Showing papers on "Signal published in 1990"

On a simple algorithm to calculate the 'energy' of a signal

Abstract: A simple algorithm is derived that permits on-the-fly calculation of the energy required to generate, in a certain sense, a signal. The results of applying this algorithm to a number of well-known signals are shown. Some of the invariance and noise properties of the algorithm are derived and verified by simulation. The implementation of the algorithm and its application to speech processing are briefly discussed. >

Implantable ambulatory electrocardiogram monitor

Abstract: An implanted programmable ambulatory electrocardiography (AECG) patient monitoring device that senses and analyzes electrocardiographic signals from at least one subcutaneous precordial sensor chronically and frequently to detect electrocardiogram and physiological signal characteristics predictive of malignant cardiac arrhythmias. The device includes telemetric capabilities to communicate a warning signal to an external device when such arrhythmias are predicted.

A network model of catecholamine effects: gain, signal-to-noise ratio, and behavior

Abstract: At the level of individual neurons, catecholamine release increases the responsivity of cells to excitatory and inhibitory inputs. A model of catecholamine effects in a network of neural-like elements is presented, which shows that (i) changes in the responsivity of individual elements do not affect their ability to detect a signal and ignore noise but (ii) the same changes in cell responsivity in a network of such elements do improve the signal detection performance of the network as a whole. The second result is used in a computer simulation based on principles of parallel distributed processing to account for the effect of central nervous system stimulants on the signal detection performance of human subjects.

In vivo proton spectroscopy in presence of eddy currents

Abstract: Spatially localized methods in spectroscopy often operate with magnetic field gradients for volume selection. The eddy currents induced by these gradients produce time-dependent shifts of the resonance frequency in the selected volume, which results in a distortion of the spectrum after Fourier transformation. In whole-body systems the complete compensation of eddy currents is a difficult procedure. To avoid this, a correction method is proposed for proton spectroscopy, which uses the signal of prominent water protons as a reference for the water-suppressed signal. The correction is performed in the time domain, dividing the water-suppressed signal by the phase factor of the water signal for each data point. The corrected spectra have a good resolution as shown by phantom measurements and brain and muscle spectra of volunteers.

High-resolution incoherent imaging of crystals

Abstract: A Bloch-wave analysis shows how a signal dependent on the electron intensity at the atom sites can be used to form an incoherent image of a crystal structure. To a good approximation the image is given by a convolution of a compositionally sensitive object function with an appropriate resolution function, and as such can be predicted and interpreted intuitively. Information on a scale below the resolution limit can be interpreted by deconvolution.

Electronic endoscope apparatus capable of warning lifetime of electronic scope

Abstract: In an electronic endoscope apparatus, comprising: there are provided an electronic scope having an image sensor at a distal end thereof and an angle operation portion adjacent to the image sensor; a scope unit coupled with the electronic scope, including an endoscopic operation switch mechanically connected to the electronic scope, a scope computer for processing a switch operation signal derived from the endoscopic operation switch so as to obtain first use-history data on the operation switch, and a memory device for temporarily storing the first use-history data therein; and, a main unit including a signal processor for processing an image signal derived from the image sensor so as to produce an endoscopic image signal of a biological body under medical examination, a system computer for fetching the use-history data on the operation switch from the memory device via the scope computer, and a display unit for selectively displaying an endoscopic image of the biological body in response to the endoscopic image signal and use-history information in response to the fetched used-history data.

ESPRIT-estimation of signal parameters via rotational invariance techniques

Abstract: High-resolution signal parameter estimation is a problem of significance in many signal processing applications. Such applications indude direction-of-arrival estimation, system identification, and time series analysis. A novel approach to the general problem of signal parameter estimation is described. Although discussed in the context of directionof- arrival estimation, ESPRIT can be applied to a wide variety of problems. It exploits an underlying rotational invariance among signal subspaces induced by an array of sensors with a translational invariance structure. The technique, when applicable, manifests significant performance and computational advantages over previous algorithms such as Burg's maximum entropy method, Capon's maximum likelihood method, and Schmidt's multiple signal classification.

