Showing papers on "Noise (electronics) published in 1980"

On the statistics of K-distributed noise

Abstract: When the number of steps in a random walk varies, the distribution of the resultant vector components in the limit of large mean step number may be non-Gaussian The statistics and temporal correlation properties of one class of such non-Gaussian limit distributions are derived and some of its potential applications are reviewed briefly

Noise and error rate performance of semiconductor laser amplifiers in PCM-IM optical transmission systems

Abstract: Applications of semiconductor laser amplifiers in intensity modulated digital optical transmission systems were studied theoretically. An optical linear amplifier repeater between electronically regenerating terminal repeaters and an optical linear preamplifier in front of a photodetector in an electronically regenerating repeater are discussed. Both traveling-wave type and Fabry-Perot cavity type laser amplifiers are considered. The noise and error rate performance in these systems are evaluated using formulations for semiconductor laser amplifiers. The mean and variance in the optical amplifier output photons calculated by the photon master equation [1] is used to obtain the worst case variance in the equalized output voltage [2] for these systems. The required receiving power reduction from direct detection scheme by a preamplifier system and the repeater spacing expansion between two electronically regenerating terminals by an optical linear amplifier repeater system are delineated.

A Modified Monte-Carlo Simulation Technique for the Evaluation of Error Rate in Digital Communication Systems

Abstract: Digital communication systems are frequently operated over nonlinear channels with memory. The analysis of the performance of these systems is difficult and no complete analytical treatment of the problem has been obtained before. Several recent efforts have been directed toward the computation of error probabilities via Monte-Carlo simulation using a complete system model. These simulations require excessively large sample sizes and are not practical for estimating very low values of error probabilities. This paper presents a modified Monte-Carlo simulation technique for estimating error probabilities in digital communication systems operating over nonlinear channels. An importance-sampling technique is used to modify the probability density function of the noise process in a way to make simulation possible. Theoretical results as well as realistic examples are presented, showing that the number of samples needed for simulation is reduced considerably.

On the distribution of the heights of sea waves: Some effects of nonlinearity and finite band width

Abstract: It is shown that some recent data on the crest-to-trough heights of sea waves are fitted just as well as by the one-parameter Rayleigh distribution as by the two-parameter Weibull distribution, provided that the rms amplitude a-bar is taken as 0.925(2m/sub 0/)/sup 1/2/, where m/sub 0/ is the lowest moment of the frequency spectrum. Reasons why the ratio a-bar/(2m/sub 0/)/sup 1/2/, should differ from unity are discussed. It is shown that the effect of finite wave steepness would be to increase the radio by a factor (1+1/2(ak)/sup 2/ approximately, contrary to observation. The effect of finite band width is estimated from a model assuming low background noise superposed linearly on a delta function spectrum. For narrow band widths one obtains the formula a-bar/sup 2//2m/sub 0/=1-0.734v/sup 2/, where v is the rms spread of the noise about the mean frequency. Values of v/sup 2/ corresponding to Pierson-Moskowiez spectra give results in close agreement with observation.

Response of a correlated double sampling circuit to 1/f noise [generated in CCD arrays]

Abstract: Correlated double sampling (CDS) was introduced by White et al. (1974) as a technique for removal of switching transients and elimination of the Nyquist (reset) noise, both of which are associated with charge sensing circuits employed in charge-coupled device arrays. An additional advantage is the attenuation of the 1/f noise component in the charge sensing circuits due to the zero in the CDS noise transfer function at the origin (/spl omega/=0). The effect of the CDS circuit on the reset noise and Johnson-Nyquist (white) noise in the associated circuitry has been adequately described (see ibid., vol.SC-11, no.1, p.147, 1976). The author presents an analysis of the effect of the CDS circuit on the 1/f noise component generated in the preceding CCD circuitry.

A high performance low power CMOS channel filter

Abstract: A new CMOS PCM channel filter is described, which includes transmit and receive filters on a single die. This chip displays an idle-channel noise of typically 0 dBrnC0, a power supply rejection ratio of 40-50 dB at 1 kHz, and a fully operational power dissipation of only 35 mW, making it very cost effective in telecommunication switching systems. The design of this chip, including architectural, switched capacitor filter, and amplifier considerations is described, and typical experimental results are presented.

Frequency dependence of modal noise in multimode optical fibers

Abstract: Under certain conditions a changing speckle pattern exists at the output plane of a multimode fiber, resulting in modal noise which can degrade the error performance of a fiber data link. Fiber motion is the usual cause of such speckle change, and Daino et al. have studied the first-order statistics of such modal noise, assuming a single frequency source. But source frequency variation can also cause modal noise; and source frequency diversity has been shown effective in its reduction. In this paper we use a speckle theory approach to study the frequency dependence of modal noise. We have measured and analyzed the correlation of two speckle patterns as a function of source frequency difference, and the speckle spatial frequency distribution as a function of fiber parameters. We have also measured the speckle contrast as a function of fiber length for several sources and fiber types. Such information permits the prediction of the modal noise statistics, from which corresponding changes in error rates can be derived.

