Showing papers on "Noise (electronics) published in 1992"
TL;DR: By preparing correlated states, here called squeezed spin states, the signal-to-noise ratio in spectroscopy can be increased by approximately N 1/2 in certain cases over that found in experiments using uncorrelated states.
Abstract: We investigate the quantum-mechanical noise in spectroscopic experiments on ensembles of N two-level (or spin-1/2) systems where transitions are detected by measuring changes in state population. By preparing correlated states, here called squeezed spin states, we can increase the signal-to-noise ratio in spectroscopy (by approximately ${\mathit{N}}^{1/2}$ in certain cases) over that found in experiments using uncorrelated states. Possible experimental demonstrations of this enhancement are discussed.
706 citations
TL;DR: In this article, the inversion method used is based on smoothness-constrained least-squares and finite-element methods, and an appropriate block discretization is obtained by dividing the target region into square blocks of size equal to half the minimum electrode spacing.
Abstract: Some factors affecting the resolution and accuracy of resistivity tomography are examined using numerical simulation. The inversion method used is based on smoothness-constrained least-squares and finite-element methods. An appropriate block discretization is obtained by dividing the target region into square blocks of size equal to half the minimum electrode spacing. While the effect of the damping factor on the resolution is significant, the resolution is not very sensitive to Gaussian noise as long as the damping factor is properly chosen, according to the noise level. The issue of choosing an optimum electrode array should be considered at the planning stage of a survey.
When the instrumental accuracy is high, the dipole-dipole array is more suitable for resolving complex structures than the pole-pole array. The pole-dipole array gives somewhat less resolution than the dipole-dipole array but yields greater signal strength; thus, the pole-dipole array may be a good compromise between resolution and signal strength. The effect of an inhomogeneity located outside the target region may be very small if block discretization is done so as to represent the resistivity variations in both the target and outside regions.
537 citations
Journal Article•
TL;DR: In this article, the authors investigated the quantum-mechanical noise in spectroscopic experiments on ensembles of N two-level (or spin-1/2) systems where transitions are detected by measuring changes in state population.
Abstract: We investigate the quantum-mechanical noise in spectroscopic experiments on ensembles of N two-level (or spin-1/2) systems where transitions are detected by measuring changes in state population. By preparing correlated states, here called squeezed spin states, we can increase the signal-to-noise ratio in spectroscopy (by approximately ${\mathit{N}}^{1/2}$ in certain cases) over that found in experiments using uncorrelated states. Possible experimental demonstrations of this enhancement are discussed.
518 citations
TL;DR: Both of the FMS methods, which require modulating the laser at frequencies >/= 150 MHz, give relatively poor results due to inefficient coupling of the modulation waveform to the laser current, and the re ults obtained agree well with theory.
Abstract: Wavelength modulation spectroscopy (WMS) and one-tone and two-tone frequency modulation spectroscopy (FMS) are compared by measuring the minimum detectable absorbances achieved using a mid-IR lead-salt diode laser. The range of modulation and detection frequencies spans over 5 orders of magnitude. The best results, absorbances in the low-to-mid 10−7 range in a 1-Hz bandwidth, are obtained by using high-frequency WMS (10-MHz detection frequency) and are limited by detector thermal noise. This sensitivity can provide species detection limits well below 1 part per billion for molecules with moderate line strengths if multiple-pass cells are used. High-frequency WMS is also tested by measuring the absorbance due to tropospheric N2O at 1243.795 cm−1. WMS at frequencies <100 kHz is limited by laser excess (1/f) noise. Both of the FMS methods, which require modulating the laser at frequencies ≥150 MHz, give relatively poor results due to inefficient coupling of the modulation waveform to the laser current. The results obtained agree well with theory. We also discuss the sensitivity limitations due to interference fringes from unintentional etalons and the effectiveness of etalon reduction schemes.
378 citations
TL;DR: It is demonstrated that detection of these signals by a wideband radiometer can be considerably more difficult in practice than is indicated by the standard result.
