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Showing papers on "Noise measurement published in 1986"


Journal ArticleDOI
TL;DR: In this paper, the effect of the common process noise on the fusion of the state estimates of a target based on measurements obtained by two different sensors is examined in a multisensor environment where each sensor has its information processing (tracking) subsystem.
Abstract: This note deals with the effect of the common process noise on the fusion (combination) of the state estimates of a target based on measurements obtained by two different sensors. This problem arises in a multisensor environment where each sensor has its information processing (tracking) subsystem. In the case of an ?-s tracking filter the effect of the process noise is that, over a wide range of its variance, the uncertainty area corresponding to the fused estimates is about 70 percent of the single-sensor uncertainty area as opposed to 50 percent obtained if the dependence is ignored.

527 citations


Journal ArticleDOI
TL;DR: In this article, a low-noise high-frequency transresistance amplifier was used to accurately measure broadband noise in MOSFETs with small widths and submicrometer channel lengths.
Abstract: A low-noise high-frequency transresistance amplifier has been used to accurately measure broad-band noise in MOSFET's with small widths and submicrometer channel lengths The technique allows noise characterization up to frequencies of 100 MHz of the small devices available as process test arrays from different fabrication lines The noise in the different portions of the I-V characteristics of submicrometer MOSFET's has been characterized and shown to be greater by factors of 2 to 4 than the noise expected from long-channel noise theory

310 citations


Journal Article
TL;DR: It is found that nearly optimum performance can be obtained in a simple delay and sum beamformer by shading to reduce sidelobes and modest oversteering to reduce mainlohe width without too large a reduction in mainlobe sensitivity.
Abstract: The problem considered is that of designing endfire line array shadings which provide a useful amount of supergain without extreme sensitivity to random errors. Optimum shading weights are obtained subject to a constraint on the gain against uncorrelated white noise. The results of optimum array gain versus white noise gain constraint are presented parametrically for arrays of different interelement spacings, and different noise fields. Results are presented for spherically and cylindrically isotropic noise, and other wavenumber limited noise fields, used in modeling ocean ambient noise. It is found that nearly optimum performance can be obtained in a simple delay and sum beamformer by shading to reduce sidelobes and modest oversteering to reduce mainlohe width without too large a reduction in mainlobe sensitivity.

277 citations


Journal ArticleDOI
TL;DR: The basic concept of the Eigensystem Realization Algorithm for modal parameter identification and model reduction is extended to minimize the distortion of the identified parameters caused by noise.
Abstract: The basic concept of the Eigensystem Realization Algorithm for modal parameter identification and model reduction is extended to minimize the distortion of the identified parameters caused by noise. The mathematical foundation for the properties of accuracy indicators, such as the singular values of the data matrix and modal amplitude coherence, is provided, based on knowledge of the noise characteristics. These indicators quantitatively discriminate noise from system information and are used to reduce the realized system model to a better approximation of the true model. Monte Carlo Simulations are included to support the analytical studies.

237 citations


Journal ArticleDOI
TL;DR: This paper proposes a solution to this unknown noise covariance problem for the case when the noise field is invariant under two measurements of the array covariance, and presents a new algorithm for this case.
Abstract: In eigenstructure methods for direction of arrival estimation of signal wavefronts, the additive noise is assumed to be spatially white, i.e., of equal power and uncorrelated from sensor to sensor. When the noise is nonwhite but has a known covariance, we can still handle the problem through prewhitening. However, there are no techniques presently available to deal with completely unknown noise fields. In this paper, we propose a solution to this unknown noise covariance problem for the case when the noise field is invariant under two measurements of the array covariance; situations where this assumption is valid are not uncommon in sonar applications. In fact, the idea has been used in certain so-called "despoking" algorithms for conventional beamformers. Results of computer simulations carried out to compare the performance of the new algorithm to earlier methods are also presented.

192 citations


Journal ArticleDOI
TL;DR: It is shown that nonlinear filters based on these means behave well for both additive and impulse noise and they preserve the edges better than linear filters, and they reject the noise better than median filters.
Abstract: The use of nonlinear means in image processing is introduced. The properties of these means in the presence of different types of noise are investigated. It is shown that nonlinear filters based on these means behave well for both additive and impulse noise. Their performance in the presence of signal dependent noise is satisfactory. They preserve the edges better than linear filters, and they reject the noise better than median filters.