Nonlinear distortions and noise in optical communication systems due to fiber connectors

Abstract: The transmission characteristics of optical fiber connectors are analyzed in detail in order to calculate nonlinear distortions and noise due to instable speckle patterns. The fluctuation amplitude of the transmission loss and its sensitivity, with respect to a wavelength shift of the laser source, are determined for coherent and partially coherent laser sources. Nonlinear distortions due to fiber connectors yield a second-order harmonic distortion of typically -36 dB for a single-longitudinal mode injection laser, and typically -65 dB for a multimode laser. The noise performance has also been estimated for both low frequency and high frequency fluctuations.

Computer analysis of hoarseness.

Abstract: The harmonic components in hoarse voice were separated from the noise components by using a small laboratory computer. The ratio of harmonics to noise or S/N ratio, was calculated and compared with...

1/f Noise in (Hg, Cd)Te photodiodes

Abstract: In this article we present results of experiments to characterize 1/ f noise in Hg 0.7 Cd 0.3 Te n+-on-p junction photodiodes. Under zero-bias voltage conditions, the photodiodes display no 1/ f noise, even in the presence of large photocurrents. Under reverse-bias voltage operation, 1/ f noise is observed. In these experiments, the 1/ f noise was measured as a function of temperature, diode bias voltage, and photon flux. Since these parameters varied the relative contributions of the various current mechanisms, the diode current mechanism responsible for 1/ f noise was isolated. It was found that 1/ f noise is independent of photocurrent and diffusion current but is linearly related to surface generation current. It is proposed that 1/ f noise in reverse-biased (Hg, Cd)Te photodiodes is a result of modulation of the surface generation current by fluctuations in the surface potential.

Laser gyro at quantum limit

Abstract: We show that a certain fundamental limit applies to the accuracy of all optical rotation sensors which use laser light as a probe. We derive this fundamental rotation-rate uncertainty from the Heisenberg uncertainty relations and Glauber's minimum uncertainty states. The same relationship is obtained from a spontaneous-emission noise formulation. We present experimental data on a (nondithered) four-frequency ring laser gyroscope for which this limit is attained.

Current transient spectroscopy: A high-sensitivity DLTS system

Abstract: A deep-level transient spectrometer (DLTS) has been built that measures current transients, rather than the usual capacitance transients, in p-n junctions. The system was developed to optimize sensitivity for the study of low-concentration processing-induced defects. An analysis of its performance as a function of timing parameters is presented. A noise analysis of both capacitance and current transient measurement is presented, showing that neither method has an inherent sensitivity advantage, and that both should be capable of detection limits of about 10-7to 10-8of the shallow doping concentration. Noise measurements indicate that a detection limit of 10-7times the doping has been obtained. Spectra of a processed p+-n diode with no intentional contamination show several defect levels in the 10-5N D , or 1010cm-3, range. Spectra of gold-doped p+-n diodes yield emission data in good agreement with accepted values.

Application of Monte Carlo techniques to hot carrier diffusion noise calculation in unipolar semiconducting components

Abstract: It is shown in this paper that Monte Carlo techniques are available for a complete study of unipolar semiconducting components for both diffusion noise properties and static characteristics. This necessitates taking into account space-charge reaction by integration of Poisson's equation. Two possible methods are proposed and carried out in a unidimensional treatment. Emphasis is given to the various problems which are encountered, especially those concerning the reliability of the solutions. In the first of the two methods (single carrier) the validity of classical electrokinetics equations is investigated, showing the influence of possible relaxation effects in a component. In the second method (multicarrier), it is shown that diffusion noise properties are approachable by observation and spectral analysis of current or voltage fluctuations at the ends of the component.

A 5 V-only 64K dynamic RAM based on high S/N design

Abstract: A 5 V-only 64K dynamic RAM is designed and fabricated using double poly-Si technology based on the 3 /spl mu/m design rule. The design features of this dynamic RAM are described. In particular, memory cell and S/N (signal/noise) designs are focused of a dynamic RAM with an on-chip bias generator. The device fabricated provides a typical access time of 120 ns and a 170 mW operating power, with minimized sense noise of less than 50 mV.

