Showing papers on "Noise (electronics) published in 1970"

Noise in solid-state devices and lasers

Abstract: A survey is given of the most important noise problems in solid-state devices. Section II discusses shot noise in metal-semiconductor diodes, p-n junctions, and transistors at low injection; noise due to recombination and generation in the junction space-charge region; high-level injection effects; noise in photodiodes, avalanche diodes, and diode particle detectors, and shot noise in the leakage currents in field-effect transistors (FETs). Section III discusses thermal noise and induced gate noise in FETs; generation-recombination noise in FETs and transistors at low temperatures; noise due to recombination centers in the space-charge region(s) of FETs, and noise in space-charge-limited solid-state diodes. Section IV attempts to give a unified account of 1/f noise in solid-state devices in terms of the fluctuating occupancy of traps in the surface oxide; discusses the kinetics of these traps; applies this to flicker noise in junction diodes, transistors, and FETs, and briefly discusses flicker noise in Gunn diodes and burst noise in junction diodes and transistors. Section V discusses shot noise in the light emission of luminescent diodes and lasers, and noise in optical heterodyning. Section VI discusses circuit applications. It deals with the noise figure of negative conductance amplifiers (tunnel diodes and parametric amplifiers), and of FET, transistor, and mixer circuits. In the latter discussion capacitive up-converters, and diode, FET, and transistor mixers are dealt with.

Image Formation for Coherent Diffuse Objects: Statistical Properties

Abstract: The properties of the amplitude and illuminance of the images of coherently illuminated diffuse objects are studied. Uniform and nonuniform objects are considered. The image illuminance is considered to result from a linear transformation of a nonstationary gaussian stochastic process followed by a square-law detection. Expressions are obtained for the mean, autocorrelation, variance, and spatial power spectral density of the amplitude and of the illuminance. Interpretation of the results led to conclusions concerning the speckle size, the noise power in the image, and the transfer function of an optical system when the object diffuses coherent light. When the autocorrelation width of the random fluctuations of the object amplitude is small compared to the impulse response of the system, the mean illuminance in the image plane is that which would be given by an incoherent object having the same luminance as the object considered; the average speckle size is equal to that of the impulse response of the system; the average transfer function of the system is the incoherent transfer function; and the distribution of the noise spatial frequencies does not depend upon the form of the signal, but only upon its total energy. Other results concerning the image statistics have also been obtained.

Physical model for burst noise in semiconductor devices

Abstract: A physical model for burst noise in p−n junction devices is presented. It is proposed that burst noise results when the current through a defect is modulated by a change in the charge state of a single recombination-generation center located adjacent to the defect. The burst noise amplitude and pulse widths are related to the basic properties of the recombination-generation center and the defect. The model leads to a simple interpretation of the equivalent circuit for diodes which exhibit this type of noise.

Chapter 6 The Pyroelectric Detector

Abstract: Publisher Summary This chapter discusses the exploitation of the effect as a means of detecting infrared radiation. Any sensitive thermometric element can, in principle, be used as a thermal infrared detector. When the pyroelectric detector absorbs radiation, its temperature rises, changing its surface charge. To calculate its performance, both the thermal and electrical characteristics must be considered in detail and the sources contributing to the detector's noise must be enumerated. There are three ways in which a pyroelectric detector may be used: (1) To detect a signal modulated at a constant angular frequency ω ; (2) by combining a detector operating in this mode with a frequency-equalizing amplifier, a receiver with a very short (less than 1 μsec) response time suitable for observing transient signals, such as laser pulses, may be produced; and (3) the pyroelectric element can be used to store the total charge liberated by a transient signal.

The behavior of analog communication systems

Abstract: We consider the problem of transmission of analog data over a noisy channel. It is assumed that the channel input is of the form \surd S f(t, X) , where X is an n -dimensional source vector, and S is the allowable transmitted power. The performance of any given modulation scheme f(t, \cdot ) as a function of the transmitted power S is studied. Lower bounds on the average distortion produced by noise for a class of distortion functions are derived. These bounds relate the "smoothness" of modulation techniques to the minimum error that can be achieved with them. It is shown that when the analog source emits a sequence of mutually independent real random variables at a rate of R per second, the mean-square error that is associated with any practical modulation scheme f(t, \cdot) decays no faster than S^{-2} as the signal power S \rightarrow \infty . It follows that in the case of a band-limited additive white Gaussian channel no single modulation scheme f(t, \cdot ) can achieve the ideal rate-distortion bound on the mean-square error for all values of S , if the channel bandwidth is larger than the source rate R .

