Showing papers on "Noise measurement published in 1984"

Phase Noise in Signal Sources

Abstract: This book contains a thorough treatment of phase noise, its relationship to thermal noise and associated subjects such as frequency stability. The design of low phase noise signal sources, including oscillators and synthesisers, is explained and in many cases the measured phase noise characteristics are compared with the theoretical predictions. Full theoretical treatments are combined with physical explanations, helpful comments, examples of manufactured equipment and practical tips. Overall system performance degradations due to unwanted phase noise are fully analysed for radar systems and for both analogue and digital communications systems. Specifications for the acceptable phase noise performance of signal sources to be used in such systems are derived after allowing for both technical and economic optimisation. The mature engineer whose mathematics may be somewhat rusty will find that every effort has been made to use the lowest level of mathematical sophistication that is compatible with a full analysis and every line of each mathematical argument has been set out so that the book may be read and understood even in an armchair. Due to a novel approach to the analytical treatment of narrow band noise, the book is simple to understand while simultaneously carrying the analysis further in several areas than any existing publication.

A Prony method for noisy data: Choosing the signal components and selecting the order in exponential signal models

Abstract: Prony's method is a simple procedure for determining the values of parameters of a linear combination of exponential functions. Until recently, even the modern variants of this method have performed poorly in the presence of noise. We have discovered improvements to Prony's method which are based on low-rank approximations to data matrices or estimated correlation matrices [6]-[8], [15]-[27], [34]. Here we present a different, often simpler procedure for estimation of the signal parameters in the presence of noise. This procedure has received only limited dissemination [35]. It is very close in form and assumptions to Prony's method. However, in preliminary tests, the performance of the method is close to that of the best available, more complicated, approaches which are based on maximum likelihood or on the use of eigenvector or singular value decompositions.

Threshold Detection in Narrow-Band Non-Gaussian Noise

Abstract: The Middleton Class A narrow-band non-Gaussian noise model [9]-[12] is examined. It is shown that this noise model (which is known to fit closely a variety of non-Gaussian noises) can itself be closely approximated by a computationally much simpler noise model. It is then shown by numerical examples that, for the problem of locally optimum detection, the simplest form of this approximation yields nearly optimal (asymptotic) performance. The performance of other simple suboptimal threshold detectors in Class A noise is also examined. Finally, a useful relationship between the Class A model and the e-mixture model is developed.

Noise on Residential Power Distribution Circuits

Abstract: This paper presents electromagnetic noise measurements on power distribution circuits in the frequency range of 5-100 kHz. Since this noise is due primarily to appliances such as universal motors, light dimmers, television receivers, and certain switching power supplies located on the secondary side of the distribution transformer, the noise varies dramatically with time as these appliances are turned on and off. Measurements of the noise inserted into the distribution circuit by several representative appliances are presented. The noise measurement technique itself, as well as the resulting measurements, are described. Background noise which is present in the absence of such appliances was also measured. These noise measurements are important for the design of communications systems, such as distribution-line carrier, which operate in the 5-20 kHz region and use the distribution line as a communications medium.

Signal/noise separation and velocity estimation

Abstract: A signal/noise separation must recognize the lateral coherence of geologic events and their statistical predictability before extracting those components most useful for a particular process, such as velocity analysis Events with recognizable coherence we call signal; the rest we term noise Let us define “focusing” as increasing the statistical independence of samples with some invertible, linear transform L By the central limit theorem, focused signal must become more non‐Gaussian; the same L must defocus noise and make it more Gaussian A measure F defined from cross entropy measures non‐Gaussianity from local histograms of an array, and thereby measures focusing Local histograms of the transformed data and of transformed, artificially incoherent data provide enough information to estimate the amplitude distributions of transformed signal and noise; errors only increase the estimate of noise These distributions allow the recognition and extraction of samples containing the highest percentage of sig

Optimal design of state - space digital filters by simultaneous minimization of sensitivity and roundoff noise

Abstract: The relation between a newly defined sensitivity measure and the noise power gain for scaled filters is given. By means of this relation it is shown that the necessary and sufficient condition to minimize the noise power gain is to minimize the sensitivity measure for unsealed filters. It is shown that the minimization of this sensitivity measure can be carried out without taking into account the dynamic range constraint. A procedure for the simultaneous minimization of the sensitivity measure and the noise power gain is also given.

