Showing papers on "Signal published in 1988"

An Introduction to Signal Detection and Estimation

Abstract: Preface I. Introduction II. Elements of Hypothesis Testing III. Signal Detection in Discrete Time IV. Elements of Parameter Estimation V. Elements of Signal Estimation VI. Signal Detection in Continuous Time VII. Signal Estimation in Continuous Time References Index

Signal enhancement-a composite property mapping algorithm

Abstract: A signal enhancement algorithm is developed that seeks to recover a signal from noise-contaminated distorted measurements made on that signal. This object is achieved by utilizing a set of properties which the signal is known or is hypothesized as possessing. The measured signal is modified to the smallest degree necessary to sequentially possess each of the individual properties. Conditions for the algorithm's convergence are established in which the primary requirement is that a composite property mapping be closed. This is a relatively unrestricted condition in comparison to that required of most existing signal-enhancement algorithms. >

Pharmaceutical compositions containing a magnetically detectable material

Abstract: A pharmaceutical preparation is provided for oral or anal administration containing, in addition to a selected pharmacologically active agent, at least one magnetic material capable of reacting to an externally acting magnetic field of an electronic monitoring device, so that after administration to a patient, a signal is produced that is selectively detectable by such a monitoring device, thus providing information on whether the preparation has been taken or not by the patient and/or facilitates locating the preparation or the magnetic material in the region of the gastrointestinal tract of the patient.

Patch-clamp techniques for time-resolved capacitance measurements in single cells.

Abstract: Two methods are described for estimation of passive cell parameters such as membrane capacitance, membrane conductance and access resistance in tight-seal whole cell recording. Both methods are restricted in their application to cases where the cell under study can be approximated by a simple three-component network with linear properties over some voltage range. One method, referred to as the time domain technique, requires only standard electrophysiological equipment and a computer. Parameters are derived from an analysis of capacitive transients during square wave stimulation. It is readily adaptable to wide variations in experimental parameters. Particurlarly, it is equally applicable to the “slow whole-cell” configuration (access resistance in the range 100 MΩ to 1 GΩ) and to normal whole-cell measurements (access resistance typically 10 MΩ). The other method applies a sine wave command signal to the cell and employs a lock-in amplifier to analyse the resulting current signal. Two modes of operating the lock-in amplifier are described. One mode provides an output signal directly proportional to small changes in capacitance at maximum resolution (1–10 fF). The other mode, in conjunction with a digital computer, supplies estimates of all passive cell parameters, as does the time domain technique, but with a large amount of data reduction performed by the lock-in amplifier itself. Due to the special hardware, however, this method is not as flexible as the time domain technique.

Introduction to Digital Signal Processing

Abstract: An Introduction to Digital Signal Processing is written for those who need to understand and use digital signal processing and yet do not wish to wade through a multi-semester course sequence. Using only calculus-level mathematics, this book progresses rapidly through the fundamentals to advanced topics such as iterative least squares design of IIR filters, inverse filters, power spectral estimation, and multidimensional applications--all in one concise volume.

Matched field processing: source localization in correlated noise as an optimum parameter estimation problem

Abstract: Matched field processing is a parameter estimation technique for localizing the range, depth, and bearing of a point source from the signal field propagating in an acoustic waveguide. The signal is observed at an array in the presence of additive, spatially correlated noise that also propagates in the same ocean environment as the signal. In a weak signal‐to‐noise situation this parameter estimation requires the maximum exploitation of the physics of both the signal and noise structure which then must be coupled to optimum methods for the signal processing. We study the physics of this processing by modeling the ocean environment as a waveguide that is horizontally stratified with an arbitrary sound‐speed profile in the vertical. Thus, the wave equation describes the underlying structure of the signal and noise, and the signal processing via the generation of the replica fields. Two methods of array processing are examined: (i) the linear cross correlator (Bartlett) and (ii) the maximum likelihood method ...

Comparison between optical and electrical interconnects based on power and speed considerations

Abstract: Conditions are determined for which optical interconnects can transmit information at a higher data rate and consume lc3s power than the equivalent electrical interconnections. The analysis is performed for free-space optical intrachip communication links. Effects of scaling circuit dimensions, presence of signal fan-out, and the use of light modulators as optical signal transmitters are also discussed.

Low-noise techniques in detectors

Abstract: We concentrate in this review on the fundamentals of low-noise techniques and on understanding the limits in the charge signal measurements. Charge collection and signal formation in detectors, the origin and properties of noise, noise and amplification of charge, and detectors and signal processing are discussed. (AIP)

Accurate quantification of in vivo 31P NMR signals using the variable projection method and prior knowledge.

Abstract: Free induction decay signals are analyzed by fitting a model function directly in the time domain. No starting values are needed for linear model parameters, and omission of corrupted data points poses no problems. A significant gain of accuracy is achieved by imposing prior knowledge about the model parameters. © 1988 Academic Press, Inc.