Medical instrument location means

Abstract: An instrument location determining device which has a radiating element forming part of the instrument to be inserted into an object. The element radiates a signal and the signal is detected by at least one receiving element. A signal energy level measurement device is coupled to the receiving element and it produces an energy level value for each one of the receiving elements. The distance of the radiating elements from the receiving element is calculated from the measured energy level values received by each of the receiving elements. The measured distance is then indicated to an operator of the instrument so that he can locate the instrument within the object.

Control device having multiple degrees of freedom

Abstract: A hand-held joystick has spaced-apart groups of accelerometers and is free to move or rotate on multiple axes. Each group has, for example, three mutually perpendicular accelerometers, with each one producing an electrical signal responsive to linear acceleration along one axis. The signals are combined to derive a definition of acceleration of the joystick along the three mutually perpendicular linear axes and/or rotation about these axes. The combined signal is used by an electrical control system which provides input to a device being controlled. The signal to the device under control is responsive to the motion of the joystick.

Electrical signal processing techniques in long-haul fiber-optic systems

Abstract: The potential for electrical signal processing to mitigate the effect of intersymbol interference in long-haul fiber-optic systems is discussed. Intersymbol interference can severely degrade performance and consequently limit both the maximum distance and data rate of the system. Several techniques for reducing intersymbol interference in single-mode fiber systems with single-frequency lasers are presented, and those techniques which are appropriate at high data rates in direct coherent detection systems are identified. The performances of linear equalization (tapped delay lines), nonlinear cancellation (variable threshold detection), maximum-likelihood detection, coding, and multilevel signaling are analyzed. The results for a simulated binary 8-Gb/s system show that simple techniques can be used to reduce intersymbol interference substantially, thereby increasing the system margin by several decibels. A six-tap linear equalizer increases the dispersion-limited distance (due to chromatic or polarization dispersion) by 20% (or reduces the optical power penalty by as much as a factor of two) in direct detection systems, even when the distortion is nonlinear. A nonlinear cancellation technique (adjusting the decision threshold in the detector based on previously detected bits) can more than double the dispersion-limited distance and/or data rate. >

Medication infusion system having optical motion sensor to detect drive mechanism malfunction

Abstract: An optical motion sensor is provided for monitoring movement of a mechanical device, particularly such as an infusion pump of the type used for controlled delivery of medication to a patient. The motion sensor includes a disk member mounted upon a selected mechanical output component driven by the infusion pump, such that the disk member undergoes displacement during normal pump operation. The disk member defines a pattern of reflective and substantially nonreflective surface zones which are alternately illuminated by a light source during normal pump operation. A light detector responds to the level of reflection from the disk member to provide an output signal which varies according to disk member displacement. This output signal is connected to a controller for comparison with drive signals supplied to the infusion pump, to verify proper mechanical output operation of the pump.

System and method for attracting shoppers to sales outlets

Abstract: A system and method for evaluating responses to broadcast programs, such as televison programs, includes an instructional signal modulated onto a signal transmitted concurrently with the television program, or time-multiplexed with a television. At each of a plurality of remote receiving stations, one or more members of a remote audience has the opportunity to respond to a situation presented in the television program by entering a response on a keyboard. The system includes, at each remote receiving station, a memory responsive to the instructional signal for storing acceptable responses, and a comparison circuit for comparing responses entered at the keyboard with those stored in the memory. Also provided is electronic circuitry for scoring the responses in accordance with commands from the instructional signal, and a recording device for providing a permanent record of the audience score at each of the remote receiving stations. Scoring is performed at differing levels of difficulty, set by a host or by a contestant, with credit being given also for the length of time required for response. The mode of response includes the use of a key word or phrase. Alternatively, the program may be presented by a prerecorded message accessible by telephone from a remote station with regulation from a central station. A prize-winning respondent can select a product from a listing and apply the value of a prize to the purchase price of the selected product.