Phase noise and AM noise measurements in the frequency domain

Abstract: I INTRODKTI~N II FUNDAMENTAL CONCEPT A Voise Sidebands B Spectral Denstty C Spectral Denstries of Phase Fluctuations in the Freguency Domain D Modulation Theory and Spectral Density Relationships E Noise Processes F Integrated Phase Noise G AU Noise tn the Frequency Domain III PHASE-NOISE MEASUREMENTS USING THE TWO-OWLLATOR TECHNIQUE A TWO NOISY Oscrllators B Automated Phase-Noise Measurements Using the Two-Oscillator Technique C Calibration and Measurements Using the Two-Oscillator S,vstem IV SINGLE-OSCILLATOR PHASE-NOISE MEASUREMENT SYSTEMS AND TECHNIQUES A The Delay Line as an FM Discriminator B Calibration and Measurements Using rhe Delay Line as an FM Discriminator C Dual DelayLine Discriminator D MillimeterWace Phase-Noise Measurements REFERENCE 355 157

Analysis and Design of a Single-Resonator GaAs FET Oscillator with Noise Degeneration

Abstract: This paper presents an analysis of a low-noise dielectric resonator GaAs FET oscillator in a frequency-locked loop (FLL), which is used for FM noise degeneration. In this circuit, one resonator serves both as the frequency-determining element of the oscillator and as the dispersive element of the discriminator. The results of the analysis are used to generate design guidelines. These guidelines were followed in an experimental realization of an X-band circuit. The measured FM noise was--120 and--142 dBc/Hz at 10- and 100-kHz offset frequencies, respectively, and corresponded closely to predicted results.

Noise in Receiving Systems

Abstract: A systematic and unified treatment of thermal noise from an engineering viewpoint. This reference presents the methods used for characterizing and measuring thermal noise in RF communication systems and components. Defines power gain and its applicability to noise problems, shows how to calculate the final signal-to-noise ratio in RF systems using the known gains and noise temperatures of individual system building blocks, and discusses the dependence of dynamic range on the noise factor and noise temperature of a given transducer.

Deep-level analysis in (AlGa)As—GaAs 2-D electron gas devices by means of low-frequency noise measurements

Abstract: Low-frequency noise of (AlGa)As-GaAs heterostructures grown by molecular-beam epitaxy was investigated. The temperature of the samples was varied between 100 and 400 K. In the frequency range from 1 Hz to 25 kHz noise spectra can be described as superposition of several generation-recombination (GR) noise components. Four deep levels (E = 0.40, 0.42, 0.54, 0.60 eV) were detected, three of which are in agreement with those measured independently by deep-level transient spectroscopy (DLTS).

Psychological study on Leq as a measure of loudness of various kinds of noises

Abstract: The application of Leq as a measure of loudness of various noises is investigated. Nine kinds of noise sources, -aircraft noise, super express train noise, train noise, road traffic noise, speech, music, impulsive noise, artificial level-fluctuating noise and steady state noise-are used as stimuli. The duration is about10sec except for impulsive noise. Four kind levels are used in each noise source, therefore36stimuli are contained in a stimulus series. They are presented in random order and their loudness are judged by magnitude estimation. As a result of experiment, it is found that Leq can be used as a good measure of the loudness of various noises as a first approximation. Strictly speaking, however, there is a slight, but systematical deviation from Leq in PSE's of some noise sources. This fact suggests that it is necessary to add some factors to Leq in order to decide the permissible levels of these noise sources.

The effect of numbers of noise events on people’s reactions to noise: An analysis of existing survey data

Abstract: The effect of the number of noise events on noise annoyance has been examined in an analysis of data from large-scale social surveys. The relative impact of noise level and number on human reactions is measured by the decibel equivalent number effect (k) expressed as the number of decibels which have an effect equivalent to that of a tenfold increase in number of events. Values of k differ between surveys but none is significantly greater (p greater than 0.05) than the value of k = 10 which is implicit in Leq or Ldn. The mean of the existing data provide a best estimate of k = 5. Although there are some surveys in which annoyance decreases as numbers of events increase above about 150 a day, the available evidence is not strong enough to reject the conventional assumption that reactions are related to the logarithm of the number of events. The conventional assumption that the effects of number and peak noise level are additive cannot be rejected with these data. Differences between the surveys' estimates of the effect of number of events remained large even when equivalent questionnaire items and definitions of noise events could be used. The most likely explanations for inconsistent estimates are (1) errors in specifying the values of noise parameters, (2) the effects of unmeasured acoustical and area characteristics which are correlated with noise level or number, and (3) large sampling errors which are due to community differences in response to noise. Multipoint annoyance scales give more reliable estimates than do dichotomous "very annoyed" measures. It is concluded that significant improvements in the knowledge about the effects of numbers of noise events will only occur if surveys include large numbers of study areas, a requirement which can only be met if economical noise measurement techniques are developed which have known levels of precision.