Conversion Gain in MM-Wave Quasiparticle Heterodyne Mixers,

Abstract: We report the observation of heterodyne mixing in superconductor‐insulator‐superconductor tunnel junctions with significant conversion gain and with a noise temperature comparable to the photon noise limit. (Double sideband L−1=1.400.14, TM≲1.5 K at 36 GHz.) The mixing arises from the strong nonlinearity in the quasiparticle tunneling currents at voltages comparable to the full energy gap. Gain is observed when the onset of quasiparticle current is sufficiently sharp that quantum effects are important. The observed gain is in good quantitative agreement with calculations based on the work of Tucker. It should make possible the construction of photon‐noise‐limited microwave heterodyne receivers.

1f Noise in p-n diodes

Abstract: 1 f Noise calculations and experiments are presented for silicon p-n diodes. The experimental results can be explained by assuming that the 1 f noise is due to fluctuations in the mobility of free carriers. The ratio between the 1 f noise density and the shot noise density in p-n diodes is characterized by the corner frequency fc where the 1 f noise equals the shot noise. In long diodes the corner frequency is proportional to Hooge's empirical 1 f noise constant α ≈ 10-3, and inversely proportional to the minority carrier lifetime in the base. In short diodes the frequency fc is related to the constant α, the width of the base, and the contact recombination velocity.

Niobium nanobridge dc SQUID

Abstract: For the first time high‐resolution electron beam contamination lithography has been used to produce active sensing devices. dc SQUID’s (Superconducting quantum interference devices) with linewidths as small as 30 nm have demonstrated a minimum intrinsic energy resolution of 3h. This is the best value for any SQUID to date and approaches the limit ≈ h set by the uncertainty principle. The dependence of voltage noise on SQUID parameters is in agreement with a new small‐signal model of SQUID noise.

1/f; noise model for MOSTs biased in nonohmic region

Abstract: Relations are derived for the 1/f; noise current and for the equivalent input noise voltage of a MOST biased in the nonlinear region. The experimentally obtained results are in agreement with the calculations. In addition the value of power spectrum of the noise current is related to that in the ohmic region. In the last region the 1/f; noise appears to be caused by mobility fluctuations of the charge carriers. In the nonohmic region, the noise consists of two contributions: (i) mobility fluctuations and (ii) number fluctuations in the charge carriers due to fluctuations of the effective gate voltage induced by mobility fluctuations.

Intrinsic noise of semiconductor lasers in optical communication systems

Abstract: The upper limit of the achievable signal-to-noise ratio in optical communication systems is determined by the intrinsic laser noise due to quantum fluctuations inside the laser cavity. This achievable signal-to-noise ratio depends on the way in which different lasing modes are detected; wavelength filtering and material dispersion may yield a significant deterioration of the signal-to-noise ratio. It is concluded from theoretical calculations and from measurements on V-groove lasers that a d.c. signal-to-noise ratio of about 70 dB may be achieved for a noise bandwidth of 10 MHz.

Applications of a Low Noise Potentiostat in Electrochemical Measurements

Abstract: Measurements on two electrochemical systems, copper in copper sulfate and aluminum in boric acid/tetraborate buffer, have been carried out by recording the amplitude spectrum of the fluctuations in the current density. For these measurements, a low noise potentiostat developed and built at NBS was employed. In the case of copper, the current spectra are found to be the deterministic response of the electrode to the noise voltage generated by the potentiostat. The electrode characteristics for charge‐transfer and for diffusion could be obtained from the impedance plots derived from the measurements when the level of the applied signal was of the order of 10−7V. In the case of aluminum, the deterministic response observed in the absence of pitting gave way to random fluctuations in the current in conditions leading to pitting. It is shown that the onset of pit formation can be detected from noise measurements. The significance of the information obtained in electrochemical noise measurements is briefly discussed.

Automatic measuring device for impedances in the low and very low frequencies range

Abstract: An automatic method to determine impedances at frequencies too low to be covered by standard techniques is presented. The frequency scanning as well as the measurement itself are automated. Particularly accurate results can be obtained, with possibly a great deal of noise rejection, whatever the ratio between the imaginary and real parts of the impedance is.

Super low-noise GaAs MESFET's with a deep-recess structure

Abstract: Super low-noise GaAs MESFET's for replacement of parametric amplifiers have been successfully developed by adopting a deep-recess structure. The structure of a 0.5-µm gate in a deeply recessed region with a cylindrical edge shape has enabled reduction of the source resistance to a half of that of conventional flat-type MESFET's. The noise figure was improved by more than 0.5 dB by this reduction of the source resistance, and less than 2.0-dB noise figure has been reproducibly obtained at 12 GHz. The best noise figures were 0.7 dB (14.9-dB gain) at 4 GHz and 1.68 dB (10.7-dB gain) at 12 GHz. The developed MESFET's were applied to two-stage amplifiers of 11.7-12.2-GHz band, and the noise figure obtained was 2.16 dB ( T_{e}: 185 K) at room temperature and 1.94 dB ( T_{e}: 163 K) at 0°C. This performance is good enough to replace some of parametic amplifiers.