High speed digital telemetry system for implantable devices

Abstract: A high speed digital telemetry system (10) includes a transmitter (12) and a receiver (14), at least one of which is adapted for use in an implantable device. The transmitter includes a data encoder (14), modulator (16), transmitting coil (20), and transmitting coil drive circuit (18). The data encoder examines prescribed incoming data bits and prior encoded data bits, generating an encoded data stream (36) that includes a data transition only when a prescribed correlation is noted amongst the examined bits. The modulator modulates a carrier signal (34) with the encoded data stream, causing a phase reversal of the carrier at each data transition of the encoded data stream. The transmitting coil drive circuit applies the modulated carrier (38) to the transmitting coil. The receiver includes a receiving coil (22) and associated amplifier (24) and bandpass filter (26) for detecting the transmitted modulated carrier. The bandpass filter is centered at the frequency of the carrier, passing the carrier only when no phase reversals are present. This results in an on-off signal at the frequency of the carrier. An AM detector (28) detects when the signal is present and when it is not, and appropriate decision logic (30) applies a suitable acceptance criteria to the detected signal to define the received binary data.

Single chip transponder device

Abstract: A transponder device receives a carrier signal from an interrogator unit. This carrier signal, of frequeny F, is rectified by a rectifying circuit in order to generate operating power. Logic/timing circuits derive a clock signal and second carrier signal of frequency F/n from the received carrier signal. This clock signal reads a unique identifying data word from a programmable read only memory (PROM). The data word is encoded and mixed with the carrier signal in a balanced modulator circuit. The output of the balanced modulator is transmitted to the interrogator unit where it is decoded and used as an identifying signal. The identifying signal identifies the particular transponder device from which it originated. The rectifier and balanced modulator circuits are realized from the same diode elements. All electrical circuits of the transponder device are realized on the same monolithic semiconductor chip. In one embodiment, an antenna receiving/transmitting coil is also part of the chip, being placed around the periphery thereof. In alternative embodiments, various hybrid elements may be connected to the monolithic elements in order to realize additional functions, such as adjustable tuning of the receiving circuit, independent crystal frequency control, and battery-powered operation.

Digital spectra of nonuniformly sampled signals: fundamentals and high-speed waveform digitizers

Abstract: A digital spectral representation of a nonuniformly sampled signal is derived, and a spectrum analysis of a nonuniformly sampled sinusoid is presented. It is found that the spectrum of a nonuniformly sampled sinusoid comprises uniformly spaced line spectra; in addition, the signal-to-noise ratio is obtained in closed form. The theories are then applied to analyze the harmonic distortion introduced in high-speed waveform digitizers due to time-base errors. Specifically, waveform digitizers are analyzed which utilize interleaving/multiplexing and random equivalent time-sampling techniques and the monolithic A/D converter technology to extend their capabilities. Theoretical results are confirmed by experimental results with a real waveform digitizer. >

Electric power steering apparatus

Abstract: An electric power steering provides a differential compensating circuit (54) in which a command current signal is added with a derivative of the command signal to provide a compensated current signal to a control circuit (28) for varying the current to an electric motor (11) arranged to provide power assistance to a steering rack (6). The apparatus provides signals representative of torque and vehicle speed to a function generator (50) to provide a first command signal which is added with a seif-centering command current and the output is provided to give a second command current which is effectively the first command current limited in dependence upon the vehi- de speed. The second command current is operated upon by the differential compensating circuit (54) to obtain the compensated current signal.

Optical communications network

Abstract: A passive, all optical communications network is provided in which a single optical source in a central station serves many outstations (e.g. telephones in customers' premises). Time division multiplexed optical signals from a laser source are transmitted along a single optical fibre (14) from a central station (4). The signal is split between several secondary fibers at a first splitter (10) (e.g. array of passive couplers) and between further sets of fibers at a second set of splitters (12). At this stage there are 120 individual fibres to customers' premises (8). Digital speech or data is sent back to the central station by a laser in the customers' premises operating in a low duty-cycle mode. The 120 data streams are interleaved at the branching points.

Advanced Topics in Signal Processing

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High resolution velocity estimation for all digital, AC servo drives

Abstract: Because the position transducers commonly used in AC servo drives (optical encoders and electromagnetic resolvers) do not inherently produce a true, instantaneous velocity measurement that can be used for full closed-loop velocity and position control, some signal processing technique is generally used to estimate the velocity at each sample instant. This estimated signal is then used as the velocity feedback signal for the velocity loop control. The authors present an analysis of the limitations of such approaches and offer an approach that optimally estimates the velocity at each sample instant. The approach is shown to offer a significant improvement in command driven systems and to reduce the effect of quantized angular resolution, which limits the ultimate performance of all digital servo drives. The noise reduction is especially relevant for AC servo drives due to the high current loop bandwidths required for their correct operation. Improved measurement performance over a classical DC tachometer is demonstrated. >

Method and apparatus for protection of signal copy

Abstract: An apparatus for the protection of signal copy for preventing unauthorized copying of music software such as records, compact discs and music tape by recording is arranged such that when recording audio signals on a medium, certain supplemental information is added to the audio signal to be recorded, and in the process of copying by reproducing this medium, when the supplemental signal is detected in the reproduced signal, the copying action is stopped to protect it from being copied.

