Showing papers on "Signal published in 1975"

Theory and application of digital signal processing

Abstract: sprightly style and is interesting from cover to cover. The comments, critiques, and summaries that accompany the chapters are very helpful in crystalizing the ideas and answering questions that may arise, particularly to the self-learner. The transparency in the presentation of the material in the book equips the reader to proceed quickly to a wealth of problems included at the end of each chapter. These problems ranging from elementary to research-level are very valuable in that a solid working knowledge of the invariant imbedding techniques is acquired as well as good insight in attacking problems in various applied areas. Furthermore, a useful selection of references is given at the end of each chapter. This book may not appeal to those mathematicians who are interested primarily in the sophistication of mathematical theory, because the authors have deliberately avoided all pseudo-sophistication in attaining transparency of exposition. Precisely for the same reason the majority of the intended readers who are applications-oriented and are eager to use the techniques quickly in their own fields will welcome and appreciate the efforts put into writing this book. From a purely mathematical point of view, some of the invariant imbedding results may be considered to be generalizations of the classical theory of first-order partial differential equations, and a part of the analysis of invariant imbedding is still at a somewhat heuristic stage despite successes in many computational applications. However, those who are concerned with mathematical rigor will find opportunities to explore the foundations of the invariant imbedding method. In conclusion, let me quote the following: "What is the best method to obtain the solution to a problem'? The answer is, any way that works." (Richard P. Feyman, Engineering and Science, March 1965, Vol. XXVIII, no. 6, p. 9.) In this well-written book, Bellman and Wing have indeed accomplished the task of introducing the simplicity of the invariant imbedding method to tackle various problems of interest to engineers, physicists, applied mathematicians, and numerical analysts.

Characterization of cyclostationary random signal processes

Abstract: Many communication and control systems employ signal formats that involve some form of periodic processing operation. Signals produced by samplers, scanners, multiplexors, and modulators are familiar examples. Often these signals are appropriately modeled by random processes that are cyclostationary (CS), i.e., processes with statistical parameters, such as mean and autocorrelation, that fluctuate periodically with time. In this paper we examine two methods for representing nonstationary processes that reveal the special properties possessed by CS processes. These representations are the harmonic series representation (HSR) and the translation series representation (TSR). We show that the HSR is particularly appropriate for characterizing the structural properties of CS processes and that the TSR provides natural models for many types of communication signal formats. The advantages gained by modeling signals as CS processes rather than stationary processes is illustrated by consideration of the optimum filtering problem. We present general solutions for filters that minimize mean-square error for continuous-waveform estimation, and we discuss several specific examples for the particular case of additive noise. These examples demonstrate improvement in performance over that of filter designs based on stationary models for the signal processes.

Apparatus for generating a nutating electromagnetic field

Abstract: A field (e.g., a magnetic field) which nutates about a pointing vector is used to both track or locate an object in addition to determining the relative orientation of this object. Apparatus for generating such a field includes mutually orthogonal coils and circuitry for supplying an unmodulated carrier, hereafter called DC signal, to one coil and an AC modulated carrier signal, hereafter called AC signal, to at least one (usually two) other coil, such that the maximum intensity vector of a magnetic field produced by the currents in the coils nutates about a mean axis called the pointing vector direction of the field.

System for visually determining position in space and/or orientation in space and apparatus employing same

Abstract: Visual system for determining position in space and/or orientation in three-dimensional space for purposes, for example, of directing or instructing an industrial robot to perform manipulative acts and apparatus employing the visual system. The system includes a portable object arbitrarily movable in three-dimensional space and possessing the discernible properties of position in space and/or orientation in space. One or more sensors extract visual information or image data from the portable object and convert the same to an electric signal or signals. A computer is connected to receive the signal or signals which are analyzed and, in the case of the industrial robot, the information obtained is used to prepare operating instructions.

Linear estimation of nonstationary signals

Abstract: The efficacy of linear prediction for speech analysis depends upon the degree to which the speech signal is stationary within an analysis interval. For this reason the speech signal is usually divided into small intervals during each of which the signal is assumed to be stationary. The formulation described in this paper is aimed at accomodating the nonstationarity more automatically by allowing the linear estimate of the speech signal to be time varying.Subject Classification: 70.40, 70.65.

