Showing papers on "Signal published in 1981"

Interpolation and decimation of digital signals—A tutorial review

Abstract: The concepts of digital signal processing are playing an increasingly important role in the area of multirate signal processing, i.e. signal processing algorithms that involve more than one sampling rate. In this paper we present a tutorial overview of multirate digital signal processing as applied to systems for decimation and interpolation. We first discuss a theoretical model for such systems (based on the sampling theorem) and then show how various structures can be derived to provide efficient implementations of these systems. Design techniques for the linear-time-invariant components of these systems (the digital filter) are discussed, and finally the ideas behind multistage implementations for increased efficiency are presented.

Digital signal processing for sonar

Abstract: This paper is a tutorial which describes "main stream" sonar digital signal processing functions along with the associated implementation considerations. The attempt is to promote further cross-fertilization of ideas among digital signal processing applications in sonar, radar, speech, communications, seismology, and other related fields.

Television viewing center system

Abstract: At least two television reception tuners are used in a viewing center system, one for the television signals and the other for supplementary information transmitted during the blanking intervals and separated in the reception center by a data separation stage. A programmable control stage including a microprocessor accepts information not only from the data separator, but also from a manual remote control input device and from a timing control stage. A signal source switching unit for both the audio part and the composite video part of television signals is controlled by the microprocessor and interconnects signal sources including the tuners and auxiliary equipment, such as recording devices, a local camera, television games, and so on, with audio and video output devices. A digital data bus provides control to the various input and output devices.

An overview on the time delay estimate in active and passive systems for target localization

Abstract: Sonar and radar systems not only detect targets but also localize them. The process of localization involves bearing and range estimation. These objectives of bearing and range estimation can be accomplished actively or passively, depending on the situation. In active sonar or radar systems, a pulsed signal is transmitted to the target and the echo is received at the receiver. The range of the target is determined from the time delay obtained from the echo. In passive sonar systems, the target is detected from acoustic signals emitted by the target, and it is localized using time delays obtained from received signals at spacially separated points. Several authors have calculated the variance of the time delay estimate in the neighborhood of true time delays and have presented their results in terms of coherence function and signal and noise autospectra. Here we analyze these derivations and show that they are the same for the case of low signal-to-noise ratio (SNR). We also address a practical problem with a target-generated wide-band signal and present the Cramer-Rao lower bound on the variance of the time delay estimate as a function of commonly understood terms such as SNR, bandwidth, observation time, and center frequency of the band. The analysis shows that in the case of low SNR and when signal and noise autospectra are constants over the band or signal and noise autospectra fall off at the same rate, the minimum standard deviation of the time delay estimate varies inversely to the SNR, to the square root of the product of observation time and bandwidth, and to the center frequency (provided W^{2}/12 f\min{0}\max{2} \ll 1 , where W = bandwidth and f_{0} = center frequency of the band). The only difference in the case of a high SNR is that the standard deviation varies inversely to the square root of the SNR, and all other parameter relationships are the same. We also address the effects of different signal and noise autospectral slopes on the variance of the time delay estimate in passive localization.

Signal Delay in RC Tree Networks

Abstract: In MOS integrated circuits, signals may propagate between stages with fanout. The MOS interconnect may be modeled by an RC tree. Exact calculation of signal delay through such networks is difficult. However, upper and lower bounds for delay that are computationally simple are presented here. The results can be used (1) to bound the delay, given the signal threshold; or (2) to bound the signal voltage, given a delay time; or (3) to certify that a circuit is "fast enough", given both the maximum delay and the voltage threshold.