Abstract: The standard analysis of the radiometric detectability of a spread-spectrum signal assumes a background of stationary, white Gaussian noise whose power spectral density can be measured very accurately. This assumption yields a fairly high probability of interception, even for signals of short duration. By explicitly considering the effect of uncertain knowledge of the noise power density, it is demonstrated that detection of these signals by a wideband radiometer can be considerably more difficult in practice than is indicated by the standard result. Worst-case performance bounds are provided as a function of input signal-to-noise ratio (SNR), time-bandwidth (TW) product and peak-to-peak noise uncertainty. The results are illustrated graphically for a number of situations of interest. It is also shown that asymptotically, as the TW product becomes large, the SNR required for detection becomes a function of noise uncertainty only and is independent of the detection parameters and the observation interval. >
339 citations
IBM1
TL;DR: The wave-packet approach is presented as a physically intuitive alternative to the existing approaches to mesoscopic noise, and leads to identical results for one-dimensional leads and multichannel leads.
Abstract: Noise in conductors transmitting electrons coherently between attached reservoirs is calculated by following wave packets incident on the sample. The Pauli principle restricts the occupation of wave packets, spreading electrons more uniformly among the available packets, and thus reducing the noise below that of the classical shot-noise expression for totally uncorrelated electrons. After a brief review of the results for one-dimensional leads, we treat the case of the sample attached to two multichannel leads. A proper choice of basis for the wave packets permits this case to be reduced to that of a set of independent parallel one-channel samples. This picture is extended to the case of excess noise in multiterminal samples at zero temperature, leading to anticorrelated fluctuations between different leads. The anticorrelated fluctuations are analyzed, in particular detail for a Y-shaped three-lead sample. Our wave-packet approach is presented as a physically intuitive alternative to the existing approaches to mesoscopic noise, and leads to identical results.
337 citations
TL;DR: In this paper, the sensitivity of magnetic-resonance current-density imaging (CDI) to random noise and systematic errors was analyzed with the goal of providing a protocol for achieving a targeted noise performance.
256 citations
TL;DR: In this paper, the effect of dead space on the statistics of the gain in a double-carrier-multiplication avalanche photodiode (APD) was determined using a recurrence method.
Abstract: The effect of dead space on the statistics of the gain in a double-carrier-multiplication avalanche photodiode (APD) is determined using a recurrence method. The dead space is the minimum distance that a newly generated carrier must travel in order to acquire sufficient energy to become capable of causing an impact ionization. Recurrence equations are derived for the first moment, the second moment, and the probability distribution function of two random variables that are related, in a deterministic way, to the random gain of the APD. These equations are solved numerically to produce the mean gain and the excess noise factor. The presence of dead space reduces both the mean gain and the excess noise factor of the device. This may have a beneficial effect on the performance of the detector when used in optical receivers with photon noise and circuit noise. >
251 citations
TL;DR: In this article, the scaling properties of the prediction error as a function of time are used to distinguish between chaos and random fractal sequences, a particular class of coloured noise which represent stochastic (infinite-dimensional) systems with power-law spectra.
Abstract: NONLINEAR forecasting has recently been shown to distinguish between deterministic chaos and uncorrelated (white) noise added to periodic signals1, and can be used to estimate the degree of chaos in the underlying dynamical system2. Distinguishing the more general class of coloured (autocorrelated) noise has proven more difficult because, unlike additive noise, the correlation between predicted and actual values measured may decrease with time—a property synonymous with chaos. Here, we show that by determining the scaling properties of the prediction error as a function of time, we can use nonlinear prediction to distinguish between chaos and random fractal sequences. Random fractal sequences are a particular class of coloured noise which represent stochastic (infinite-dimensional) systems with power-law spectra. Such sequences have been known to fool other procedures for identifying chaotic behaviour in natural time series9, particularly when the data sets are small. The recognition of this type of noise is of practical importance, as measurements from a variety of dynamical systems (such as three-dimensional turbulence, two-dimensional and geostrophic turbulence, internal ocean waves, sandpile models, drifter trajectories in large-scale flows, the motion of a classical electron in a crystal and other low-dimensional systems) may over some range of frequencies exhibit power-law spectra.