Introduction to Digital Signal Processing

Abstract: From the Publisher: A solid reference book on digital signal processing and digital filter theory for graduate students,the electrical engineer,geologist and mechanical engineer. This book presents the most current information available with computer-oriented projects integrated throughout. It assumes prior knowledge of signals and systems/circuits.

Cardiovascular variability signals: towards the identification of a closed-loop model of the neural control mechanisms

Abstract: The authors consider parametric methods for processing cardiovascular signals and try to provide a global, although indirect evaluation of some neural regulatory activities. In particular, the variability signals of the heart rate (under the form of interval tachogram) and arterial blood pressure (systogram) together with respiratory movement signal (respirogram) are considered as inputs to a closed-loop model which describes a few aspects of the physiological interactions among the signals themselves. The identifiability of the transfer function of the model is demonstrated from the joint process black-box description of the signals. A direct identification procedure is proposed dividing the system into two dynamic adjustment models. A few suggestions are deduced on how and where the respirogram enters the model and on the genesis of the 10-s rhythm, parameters relevant to the Starling effect, Windkessel model, and the gain of baroreceptor mechanisms. The approach presented is intended also to provide a general frame for closed-loop identification in different pathophysiological conditions. >

An analysis of fast imaging sequences with steady-state transverse magnetization refocusing.

Abstract: Recently, several groups have proposed and demonstrated the use of rapid imaging methods, using short pulse repetition times and gradient-reversal echoes. Here, we analyze the behavior of the magnetization and the resulting image contrasts in such sequences for the case where the pulse repetition time TR is of the order of, or shorter than, the transverse relaxation time T2, and the transverse magnetization is not destroyed between phase-encoding cycles. Exact analytical expressions describing the signal evolution between the pulses are derived, taking into account the effects of resonance offsets and flip angles, and examining the influence of constant-phase or alternate-phase RF pulse trains. It is shown that for typical imaging sequences two distinct echo signals will develop between pulses, which may have a detrimental effect on image quality if they partially overlap within the sampling window. It is shown that artifact-free images can be obtained only if the two echo signals overlap precisely, which seems technically close to impossible to achieve, or if they are sufficiently separated in time to allow sampling of only one of the signals.

Personal alarm system

Abstract: Personal alarm system which comprises a portable transmitter unit (10) which is intended to be worn or to be manually carried by the user, and which is operable by the user at any particular location to transmit an alarm signal in an emergency and which is to be received by a central receiving station (41) so that appropriate action can be initiated in response thereto. The transmitter unit is electrically operable and includes means (15) for transmitting pulsed infra-red alarm signals which can be picked-up by an infra-red signal receiver at the location of the user, and then retransmitted as an oscillating electrical signal via direct wiring (38, 39, 40, 42, 43) to the central receiving station (41) as a warning signal indicative at location monitoring points (43, 44) of the location from which the emergency call has been made.

Ranging and velocimetry signal generation in a backscatter-modulated laser diode.

Abstract: A compact self-aligning laser radar has been constructed for coheren ranging and velocimetry using a laser diode modulated by feedback from light scattered from a diffusing target. The phenomenology of beat-signal generation in the device is discussed from both experimental and theoretical points of view. The ac-coupled modulation waveform is asymmetric (similar to a sawtooth) and different for the two propagation directions of the light leaving the diode. Atheoreticalmodel, based on the mode structure ofathree-mirrorFabry-Perot cavity, describes signal generation in these experiments and accounts for the asymmetric waveform.

Adaptive, programmable signal processing and filtering for hearing aids

Abstract: A hearing aid system utilizes digital signal processing to correct for the hearing deficit of a particular user and to maximize the intelligibility of the desired audio signal relative to noise. An analog signal from a microphone is converted to digital data which is operated on by a digital signal processor, with the output of the digital signal processor being converted back to an analog signal which is amplified and provided to the user. The digital signal processor includes a time varying spectral filter having filter coefficients which can be varied on a quasi-real time basis to spectrally shape the signal to match the hearing deficit of the user and to accommodate ambient signal and noise levels. The coefficients of the spectral filter are determined by estimating the energy in several frequency bands within the frequency range of the input signal, and using those energy estimates to calculate desired gains for the frequency bands and corresponding spectral filter coefficients. The spectral energy analysis may be carried out using pairs of high pass and low pass digital filters in cascade relation, with the output of each low pass filter being provided to the next pair of high pass and low pass filters. The rate at which output data is provided from the filters in each pair may be reduced from the sample rate of input data by one half for succeeding pairs of filters in the cascade to thereby reduce the computation time required.