191 citations


Journal ArticleDOI
TL;DR: A review of the last 10 years of research on impulse noise reveals certain insights and perspectives on the biological and audiological effects of exposures to impulse noise.
Abstract: A review of the last 10 years of research on impulse noise reveals certain insights and perspectives on the biological and audiological effects of exposures to impulse noise. First, impulse noise may damage the cochlea by direct mechanical processes. Second, after exposure to impulse noise, hearing may recover in an erratic, nonmonotonic pattern. Third, even though the existing damage‐risk criteria evaluate impulse noise in terms of level, duration, and number, often parameters such as temporal pattern, waveform, and rise time are also important in the production of a hearing loss. Fourth, the effects of impulse noise are often inconsistent with the principle of the equal energy hypothesis. Fifth, impulse noise can interact with background continuous noise to produce greater hearing loss than would have been predicted by the simple sum of the individual noises.

176 citations


Journal ArticleDOI
TL;DR: An efficient algorithm is presented for estimating a covariance matrix consisting of a low-rank signal term and a full-rank noise term, indicating that the proposed algorithm reduces the variance of some commonly used spectral estimators in off-target directions, without impairing their detection and resolution properties.
Abstract: An efficient algorithm is presented for estimating a covariance matrix consisting of a low-rank signal term and a full-rank noise term, known apart from a scalar factor. For each sample of the vector of sensor outputs, the algorithm approximates, in the least-squares sense, a rank-one update of the covariance matrix, under the side condition that the rank of the signal term remains bounded. If the model noise is spatially colored, the least-squares approximation is preceded by spatial prewhitening, It is shown that if the rank of the signal term is small compared to the number of sensors, then the proposed algorithm requires substantially less computational work than conventional averaging. Some simulation results are included, indicating that the proposed algorithm reduces the variance of some commonly used spectral estimators in off-target directions, without impairing their detection and resolution properties.

140 citations


Journal ArticleDOI
R. Tkach1, A. Chraplyvy2
TL;DR: In this article, measurements and calculations of interferometrically demodulated phase noise in an InGaAsP DFB laser were performed and the results led to a novel method of laser linewidth measurement.
Abstract: Measurements and calculations of interferometrically demodulated phase noise in an InGaAsP DFB laser are reported. The results led to a novel method of laser linewidth measurement. The effect of this noise on a DPSK coherent system is considered.

131 citations


Journal ArticleDOI
TL;DR: The problem of estimating time-varying harmonic components of a signal measured in noise is considered, and a new class of filters, akin to recursive frequency-sampling filters, is developed for inclusion in a parallel bank to produce sliding harmonic estimates.
Abstract: The problem of estimating time-varying harmonic components of a signal measured in noise is considered. The approach used is via state estimation. Two methods are proposed, one involving pole-placement of a state observer, the other using quadratic optimization techniques. The result is the development of a new class of filters, akin to recursive frequency-sampling filters, for inclusion in a parallel bank to produce sliding harmonic estimates. Kalman filtering theory is applied to effect the good performance in noise, and the class of filters is parameterized by the design tradeoff between noise rejection and convergence rate. These filters can be seen as generalizing the DFT.

114 citations


Proceedings ArticleDOI
S. Foster1
07 Apr 1986
TL;DR: The proposed method is a variation on this scheme wherein the system is probed twice using sequences chosen from among the Golay codes, which have the remarkable property that their autocorrelation functions have complementary side-lobes.
Abstract: This paper describes a digital processing technique for measuring the impulse response of a system. The method utilizes "complementary" codes as described by Golay in 1961 and has been employed by designers of radar, communications and other equipment. This paper discusses the implementation of the technique in a device that measures the impulse response of audio bandwidth systems. The paper begins by describing the general problem of impulse response measurement using digital methods. This leads to a "unit pulse" response sequence that completely characterizes a bandlimited, linear and time-invariant system. Next, Schroeder's (1979) method of probing the system with pseudo-random noise and correlating the result to obtain an estimate of this response is discussed. Our method is a variation on this scheme wherein the system is probed twice using sequences chosen from among the Golay codes. These codes have the remarkable property that their autocorrelation functions have complementary side-lobes. Finally, the response of a speaker/microphone pair is measured using the proposed method.