Environmental mapping system

Abstract: A circuit which detects environmental sources of echos received by a pulscho system such as a radar and classifies the sources of the echo at each range resolution cell as either short-pulse interference, rain clutter or jamming, distributed land clutter, an isolated target or thermal noise. The circuit implements on the screen of a cathode ray tube a digital map of a selected echo source type by modulating the electron beam intensity with a binary digit (0 or 1) at each increment of the sweep corresponding to a range resolution cell. The circuit utilizes a pulse-to-pulse noncoherent subtraction to remove correlated echos, leaving only uncorrelated type echos. Short-pulse interference is then detected and the uncorrelated echo component is compared to thermal noise to determine if rain clutter or noise jamming is present. The threshold for either target detection or land clutter is determined from the uncorrelated echo component, and all correlated targets and land clutter are next detected. The correlated echos are separated into distributed land clutter and isolated targets by the following procedure: the isolated targets are required to have uncorrelated echos on each side of them in range. Finally, if no detection of any of these types is made, thermal noise is declared.

Wigner distribution and ambiguity function

Abstract: The Wigner phase space distribution and the Woodward radar ambiguity function have each been optically realized in idealized situations. The realistic performance will be assessed under simulated noise and clutter. A general cross Wigner distribution and cross ambiguity function are also compared as to their advantage in signal analysis. The cross Wigner distribution is a general convolution of non‐zero frequency while the cross ambiguity function is a general correlation of non‐zero frequency. The former is commutative while the latter is not. The significance of this difference is discussed. While the ambiguity function is generally complex, the Wigner distribution is real but not always positive. Both are known to be intermediate signals and are related through a double Fourier transform. However, optical equivalence of one from the other has not been demonstrated. Bartelt et al1 have only produced the even part of the signal whose Wigner distribution is jpositive. Marks et al2 have presented in the noise‐free case the modulus of the ambiguity function, which is known as the ambiguity surface in the radar community. The present extension with noise and clutter provides a better understanding of the optimum condition for signal to noise ratio. Such a comparison study, which takes into account both knowledge of quantum mechanical symmetry and practical experience of radar clutter and noise, turns out to be fruitful.

A Unified Theory of 1/f Noise and Dielectric Response in Condensed Matter.

Abstract: : A theoretical model of mobility fluctuations that has a 1/f power spectra in electric current conducting materials and devices is presented. The theory traces the origin of the 1/f noise to some rather uncommon electronic or ionic energy structure and excitations which have been identified earlier to be responsible for the remarkable universal dielectric response behavior of condensed matter. The relation between the ubiquitous 1/f noise and the universal 1/omega to the (1-n) power low frequency dielectric response in current conducting material is pointed out and emphasized. We have thus a unified theory explaining on the same basis both physical phenomena with a single physical picture. (Author)

Fiber Optics Receiver Error Rate Prediction Using the Gram-Charlier Series

Abstract: This paper applies the Gram-Charlier series method to the caculation of error probabilties in digital optical receivers. This method allows the calculation of "exact" error probabilities including the effects of avalanche noise, thermal noise, and arbitrary posidetection processing filter. The predictions of this method are compared with those of a simple Gaussian approximation and with the Chernoff bounds. Finally, the effects of modal noise are included in the theory, and some specific cases are explored numerically.

Introduction to Communication Science and Systems

Abstract: 1. Antennas and Transmission.- 2. Sources of Noise.- 3. Signals and Frequencies.- 4. Modulation and Noise.- 5. The Link between Continuous and Pulsed Signals-Sampling and Digitization.- 6. Autocorrelation and Stationarity.- 7. Pulse Shape, Filtering, and Arraying.- 8. Random Pulses and the Gaussian Distribution.- 9. Random Processes and Gaussian Signals and Noise.- 10. Some Aspects of Data Transmission.- 11. Limits to Error Performance: Information Theory.- 12. Applying Information Theory-Coding and Randomization.- 13. Sources, Source Encoding, and Source Characterization.- References.

Analysis and measurement of the modal-noise probability distribution for a step-index optical fiber

Abstract: With a sufficiently narrow source spectrum, and either fiber movement or source frequency shift, a changing speckle pattern exists at a multimode-fiber output plane that results in modal noise. Daino and co-workers [Electron. Lett. 15, 755 (1979)] have obtained the noise probability density function (PDF) for a fiber of arbitrary refractive-index profile in the limiting cases in which the number of speckles seen by the detector is either very small or very large. We show that, in the special case of a step-index fiber, the PDF is a gamma distribution of argument M′, where M′ is the number of degrees of freedom in the speckle pattern. We report measurements of the PDF that show good agreement with calculated gamma distributions.