最低要求,即M^#〉500。这也是判别是否是1／f噪声的依据。往后还可得知,1／f噪声的熵S^#值为S^#=A×10^-20尔格／度。S^#极小,是所有1／f噪声的共性。A不同则表现了1／f的个性。     

再论1/f噪声的动力学统计理论

在《1/f噪声的动力学统计理论》一文中,为了突出重点,攻克主要矛盾,因而对1/f噪声的某些特点,如实验上发现的1/f噪声的功率谱S(f)为什么总是1/fM能谱和功率谱S(f)为何是同一函数等等,当时未能深入追究,本文除了弥补这些不足之外,还从“零点能”与“暗物质”而引发的“背景能量的涌动”这个深层次上来解释普适关系式:S(f)∝logf/f。     

1/f噪声参数测试与估计

1/f噪声是激光器可靠性评价的标准,而对大功率半导体激光器中1/f噪声进行测试研究的关键是对其参数进行准确估计,本文运用最小二乘直线拟合的方法,通过与信噪比相结合,计算出对应的1/f参数,再利用小波逆变换重建1/f噪声.从实验结果可以看出,该方法能较好地重建出1/f噪声,而且估计出的1/f噪声参数误差率较低,说明该方法有较好的可行性.     

利用几何插值法合成1/f噪声

提出了通过对均匀分布的随机序列进行几何插值而合成 1/ f噪声的方法 ,探讨了 1/ f噪声具有的自相似结构的分形特征 .理论分析和数值仿真结果表明该方法在给定的频率范围内有较好的逼近效果     

基于电/磁转换的海洋电场检测方法

传统的直接电测量方法受1/f噪声限制,在低频处信号与噪声发生混叠,难以实现高水平低噪声测量。该文提出一种基于电/磁转换的海洋电场低噪声检测方法,将电信号转化为磁信号,通过微机械的方法将磁信号调制到高频,有效避开低频1/f噪声影响。设计一种实现电/磁转换功能的微机械结构,利用TMR电阻构成惠斯通电桥测量磁信号,实现海洋电场的高水平低噪声检测。仿真与实验结果在1 Hz处噪声分别达到1.16 nV/(Hz)~(1/2)和1.41 nV/(Hz)~(1/2),优于传统电测量方案的噪声水平,验证该方法的有效性。     

CCD相机视频处理电路设计

为了提高CCD相机的成像质量,对CCD的噪声进行了分类和分析,设计了高信噪比的视频处理电路。讨论了针对复位噪声和1/f噪声进行处理的相关双采样电路的原理。以专用视频处理芯片VSP2270和FPGA为核心设计了视频处理电路。最后结合CCD驱动电路,进行了图像采集和信噪比测试实验。实验结果表明,视频处理电路在本身引入噪声较小的同时,有效地抑制了CCD复位噪声、1/f噪声等噪声。数据输出率为20MHz时,整机系统信噪比高达58.4dB。基本满足星图成像的应用要求。     

基于小波变换的主动水声信号检测

信号检测是水声信号处理领域的研究重点之一。文章通过对水下航行器自噪声特性的研究，发现其具有1／f衰减特性，同时利用小波变换对1/f信号有类似K—L展开的作用，提出了一种基于小波变换的信号检测方法，对1/f噪声背景下的主动水声信号进行了检测；文中详细推导了相应的检验统计量及其统计分布特性；同时，将该方法与匹配滤波器、能量检测器的检测性能进行了比较，仿真试验结果表明了本方法的有效性。     

高压水泵的噪声治理

一、概述 天津人民农药厂新建的泵房,噪声高达104dB(A),机房外5m处的噪声高达90dB(A)以上,直接影响值班人员的身心健康和周围的环境。为此,我厂接受委托对其进行了治理。 泵房为钢筋混凝土建筑,长宽高分别为10×5×3.5m。内装两台6S6单级双吸式水泵,所配电机为J02-91-2,功率为55kW,转速为2950r/min,经测定泵房噪声为104dB(A),其频谱如图1所示。     

亚纯函数族一个结果的研究

设F是区域D上的一亚纯函数族,k是一个正整数,H(f,f1,……f(k))是一个微分多项式,且(Γ/γ)H<(k+1)。如果对于任意的f(z)∈F,f(z)的零点重数≥k+1,极点重级至少为2,且f(k)(z)+H(f,f1,……f(k)≠1),则F在区域D上是正规的。     