198 citations
TL;DR: In this article, the Coulomb blockade electrometer was shown to have a 1/f power spectrum with a charge noise of 3×10−4 e/√Hz and an energy sensitivity EN of 3 ×104 ℏ at 10 Hz.
Abstract: We have measured the noise of a Coulomb blockade electrometer. Below 100 Hz, the noise referred to the input charge has a 1/f power spectrum with a charge noise of 3×10−4 e/√Hz and an energy sensitivity EN of 3×104 ℏ at 10 Hz. The 1/f noise probably results from the stochastic occupation of charge traps which could in principle be eliminated. The theoretical noise floor is set by shot noise, and indirect measurements show that this contribution to EN can be as small as 1.5 ℏ, suggesting that the electrometer will be a quantum limited amplifier if the 1/f noise can be eliminated.
164 citations
TL;DR: This chapter discusses studies of nonstationary fluctuations of sodium currents in bovine adrenal chromaffin cells for estimating the temperature and pressure dependence of the conductance of voltage-activated sodium channels as an application of the analysis method.
Abstract: Publisher Summary This chapter discusses studies of nonstationary fluctuations of sodium currents in bovine adrenal chromaffin cells for estimating the temperature and pressure dependence of the conductance of voltage-activated sodium channels as an application of the analysis method. The procedure presented allows a rapid analysis of noise records obtained under nonideal experimental conditions based on objective selection criteria. Although single-channel analysis surpasses noise analysis in many instances, there are still regimes, where it cannot be successfully applied for various reasons. In this regard, nonstationary noise analysis retain its value for electrophysiological research in particular, as ever fainter electrical signals are being investigated in biological membranes. To demonstrate the methods, the temperature and pressure dependence of the sodium channel conductance are measured, and in both respects, the sodium channel shows features similar to other ion channels. Both findings are in accord with the physical picture of a rather free ion diffusion through the channel pore which, unlike the channel gating mechanism, does not involve protein rearrangements associated with measurable activation volumes.
TL;DR: In this article, a nonlinear model of synchronized oscillators is presented for phase-noise characterization of optically controlled subharmonically injection-locked oscillators, which allows FM noise degradation at large-signal levels to be predicted easily and accurately.
Abstract: A method for the phase-noise characterization of optically controlled subharmonically injection-locked oscillators that is based on a nonlinear model of synchronized oscillators is presented. It allows FM noise degradation at large-signal levels to be predicted easily and accurately. The theoretical analysis shows that (1) the nth-order subharmonic injection locking oscillator is primarily locked by the nth harmonic output of an injected signal, which is generated by the nonlinearity of the active device; (2) the minimum FM noise degradation factor of the nth-order subharmonically locked oscillator is n/sup 2/ when the injection power is sufficiently strong; and (3) a subharmonic injection locking LO with low injection power, good FM noise degradation, and large locking range can be designed by determining the optimum injection power level, by selecting the optimal nonlinear multiplication factor, and by decreasing the intrinsic noise level of the active device. The experimental results confirm the accuracy of the analysis. >
TL;DR: In this article, a simple-man's model for the random telegraph signal (RTS) noise amplitude in a submicrometer MOSFET is presented, where the channel resistance modulation for a specific trap can be expressed as a product of the normalized scattering cross section and of the fractional conductivity change.
Abstract: A simple-man's model for the random telegraph signal (RTS) noise amplitude in a submicrometer MOSFET is presented. It is shown that the channel resistance modulation for a specific trap can be expressed as a product of the normalized scattering cross section and of the fractional conductivity change. The model qualitatively describes the experimental temperature and drain current dependence of the RTS amplitude and allows evaluation of the influence of the trap location and nature on the wide scatter in values observed. >
TL;DR: A method of spectrum estimation using group delay functions is proposed that exploits the additive property of the Fourier transform (FT) phase to extract spectral information of the signal in the presence of noise.
