Showing papers on "Signal published in 1970"

Angiographic injector equipment

Abstract: An angiographic injector control system for delivering a controlled volume of injection fluid is described. The injector has a motor driven piston for ejecting fluid from a syringe cartridge contained within a pressure jacket. The drive motor is operated in accordance with a command voltage corresponding to an incremental position of the injector piston, the command position signal also corresponding to the volume of fluid to be ejected from the cartridge. This command position voltage signal is compared to an actual position voltage to produce an error signal for operating the drive motor, whereby the syringe piston follows the position command signal. Volume selector means produce a volume signal corresponding to a desired maximum volume of fluid to be ejected; this volume signal is compared to the sum of the position command increments, producing a stop signal when the position command signal equals or exceeds the volume limit signal. Thus, the injector control system regulates the injection of fluid by sensing and controlling the position of the injector piston.

Optical parametric device

Abstract: An optical parametric device is described which may be used as an amplifier, oscillator, or frequency converter, and which is operable in the infrared or visible spectral regions. The device utilizes a dielectric optical waveguide or tuned cavity, which structure may comprise the depletion layer of a semiconductor junction, the dielectric material of which exhibits nonlinear susceptibility. An intense, appropriately oriented, optical pump induces a non-linear electric polarization in the material of the dielectric structure. Traveling wave or discrete circuit parametric interaction occurs within the structure between the pump and an input signal. Under appropriate conditions, oscillation, amplification, and/or frequency conversion may be obtained.

Electronic surveillance system

Abstract: An electronic surveillance system in which a passive label is attached to goods to be placed under surveillance and the label is interrogated by electromagnetic signals from a transmitter, the label acting to transmit a reply signal to a receiver which gives a characteristic response in the presence of a label, the transmitter being arranged to transmit signals, preferably two, at widely different frequencies and the label acts to mix these frequencies to produce a reply signal which is distinct from the original transmitted signal. The receiver is provided with a signal processing system which analyses and compares characteristics of the transmitted signal and the reply signal and produces different responses in the presence or absence of a label.

Adaptive delta modulation with a one-bit memory

Abstract: We propose a delta modulator which, at every sampling instant r, adapts its step-size (for a staircase approximation to the input signal) on the basis of a comparison between the two latest channel symbols, C r and C r-1 Specifically, the ratio of the modified step-size m r to the previous step size m r-1 is either +P or — Q depending on whether C r and C r-1 are equal or not (We recall that, in delta modulation, C r represents the polarity of the difference, at the sampling instant r, between the input signal X r and the latest staircase approximation to it, Y r-1 ) A simulation of the delta modulator with a band-limited speech input has revealed that PQ = 1 and P ⋍ 15 represent optimal adaptation characteristics, on the basis of signal-to-error ratios, over an important range of sampling frequencies; and that at 60 kHz, delta modulation with these adaptation parameters compares favorably with 7-bit logarithmic PCM, which reproduces speech with good telephone quality We present several graphical results from this simulation, and include an evaluation of the effect of independent channel errors on the adaptive delta modulator We proceed to suggest a heuristic theory of the delta modulator which explains the optimality of the condition PQ = 1, and develops an upper bound of 2 for the optimum value of P We conclude with a summary of results from a video simulation which revealed that aforementioned optima for P and Q apply to a video signal

High‐Resolution NMR Study of Relaxation Mechanisms in a Two‐Spin System

Abstract: A description of nuclear spin–spin and spin–lattice relaxation is presented for a system of two coupled nonequivalent spin−12 nuclei subject to mutual dipole–dipole interaction and interactions with external magnetic species Expressions are derived for the six transition probabilities linking the four energy levels, in terms of an internal dipole–dipole relaxation parameter TD, external relaxation parameters TXA for nucleus A and TXB for nucleus B, and the degree of correlation (C) between the interactions of A and B with external magnetic species These molecular relaxation parameters are related to the initial rates of recovery of the NMR signal intensities after a selective pulse has rotated the magnetization vector of a chosen line through π radians in the rotating frame of reference A small general‐purpose computer has been used to control these pulse experiments and to program a synthesizer to provide the required stable audiofrequency signals Measurements have been made on the high‐resolution pr