A novel impedance pattern for fast noise measurements

Complete noise characterization of an active device implies the extraction of the minimum noise figure (F_min), noise resistance (R_n), and optimum value of the complex input reflection coefficient (Γ_opt). Such quantities can be obtained through a minimum of four noise figure measurements, associated to four different reflection coefficients at the input of the DUT, (Γ_in,k k = 1 · · · 4), forming an "impedance pattern." Measurement redundancy is usually required to reduce overall uncertainty, therefore forcing one to use, for the synthesis of a large number of different terminations, an impedance tuner. This paper introduces a novel four-points input pattern, which becomes an "optimum" trade-off between accuracy and complexity, while avoiding the use of a tuner: a drastic reduction in cost and complexity of the measurement bench therefore results     

Noise characteristics of an ideal shunted Josephson junction

Detailed computer simulations have been made of the effect of intrinsic noise current on the I-V characteristic and voltage noise spectral density S _v (f) of an ideal Josephson element shunted by a capacitor and resistor. The minimum value of the parameter _c at which hysteresis appears in the quasistatic I-V characteristic is greater than the noise-free value of 1. Moreover, as _c is increased, a region of large differential resistance R _d appears in the I-V characteristic that is associated with a large increase in S _V(0). In this regime the noise current is seen to cause random switching between the superconducting and nonzero voltage states. For all bias conditions, S _V(f) > R _d ²S_I(f) where S _I(f) is the spectral density of the intrinsic current noise. A comparison is made between these results and previous calculations. The implications for low-noise superconducting devices are discussed.     

A simple analysis of the Dick effect in terms of phase noise spectral densities

In cold-atom frequency standards based on the Ramsey double interaction method, the phase noise of the interrogating signal appears as a random "end-to-end phase difference", thereby introducing frequency noise in the loop. This phenomenon is analyzed in this paper in the Fourier frequency domain, using phase noise power spectral densities S(phi)(f). In continuously operated standards, the excess noise thus introduced is servoed out in the long term to become eventually smaller than the atomic shot noise, whereas in standards with pulsed operation the phase noise around even harmonics of the pulse rate is down-converted by aliasing to base band. This latter mechanism is referred to in the literature as Dick effect. In this paper, a model of the frequency control servo system is proposed, in which the input signal is the (known) local oscillator (LO) phase noise S(phi)(f) and the output signal is the (unknown) phase noise S(phi)(f) of the standard in closed loop operation. The level of excess white frequency noise added by aliasing on the stabilized LO through the Dick effect can be related analytically to the characteristics of the free LO phase noise. From this, the stability limitation (with slope tau(-1/2)) typical of the Dick effect can then be obtained by the usual conversion formulas based on the power law model.     

Up-converted 1/f PM and AM noise in linear HBT amplifiers

In this paper we describe a technique to predict the 1/f phase modulation (PM) and 1/f amplitude modulation (AM) noise due to up-conversion of 1/f baseband current noise in microwave heterojunction bipolar transistor (HBT) amplifiers. We obtain an accurate model for the amplifier and find the expression for voltage gain in terms of DC bias, transistor parameters, and circuit components. Theoretical 1/f PM and AM noise sensitivities to 1/f baseband current noise are then found by applying the definitions of PM and AM noise to the gain expression of the amplifier. Measurements of PM and AM sensitivities at 500 MHz and 1 GHz were in good agreement with the values predicted by theory, verifying the validity of this technique. This method can be used to optimize amplifier design for low PM and AM noise. We show that the amplifier PM noise can be reduced by 9 dB by adjusting the value of the input coupling capacitor.     

Analysis of the Internal Noise of Quartz-Crystal Oscillators

This paper describes the influence of the parallel capacitance of a quartz-crystal resonator on the amplitude-frequency coupling and particularly on the internal noise spectra of the oscillator working at the series resonance. A theoretical analysis which is a first order perturbation method is used. It is shown that the parallel capacitance of the quartz-crystal resonator increases the amplitude-frequency coupling and drastically modifies both amplitude and phase spectra of the internal noise. The 1/f2 phase spectrum of the internal thermal noise is transformed into a white phase spectrum for noise component frequencies greater than f0 + f? or less than f0 - f?, where f0 is the resonator series resonant frequency and f?, the difference between antiresonant and resonant frequencies of the quartz crystal. A "noise quieting" phenomenon appears when the noise component frequencies are in the vicinity of the antiresonant frequency fp. A good agreement between theoretical and experimental results for different values of the parallel-capacitance proves the validity of the mathematical model.     