Journal ArticleDOI
Hajime Aoi1, Makoto Saitoh1, Nobumasa Nishiyama1, Reijiro Tsuchiya1, Takashi Tamura1 
TL;DR: In this article, the reverse DC erase noise of thin metal film media was investigated using a new method: the reverse dc erase media noise measuring method, which showed a sharp peak at the field around coercive force Hc.
Abstract: The noise of longitudinal thin metal film media is experimentally investigated using a new method: the reverse DC erase media noise measuring method. The reverse DC erase noise of thin metal film shows a sharp peak at the field around coercive force Hc. The maximum reverse DC erase noise has a strong correlation to the signal recorded noise. Media with large noise has low D 50 and also low Overwrite S/N.

Journal ArticleDOI
TL;DR: The limits of adaptive quantization to reduce intrinsic noise are presented, and it is shown that a signal processing approach is especially convenient to measure the performances of a detector based on the Hough transform.
Abstract: Exact predictions of the performances of the Hough detection of straight lines in two-dimensional images are presented for rectangular and circular retinas, in Cartesian and normal parameterization, in the case of noisy signals. Detection of circles, under the same assumptions, is discussed. The limits of adaptive quantization to reduce intrinsic noise are presented, and it is shown that a signal processing approach is especially convenient to measure the performances of a detector based on the Hough transform.

Proceedings ArticleDOI
06 Nov 1986
TL;DR: The SWIFET multiplexer, including necessary circuitry for BIB detector readout, has been designed and fabricated using a newly developed process for cryogenic (<20K) MOS electronics which avoids anomalies (lack of device isolation, excess noise, and long time constants) associated with conventional silicon processes as mentioned in this paper.
Abstract: Blocked-Impurity-Band (BIB) extrinsic silicon (Si:As) detectors have demonstrated high sensitivity and quantum efficiency in the long wavelength infrared (LWIR) spectral region (to 28 microns) as well as wide frequency response, low optical crosstalk, nuclear radiation hardness, and stable, predictable performance. Furthermore, it has been demonstrated that SWItched mosFET (SWIFET) multiplexers provide a low noise readout approach for use with BIB detectors. This paper describes the state-of-the-art of multiplexed BIB detector hybrid focal plane arrays (HFPAs). The principle of operation and performance of optimized BIB and Back Illuminated BIB (BIBIB) detectors are presented. The SWIFET multiplexer, including necessary circuitry for BIBIB detector readout, has been designed and fabricated using a newly developed process for cryogenic (<20K) MOS electronics which avoids anomalies (lack of device isolation, excess noise, and long time constants) associated with conventional silicon processes. A description of the design and operation of this multiplexer is given. A number of uniform, highly responsive, 500 element HFPAs have been fabricated and their performance evaluated. The characterization measurements, to be described in the paper, include evaluation of detector dark current, responsivity, noise for various operating conditions, and uniformity of array characteristics. The results obtained and presented demonstrate that focal plane arrays with excellent, unprecedented, LWIR performance have been realized with Blocked-Impurity-Band detector technology.

Proceedings ArticleDOI
07 Apr 1986
TL;DR: This paper reports on recognition experiments conducted with a "simulated stress" data base using a baseline algorithm and its modifications, which show that these algorithms perform acceptably well for a vocabulary of 105 words under normal conditions, but degrade by an order of magnitude under the "stress" conditions.
Abstract: Speech recognizers trained in one condition but operating in a different condition degrade in performance. Typical of this situation is when the recognizer is trained under normal conditions but operated in a stressful and noisy environment as in military applications. This paper reports on recognition experiments conducted with a "simulated stress" data base using a baseline algorithm and its modifications. These algorithms perform acceptably well (1 % substitution rate) for a vocabulary of 105 words under normal conditions, but degrade by an order of magnitude under the "stress" conditions. The experiments also show that the speech production variation caused by noise exposure at the ear is far more deleterious than ambient acoustic noise with a noise cancelling microphone.