Abstract: A method of spectrum estimation using group delay functions is proposed. This method exploits the additive property of the Fourier transform (FT) phase to extract spectral information of the signal in the presence of noise. The phase is generally featureless due to random polarity and wrappings, but the group delay function can be processed to derive significant information such as peaks in the spectral envelope. In the resulting spectral estimates obtained the resolution properties of the periodogram estimate are preserved while the variance is reduced. Variance caused by the sidelobe leakage due to windows and additive noise are significantly reduced even in the spectral estimate obtained using a single realization of the observation peak. Resolution is primarily dictated by the size of the data window. The method works even for high noise levels. The results of this procedure are demonstrated through two illustrative examples: estimation of sinusoids in noise and estimation of the narrowband autoregressive process in noise. >
TL;DR: In this article, the effect of dead space on the mean gain, the excess noise factor, and the avalanche breakdown voltage for Si and GaAs avalanche photodiodes (APDs) with nonuniform carrier ionization coefficients are examined.
Abstract: The effect of dead space on the mean gain, the excess noise factor, and the avalanche breakdown voltage for Si and GaAs avalanche photodiodes (APDs) with nonuniform carrier ionization coefficients are examined. The dead space, which is a function of the electric field and position within the multiplication region of the APD, is the minimum distance that a newly generated carrier must travel in order to acquire sufficient energy to become capable of causing impact ionization. Recurrence relations in the form of coupled linear integral equations are derived to characterize the underlying avalanche multiplication process. Numerical solutions to the integral equations are obtained and the mean gain and the excess noise factor are computed. >
TL;DR: Three techniques of experimentally determining the modulation transfer function (MTF) of an idealized imaging system are modeled theoretically to determine the noise in the calculated MTFs as a function of spatial frequency resulting from both quantum fluctuations and stochastic detector noise.
Abstract: The modulation transfer function (MTF) of an idealized imaging system can be determined from the Fourier transform of the system's line-spread function (LSF). Three techniques of experimentally determining the LSF require imaging either a slit, wire, or edge. In this paper, these three techniques are modeled theoretically to determine the noise in the calculated MTFs as a function of spatial frequency resulting from both quantum fluctuations and stochastic detector noise. The techniques are compared using the signal-to-noise ratio (SNR) in the MTF, defined as the ratio of the MTF value to the standard deviation in an ensemble of MTF determinations from independent measurements. It is shown that for a specified photon fluence, the edge method MTF has the highest SNR at low spatial frequencies, while that of the slit method is superior at high frequencies. The wire method SNR is always inferior to that of the slit technique. This suggests that the edge method is preferable for measuring parameters such as the low-frequency drop, and the slit method is preferable for determining high-frequency response. The cross-over frequency at which the slit and edge methods are equal (f(e)) for quantum-noise limited systems is a function of the slit width and the length over which the LSF is measured. For detector-noise limited systems, f(e) is dependent on the slit width only. The SNR in all but the quantum-noise limited slit method can therefore be increased by decreasing the length over which the LSF is measured, smoothing the tails of the LSF, or by fitting the tails to an analytic expression.
TL;DR: The spectral ratio method as mentioned in this paper is based on the concept that although the spectral radiances are very sensitive to small changes in temperature the ratios are not, and only an approximate estimate of temperature is required thus, for example, we can determine the emissivity ratio to an accuracy of 1% with a temperature estimate that is only accurate to 12.5 K.
TL;DR: Using dynamical mean-field equations, the activity and the maximal Lyapunov exponent of the network in dependence of a nonlinearity (gain) parameter and the noise intensity are calculated.
Abstract: We study discrete parallel dynamics of a fully connected network of nonlinear elements interacting via long-range random asymmetric couplings under the influence of external noise. Using dynamical mean-field equations, which become exact in the thermodynamical limit, we calculate the activity and the maximal Lyapunov exponent of the network in dependence of a nonlinearity (gain) parameter and the noise intensity.
TL;DR: In this paper, the effects of frequency shift averaging on fading noise reduction are clarified theoretically, and the relationships between measurement accuracy and other parameters, such as spatial resolution and frequency variation range, are derived.
