Signal Analysis Approach Research Articles

Consideration of three-dimensional frequency characteristics of inter-field signal processing closed in a frame

This paper focuses on the three-dimensional frequency characteristics of inter-field signal processing closed in a frame. This is a form of inter-field image processing using two fields of one frame (also called field-merge processing) that is employed in digital image compression. This often-used closed-frame processing occurs when signals are processed in frame-based image simulations. It is a time-variant system, i.e., the field of a frame used in processing alternates between past and future. A conventional signal analysis approach cannot be used to analyze its frequency characteristics. This paper introduces a new method that we have developed to express inter-field signal processing closed in a frame (hereafter referred to as closed-frame signal processing) by a time-invariant system. The results of analyzing the three-dimensional frequency characteristics are also presented. Closed-frame signal processing is being used to improve the quality of HDTV MUSE pictures. With this new method, we were able to calculate the three-dimensional frequency characteristics of the new MUSE system. We also measured the three-dimensional frequency characteristics in an experiment, and compared the measurements with theoretical values. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(4): 23–32, 1999

Small signal frequency response of a linear dispersive single-mode fiber near zero first-order dispersion wavelength

A theory describing the propagation of signal and noise through a lossless linear dispersive singlemode fiber near zero first-order dispersion point is presented. Using the small signal analysis approach, this theory has been applied to modulation and noise characteristics of a laser diode, emitting near the fiber zero-dispersion wavelength, to obtain the small signal frequency response and the signal relative intensity noise (RIN) at the output of the fiber. It has been shown that, for very long broad-band transmission lines, dispersion effects may be no longer negligible also at zero-dispersion wavelength.

Non-destructive testing and evaluation for structural integrity

Reliable performance of a component or structure depends on pre-service quality of the component and in-service degradation of the component under operating conditions. The role of non-destructive evaluation (NDE) in ensuring pre-service quality and also monitoring in-service degradation to avoid premature failure of the components/structures is ever increasing. There are many NDE techniques based on various physical principles. The end objective of NDE is detection and characterisation of anomalies such as defects, stresses and microstructural degradations in materials. This is accomplished by establishing correlation between a nondestructively measured physical/derived parameter and quantitative information on defects/stresses/microstructures. The NDE information together with design parameters are taken into consideration for evaluation of integrity and life assessment of the components/structures. In this paper, a brief description of the physical concepts of NDE methods and the physical/derived parameters that are used for assessing defects, stresses and microstructures are given. A few case studies highlighting the importance of non-destructive testing and evaluation for structural integrity assessment are also discussed based on the investigations carried out at the authors’ laboratory. Emerging concepts like intelligent processing of materials, expert systems, neural networks, use of multisensors with fusion of data and exploitation of signal analysis and imaging approaches are also addressed in this paper.

Study of the effect of the C/sub max//C/sub min/ ratio on the performance of back-to-back Barrier-N-N (bbBNN) varactor frequency multipliers

The effect of the C/sub max//C/sub min/ ratio on the performance of planar back-to-back Barrier-N-N/sup +/ (bbBNN) frequency multipliers is studied. A simplified physical model of the device is used to relate the electrical characteristics to the material and the structural parameters. Multiplication efficiency is evaluated using a large signal analysis approach. Results indicate that if the optimum device size for a given frequency is used, a high C/sub max//C/sub min/ ratio results in high efficiency. >

Experimental performance of a back-to-back barrier-N-N/sup +/ varactor tripler at 200 GHz

This paper describes the performance of planar back-to-back barrier-N-N/sup +/ (bbBNN) devices for frequency multiplier applications. A tripling efficiency of 3.3% has been achieved using these devices in a 200 GHz crossed waveguide mount. This is the first experimental result with a bbBNN waveguide frequency multiplier. A technique has been developed for characterizing planar bbBNN devices with a network analyzer, which gives both the series resistance and voltage dependent capacitance of the device. The experimental results are compared with the theoretical multiplier performance, calculated using a large signal analysis approach.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Application of nonlinear dynamics for noise reduction in measured signatures containing broadband information