Method and apparatus for locating and measuring wave guide discontinuities

Abstract: An intermittent pulsed carrier signal having a frequency of approximately 10 gigahertz and on for approximately 10 nanoseconds duration is transmitted through a wave guide. Wave guide discontinuities reflect a portion of the incident pulse, and these reflected signals are detected and compared to the incident pulse relative to time and amplitude differences. The discontinuity point in the wave guide is then directly determined using time domain reflectometry, from the time interval for the signal to reach the discontinuity and for the reflected wave totravel back along the wave guide and be detected. As the intensity of the reflected signal is functionally related to the magnitude of the fault, a display of the reflected signal magnitude, compared to the incident signal magnitude, will indicate the magnitude of the wave guide discontinuity.

A Method for Calculating the Output Pressure Waveform from an Air Gun

Abstract: Summary The signal from an air gun is assumed to behave as if it were derived from an oscillating spherical air bubble in water. The theory of the oscillations of spherical bubbles according to Gilmore is used in conjunction with experimental evidence to derive the complete set of equations necessary to calculate the shape of the radiated pressure waveform anywhere in the water. It is believed that this method will be useful in the design of signal processing techniques and also to improve the design of existing air gun profiling systems.

Chapter 6 The Pyroelectric Detector

Abstract: Publisher Summary This chapter discusses the exploitation of the effect as a means of detecting infrared radiation. Any sensitive thermometric element can, in principle, be used as a thermal infrared detector. When the pyroelectric detector absorbs radiation, its temperature rises, changing its surface charge. To calculate its performance, both the thermal and electrical characteristics must be considered in detail and the sources contributing to the detector's noise must be enumerated. There are three ways in which a pyroelectric detector may be used: (1) To detect a signal modulated at a constant angular frequency ω ; (2) by combining a detector operating in this mode with a frequency-equalizing amplifier, a receiver with a very short (less than 1 μsec) response time suitable for observing transient signals, such as laser pulses, may be produced; and (3) the pyroelectric element can be used to store the total charge liberated by a transient signal.

Television telephone system

Abstract: A television-telephone system for information transmission in a subscriber-subscriber communication mode or subscriber-computer communication mode, wherein the information transmission is effected between an information receiving party and a transmitting party, which may be a computer. A position indicating signal can be sent back from the receiving party to the transmitting party by using a light-pen and a signal switching network. The position indicating signal is sent to the transmitting party to indicate a command of the receiving party by displaying the position indicating signal superposed on the transmitted picture, or this indication information may be further processed and utilized by the transmitting party to form a definite digital indication of the position information.

Apparatus for monitoring recurrent waveforms

Abstract: An electrocardiogram waveform is monitored by superimposing the waveform complexes upon a stored waveform complex representative of a ''normal'' complex, using derived reference levels and timing data and then integrating successive segments of a waveform complex, measuring the difference between the integrated value of each segment in the complex and the integrated value of a corresponding segment of a normal waveform complex, quantitatively summing the differences and producing a signal and/or record if the total difference exceeds a predetermined value.