Abstract: The characteristics of fading noise in Rayleigh backscattering measurements made with coherent lightwaves such as in coherent-OTDR (optical time-domain reflectometry) and coherent-OFDR (optical frequency-domain reflectometry) are studied. The effects of frequency shift averaging on fading noise reduction are clarified theoretically, and the relationships between measurement accuracy and other parameters, such as spatial resolution and frequency variation range are derived. The calculated results of loss measurement accuracy are in good agreement with experimental data. The formula can also be applied to low-coherence interferometric OTDR. >
TL;DR: The sensitivity of several recent proposals for precision phase measurement is calculated, and it is shown that no proposal to date beats the sensitivity believed achievable by squeezed state interferometry.
Abstract: We investigate the quantum mechanical bound to how precisely we can determine a phase shift given only a constraint on the mean total number of photons available. By considering how quickly one can gain information from data analysis, we derive the sensitivity achievable (in principle) for measurements involving even highly non-Gaussian noise. Using these results we calculate the sensitivity of several recent proposals for precision phase measurement, and show that no proposal to date beats the sensitivity believed achievable by squeezed state interferometry.
TL;DR: In this paper, the authors developed prescriptions to predict profile fitting errors for Gaussian emission lines perturbed by white noise, which can be generalized to more complicated signal-dependent noise models of common astronomical detector systems.
Abstract: Landman et al. (1982) developed prescriptions to predict profile fitting errors for Gaussian emission lines perturbed by white noise. We show that their scaling laws can be generalized to more complicated signal-dependent 'noise models' of common astronomical detector systems.
TL;DR: It is concluded that in most cases mechano-electrical transduction of the bundles' Brownian motion causes this correlation, and the existence of a fast reverse (electro-mechanical) transduction mechanism to be common in these cells.
TL;DR: In this article, the difference between the noise gain associated with dark current and the photoconductive gain in quantum well infrared photodetectors is discussed in light of recent experiments.
Abstract: The difference between the noise gain associated with dark current and the photoconductive gain in quantum well infrared photodetectors is discussed in light of recent experiments. The theoretical model is based on a single key parameter: the electron trapping probability. An empirical expression for the trapping probability or, alternatively, the electron escape probability is proposed. Using the dark current, the gain, the trapping probability expressions, and the device operating temperature for achieving background limited infrared performance is discussed.
TL;DR: The noise spectra of paramagnetic salt thermometers that were coupled to thermal reservoirs at 2 K were found to be in very good agreement with the predictions of the fluctuation-dissipation theorem.
Abstract: We report the first quantitative measurements of spontaneous temperature fluctuations in a physical system well modeled by a canonical ensemble. Using superconducting magnetometers and a carefully controlled thermal environment, we have measured the noise spectra of paramagnetic salt thermometers that were coupled to thermal reservoirs at 2 K. The noise spectra were found to be in very good agreement with the predictions of the fluctuation-dissipation theorem. Our observations are at variance with some interpretations of fluctuations in the canonical ensemble.
TL;DR: In this article, an abstract stochastic Navier-Stokes equation with multiplicative white noise is considered, and the existence and uniqueness of a solution are proved for small initial data.
Abstract: An abstract stochastic Navier-Stokes equation with multiplicative white noise is considered. 2-dimensional Navier-Stokes equations with noise depending on first order derivatives of the solution are covered by the abstract model. Existence and uniqueness of a solution is proved for small initial data, and the associated local stochastic flow is constructed
TL;DR: The results of this study suggest that the use of a scientific-grade CCD allows for very good low-contrast discrimination and moderate spatial resolution under conditions simulating mammography, but the current prototype is limited to a 9 x 9-cm2 field of view.
Abstract: The physical characteristics of a charge‐coupled device(CCD)image detector were evaluated, as well as its potential as a digital imagingdevice for small field mammographic applications such as preoperative needle localization. The detectionsystem is based on a 2048×2048 pixel CCD operated in 1024×1024 mode. The CCD was optically coupled to an intensifying screen via a lens, without intermediate intensification. The thermal noise was suppressed to 0.15 electrons pixel−1s−1 by cooling the CCD with liquid nitrogen. The dominant source of noise was attributed to the on‐chip amplifier during the readout process that was performed at 50 000 pixels s−1. The measured readout noise level was 15 electrons per pixel. The low‐noise characteristics of this CCD prototype detector produced encouraging results under conditions simulating mammography, with a signal level close to one electron per pixel for each detected x ray. The mean glandular dose to the breast, based on the entrance exposure measured from a standard mammographic phantom would be 1.52 mGy (152 mrad). The ultimate spatial resolution of the system was approximately 8 cycles/mm but it was limited to about 5 cycles/mm when operated in the 1024×1024 imaging mode. Other physical characteristics of the system such as optical coupling efficiency, exposure response, and signal‐to‐noise ratio were evaluated. The results of this study suggest that the use of a scientific‐grade CCD allows for very good low‐contrast discrimination and moderate spatial resolution under conditions simulating mammography, but the current prototype is limited to a 9×9‐cm2 field of view. The results of this study suggest that with realistic improvements in the optical coupling via a faster lens or fiberoptic coupling, additional improvements in image quality and dose are feasible.