Photoacoustic Effect with Solids: A Theoretical Treatment

Abstract: Chopped light impinging on a solid sample in an enclosed cell produces an acoustic signal within the cell. A derivation for the acoustic pressure supports the experimental observation that optical ...

Distribution network power line communication system

Abstract: A distribution network power line communication system which includes coupling means for applying a carrier current communication signal to the polyphase primary distribution conductors with a proportional relationship between the signal voltages applied to the various conductors selected to provide a predetermined propagation mode. Impedance elements are connected between the conductors at selected points remote from the coupling point, such as at the location of unbalanced loads, line taps, branches, capacitor banks, distribution transformers, and other line discontinuities which may cause mode conversion. The impedance elements are selected and connected to re-establish the predetermined propagation mode.

Angular position sensing and control system, apparatus and method

Abstract: A structural body is monitored in angular position about at least one axis by utilizing a level sensor and a sensor responsive to angular motion of the body about the axis being monitored. An output indicative of long term angular variations of the body about the axis is provided by the level sensor and short term angular variations are indicated by the output from the sensor responsive to angular motion about the axis. The signals indicative of long term and short term angular variations are combined to provide a broad band output signal indicative of angular position which is immune to high frequency translational variations appearing at the level sensor output, but which is responsive to high frequency angular inputs. The fast response angular sensor output is compared with the slow response level sensor output and an error signal is produced which drives the angular sensor output signal into coincidence with the level sensor output signal. The combined broad band angular output indication may be utilized for angular position monitoring for controlling one part of a machine relative to a predetermined external angular position reference for driving a stable platform to assume a predetermined angle about the axis.

Spread spectrum demodulator

Abstract: Demodulation of a wideband spread spectrum four-phase PSK (phase shift keyed) modulated carrier signal is accomplished by means of a correlator which phase shifts the modulated carrier signal as a function of a locally generated PN (pseudo-noise) sequence to provide a narrow band two-phase PSK modulated carrier signal. The two-phase modulated signal is fed to a matched filter wherein undesired signal components are removed so as to provide an IF (intermediate frequency) signal. A carrier recovery phaselock loop demodulates the two-phase modulated IF signal to provide a baseband signal. A timing recovery loop operates upon the baseband signal to provide timing signals for the locally generated PN sequence to synchronize the local PN sequence with the modulated carrier sequence. A bit timing loop and a sample and hold means operate upon the baseband signal to detect the modulating data to provide an output signal which is a function of the modulating data.

Spread spectrum correlation receiver

Abstract: A spread spectrum communication system having a correlation receiver for decoding an information signal transmitted on a pseudo-noise (PN) carrier. The receiver synchronizes to the transmitted signal by performing a continuous sequence of correlations until a correlation output exceeding a predetermined threshold level is detected. Thereafter, the receiver performs a plurality of correlations during a sampling interval which is timed to occur at approximately the time when high subsequent correlation output signals are likely to appear. After enhancement through adaptive filter processing, the correlation outputs generated during each sampling interval are accumulated (integrated and the summed output present at the end of the sampling interval is representative of the transmitted data message (a binary bit). The adaptive filter develops and stores weighting values representing the expected signal strength of the correlation outputs and the actual correlation outputs are multiplied by the weighting values. Received signal energy representing atmospheric and specular multipath signal components are detected and channeled to the accumulator along with the main signal component. The accumulator thus realigns the multipath signals with the main signal, resulting in a significant increase in processing gain. An audio version of the system is also disclosed.

Distribution network power line communication system including addressable interrogation and response repeater

Abstract: A distribution network power line communication system which is divided into addressable communication zones defined by repeaters located at the distribution transformers of the distribution network. Each repeater, when uniquely addressed by an interrogation signal from an interrogating source, strips its address from the interrogation signal and sends the resulting modified interrogation signal to its associated remote communication terminals, by-passing the associated distribution transformer. A timely, error-free response signal from a remote communication terminal is modified by a repeater to include the repeater address, and the modified response signal is sent back to the interrogating source. The binary base band interrogation and response signal information is preferably pulse width modulated to provide a self clocking format, and this self clocking signal is passed through two stages of frequency modulation to provide a signal which makes the receivers thereof substantially immune from drift.