On the Probability Density of Signal-to-Noise Ratio in an Improved Adaptive Detector. Part 1

Abstract: : Document describes an approximate probability distribution for the SNR (signal-to-noise ratio) of an improved adaptive detector in near rank-1 gaussian noise where the filter weights are computed using the principal eigenvectors of the estimated noise covariance matrix. The noise consists of two components, a strong rank-1-covariance interference component plus white noise. Computer simulation is used to verify the approximating SNR distribution and show that it is accurate even for small sample size and low interference-to- noise ratios.

The implementation of digital filters using a modified Widrow-Hoff algorithm for the adaptive cancellation of acoustic noise

Abstract: The active reduction of noise is an application of the principle of superposition in which an unwanted noise signal is detected by a microphone and processed by an electronic controller to produce an equal amplitude, 180° out-of-phase cancellation signal. The signal is then appropriately amplified and injected back into the space by a loudspeaker. This paper describes an electronic controller based on a digital implementation of transversal filters using a modification of the Widrow-Hoff Least-Mean-Squared Algorithm. In the case of active noise reduction there is no signal to enhance and all of the detected input must be cancelled. Further, the time required for the physical acoustic wave must be taken into consideration for the system to work.

Signal and noise estimation from seismic reflection data using spectral coherence methods

Abstract: Spectral coherence analysis is unrivaled as a quantitative tool over a range of practical problems in seismic interpretation, data processing, quality assessment for data acquisition, and research. Its great virtue is its ability to supply the detailed error information necessary for a thorough interpretation of results. Ordinary coherence analysis is employed in line intersection analysis and the design of filters to cross-equalize differently acquired seismic sections in a given area; both ordinary and partial coherence methods are indispensable in matching synthetic seismograms and seismic data; and multiple coherences are used to estimate the coherent signal and incoherent noise content of seismic sections and gathers. The precise meaning of the signal and noise estimates output by coherent analysis has to be related to the particular technique employed and the type of data input to it. The principles and procedures for analyzing seismic data with these methods are reviewed and illustrated with practical examples.

Characterization of GaAs FET's in Terms of Noise, Gain, and Scattering Parameters through a Noise Parameter Test Set

Abstract: A method for the complete characterization of GaAs FET's in terms of noise parameters (F/sub o/,Gamma/sub on/, R/sub n/), gain parameters (G/sub ao/, Gamma /sub og/, R/sub g/), and of those scattering parameters ( S/sub11/, S/sub22/|,S/sub12/| S/sub21|, /spl angle/S/sub 12/S/sub 21/ ) that are needed for low-noise microwave amplifier design is presented. The instrumentation employed, i.e., a noise-figure measuring system equipped with a vectorial reflectometer, as well as the time consumption, are the same required for the determination of noise parameters only through conventional methods. The measuring setup and the experimental procedure are described in detail. Considerations about the computer-aided data processing technique are also provided. As an experimental result, the characterization of a sample device versus frequency (4-12 GHz) and drain current is reported. A comparison between the scattering parameters provided by the method and those measured by means of a network analyzer is also included.

A system for reducing the noise in a television signal

Abstract: The amount of noise reduction of a television signal produced by averaging corresponding pixels from one frame to the next is reduced by a correction factor when motion in the picture is detected. In order to prevent very active motion from disturbing detection of the noise level, a noise level measurement signal is subjected to a hold of its value in a time briefly preceding a highly active motion in the picture until a time shortly after the end of such highly active motion. The motion signal is processed so as to provide such a hold only when motion is highly active in the picture, and that signal is prolonged in a further circuit so that it will have a duration long enough to cover build-up of that motion and its trailing off, when the noise measurement signal is delayed by about half of the prolongation, so that the noise measurement level that is held corresponds to the noise level prior to the buildup of the motion which shortly thereafter becomes highly active. The noise value thus held controls the size of the correction factor (k) produced by the presence of the motion signal.