Nuclear magnetism logging

Abstract: Method and apparatus for analyzing earth materials in situ along a bore hole on the basis of their nuclear magnetic properties. A logging instrument is passed through the bore hole with means to subject a region including earth material in situ to a relatively strong D.C. magnetic field, which may be oriented in any direction and which may be relatively inhomogeneous, for polarizing susceptible nuclei in said material, including selected nuclei therein. The logging instrument also contains means for applying an alternating magnetic field to the same region, including polarized nuclei therein, in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field. While the alternating field is being applied, the D.C. polarizing field in the region including said material is terminated within a predetermined time interval, i.e., turned off sufficiently slowly to provide an adiabatic variation of the D.C. field and sufficiently quickly to terminate the D.C. field within a time interval less than the characteristic thermal relaxation time of the selected nuclei. Since the frequency of the alternating field is such that it produces resonance in the earth''s field alone, turning off the polarizing field sweeps the nuclei onto driven resonance. The alternating field is then abruptly terminated in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s relatively homogeneous magnetic field. A characteristic of the resulting free precession condition of the selected nuclei is detected. In accordance with a preferred embodiment, the free precession condition is detected by phase coherent detection utilizing a reference signal produced in timed correlation with the alternating field. Advantageously, in accordance with a further feature of the invention, computer of average transient signal averaging techniques, such as the type known as boxcar integration (digital or analogue), are employed for enhancement of the detected free precession signal with respect to the noise.

Dual-slope and analog-to-digital converter wherein two analog input signals are selectively integrated with respect to time

Abstract: An electrical integrating circuit arrangement is disclosed which is especially suitable for use in combination with timing means in dual-slope analog-to-digital converters because it operates with time controlled closure of a single, low-impedance switching device of the single-pole, single-throw type to effect selective time integrations of two D.C. input signals; an analog signal and an oppositely directed reference current. The integrating arrangement comprises an operational amplifier having inverting and non-inverting inputs and feedback to the inverting input through a capacitor. The analog signal source may be permanently connected to the non-inverting input whereas the second input signal is similarly connected to the inverting input through a resistance. The switching device is closed to connect the second input signal end of the resistance to a source of potential. Timed closure of the switching device by the timing means causes the integrating arrangement to generate two successive voltage ramps having slopes which are respective functions of the two signals exclusive of one another. The instant combination may be utilized to advantage in the digitalization of bipolar analog signals.

Position-indicating system

Abstract: A position-indicating system, determining the coordinates of a point of a surface to which static force is applied, comprises a rigid plate which is fixed to the surface by means of at least three spaced-apart sensors. These sensors delivering each an output signal which is proportional to its distance from the point of application of the force. These signals are then processed in an electronic unit generating two voltages which represent the coordinates of the point of application of the force to the surface, as measured with reference to two axes determined by the three sensors.

Spread-spectrum position monitoring system

Abstract: Disclosed are systems capable of monitoring the positions of vehicles even under the multipath transmission conditions as may exist in a city. In one such system each vehicle contains apparatus which, without being interrogated, repetitively transmits a uniquely coded spread-spectrum identification signal asynchronous to the repetitive identification signals transmitted by all other system vehicles. The signal from each vehicle is received at a plurality of antenna locations and supplied to a central station where it is pulse compressed by a matched filter set to provide information from which the identity of the vehicle can be determined. The received signals are additionally processed at the central station to determine relative differences in the time of arrival of the signals at each antenna in order to determine the vehicle''s position.

Synchronization and position location system

Abstract: A master station and N slave stations include synchronization equipment to enable each of the stations to have access to a common repeater in a different one of M time slots of a TDM format at the repeater, there being motion between the master and slave stations and the repeater. Each time slot is employed on a push-to-talk basis for N/M slave stations. The master station propagates a reference sync burst through the repeater. Each of the stations receive this master sync burst from the repeater. The master station adjusts the frequency of the timing signals therein to compensate for the doppler shift experienced in the propagation path from the master station to the repeater and each of the slave stations adjusts the frequency of the timing signals therein to compensate for the doppler shift experienced in the propagation path from each of the slave stations to the repeater so that the desired frequency of the timing signals is present at the repeater. The master station in response to the received master sync adjusts its timing signals so that the signals propagated therefrom arrive in the proper time slot of the TDM format at the repeater. Each of the slave stations propagate a different low power level, psuedo noise code ranging signal through the repeater to the master station. The phase information of this ranging signal is detected in the master station, coded, and transmitted to the appropriate one of the slave stations. This phase information is responded to in the appropriate slave station to adjust the phase of its timing signals so that data bursts of each of the slave stations appear in the proper time slot of the TDM format at the repeater. The ground station responds to the phase of the received master reference signal and the phase information of the ranging signal to provide a measure of the satellite-to-slave station range at the ground station. In a single satellite system, the altitude of the slave stations and the rate of change or range, obtained from measuring the doppler of the carrier signal received at the associated slave station and is transmitted to the ground station in slow speed data channels provided during the synchronizing interval of each of the data bursts. These two bits of information together with the satellite-to-slave station range enables the ground station to locate the position of a particular slave station. In a two satellite system, the equipment for determining the satellite-toslave station range is duplicated for cooperation with a second satellite so that the altitude of the slave station and the satellite-to-repeater range for both satellites enable the position location of a particular slave station at the ground station.