Plural receiving and recording television system

Abstract: A combination of a television receiver and a television signal recording and/or reproducing apparatus, such as a so-called video tape recorder, forming a television system for receiving, recording and/or reproducing television signals and displaying images thereof, wherein the television receiver portion contains two separate signal selecting and receiving circuitries each including a separately tunable tuner, an intermediate frequency stage and a detector stage, and specific television signals received by the respective circuitries are selectively applied by selecting switches in the television receiver portion to the display stage of the portion of the television receiver for display of images or to the portion of the signal recording and/or reproducing apparatus for recording

Distribution network powerline carrier communication system

Abstract: A distribution powerline carrier communication system for providing distribution automation functions. The communication system includes a distribution powerline, with inductive couplers and frequency translating repeaters cooperating to circumvent signal obstructions, such as distribution transformers, and to increase the signal strength. The inductive couplers pick up the communication signals without metallic contact to the primary distribution lines, and the repeaters change the frequency band of the communication signals, enabling the amplifier gain of the repeaters to be selected without limitation due to undesirable feedback and oscillation.

Sound system engineering

Abstract: 1. Mathematics for Audio Systems 2. Using the decibel 3. Interfacing Electrical and Acoustical Systems 4. Loudspeaker Directivity and Coverage 5. The Acoustic Environment 6. Audio and Acoustic Measurements 7. Large Room Acoustics 8. Small Room Acoustics 9. Designing for Acoustic Gain 10. Designing for Speech Intelligibility 11. Microphones 12. Loudspeakers and Loudspeaker Arrays 13. Signal Delay and Signal Synchronization 14. Signal Processing 15. Sound System Equalization 16. Putting it all together and keeping it all together Appendix 1 Symbols and Abbreviations Appendix 11 Wiring Practices

Seismic signal processing

Abstract: Seismic prospecting for oil and gas has undergone a digital revolution during the past decade. Most stages of the exploration process have been affected: the acquisition of data, the reduction of this data in preparation for signal processing, the design of digital filters to detect primary echoes (reflections) from buried interfaces, and the development of technology to extract from these detected signals information on the geometry and physical properties of the subsurface. The seismic reflection is genenlly weak, and it must be strengthened by the use of signal summing (stacking) procedures. The determination of depths to a target horizon requires knowledge of the propagational velocities of seismic stress waves, and a wealth of technology has evolved for this purpose. More recently, it has been possible to relate signal amplitude to the physical properties of the medium traversed and, in particular, to make inferences about the oil and gas content of the buried rocks. Much of the exploration effort occurs in offshore areas, where reverberations in the water layer mask reflections from below. The method of predictive deconvolution has been most effective in its ability to attenuate these reverberations, making it possible to detect reflections from structures at depth. Seismic signal processing is neither pure science nor pure art, and offers a continuing challenge to the practitioners of both cultures.

Signal processor method and apparatus

Abstract: Method and apparatus for processing input binary encoded analog signals to precisely determine the time occurrence of positive-going and negative-going transitions. Such digital signals result, for example, when bar codes (e.g. Universal Product Codes) are optically scanned. Transitions are determined by detecting the zero crossings, at selected gating times, of the second derivative of the input signals. The selected gating times occur whenever the first derivatives of the input signals exceed a threshold level. The threshold level is determined in one embodiment by peak-to-peak detecting the input signals and adding this value to a rectified noise measurement signal.

The complex envelope in seismic signal analysis

Abstract: Some practical implications of the complex envelope representation of seismic signals are presented. Beginning with a look at an artificially constructed signal and proceeding to seismic records, it is seen that the complex envelope is more amenable to visual interpretation than the real signal itself. This is attributed to the natural separation of amplitude information from angle information afforded by the complex representation, and examples of arrival time measurement and P -coda correlation suggest that this leads to concrete seismological benefits. On this basis, it is suggested that the complex envelope may be a useful tool in seismic signal analysis.