Journal ArticleDOI
TL;DR: This work considers the restoration of images degraded by a class of signal-uncorrelated noise, which is possibly signal-dependent, and presents a new noise smoothing technique which is called the noise updating repeated Wiener (NURW) filter.
Abstract: We consider the restoration of images degraded by a class of signal-uncorrelated noise, which is possibly signal-dependent. Some adaptive noise smoothing filters, which assume a nonstationary mean, nonstationary variance image model implicitly or explicitly, are reviewed, and their performances are compared by the mean-squares errors (MSES) and by the human subjective judgment. We also present a new noise smoothing technique which is called the noise updating repeated Wiener (NURW) filter. Explicit noise variance updating formulas are derived for the NURW filter. The performance is improved both in the MSE sense and in the vicinity of edges by subjective observation.

Proceedings ArticleDOI
01 Apr 1986
TL;DR: This work applies a method based on noise masking to recognizers based on whole-word pattern matching using both DTW and Markov model algorithms and gives improved training where training in noise is essential because of voice quality changes that are a consequence of the noise.
Abstract: There are significant applications of speech recognition where a poor signal-to-noise ratio seriously degrades performance. In many cases the noise properties are constant or change only slowly. Klatt has proposed a solution based on noise masking and Bridle et al. one on noise marking. Our approach extends their techniques to make fuller use of the available data and we apply our method to recognizers based on whole-word pattern matching using both DTW and Markov model algorithms. The method also gives improved training where it is convenient for this to be done in a noisy environment, or where training in noise is essential because of voice quality changes that are a consequence of the noise.

Journal ArticleDOI
TL;DR: In this paper, a novel procedure for determining the noise parameters of microwave two-ports is introduced, in which the computations necessary to find the noise parameter from the set of measurements of noise temperature (noise figure) are greatly simplified.
Abstract: A novel procedure for determining the noise parameters of microwave two-ports is introduced. In this procedure, the computations necessary to find the noise parameters from the set of measurements of noise temperature (noise figure) are greatly simplified. The assessment of accuracy with which the noise parameters can he determined from a given set of measurement data is straightforward.

Journal ArticleDOI
TL;DR: In this paper, the 1/f noise of short-channel n-type MOSFET's is measured in the weak inversion regime before and after an electrical stress.
Abstract: The 1/f noise of short-channel n-type MOSFET's is measured in the weak inversion regime before and after an electrical stress. The noise increase which follows the aging is shown to be due to an electrically induced generation of traps in the gate oxide rather than fast interface states. Noise experiments prove that the degradation occurs in a narrow region (less than 50 nm) near the drain. Created traps also appear to have an inhomogeneous energy profile.

Journal ArticleDOI
TL;DR: Several types of noise in remote-sensing systems are treated to provide enhanced understanding of the relationship of noise sources to both analysis results and sensor design, including how sensor noise interacts with atmospheric effects to degrade accuracy.
Abstract: Several types of noise in remote-sensing systems are treated. The purpose is to provide enhanced understanding of the relationship of noise sources to both analysis results and sensor design. The context of optical sensors and spectral pattern recognition analysis methods is used to enable tractability for quantitative results. First, the concept of multispectral classification is reviewed. Next, stochastic models are discussed for both signals and noise, including thermal, shot and quantization noise along with atmospheric effects. A model enabling the study of the combined effect of these sources is presented, and a system performance index is defined. Theoretical results showing the interrelated effects of the noise sources on system performance are given. Results of simulations using the system model are presented for several values of system parameters, using some noise parameters of the Thematic Mapper scanner as an illustration. Results show the relative importance of each of the noise sources on system performance, including how sensor noise interacts with atmospheric effects to degrade accuracy