Filters for common resampling tasks

Abstract: Even though a signal is sampled, we may have certain rules about inferring the values between the sample points The most common assumption made in signal processing is that the signal is bandlimited to an extent consistent with the sampling rate, ie that the values change smoothly between samples The Sampling Theorem guarantees that a continuous signal can be reconstructed perfectly from its samples if the signal was appropriately bandlimited prior to sampling [Oppenheim 75] Practically speaking, signals are never perfectly bandlimited, nor can we construct a perfect reconstruction filter, but we can get as close as we want in a prescribed manner

A frequency synthesiser

Abstract: A frequency synthesiser comprising a phase locked loop having a reference oscillator (8) coupled to a first input of a comparator (6), a voltage controlled oscillator (VCO) (2) for providing an output signal, which output signal is fed back by way of a divider circuit (4) or dividing the output fequency by a factor N to a second input of said comparator, the output of the comparator being applied to a control input of the VCO, and including input means for applying a modulating signal in binary format via integrator means (26) for control of the divider circuit, and means having a predetermined transfer function (22) coupling said modulating signal to the control input of the VCO whereby to provide a modulation of the output signal in desired format.

Differentiating sonar reflections from corners and planes by employing an intelligent sensor

Abstract: A multitransducer, pulse/echo-ranging system is described that differentiates corner and plane reflectors by exploiting the physical properties of sound propagation. The amplitudes and ranges of reflected signals for the different transmitter and receiver pairs are processed to determine whether the reflecting object is a plane or a right-angle corner. In addition, the angle of inclination of the reflector with respect to the transducer orientation can be measured. Reflected signal amplitude and range values, as functions of inclination angle, provide the motivation for the differentiation algorithm. A system using two Polaroid transducers is described that correctly discriminates between corners and planes for inclination angles within +or-10 degrees of the transducer orientation. The two-transducer system is extended to a multitransducer array, allowing the system to operate over an extended range. An analysis comparing processing effort to estimation accuracy is performed. >

Method and apparatus for correcting for clock and carrier frequency offset, and phase jitter in multicarrier modems

Abstract: A method of correcting for the impairments of phase jitter and frequency offset imposed by a transmission medium and of a clock frequency difference between a transmitting and a receiving multicarrier modem is disclosed. The method comprises two modes: a training mode that uses pilot tones, and a data mode that uses random data modulated onto many carriers. During the training mode the frequencies of the phase jitter are estimated, and the parameters of a correcting signal are initialized; during the data mode the correcting signal is used to compensate for the impairments, and then is updated from an estimate of the phase error.

Video transmission and control system utilizing internal telephone lines

Abstract: A video transmission system for facilitating transmission of video and control signals, particularly infrared remote control signals, between different locations in a residence using existing telephone wiring. Simultaneous transmission of signals of both types over active telephone lines is possible without interference with telephone communications. Transmission succeeds without requiring special treatement of the video signals beyond RF conversion, despite signal attenuation inherent in transmission over the telephone line media. Two or more video sources may be tied into the system, and selected as desired. Remote control signals generated in one room may be utilized without requiring a clear line of sight between the remote control device and the receiver.

Stability of the random neural network model

Abstract: In a recent paper [1] we have introduced a new neural network model, called the Random Network, in which "negative" or "positive" signals circulate, modelling inhibitory and excitatory signals. They are summed at the input of each neuron and constitute its signal potential. The state of each neuron in this model is its signal potential, while the network state is the vector of signal potentials at each neuron. If its potential is positive, a neuron fires, and sends out signals to the other neurons of the network or to the outside world. As it does so its signal potential is depleted. We have shown that in the Markovian case, this model has product form, i.e. the steady-state probability distribution of its potential vector is the product of the marginal probabilities of the potential at each neuron. The signal flow equations of the network, which describe the rate at which positive or negative signals arrive to each neuron, are non-linear, so that their existence and uniqueness is not easily established except for the case of feedforward (or backpropagation) networks [1]. We examine two sub-classes of networks: balanced, and damped networks and obtain stability conditions in each case. A hardware implementation of these networks is also suggested.

Colorimeter and calibration system

Abstract: Apparatus for monitoring, converting and calibrating the spectra displayed by a colored object, using wavelength dispersion provided by a variable wavelength filter. The apparatus may serve as a spectrophotometer, as a colorimeter, or as a spectroradiometer or other device that monitors and calibrates a light signal by decomposition of the signal into a wavelength distribution. The apparatus may also be used as part of a feedback network to monitor and correct colors displayed by a color monitor, color printer, color scanner or other similar peripheral device controlled by a computer that is part of the network.