Apparatus and method for transmitting binary-coded information

Abstract: An apparatus is disclosed for transmitting binary-coded information over a fiber-optic link which provides a link monitor to indicate whether the fiber-optic link is intact and operating. The binary-coded information is translated into a pulse-coded signal which provides a positive pulse for a positive-going transition in the binary signal and a negative pulse for a negative-going transition in the binary signal. In addition, a refresh pulse of the same polarity as the preceding pulse is provided whenever there has been no pulse for a predetermined amount of time.

Noise cancellation apparatus

Abstract: An array of independent sound cancellation units is arranged over a vibrating noise generating surface. Each unit includes an arrangement of acoustic transducers (sensors) positioned adjacent the surface to obtain an electrical average of the local acoustic noise generated by a predetermined zone of the surface. The summed average is changed in phase and gain by an active filter whose output drives an acoustic projector also positioned adjacent the surface and the acoustic output of which sums with the original noise signal in the acoustic far field, thus tending to cancel the noise. In essence, each vibrating surface zone and its associated sound cancellation unit tend to form an acoustic doublet. A signal indicative of the projector output is used as a feedback signal, with appropriate time delays, to cancel the effect of the projected output signal being picked up by the unit's transducers, and to cancel the effect of the output of other projectors of the array.

Cash dispensing system

Abstract: A cash dispensing system having a central computer and associated memory for maintaining customer account records, a plurality of remote transaction terminals and a communication path connecting the remote terminals with the computer. Each of the remote terminals includes a signal generator for generating data representative of a desired transaction in response to a customer-initiated operation, and for transferring that data to the computer via the communication path. The computer includes means responsive to the transaction data to generate a customer information file (CIF) signal and to transfer that signal to the remote terminal. The CIF signal is representative of a predetermined number associated with the customer. Each remote terminal includes a cash dispensing apparatus which includes a personal identification number (PIN) signal generator, a security device, a PIN signal transfer means, a CIF signal receiving means, and a cash dispenser. The PIN signal generator provides a PIN signal in response to a manual operation performed by a customer, with the PIN signal being representative of a predetermined number associated with the customer and bearing a predetermined relationship to the CIF signal. The security device includes the comparator for generating a DISPENSE signal when an applied PIN and CIF signal bear the predetermined relationship. The PIN signal transfer means provides a direct signal path for the PIN signal from the PIN signal generator to the security device. The CIF signal receiving means provides a means for receiving a CIF signal from the computer by way of the communication path and for transferring that received signal to the security device. The cash dispenser includes a cash storage portion and a dispensing mechanism for dispensing one or more units of the stored cash in response to applied DISPENSE signals.

Ultrasonic imaging method and apparatus

Abstract: The ultrasonic imaging method and apparatus comprises an ultrasonic wave transducer supplied with recurrent multifrequency energy pulses for pulse insonification of an object under investigation with ultrasonic waves. Resultant echo waves from the object are directed onto the transducer for converting the same to electrical signals which are supplied to a signal processor which includes a variable bandpass filter. One or more of the filter characteristics are varied as a function of depth from which the echo signals are returned for enhanced resolution and signal-to-noise ratio of the received signal. Preferably, the filter is matched to the noise and signal spectra of the system. For A scan and B scan operations wherein reverberated acoustic pulses are derived from a range of depths a time variable filter is employed for time varying operation thereof.

Current carrier communication system

Abstract: A current carrier communication system for selectively transmitting binary electrical signals from a first location to a second location over the AC power lines in a AC power distribution network in a building comprising a first tone generating means operatively connected to a first source of binary electrical signals for generating a first tone signal at a first frequency, a second tone generating means operatively connected to a second source of binary electrical signals for generating a second tone signal at a second frequency, linear tone summing means operatively connected to the first and second tone generating means for generating a modulating signal output that is a linear sum of the first and second tone signals, a source of RF signals connected to said linear tone summing means to produce a modulated RF output signal modulated by the modulating signal output of the linear tone summing means to the AC power lines, receiver coupling means at said second location directly coupled to receive said modulated RF output signal therefrom, a TRF multi-stage receiver connected for receiving the modulated RF output signal from the AC power lines and producing an amplified modulated RF output signal corresponding to the received modulated RF output signal, demodulation means operatively connected to the TRF receiver for demodulating the received signal, a first phase locked loop detector connected to the demodulation means for detecting the presence of the first tone in the demodulated signal and a second phase locked loop detector connected to the demodulation means for detecting the presence of the second tone in the demodulated signal.