Ground proximity warning system utilizing radio and barometric altimeter combination

Abstract: A ground proximity warning system for an aircraft which produces a warning signal when the rate of descent of the aircraft exceeds a limiting value determined by the aircraft altitude. The rate of descent of the aircraft is calculated from a combination of measurements of the altitude of the aircraft above ground and the barometric altitude of the aircraft. A signal representing the rate of change of the altitude of the aircraft above ground is limited, to minimize false warnings as a result of surface irregularities. The barometric portion of the system is disabled during take-off run and the initial portion of the aircraft climb-out to avoid a false warning resulting from an increased barometric pressure condition during this maneuver. The limits on the aircraft altitude rate signal are modified in accordance with the flight mode of the aircraft, to reduce the sensitivity of the warning system during the final stage of a landing approach. The warning system provides an alarm to the pilot which is an audio tone modulated at a low frequency repetition rate. A soft warning is actuated when the sink rate of the aircraft exceeds a desired level for the altitude at which the aircraft is operating. If the aircraft is also below a limiting altitude, a hard warn signal is provided. The repetition rate of the warning signal, while in a soft warn condition, is a function of the difference between the altitude of the aircraft and the altitude at which the sink rate would be proper. A complementary filter with which the altitude rate signals are combined, includes an operational amplifier connected in an unloading amplifier configuration with a resistive circuit connecting one input signal with the amplifier and a capacitive circuit connecting the other input signal with the amplifier, the resistive and capacitive input circuits forming a low pass filter for the first signal and a high pass filter for the second signal.

Lightning channel reconstruction from thunder measurements

Abstract: The geometry of lightning channels can be reconstructed from thunder data obtained with an array of microphones. In this acoustic technique we divide a thunder record into a series of short contiguous time periods and, by using cross-correlation analysis, determine the direction of propagation of the predominant acoustic signal received during each of the time periods. If the atmospheric temperature and wind profiles are known, we can accurately trace the acoustic signals to their points of origin. The set of points generated in this manner from the complete thunder record delineate the geometry of the lightning channel. In application the accuracy of the channel reconstruction is limited by incomplete wind and temperature data; an example is given that reconstructs a lightning channel with an estimated error in the channel position of ≈10%. This technique is of particular value in investigating the nature of lightning channels inside clouds and in mapping the source regions supplying charge for lightning.

Vehicle command and control system

Abstract: A dual frequency ranging and communication system for communicating with and locating mobile vehicles in a multipath environment such as an urban center. This system functions in urban areas for both communication and ranging where line of sight radiation techniques may not properly function. A plurality of remote relay stations are located at points throughout the urban area, each station receiving and transmitting coded digital data and tone signals, the tone signals being used for phase ranging. Each of the vehicles is equipped with a transponder responsive only to the radio signal having a formatted message including the vehicle identification code with a ranging tone suitably impressed thereon. The formatted signal is transmitted from one of the relay stations at a first frequency and picked up by a preselected number of other relay stations as well as by the vehicle transponder. The vehicle transponder in turn generates a reply signal at a second frequency containing message data and a tone signal modulated on the second frequency for use in ranging, all of which signals are processed at a central location.