Automatic stance-swing phase detection from accelerometer data for peroneal nerve stimulation

Abstract: The development of implantable peroneal nerve stimulators has increased interest in sensors which can detect the different phases of walking (stance and swing). Accelerometers with a potential for implantation are studied as detectors for the swing phase of walking to replace footswitches. Theoretically, one can show that accelerometers can be used to distinguish between stance and swing phase. Using accelerometers attached between the ankle and knee joints, the equivalent acceleration of the ankle joint was calculated. This resulted in a typical and reproducible signal in which the different walking phases were identified. Automatic detection algorithms based on cross-correlation calculations were developed and tested. Measurements from four healthy and four hemiplegic subjects resulted in a total of 317 and 272 steps, respectively. The testing of one of the hemiplegic subjects was considered to be a failure due to large disturbances in the acceleration signal during the swing phase of walking, which may be related to the use of crutches. >

Method and apparatus for sound responsive tactile stimulation of deaf individuals

Abstract: A tactile aid for deaf individuals includes a conveniently wearable array of vibration transducers mounted on a flexible carrier strip so as to be positionally biased toward the individuals's skin. Each transducer includes an enclosed magnetically vibratable cantilevered beam, an angled mounting slot to effect the positional bias mounting on the strip, and contact pads rather than conventional pin connectors to both reduce mass and facilitate electrical connection to contact pads on carrier strips in the form of printed circuit boards. Received acoustic signals are processed in at least first and second formant circuits each sub-divided into plural sub-bands corresponding to the number of transducers. In each formant circuit the corresponding formant frequency and amplitude are measured, averaged over a predetermined number of cycles, and a voltage corresponding to the measured amplitude is provided on a corresponding sub-hand channel to pulse width modulate a pulse train employed to excite the transducers. Spectral resolution can be increased by averaging the amplitude/frequency measurements over fewer cycles. Glottal pulses in the speech signal are monitored to provide a glottal rate signal at a stepped down frequency related to the actual glottal rate. The channel amplitude is modulated by the glottal signal to cause alternation of transducer excitation at the related glottal rate. Additional formants may be detected to derive additional information in the excitation signal.

Apparatus and method for reading data from an image detector

Abstract: A image detector includes an array of photodetectors arranged in n rows and m columns with at least a portion of the photodetectors in each column being selectively connected to a common column output signal line by a selector means. The image information is read out of the photodetectors by sequentially selecting groups of rows starting with a row near the middle of the array and then sequentially selecting other groups of rows on alternate sides of the array middle. As image data is read out of the photodetectors in the selected row group, groups of column outlet lines are coupled together to provide a combined output signal. This readout technique provides a reduction in the image data and reduces the likelihood of signal degradation for the central portion of the image.

Spread-spectrum identification signal for communications systems

Abstract: A spread-spectrum signal which conveys identifying information for an associated information signal is superimposed on the associated signal and transmitted therewith. Such identifying information distinguishes between voice and data information signals and between different types of data information signals. Such identification can be used for a variety of purposes within a communications network, such as facility and equipment selection, equipment disablement and bypass, setting communications parameters, e.g., speed, and inhibiting communications upon fault detection.

Data protection by detection of intrusion into electronic assemblies

Abstract: The present invention provides an intrusion barrier for protecting against mechanical or chemical intrusion into an electronic assembly, especially one containing volatile memory. It includes a screen material surrounding the electronic assembly which screen material has formed thereon fine conductive lines in close proximity to each other. The lines are formed of conductive particles of material dispersed in a solidified matrix of a material which looses its mechanical integrity when removed from the screen. An electrical supply and signal detection circuit is provided which generates an output signal responsive to a given change in resistance of the conductive lines, such that if the resistance changes are a result of a mechanical or chemical attack, a signal is generated which can cause the erasure of the volatile memory. Also, preferably radiation detection and temperature sensing circuits are provided to cause erasure of the volatile memory responsive to detection of a given intensity of radiation or a temperature below a given value.