Surface state related noise in MOS transistors

Abstract: The theory of surface state effects on 1 ƒ noise in p−n junctions is extended to explain low-frequency excess noise in MOS transistors. Experimental results are critically compared to theory. The results show that low-frequency excess noise in MOS transistors is due to the fluctuation of charge density in the conduction channel caused by the surface potential fluctuation. The fluctuation of the surface potential is introduced by the random charge occupancy of surface states. The low-frequency excess noise in MOS transistors is found to be proportional to the surface state density and the square of the transconductance of the device, and inversely proportional to the gate area and the square of the unit area gate-insulator capacitance. It is also shown that the surface state density when the surface is strongly inverted can be obtained from noise measurements. Finally it is shown that by proper heat treatment it is possible to reduce the low-frequency excess noise of MOS transistors.

Random input and correlation methods to improve the singal-to-noise ratio in chromatographic trace analysis

Abstract: A method to establish a chromatogram by pseudo random injection and cross correlation techniques is described. It is possible to accumulate a peak from a detector outputsignal, buried in backgroundnoise.

Communication theory for the free-space optical channel

Abstract: The current understanding of quantum detectors, the noise mechanisms which limit (are basic to) their operation, and their application to optical communications (theory) is summarized. In this context, we are considering channels in which the electromagnetic field is not subjected to any propagation effects other than a geometric loss. (Such a channel would exist between satellites.) Consequently, we will concentrate on optimum time processing using the tools of statistical communication theory. Fundamental to the study of a detection process is the need to develop a good mathematical model to describe it [1]-[6]. Therefore, approximately one-fifth of the paper is devoted to establishing, in a semi-classical analysis, the quantum detector output electron number as a conditional Poisson process with the conditioning variable being the modulus of the electromagnetic field. Once this has been established, these results are used to derive various limiting probability densities related to actual practice. Although the mathematical details are omitted, these results will be presented from the viewpoint of orthogonal function expansions and interpreted in terms of an eigenspace. The resulting current flow is analyzed next as a shot noise process, and the power density spectrum is calculated. Attention is focused on isolating the signal components from the noise in terms of both the current probability density and the power density spectrum. Examples are given where appropriate. At this point, an understanding of the underlying noise processes will have been presented and attention will shift to analog and digital communications. The analog communication will be presented primarily in terms of the signal-to-noise ratio. The S/N ratio in direct detection will be presented both as a ratio of the integrals of two separate portions of the spectrum and as a ratio of two moments of the probability density describing the current. These calculations will be extended to include heterodyne detection. Digital communications will be discussed in the context of detection theory. It will be shown that the likelihood ratio is often a monotonic function of the random variable representing the number of electrons flowing. Hence optimum processing will consist of a weighted count of electrons from various counting modes. Digital design will be presented in terms of M-ary signaling, error probabilities, and information rates.

Communication through optical scattering channels: An introduction

Abstract: The theoretical possibilities of communicating through scattering channels are considered in the context of digital communication. Direct-detection, heterodyne, and optimum receivers are discussed and the near optimality of direct-detection systems is noted. It is found that the error probability depends only upon the total received signal energy if certain noise thresholds are exceeded; below these thresholds the performance deteriorates rapidly. It is often difficult to exceed the thresholds with present-day technology, but it should become possible to do so as the technology evolves.

Surface state related 1f noise in p-n junctions

Abstract: It has been shown experimentally by Hsu , Fitzgerald and Grove that the 1 f noise in p-n junctions can be increased by a particular type of surface state introduced by the application of an electric field across the oxide at elevated temperatures This paper extends their work both theoretically and experimentally, leading to an understanding of the mechanism by which surface states affect p-n junction noise The results show that for gate-controlled diodes the noise power is proportional to the product of the density of these surface states and the square of the transconductance, defined as the incremental change in forward current with gate bias For non-gate-controlled diodes an equivalent transconductance can be defined

Noise sources in transport equations associated with ambipolar diffusion and Shockley-Read recombination

Abstract: A discussion is presented of the noise sources which enter into the stochastic transport equations which govern carrier flow in SCL diodes and ordinary junction devices. The essential sources associated with diffusion (or microscopically intraband scattering) and generation-recombination (or microscopically interband transitions) are presented. The connection with thermal noise is discussed. The paper is further devoted to the manifestation of these sources in diffusion, ambipolar flow, band-band generation and recombination and Shockley-Read-Hall recombination. Both low and high injection are treated.

Noise in amplifiers

Abstract: In practically every type of research program in the physical sciences as well as in sophisticated engineering analyses, very small electrical signals must be measured and, in general, the limit of attainable precision and detectability is set by noise. This is true for the physicist and chemist performing nuclear magnetic resonance or spectroscopy experiments, for medical and biological researchers interested in evoked potentials, for geologists measuring small remanent magnetic fields in rock samples, for the metallurgist making Fermi surface measurements, and for the engineer performing vibration analysis and sensitive bridge measurements. These are only a few examples of applications in which noise plays a critical role in limiting measurement precision and signal detectability. This article discusses some of the inherent problems and describes techniques for improving signal-to-noise ratio.