Frame synchronization system

Abstract: Frame synchronization for a binary data signal having a multiframe including N frames, each of the frames including M channels and a first sync signal, at least one of the channel signals including in each of the frames a different one of (N-1) subchannel signals and a second sync signal is accomplished by employing two sync signal detectors, one being responsive to the first sync signal and a first predetermined local timing signal therefor to provide a first control signal indicative of the phase relation between these two signals and the other being responsive to the second sync signal and a second predetermined local timing signal therefor to provide a second control signal indicative to the phase relation between these two signals. The two control signals are samples by two different sampling circuits. The outputs of the sampling circuits are applied to two different decision circuits whose outputs control the timing of two cascade connected digital counters and timing signal generators used to generate necessary timing signals including the two predetermined local timing signals. The first digital counter and generator is driven by a bit rate clock which is inhibited when the decision circuit associated therewith indicates an out-of-sync condition. The second digital counter and generator is driven by a frame rate clock from the first counter and generator which is inhibited when the decision circuit associated therewith indicates an out-of-sync condition. In one embodiment, the decision circuits are dual integrators each generating two signals to separately control the inhibiting when required. In another embodiment, the decision circuits are single integrators each producing one signal to control the inhibiting when required, the signal of the decision circuit associated with the second sync signal being connected in a cooperating manner with the signal of the decision circuit associated with the first sync signal to control the inhibiting of the bit rate clock.

Binary PSK Error Probabilities with Multiple Cochannel Interferences

Abstract: Exact error probabilities are given for a binary phase-shift-keyed (PSK) signal which is transmitted over a nondistorting channel, but additively corrupted by Gaussian noise and cochannel interference. Both coherent detection and quasicoherent (noisy reference) detection are considered. The analysis admits a wide class of interferences, but numerical results are limited to interferences modeled by a sum of randomly phased sinusoids. This includes most extraneous analog frequencymodulation (FM), phase-modulation (PM), or digital PSK signals, or combinations of the same which are cochannel with the desired PSK signal.

Fingerprint identification system and method

Abstract: The specification discloses a matrix sensing device for sensing the pattern of the skin of a finger for comparison with measurements previously obtained and stored in a storage device for identification purposes. The matrix sensing device comprises a plurality of electrical conductance sensing means located in rows and columns in a planar surface for contacting the skin of a finger. Selection means is provided for sequentially selecting each sensing means row by row for sequentially measuring the electrical conductance of the skin at a plurality of points in an orderly fashion. Initially, in a first cycle, the conductance is sequentially measured and an average value obtained. Subsequently, in a second cycle, each measurement obtained is compared to the average value. From the resulting measurements there is derived a signal image of the pattern of the skin of the finger for use for identification purposes.

Communication theory for the free-space optical channel

Abstract: The current understanding of quantum detectors, the noise mechanisms which limit (are basic to) their operation, and their application to optical communications (theory) is summarized. In this context, we are considering channels in which the electromagnetic field is not subjected to any propagation effects other than a geometric loss. (Such a channel would exist between satellites.) Consequently, we will concentrate on optimum time processing using the tools of statistical communication theory. Fundamental to the study of a detection process is the need to develop a good mathematical model to describe it [1]-[6]. Therefore, approximately one-fifth of the paper is devoted to establishing, in a semi-classical analysis, the quantum detector output electron number as a conditional Poisson process with the conditioning variable being the modulus of the electromagnetic field. Once this has been established, these results are used to derive various limiting probability densities related to actual practice. Although the mathematical details are omitted, these results will be presented from the viewpoint of orthogonal function expansions and interpreted in terms of an eigenspace. The resulting current flow is analyzed next as a shot noise process, and the power density spectrum is calculated. Attention is focused on isolating the signal components from the noise in terms of both the current probability density and the power density spectrum. Examples are given where appropriate. At this point, an understanding of the underlying noise processes will have been presented and attention will shift to analog and digital communications. The analog communication will be presented primarily in terms of the signal-to-noise ratio. The S/N ratio in direct detection will be presented both as a ratio of the integrals of two separate portions of the spectrum and as a ratio of two moments of the probability density describing the current. These calculations will be extended to include heterodyne detection. Digital communications will be discussed in the context of detection theory. It will be shown that the likelihood ratio is often a monotonic function of the random variable representing the number of electrons flowing. Hence optimum processing will consist of a weighted count of electrons from various counting modes. Digital design will be presented in terms of M-ary signaling, error probabilities, and information rates.