TL;DR: It is shown that shot noise for electrons can be suppressed in resonant tunneling through a double barrier, using a classical description based on the rate equation for ``sequential'' tunneling.
Abstract: We show that shot noise for electrons can be suppressed in resonant tunneling through a double barrier, using a classical description based on the rate equation for ``sequential'' tunneling. The suppression is greatest when the escape rates through the two barriers are equal, in agreement with experiment and with the quantum-mechanical ``coherent'' model of resonant tunneling. A master equation is needed to calculate the noise, but cannot be uniquely derived from the rate equation; choices differ in the way that they describe transport between the emitter and the resonant state. Our choice for the rates, which are consistent with the exclusion principle, gives a suppression of the shot noise. We briefly discuss the results of choosing rates that are consistent with classical or Bose statistics instead of Fermi statistics. Finally, we apply our results to the two-state regime of the classical Coulomb blockade.
10 May 1992
TL;DR: Dithering methods for removing idle channel noise in sigma-delta ( Sigma Delta ) modulators are presented and pseudorandom white noise is effective if the dither signal is shaped according to the quantization noise transfer function of the modulator.
Abstract: Dithering methods for removing idle channel noise in sigma-delta ( Sigma Delta ) modulators are presented. This noise exists for all types of Sigma Delta modulators. Its structure appears as periodic impulses, the peak levels of which are much higher than their RMS values. The noise is readily apparent in the time domain, but not in the power spectrum. Relatively large dither power is required to remove this noise. Dithering with pseudorandom white noise is effective if the dither signal is shaped according to the quantization noise transfer function of the modulator. This allows the dither power to be relatively high without significantly increasing the noise in the baseband. The minimum dither power required for effectiveness is predominantly a function of the step size of the quantizer. Simulation and experimental results are presented. >
TL;DR: The authors develop and test a model of the inherent noises in cameras and suggest a locally stationary model of noise for adaptive signal processing of cameras based on ionization sensors.
Abstract: The class of cameras that are based on ionization sensors, which includes the most common charge-coupled device (CCD) and vidicon cameras, is examined. Camera signals are shown to be corrupted by direction-dependent stationary electronic noise sources and fluctuations due to the statistical nature of the sensing process. The authors develop and test a model of the inherent noises in cameras. These results are confirmed by measurement, and they suggest a locally stationary model of noise for adaptive signal processing. >
TL;DR: In this article, a novel polarization modulated direct detection (PM-DD) system for binary and multilevel transmission is presented. But the system performance is evaluated by an analytical model when the only relevant noise source is the receiver thermal noise and when erbium-doped optical amplifiers introduce amplified spontaneous emission (ASE) noise.
Abstract: A novel polarization modulated direct detection (PM-DD) system suitable both for binary and multilevel transmission is presented. At the transmitter the optical field is polarization modulated by a standard modulator. The receiver is based on the estimation of the Stokes parameters of the received optical field by means of a direct-detection optical front end and baseband electrical processing. The Poincare sphere rotation induced by the fiber is compensated by means of a purely electronic algorithm and the decision is performed in the Stokes space. The system performance is evaluated by an analytical model when the only relevant noise source is the receiver thermal noise and when erbium-doped optical amplifiers introduce amplified spontaneous emission (ASE) noise. The system is completely compatible with a direct-detection-based optical network, and it is possible to implement efficient multilevel modulation formats. >