Study and Performance Evaluation of Two Iterative Frequency-Domain Deconvolution Techniques

Abstract: The performance of two iterative frequency-domain deconvolution techniques, the optimum compensation and the Guillaume-Nahman, is evaluated. The study involved the characterization of the adaptive filters utilized to reduce the deconvolution noise. Comparisons between the two techniques are performed for various classes of signals having different levels of acquisition noise. It is found that the Guillaume-Nahman technique is potentially more accurate but more sensitive to acquisition noise. It is also found that the optimum compensation deconvolution technique uses an adaptive filtet with the passbands coinciding with the frequency bands of the signal, thus optimizing noise filtration, while the Guillaume-Nahman technique utilizes a low-pass filter for all signals.

Characterization and Measurement of Radiometer Stability

Abstract: For the characterization of radiometer noise and stability a new and very practical method is introduced. It consists of the measurement of the "Allan-variance" well known for the characterization of the stability of frequency standards. The plot of the Allan variance versus integration time allows one to determine the different types of fluctuations of the radio-meter output signal. In particular, the best range of integration time for optimum use of the system can accurately be evaluated. Theoretical considerations and experimental results are presented.

Noise suppression signal processing using 2‐point received signals

Abstract: A number of research reports has been presented on the noise suppression signal processings as one of the important technical problems. Although a reduction feeling of the noise level can be obtained by the conventional method using the one-point received signal, it has been pointed out that the program of improving the articulation is not sufficient. to solve this problem, we propose a noise suppression signal processing method using two-point received signals. As the first step, the noise suppression method is discussed assuming that the desired signal is uncorrelated to the noise. It is shown that the noise suppression filter, which is the optimum in the sense of least-mean-square error, is obtained from the correlation coefficients between the frequency components of the two-point received signals. Then a method is shown in which the two-point receiving noise suppression system can be constructed using FET based on the proposed principle. Finally, to verify the effectiveness of the proposed processing, the method is applied to the two-point received speech under room noise. the articulation tests were performed for the processed and unprocessed speeches. As a result, it was seen that the syllable articulation score could be improved by 4 to 10 percent when the correlation coefficient between the two-point received signals of the noise is 0.1 or less and that of the speech is 0.9 or more.

Nearly Optimal Detection of Signals in Non-Gaussian Noise

Abstract: : This dissertation addresses the problem of finding nearly optimal detector structures for non-Gaussian noise environments. It is assumed that the noise statistics are unknown except for a very loose characterization. Under this condition, the goal is to study adaptive detector structures that are simple, yet capable of high levels of performance. Attention is focused on the discrete-time locally optimal detector for a constant signal in independent, identically distributed noise. A definition for non-Gaussian noise is given, several common univariate density models are exhibited, and some physical non- Gaussian noise data is discussed. Two approaches in designing adaptive detector nonlinearities are presented, where it is assumed that the noise statistics are approximately stationary. Both proposals utilized simple measurements of the noise behavior to adapt the detector, and in several examples the adaptive detectors are shown capable of attaining nearly optimal performance levels. A simulation is presented demonstrating their successful application.

Noise analysis of a digital radiography system

Abstract: The sources of noise in a digital video subtraction angiography system were identified and analyzed. Signal-to-noise ratios of digital radiography systems were measured using the digital image data recorded in the computer. The major sources of noise include quantum noise, TV camera electronic noise, quantization noise from the analog-to-digital converter, time jitter, structure noise in the image intensifier, and video recorder electronic noise. A new noise source was identified, which results from the interplay of fixed pattern noise and the lack of image registration. This type of noise may result from image-intensifier structure noise in combination with TV camera time jitter or recorder time jitter. A similar noise source is generated from the interplay of patient absorption inhomogeneities and patient motion or image re-registration. Signal-to-noise ratios were measured for a variety of experimental conditions using subtracted digital images. The measured signal-to-noise ratios were found to fluctua...

Physiological, Psychological, and Social Effects of Noise

Abstract: The physiological, and behavioral effects of noise on man are investigated. Basic parameters such as definitions of noise, measuring techniques of noise, and the physiology of the ear are presented prior to the development of topics on hearing loss, speech communication in noise, social effects of noise, and the health effects of noise pollution. Recommendations for the assessment and subsequent control of noise is included.