Forward scatter optical turbidimeter apparatus

Abstract: An optical turbidimeter including a light source for generating a ribbon-shaped light beam for transmission through a fluid process stream, a first light detector for measuring the intensity of the light beam after passage through the process stream, a second light detector responsive to light scattered in the forward direction by the direct beam, spatial filtering optics for focusing the scattered light only from a center section of the direct beam onto the second detector and electronic signal processing means responsive to the signals generated by the two detectors for developing an output signal proportional to the ratio of the scattered light to the transmitted light beam.

Statistically optimal stacking of seismic data

Abstract: A theory for weighting seismic records in the stacking process has been developed from a statistical seismic model. The model applies to common‐depth‐point seismic records which have been statically and dynamically corrected; the same model applies to an ordinary stacking procedure. The model stipulates for the signal and noise components, respectively, of a seismic record that (1) the signal is coincident with and similarly shaped to the signal on other records, and (2) the noise is statistically independent of that on any other record and of the signal and has zero mean value. In accord with the model, a seismic record is completely described for the purpose of weighting by its signal scale and its signal‐to‐noise energy ratio. Several statistical procedures for evaluating these parameters for seismic field data are presented. The most favorable procedure is demonstrated with both synthetic and field seismic records.

On-Line Real-Time Digital Computer Separation of Extracellular Neuroelectric Signals

Abstract: An on-line real-time spike recognition and separation system for up to six different spikes in multiple unit extracellular records has been developed using the Micro-LINC 300 computer. Assuming biphasic potentials, the computer extracts four unambiguous variables, two in amplitude and two in time. One variable of a selected pair is plotted against the other on the computer CRT. Points representing the same class of signal will fall into clusters. Cluster boundaries for spike separation are set visually by the investigator. Output is in the form of pulses on different relay lines. The system permits waveforms to overlap up to 15 percent. Examples of system performance with real signals are presented. A comparison is made with other spike recognition systems. A simple system is presented for generating artificial test signals and a technique described for testing any spike recognition system.

Charge coupled memory with storage sites

Abstract: The specification describes a variety of charge coupled memory devices most of which are "read-only" memories in which the charge capacity of selected sites is permanently or semipermanently fixed. If charge is accumulated in these sites to the equilibrium amount and then shifted to an output site, the signal will reflect the programmed capacity of the sites.

Vehicle driver-actuated safety signal light assembly

Abstract: A driver communication signal mounted against the front windshield of a motor vehicle, visible to pedestrians and oncoming traffic and automatically energized upon brake application to indicate driver''s intention to stop. The invention provides a double light source and driver-observed light source monitoring means as well as provision to ensure good visibility even on bright sunshine days.

TELEVISION A New Schlieren Light Valve for Television Projection

Abstract: A new television projection system is described. The heart of this light valve is a deformable reflective target consisting of a thin (~2000–6000 A)metal film supported in close proximity to a glass substrate. In operation a video-modulated electron beam scans the target and deforms the metal film analogously to the intensity of the video signal. These deformations control the amount of light from the schlieren projector that falls on the screen. The mechanical and electrical performance of the deformable targets and operation of a specially designed off-axis, reflective schlieren projector are discussed. Display results for the total system are presented.