Control for a moisture sensor

Abstract: A control for a moisture sensing assembly, adapted for mounting on the inner surface of a vehicle window or windshield to control vehicle accessories such as windshield wipers, maximizes the window area being sensed in relationship to the size of the assembly and provides immunity to interference from environmental influences. In the preferred embodiment, moisture on the outer window surface is detected by first and second moisture sensors each including infrared energy radiating diodes and radiant energy detectors which detect and process radiant energy to produce a moisture signal that is a function of the moisture on the window. A synchronizing circuit intermittently actuates the radiating diode for the two sensors individually and alternatingly at equally-spaced intervals. The synchronizing circuit also inhibits the radiant energy detectors from processing the radiant energy signal except when the corresponding radiating diodes are emitting energy in order to prevent interference from the other radiating diodes and environmental influences. The synchronizing circuit includes a pair of oscillators which include capacitors and coupling devices that coordinate the discharging of the capacitors in a manner which provides equal intervals between alternating output pulses from the oscillators.

Target acquisition and tracking system

Abstract: An automatic target acquisition and tracking system has been developed for a focal plane array seeker The automatic target acquisition is achieved by three independent target acquisition algorithms, viz, the maximum likelihood classification, the video spatial clustering, and the target-to-interference ratio Each algorithm operates asynchronously and provides independent target detection results Target information is then combined hierarchically in a probabilistic fashion and prioritized The highest priority target is handed off to a dual mode tracker consisting of a minimum absolute difference correlation tracker and a centroid tracker The dual mode tracker subsequently provides a feedback signal to a proportional navigation system or other guidance/control system for directing the flight path of a munition

Characterization of single channel currents using digital signal processing techniques based on Hidden Markov Models.

Abstract: Techniques for extracting small, single channel ion currents from background noise are described and tested. It is assumed that single channel currents are generated by a first-order, finite-state, discrete-time, Markov process to which is added `white' background noise from the recording apparatus (electrode, amplifiers, etc.). Given the observations and the statistics of the background noise, the techniques described here yield a posteriori estimates of the most likely signal statistics, including the Markov model state transition probabilities, duration (open- and closed-time) probabilities, histograms, signal levels, and the most likely state sequence. Using variations of several algorithms previously developed for solving digital estimation problems, we have demonstrated that: (1) artificial, small, first-order, finite-state, Markov model signals embedded in simulated noise can be extracted with a high degree of accuracy, (2) processing can detect signals that do not conform to a first-order Markov model but the method is less accurate when the background noise is not white, and (3) the techniques can be used to extract from the baseline noise single channel currents in neuronal membranes. Some studies have been included to test the validity of assuming a first-order Markov model for biological signals. This method can be used to obtain directly from digitized data, channel characteristics such as amplitude distributions, transition matrices and open- and closed-time durations.

Inventory control system

Abstract: Apparatus for automatically determining the weight of a plurality of articles (14), each of the articles (14) having a surface portion (54) with a unique element thereon, comprises a plurality of assemblies (22) and a computer (56). Each assembly (22) includes a surface (30) for supporting an article (14), a transducer (36) in operative contact with the supporting surface (30) for producing an output signal indicative of the weight of an article (14) placed on the supporting surface (30), and a sensor (48) in operative relationship with an article (14) on the supporting surface (30) for producing an output signal indicative of the unique element on the surface portion (54) of the article. A computer (56) receives the transducer output signals and the sensor output signals and, for each article (14) on the supporting surfaces (30), computes the weight of the article based on the transducer output signal and identifies the article (14) based on the sensor output signal. The apparatus is especially useful as an inventory control system for a bar.

Battery-powered flashing superluminescent light emitting diode safety warning light

Abstract: A device includes a flashing safety warning light in which a superluminescent light-emitting diode light source (SLD1-SLDn) is driven by power driver (PD) supplied by a high frequency oscillator (HFO) with an oscillatory drive signal at a visually imperceptible but highly efficient operating frequency, the oscillatory drive signal preferably being a pulse signal of 1 to 5 KHz, to cause the light source to be illuminated and extinguished at the oscillatory drive signal frequency, such that extinction of the light source is not visually perceptible. The oscillatory drive signal is in turn gated on and off in accordance with a gating signal from a low frequency oscillator (LFO) at a low, highly visually perceptible frequency in the range of 3 to 12 Hz with a pulse duty cycle of between 10 to 60 % in order to cause the light source to be visually perceived as flashing on and off at the gating signal frequency in an attention-attracting manner.