Bidirectional communication system for electrical power networks

Abstract: An arrangement of communication components to provide communications between a central control center and various customer load locations in an electrical power distribution system. Control or interrogation signals are originated at the control center and transmitted over a suitable facility, such as a telephone line, to an FM broadcast station. The control signals frequency modulate an ultrasonic subcarrier which modulates the FM broadcast transmitter simultaneously with the normal broadcast program material. Radio receivers at the customer load locations receive, filter, and decode the broadcast signals which are used to activate the control or logic circuits associated with the customer location. A reply signal is generated at the customer location and applied to the power lines by carrier techniques. The power line carrier reply signal is remotely detected by a suitable receiver and transferred over a suitable wire line facility which terminates at the control center.

Noise reduction circuit

Abstract: A noise reduction circuit for uncompressed and randomly compressed audio signals comprises a variable gain stage providing a gain which varies with the magnitude of a DC control signal fed to a control terminal thereby, an AC to DC converter for generating a DC signal proportional to the amplitude of the AC signal fed thereto and a filter for passing middle and upper frequencies and for eliminating or substantially reducing the low frequencies fed thereto and coupled between the audio signal input and the input to said AC to DC converter.

Linear amplification using nonlinear devices and inverse sine phase modulation

Abstract: A linear amplification providing a replica of an input signal having amplitude variations is accomplished at frequencies and power levels for which linear gain elements are not available. Linear amplification is provided by separating an original bandpass input signal into two components, one of which is a constant amplitude sinusoidal component and the other of which is a low-pass envelope signal. The envelope signal is processed to produce both an inverse sine, phase modulated signal and the complex conjugate of the modulated signal. The phase variations of the modulated signal and of its complex conjugate are proportional to the inverse sine of the envelope. The modulated signal and its complex conjugate are each separately mixed with the constant amplitude sinusoidal signal to produce two constant amplitude signals which are filtered and amplified by either linear or nonlinear devices. The amplified filtered resultants are combined to produce a linearly amplified replica of the original bandpass input signal.

Method for controlling power during electrosurgery

Abstract: A control circuit forelectrosurgical units establishes a particular output signal to patient electrodes in response to condition of the patient electrodes. The duty cycle of the output signal is reduced when the patient electrodes are not in contact with the patient so as to prevent unwanted cutting and the duty cycle is increased when both patient electrodes are in contact with the patient so as to maximize the coagulation effect. The invention includes method of adjusting coagulation power by varying the duty cycle and not the amplitude of the output signal.

Cardiac monitor wristwatch

Abstract: A cardiac monitoring system easily incorporated into existing electronic digital wristwatches. The self-contained unit monitors the arterial pulse rate by means of a pair of highly directional ultrasonic transducers positioned in a special mounting in the wrist band of the watch. This special mounting also includes an integrated circuit which contains the transmitter and receiver-detector electronics for connection to the transducers. The output signal from the receiver in the special mount is fed via a shielded cable in the wrist band to the processing electronics physically located within the face mounting of the watch. The processing electronics monitors the user's pulse rate and provides a digital output indication thereof if it exceeds pre-established upper and lower threshold limits. The processing circuitry also includes means for detecting an erratic heartbeat, such as a missing pulse or other irregularities, and provides an output alarm indication, both audio and visual, when such is detected. The unit is entirely self-contained and utilizes the wristwatch's standard battery power supply. External select switches are preferably provided for selection of either a time or pulse rate readout.

Homodyne communication system

Abstract: A homodyne communication system comprising an interrogating unit and a plurality of responsive remote units wherein a continuous wave RF signal is transmitted from the interrogating unit to illuminate a remote unit. The remote unit causes a return (reply) signal to be transmitted or reflected back to the interrogating unit. A sample of the transmitted (interrogation) signal is mixed with the return signal. Amplitude nulls in the mixer output signal at given relative phase relationships between interrogation and reply signals, are substantially eliminated by selectively shifting the relative phase of the signals. Also disclosed are a homodyne communication system utilizing phase modulation to impress FSK signaling on the reply signal and an automatic vehicle location system utilizing the present invention.