Origin of 1/f PM and AM noise in bipolar junction transistor amplifiers

In this paper we report the results of extensive research on phase modulation (PM) and amplitude modulation (AM) noise in linear bipolar junction transistor (BJT) amplifiers. BJT amplifiers exhibit 1/f PM and AM noise about a carrier signal that is much larger than the amplifiers thermal noise at those frequencies in the absence of the carrier signal. Our work shows that the 1/f PM noise of a BJT based amplifier is accompanied by 1/f AM noise which can be higher, lower, or nearly equal, depending on the circuit implementation. The 1/f AM and PM noise in BJTs is primarily the result of 1/f fluctuations in transistor current, transistor capacitance, circuit supply voltages, circuit impedances, and circuit configuration. We discuss the theory and present experimental data in reference to common emitter amplifiers, but the analysis can be applied to other configurations as well. This study provides the functional dependence of 1/f AM and PM noise on transistor parameters, circuit parameters, and signal frequency, thereby laying the groundwork for a comprehensive theory of 1/f AM and PM noise in BJT amplifiers. We show that in many cases the 1/f PM and AM noise can be reduced below the thermal noise of the amplifier.     

Statistical analysis of signal and noise in magnetic recording

The noise spectrum of a tape which is AC-erased is well formulated in the literature [1] . Though, a general theory based on classical statistics, which also delivers the power-spectral density for DC- and modulation noise is still lacking. In this paper we shall derive such a theory taking into account the statistics of all relevant parameters. First a new formulation is derived for the AC-erased case, which has a general character and includes the AC-erased noise spectrum of Mann [2]. Next a clustered medium is considered and a general expression for the DC-modulation noise is obtained. Furthermore, the harmonic magnetization in a clustered medium is examined, which reveals a power spectrum consisting of three fundamental contributions, the signal power, the background noise and the modulation sidebands. A similar result is obtained with a more realistic vectorial magnetization mode for the signal magnetization. The power spectrum for the case of AC-erased and DC-erased tape has been verified by experiment. Then, taking into account the tolerances of the parameters involved, there is still a discrepancy between the experimental and theoretical AC-erased tape noise power spectrum, which can only be explained in terms of particle interaction. The analysis is general in that it includes important mechanisms such as particle clusters and partial penetration of the signal into the layer. It can be adequately used in determining the S/N ratio in magnetic recording. The author intends to write a detailed paper on this subject for the IEEE Trans. on Magnetics.     

Noise associated with reverse anneal phenomenon in high current arsenic-implanted silicon

Reverse anneal phenomenon was observed in high current arsenic-implanted silicon samples and was pronounced with increasing implantation current. Noise measurements were used to study this phenomenon, the noise spectrum was composed of 1/f noise and generation-recombination (g-r) noise. The Hooge parameter , usually a constant for the 1/f noise in homogeneous samples, was found to be a function of annealing temperature and the measured g-r noise values which may reflect the activation percentage of implanted atoms under different annealing temperatures were in good agreement with theoretical predictions.     

Phase noise in surface-acoustic-wave filters and resonators

Measurements of the phase noise modulation imparted on UHF carriers by surface-acoustic-wave (SAW) filters and resonators have been made using an HP 3047 spectrum analyzer. Three different types of SAW phase noise were observed. One type can be explained by temperature fluctuations. It is characterized by a spectral density of phase fluctuations which decreases as 1/f(2). The predominant noise mechanism in most SAW devices has a 1/f spectral density. The source of this noise is unknown, but it appears to be associated with both acoustic propagation and transduction. In filters fabricated on lithium niobate substrates, a third noise mechanism is evidenced. This mechanism produces nonstationary noise bursts that appear to originate in the transducer region. Experiments have been carried out on substrate materials, transducer metallizations, and over acoustic path lengths. The means by which low-frequency fluctuations are mixed to the carrier frequency have been studied.