Nonlinear dynamics has been of great academic interest in recent years. Its concepts have been employed as a foundation for modeling nonlinear processes in diverse fields extending from economic trends to medical dysfunctions. Although the developments of nonlinear dynamics concepts in acoustics are sparse, their application in acoustics has advantages over linear techniques in extending broadband signatures in high‐noise environments. Linear signal analysis approaches are significantly limited when the noise environment is nonstationary or when the signal duration is short. Furthermore, the application of filters alters the information content of the original broadband signals. Nonlinear dynamics methods do not suffer these limitations. Two such methods will be described for effecting noise reduction where the signal‐to‐noise ratio is zero or negative and where there is no a priori knowledge of either the signal or the noise. Signals used for demonstration include sinusoids and chaotic sequences; additiv...

New method for the assessment of neonatal respiratory sinus arrhythmia

Respiratory sinus arrhythmia (RSA) is sometimes hard to identify in neonates, in particular when the respiratory rate approaches half the mean heart rate. It is shown that the analysis of the cardiac event series may reveal RSA in cases where traditional heart rate variability analysis methods fail. A signal analysis approach to event series processing is reviewed. The validation of the spectral analysis of event series is illustrated with the help of simulation results. In accordance with this approach, the event series spectrum of a neonate shows a RSA component at 0·9 Hz, which was in agreement with the frequency of the simultaneously measured respiration. The possible implications for research into the causes of sudden infant death syndrome (SIDS) are discussed.

Statistical signal analysis for systems with mutually related input functions

Statistical signal analysis approaches have been successfully used in analyzing linear and constant parameter multiple input‐output systems. These methods have been particularly useful when input signals are not correlated. However, there are a number of systems that have measurable input signals that are related. An example is a vibrating plate under two excitation forces. When both the acceleration and force are monitored at a particular input, then they are correlated. In this paper three different approaches are used to investigate a two input‐one output system with mutually related input signals. These approaches are: (1) conventional multiple input‐output statistical signal analysis, (2) conditioned spectral analysis, and (3) a new approach, based on alternations in one of the input signals. In the last approach, the system of equations for the multiple input‐output model is solved twice for two different input signal cases. The results when these three methods are used to analyze an electrical two input‐one output model and a plate with two excitation forces will be presented and discussed in terms of the accuracy and required signal processing.

Plate vibration identification using statistical signal analysis

Theoretical and experimental investigations of baffled plate vibrations and radiated acoustic pressure were performed. The goal of these investigations was to evaluate the acoustic radiation due to each of two different excitation forces in the case when both of them were applied at the same time. A 0.25‐in.×2‐ft×2‐ft aluminum plate, simply supported at the center, was installed inside an anechoic chamber. Two concentrated forces were applied using vibration excitors. The two input‐one output, linear model and the statistical signal analysis approaches were used in the analysis. Excitations were noncorrelated, random signals. Three different input signal representations were used for comparison. These signals were force, acceleration, and acoustic pressure measured in the vicinity of the excitor‐plate connections. The statistical analysis was performed using two dual‐channel FFT analyzers interfaced with a personal computer to form a four‐channel system. The performance tests for this four‐channel system ...

Short‐range structure determination by EXAFS spectroscopy: Theory, experimental technique and spectral analysis

AbstractA physico‐chemical description of the extended X‐ray absorption fine structure (EXAFS) phenomenon is given and experimental methods for its measurement in transmission mode are indicated. Pros and cons of various procedures for careful evaluation of the experimental absorption data are described, which comprise background removal according to Victoreen's relation or by polynomial fitting and criteria for Fourier filtering methods are given. Three different approaches for EXAFS signal analysis are discussed namely fitting with parametrized amplitude and phase functions, comparison of experimental data with theoretical EXAFS spectra and Fourier transform techniques; the limits of applicability of these procedures are indicated. A critical evaluation is given for the various methods for correction of the resulting radial distribution function in order to comply with crystallographic distances. The determination of coordination numbers is discussed and the procedures are illustrated with results for metallic titanium, rutile and anatase.