Journal ArticleDOI
TL;DR: In this paper, an extension of earlier work by van der Ziel on infrared detection in Schottky-barrier diodes has been presented, where the electrons participating in the charge-transport process across the barrier are subdivided into four groups based on their initial velocity.
Abstract: Room-temperature noise measurements at 2.2, 12, and 97.5 GHz were performed on commercial silicon Schottky-barrier diodes and are shown to agree with the model presented in this work. This model is an extension of earlier work by van der Ziel on infrared detection in Schottky-barrier diodes. In the theoretical analysis, the electrons participating in the charge-transport process across the barrier are subdivided into four groups based on their initial velocity. The contribution of each group to the device conductance, susceptance, and current spectral intensity was incorporated including the effects of the transit time. By taking each of these effects into account, an accurate model which applies over a wide range of bias and frequency has been developed. Although the emphasis of this model has been on the high-frequency performance, the model also gives the correct results in the low-frequency limit.

Journal ArticleDOI
TL;DR: In this paper, a pseudomorphic InGaAs quantum-well MODFET was proposed and its noise spectra indicate the presence of low-intensity multiple g-r noise components superimposed on a reduced 1/f noise.
Abstract: Equivalent gate noise voltage spectra of 1-µm gate-length modulation-doped FET's with pseudomorphic InGaAs quantum-well structure have been measured for the frequency range of 0.01 Hz to 100 MHz and compared with the noise spectra of conventional AlGaAs/ GaAs MODFET's and GaAs MESFET's. The prominent generation-recombination (g-r) noise bulge commonly observed in the vicinity of 10 kHz in conventional MODFET's at 300 K does not appear in the case of the new InGaAs quantum-well MODFET. Instead, its noise spectra indicate the presence of low-intensity multiple g-r noise components superimposed on a reduced 1/f noise. The LF noise intensity in the new device appears to be the lowest among those we have observed in any MODFET or MESFET. The noise spectra at 82 K in the new device represent nearly true 1/f noise. This unusual low-noise behavior of the new structure suggests the effectiveness of electron confinement in the quantum well that significantly reduces electron trapping in the n-AlGaAs, and thus eliminates the g-r noise bulge observed in conventional MODFET's.

Patent
05 May 1986
TL;DR: In this article, an improved noise suppression system (400) which performs speech quality enhancement upon speech-plus-noise signal available at the input (205) to generate a clean speech signal at the output (265) by spectral gain modification is presented.
Abstract: An improved noise suppression system (400) which performs speech quality enhancement upon speech-plus-noise signal available at the input (205) to generate a clean speech signal at the output (265) by spectral gain modification. The noise suppression system includes a background noise estimator (420) which generates and stores an estimate of the background noise power spectral density based upon pre-processed speech (215), as determined by the detected minima of the post-processed speech energy level. This post-processed speech (255) may be obtained directly from the output of the noise supression system, or may be simulated by multiplying the pre-processed speech energy (225) by the channel gain values of the modification signal (245). The channel gain controller (240) produces these individual channel gain values for application to both the channel gain modifier (250) and the background noise estimator (420). Each individual channel gain value is selected as a function of (a) the channel number, (b) the current channel SNR estimate, and (c) the overall average background noise level. The technique of implementing post-processed signal to generate the background noise estimate (325) provides a more accurate measurement of the background noise energy since it is based upon much cleaner speech signal. As a result, the present invention performs acoustic noise suppression in high ambient noise backgrounds with significantly less voice quality degradation.

Journal ArticleDOI
TL;DR: A large-scale study of community reaction to aircraft noise was conducted around five Australian airports, involving interviews with over 3500 residents and the use of intensive and detailed noise measurement data.

Journal ArticleDOI
TL;DR: In this article, the use of cryogenically-cooled variable-temperature loads for accurate noise measurements of low-noise cooled amplifiers and mixers in the microwave and millimeter wave range is discussed.
Abstract: We have demostrated the use of cryogenically-cooled variable-temperature loads for accurate noise measurements of low-noise cooled amplifiers and mixers in the microwave and millimeter wave range. The input noise temperature of the amplifier or mixer can be measured with an accuracy of ±1 K or better.