Error Performance of Multiphase DPSK with Noise and Interference

Abstract: This paper is a sequel to a previous paper which considered the error performance of binary DPSK transmission for the case of noise and general cochannel interferences. The present work extends that analysis to include multiphase signaling. Whereas the binary analysis produced exact expressions for the probability of error, the extension to M -ary DPSK considered here leads to upper and lower bounds to the symbol error probability. The bounds have a ratio of 2. However, by a heuristic argument it is possible to estimate the proximity of the error probability to one of the bounds, and so the uncertainty in the approximation is small enough to make the results quite usable for systems design. Computations are displayed for quaternary ( M = 4 ) single difference (conventional) DPSK.

On the influence of hot carrier effects on the thermal noise of field-effect transistors

Abstract: The noise resistance of the field-effect transistor has been calculated taking into account high-field effects such as mobility saturation and hot carrier temperature upon the thermal noise. The result of the calculations can be represented by a practical formula. The calculated results have been compared with measurements of the noise of a junction gate FET and a MOS tetrode with short active channels. The agreement is reasonable. At room temperature the effect is moderate, but at low temperatures it is considerable.

Information transmission, modulation, and noise : a unified approach to communication systems

Abstract: Information transmission, modulation, and noise: a unified approach to communication systems , Information transmission, modulation, and noise: a unified approach to communication systems , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

An approximate method of state estimation for non-linear dynamical systems with state-dependent noise†

Abstract: In this paper a method of stochastic linearization is demonstrated for the purpose of establishing an approximate approach to solve filtering problems of non-linear stochastic systems with state-dependent noise in a Markovian framework. The models of both the dynamical system and the observation process are described by non-linear stochastic differential equations of Ito type. The principal line of attack is to expand the non-linear drift term into a certain linear function with coefficients which are determined under the minimal squared error criterion. Two methods of linearization are developed for the non-linear diffusion term. The linearized models are thus characterized by expansion coefficients dependent on both the state estimate and the error covariance. A method is given for the simultaneous treatment of the approximate structure of state estimator dynamics and of the running evaluation of the error covariance, including quantitative aspects of sample path behaviours obtained by digital simulatio...

An analytical and experimental study of nonlinearities in hologram recording.

Abstract: A theoretical analysis of the effect of recording nonlinearities upon the image reconstructed from a hologram made of a diffuse object is presented. Extensive experimental evidence which supports this theory is also given. In particular, it is shown that the magnitude of the nonlinearity noise can be calculated knowing the shape of the amplitude transmittance–exposure (Ta − E) curve, the bias transmittance (Tb), and the ratio of the reference beam to the object beam intensity (K). It is further shown that for diffuse objects the shape of the nonlinearity noise distribution can be calculated from the shape of the object.

Steady-state quantum analysis of linear systems

Abstract: A rigorous basis for the quantum analysis of the steady state of linear distributed systems is established. The analysis of a distributed system of finite length requires, for self-consistency, that excitations be stated at the boundaries of the system even in the absence of externally applied excitations. The commutators of the amplitudes at the boundaries are stated and a useful analogy with thermal noise of classical systems is established. The use of these boundary conditions enables one to formulate the theory of the steady state for distributed quantum systems. When the system under consideration is coupled to a dissipation mechanism, operator-noise sources have to be assigned to the dissipative elements. The commutation relations that must be obeyed by these noise sources are derived. This formalism enables one to analyze the steady-state operation of an attenuator and of a maser amplifier. Finally, properties of multiterminal-pair networks are discussed using the steady-state quantum approach.

Influence of External Noise on Microwave‐Induced Josephson Steps

Abstract: The influence of fluctuations on microwave‐induced Josephson steps is treated phenomenologically and it is found that the center voltage of these steps is not shifted by the disturbance. Expressions governing the step shape are obtained for various noise spectra. The theory was checked by subjecting niobium point‐contact junctions to several forms of externally generated noise. The theory does not differentiate between internal and external noise sources, so that a number of the conclusions can be extended to intrinsic fluctuations.

Overload Recovery Circuit for Charge Amplifiers

Abstract: In this paper the operation of low noise charge preamplifiers under high instantaneous pulse rates - "bursts" - is considered. An overload recovery circuit employing a field-effect transistor as the switch for the recovery current is described. The overload charge generated in the detector by the radiation burst in a time short compared to the small signal resolving time of the spectrometer may be 105 or more times larger than the charge due to a single particle to be measured between the bursts. The recovery time of the charge amplifier with the recovery circuit is less than 10 ?sec. With a conventional amplifier-filter, the recovery time of the system to within the noise level is 50 to 100 ?sec. The increase in noise due to the recovery circuit corresponds to an increase in the input capacitance of the charge amplifier of 2 pF.