Comparison of broadband noise mechanisms, analyses, and experiments on rotors

Abstract: A study is made of the various mechanisms which generate broadband noise on a range of rotors The sources considered are load fluctuations due to inflow turbulence, due to turbulent boundary layers passing the blades' trailing edges, and due to tip vortex formation Vortex shedding noises due to laminar boundary layers and blunt trailing edges are not considered as they can be prevented in most cases Various prediction methods have been reviewed and extended in some cases An extensive search was made of existing experiments and calculations based on the various prediction methods were made This study shows that present analyses are adequate to predict the spectra from a wide variety of experiments on fans, full scale and model-scale helicopter rotors, wind turbines, and propellers to within about 5 to 10 dB Better knowledge of the inflow turbulence improves the accuracy of the predictions The results of this study indicate that inflow turbulence noise depends strongly on ambient conditions and dominates at low frequencies Trailing edge noise and tip vortex noise are important at higher frequencies if inflow turbulence is weak Boundary layer trailing edge noise is important especially in the presence of large rotors; it increases slowly with angle of attack but not as rapidly as tip vortex noise, which can be important at high angles of attack for wide chord, square edge tips

Close frequency resolution by maximum entropy spectral estimators

Abstract: We study the properties of the maximum entropy spectral estimator in pure frequencies estimation. We model this situation by a sum of pure frequencies added to white noise. We study the effect of the signal-to-noise ratio, of the autoregressive filter order, and of the pure frequencies amplitude ratio on the resolving power. Neglecting the uncertainties in the autoregressive filter coefficient estimates, we show that the poles of the autoregressive filter transfer function can be classified into two families: one gives the pure frequencies and the other the white noise. By a first-order development we can specify the position of the pure frequencies associated poles. This allows us to give analytical results on the bias of the pure frequency estimation and on the resolving power. These theoretical results are confirmed and illustrated by computer simulations.

Maximum entropy power spectrum estimation with uncertainty in correlation measurements

Abstract: The purpose of this paper is to present a multidimensional MEM algorithm, valid for nonuniformly sampled arrays, which satisfies a "correlation-approximating" constraint. To this end, the correlation matching equality constraints of the usual MEM are replaced by a single inequality constraint whose form is based on a measure of the noise in the given autocovariance function (ACF). In this way, one can incorporate into the model knowledge of the noisy nature of the "given" ACF, since the "given" ACF is usually estimated from the samples of the wavefield. Specifically, the covariance matrix of the correlation estimates is used in a quadratic form that weights the difference between the "given" ACF and the one matched by the power spectrum. The maximization of entropy under this inequality constraint leads, ultimately, to a steepest-descent algorithm. The algorithm has been tested with 1-D synthetic data representing multiple sinusoids buried in additive white noise. The performance of this modified MEM algorithm is compared to a traditional MEM algorithm for extendible ACF's and for different SNR's. Examples of the MEM spectrum are given for the case of nonextendible ACF's.

Optimum and Suboptimum Space-Diversity Detection of Weak Signals in Non-Gaussian Noise

Abstract: The structure of the locally optimum space-diversity detector for coherent detection of a bandpass signal subject to amplitude fluctuations in the presence of narrow-band non-Gaussian noise is derived and its large-sample performance is evaluated. For easy implementation a suboptimum structure is proposed. It consists of local detectors performing independent local decisions and of a central processor that, working according to simple logical schemes (OR or AND), performs the global decision based on the local ones. Numerical results and a comparison between the performances of both proposed structures are presented and discussed.

Measurement and analysis of acoustic flight test data for two advanced design high speed propeller models

Abstract: The recent test program, in which the SR-2 and SR-3 Prop-Fan models were acoustically tested in flight, is described and the results of analysis of noise data acquired are discussed. The trends of noise levels with flight operating parameters are shown. The acoustic benefits of the SR-3 design with swept blades relative to the SR-2 design with straight blades are shown. Noise data measured on the surface of a small-diameter microphone boom mounted above the fuselage and on the surface of the airplane fuselage are compared to show the effects of acoustic propagation through a boundary layer. Noise level estimates made using a theoretically based prediction methodology are compared with measurements.