Architecture of rod and cone circuits to the on-beta ganglion cell

Abstract: Photoreceptors connect to the on-beta ganglion cell through parallel circuits involving rod bipolar (RB) and cone bipolar (CB) neurons. We estimated for a small patch in the area centralis of one retina the 3- dimensional architecture of both circuits. This was accomplished by reconstructing neurons and synapses from electron micrographs of 189 serial sections. There were (per mm2) 27,000 cones, 450,000 rods, 6500 CBb1, 30,300 RB, 4100 All amacrines, and 2000 on-beta ganglion cells. The tangential spread of processes was determined for each cell type, and, with the densities, this allowed us to calculate the potential convergence and divergence of each array upon the next. The actual numbers of cells converging and diverging were estimated from serial sections, as were the approximate numbers of chemical synapses involved. The cone bipolar circuit showed narrow convergence and divergence: 16 cones----4 CBb1----1 on-beta 1 cone----1 CBb1----1.2 on- beta This circuit is thought to contribute significantly to the on-beta cell9s photopic receptive field because the CBb1 has a center-surround receptive field whose center diameter is greater than the spacing between adjacent CBb1s. Consequently, the receptive fields of the CBb1s converging on a beta cell are probably largely concentric and thus mutually reinforcing in their contributions to the on-beta. The rod bipolar circuit showed a wider convergence and divergence: 1500 rods---- 100 RB----5 AII----4 CBb1----1 on-beta 1 rod----2 RB----5 AII----8 CBb1- ---2----2 on-beta The 1500 rods converging via this circuit account for the spatial extent of the beta cell9s dark-adapted receptive field. This convergence also accounts for the ganglion cell9s maintained discharge, which is thought to arise from about 6 quantal “dark events” per second. This many dark events would appear in the ganglion cell if each rod in the circuit contributed 0.004 dark events per second, and this is close to what has been measured in monkey rods (Baylor et al., 1984). Divergence in this circuit serves to expand the number of copies of the quantal signal (1 rod----8 CBb1) and so to engage large numbers of chemical synapses that provide amplification. Reconvergence at the last stage (8 CBb1----2 on-beta) may reduce (by signal averaging) the synaptic noise that would otherwise accumulate along the pathway.

Fourier Techniques in X-Ray Timing

Abstract: Basic principles of Fourier techniques often used in X-ray time series analysis are reviewed. The relation between the discrete Fourier transform and the continuous Fourier transform is discussed to introduce the concepts of windowing and aliasing. The relation is derived between the power spectrum and the signal variance, including corrections for binning and dead time. The statistical properties of a noise power spectrum are discussed and related to the problems of detection (and setting upper limits) of broad and narrow features in the power spectrum. A “dependent triar” method is discussed to search power spectra consistently for many different types of signal simultaneously. Methods are compared to detect a sinusoidal signal, a case that is relevant in the context of X-ray pulsars.

Battery state of charge indicator

Abstract: A device for indicating changes in the state of charge of a rechargeable battery including a current sensor to sense current flow into and out of the battery and to provide an output indicative of both the magnitude and direction of the current flow, a timer to provide a timing signal, and a computer programmed to compute from the output of the current sensor and the timer, a signal representative of the charge dissipated from or accumulated in the battery over a period of time. Preferably the device includes data storage to store an indicatioin of the state of charge of the battery and the computer is programmed to use the signal to update the stored data to provide an indication of the current state of charge of the battery.

Electronic still camera and image recording method thereof

Abstract: An electronic still camera includes an imaging device (20, 26), a signal conversion device (27) and a recording device (31). The imaging device (20, 26) includes a solid state imaging unit (26) and optical color filters (20) of different spectral characteristics arranged on the solid state imaging unit (26) to convert photoelectrically converting the photographed image. The signal conversion device (27) converts a signal from the imaging device into a luminance signal and two color difference signals. The recording device (31) stores image information including the luminance signal and two color difference signals into a semiconductor memory card (15).

Pulse oximetry system

Abstract: A pulse oximetry system is provided in which LEDs of two different wavelengths illuminate tissue containing arterial blood flow. A photodiode receives light from the LEDs and produces electrical signals containing pulsatile components. The components of the two wavelengths are separated and the pulsatile waveforms are monitored until signal peaks are detected at the end of diastole. The waveforms are then integrated over the systolic interval, and the integrals are combined with the signal peak values to determine an index value. The index value is used to select a value representative of oxygen saturation from a look-up table.