Image Enhancement and Film-grain Noise

Abstract: Film-grain noise severely limits the possibilities for enhancing degraded photographic images Because the grain noise increases monotonically with the photograph's mean or bias transmittance, poor signal-to-noise ratios result whenever the emulsion receives a low-contrast, high-level exposure Image degradation—such as that resulting from inadvertent camera motion—preserves the level of the exposure, but lowers the image contrast inversely at the spatial frequency in question Consequently, the observed signal-to-noise ratio and the theoretical enhanceability of the degraded image drop with increasing spatial frequency Unfortunately, the tendency for low spatial frequencies to dominate the highs in the typical object scene, and the relative importance of the highs in obtaining quality image recordings, compound the enhancement problem still further Nevertheless, Wiener-filter theory—reworked under the assumption of multiplicative film-grain noise—still provides some resolution improvement for imaging d

Low‐Frequency Variance Noise

Abstract: Variance fluctuations in 1/f noise examined with apparatus capable of responding to zero frequency signals are found to have the same magnitude as those in band‐limited 1/f noise signals. The distribution of variances in identical sample lengths is skewed to small values in the case of current noise in a carbon resistor and is symmetrical in the case of current noise in a germanium p‐n junction. The probability amplitude is normally distributed in all samples investigated, from 10 to 2400 sec long. Both the average variance and the variance of the variance are found to increase as the logarithm of the sample duration.

Electronic noise filter with means for compensating for hose reflection

Abstract: An illustrative embodiment of the present invention includes methods and apparatus for detecting pressure pulse signals from a remote signalling device in the mud line of a well while the well is being drilled and in the presence of mud pump pressure pulse noise. The apparatus and method includes placing plural pressure sensitive transducers in the mud line on the mud pump side of the flexible hose portion thereof. Electrical signals representative of the pressure in the mud line sensed by the transducers are processed to take into account the amplitude and phase shift effect of the hose. The processed signals are then combined to directionally discriminate against the mud pump noise pulses wihie detecting pulses from downhole.

Transistor noise measuring apparatus

Abstract: An improved instrument measures noise power generated by a transistor under selected test conditions. Automatic adjustment of gain from the input of the transistor under test through succeeding stages provides an accurate readout of noise generated within the transistor under test.

Thermal feedback in power semiconductor devices

Abstract: Thermal feedback (TF) is an important aspect for the thermal management of semiconductor devices and high-power density integrated circuits. Different features of positive and negative TF in transistors are reviewed and summarized for the macroscopic domain. The thermal feedback mechanism is applied to the microscopic domain of noise fluctuations in semiconductor devices. It is argued that TF may be responsible for a major part of 1/ f flicker or excess noise. Some experimental evidence is presented which supports this thermal feedback 1/ f -noise theory for bipolar and MOS field effect transistors. Device and circuit design rules for the minimization of transmitter noise are given.

Tachogenerators which determine the speed and acceleration of a rotating shaft by using two counter rotating shutters

Abstract: A tachogenerator for measuring the speed of a rotating shaft is described. The tachogenerator has two discs each with spaced peripheral slots; one disc is rotated at a constant speed and the other at the speed to be measured. A light beam is projected through the slots to a light sensitive device coupled to an electrical filter and a signal indicative of speed is obtained from the filter. Electrical noise in the signal from the light sensitive device is reduced by the filter. A further reduction in noise is obtained by using one or more pairs of light beams, with the beams diametrically opposed with respect to the discs. A light sensitive device is provided for each beam and these devices are coupled to the filter input. Instead the devices may be coupled to means for combining the pulse trains generated, to provide the output signal.

Mathematical description and computer detection of alpha waves

Abstract: Surface recordings of alpha waves are compared with narrow-band Gaussian random noise and the two are found to be indistinguishable. The three bases of comparison are the time domain, the frequency domain, and the probability density functions. Using the mathematical description of narrow-band noise, the complex demodulation technique for the detection of the alpha-wave envelope is developed and an analog computer circuit for its implementation is presented. The envelope is shown to have a Rayleigh probability density function that is completely specified by one parameter, σ x . This parameter, which is a function of time, since the EEG is a nonstationary process, should be used to summarize alpha-wave amplitude information.

A lumped-circuit study of basic oscillator behavior

Abstract: This paper presents an experimental study of the oscillations set up in a circuit consisting of a negative conductance and a multiple-resonant load. Its purpose was to verify that such a circuit can account for many of the irregular phenomena commonly observed during tuning of practical microwave solid-state oscillators; such effects as discontinuous frequency changes, low circuit Q-factors, power variations, spurious oscillations and noise conditions are all readily reproduced in a simple low-frequency analogue. There is close correspondence with a first-order analysis.