Journal ArticleDOI
TL;DR: Computer modeling methods are used to investigate the effects of measurement errors and noise on the localization accuracy of sources in the cortical region of the brain for several different ways of making MEG measurements using single channel and/or multichannel detectors.
Abstract: Magnetoencephalograms (MEG's) are increasingly being used with the moving dipole method to localize electrical sources in the brain. In this method, also known as the dipole location method, a dipolar source is moved about in a model of the head while its amplitude and orientation are also adjusted to obtain a solution dipole which gives the least squares error fit between the measured MEG's and those produced by the dipolar source. The accuracy of this solution is affected by various measurement errors such as errors in the size of the measurement grid, size of the head model, etc., and by noise in the measured MEG's. This study uses computer modeling methods to investigate the effects of these factors on the localization accuracy of sources in the cortical region of the brain for several different ways of making MEG measurements using single channel and/or multichannel detectors.

Proceedings ArticleDOI
01 Apr 1986
TL;DR: Experiments with vowel samples spoken by 64 normal control subjects and 50 patients with glottic cancer have shown that the NNE is useful for the distinction between normal and pathological voice status.
Abstract: An adaptive comb filtering method, which was initially investigated by Frazier et al. [5] for the enhancement of degraded speech due to additive noise, is applied for estimating vocal noise generated at the glottis due to pathological changes of the vocal folds. In applying the method, special emphasis is placed on the accurate determination of pitch period durations. The amount of estimated vocal noise is quantified by a novel acoustic measure, normalized noise energy(NNE). Experiments with vowel samples spoken by 64 normal control subjects and 50 patients with glottic cancer have shown that the NNE is useful for the distinction between normal and pathological voice status.

Journal ArticleDOI
TL;DR: In this paper, the authors present experimental results of GaAs Schottky-barrier diode noise measurements in the frequency range from 0.1 to 88 GHz and a detailed analysis of noise generation in these diodes which can explain the observed current and frequency dependence.
Abstract: Classic work on optimized heterodyne receivers has concentrated on the network aspects of mixers with limited emphasis on device properties. We present experimental results of GaAs Schottky-barrier diode noise measurements in the frequency range from 0.1 to 88 GHz and a detailed analysis of noise generation in these diodes which can explain the observed current and frequency dependence.

Proceedings ArticleDOI
01 Dec 1986
TL;DR: A new eigenstructure based bearing algorithm is presented that offers improved resolution and stability performance in high noise, small sample scenarios and provides a more realistic measure of orthogonality between signal and noise subspaces in a stochastic environment.
Abstract: This paper discusses the problem of accurate estimation of the bearings or directions of multiple narrowband point signal sources from data collected at a spatially distributed array of sensors. A class of high resolution algorithms based upon covariance matrix eigenstructure are reviewed and compared. The paper then presents a new eigenstructure based bearing algorithm that offers improved resolution and stability performance in high noise, small sample scenarios. The new algorithm is based on an approximate maximum likelihood criterion, that provides a more realistic measure of orthogonality between signal and noise subspaces in a stochastic environment. The algorithms to be discussed may be applied equally well to time-series spectral analysis, and other parameter estimation problems.

Journal ArticleDOI
Nobukazu Teranishi1, N. Mutoh
TL;DR: In this article, the authors proposed partition noise caused by carrier partition in the reset MOS channel to explain the sensing capacitance (C s ) dependent part and the effective reset channel length (L ) dependent parts.
Abstract: Reset noise in CCD signal charge detection is analyzed experimentally and theoretically. From a reset noise measurement experiment, it has been inferred that reset noise consists of two parts: the sensing capacitance (C s ) dependent part and the effective reset channel length ( L ) dependent part. Conventional reset noise theory, where the Johnson noise in the reset MOS channel was regarded as the only noise source, agrees with the C s dependent part of measured reset noise. However, it cannot explain the L dependent part. To explain the L dependence, the authors propose "partition noise" caused by carrier partition in the reset MOS channel. Partition noise is analyzed by the unique technique of solving the one-dimensional diffusion equation. As a result, a reset channel capacitance dependent characteristic for partition noise has been derived, which agrees with the L dependent part for measured reset noise. Consequently, in addition to Johnson noise, partition noise is found to be a noise source in CCD signal detection.