Solid-state image sensor with exposure controller

Abstract: A solid-state image sensor which detects the quantity of light incident on image sensor cells during exposure and performs exposure control in accordance with an exposure value thus obtained The solid-state image sensor is provided with a photoelectric converter having a plurality of non-destructive readout type image sensor cells arranged in a matrix form; an exposure detector for reading out stored information of predetermined ones of the image sensor cells during exposure, obtaining an added value of the stored information thus read out and detecting that the added value reaches a predetermined level; an exposure controller which is supplied with the detected signal from the exposure detector to control at least one of the charge storage time of each image sensor cell by an optical signal, the intensity of light incident on the image sensor cell and the photosensitivity of the image sensor cell; and a scanner for scanning the photoelectric converter to read out stored information of the image sensor cells during exposure

Apparatus and method for providing a logical exclusive OR/exclusive NOR function

Abstract: Circuits are illustrated using CMOS design techniques for incorporating N and P channel transistors into a circuit to obtain the functions of exclusive OR and exclusive NOR signal generation. This is accomplished by utilizing a given logic value signal as a control signal to pass the other input signal for three of the four possible logic value conditions. The fourth condition must generate the output signal from a selected one of the input signals, through the use of an inverter.

Satellite-based vehicle position determining system

Abstract: A system for determining the positions of a plurality of vehicles traveling on or above a defined sector of the earth's surface comprises a transponder carried by each vehicle for transmitting a uniquely coded beacon signal in response to a general interrogation signal, at least three repeater-carrying satellites at spaced orbital locations above the earth for receiving and retransmitting the beacon signals produced by the vehicles, and a ground station for periodically transmitting the general interrogation signal and for receiving and processing the beacon signals retransmitted by the three satellites in order to determine vehicle position. In order to avoid signal overlap and equipment saturation at the ground station, each vehicle transponder includes means responsive to the general interrogation signal for inhibiting the transmission of further beacon signals by the transponder for a predetermined time interval following the response of the transponder to the general interrogation signal. In a preferred embodiment of the invention, the inhibited interval of the vehicle transponders may be varied automatically in response to a command signal transmitted by the ground station.

The Correction of I and Q Errors in a Coherent Processor

Abstract: A method is presented for correcting the gain and phase imbalances and the bias errors of the in-phase and quadrature channels of a coherent signal processor [1] by means of coefficients which are derived from measurements of a test signal. The residual errors after correction depend upon the signal-to-noise ratio (S/N) of the test signal and the degree of filtering used in deriving the correction coefficients.

Battery operated access control card

Abstract: An access control card for use in an access control system. A battery, a wireless signal sensor such as an antenna for receiving coded wireless signals such as coded radio frequency signals generated by a card reader, a clock connected to the battery and including a receiver are connected to the antenna for supplying a received signal based upon the coded radio frequency signal. A memory for stores first and second stored codes, and a transmit circuit connected to the antenna, to the clock and to the memory compares the first stored code to the received signal and transmits the second stored code when there is a match between the received signal and the first stored code.

High impedance fault detection apparatus and method

Abstract: Apparatus is provided for detecting the presence of a high impedance arcing fault on an electrical circuit, particularly a high voltage power line. Detection of a high impedance fault is realized by monitoring the high frequency components of the alternating current in the circuit, and evaluating the high frequency components of each cycle of the alternating current using a microcomputer operating in accordance with a program of instructions, to determine the occurrence of a significant increase in magnitude of the high frequency components, and then to determine whether the increase exists for a prescribed period of time and follows a prescribed pattern. The high frequency components are monitored using a current-to-voltage transducer coupled to the electrical circuit, bandpass filters coupled to the transducer, and an analog-to-digital converter providing digitized samples of the filtered transducer output voltage signal.

System for overlaying a computer generated video signal on an NTSC video signal

Abstract: A system for overlaying a computer generated video signal on an NTSC video signal includes horizontal and vertical pulse processor circuits for generating a horizontal start signal and a vertical reset signal, respectively, in accordance with NTSC standards, and a clocking system for receiving the vertical reset signal and the horizontal start signal and for generating control signals to control the read out of video data from the video generator of a computer so that it is read out at an NTSC rate. The system further includes a video insert keyer circuit for combining the NTSC video signal and the computer generated video signal and for generating a composite video signal for transmission to a monitor or standard television.

Airborne radar jamming system

Abstract: A radar jamming signal generated by equipment carried by a target aircraft, is launched onto the leading end of a towed single wire transmission line so as to travel the length of the line as a nonradiating surface wave. A drogue radiator is attached to the trailing end of the line for radiating the jamming signal transversely of the towed line so as to be received by and cause jamming of tracking and/or fire control radar. The length of the single wire transmission line is selected so that the trailing radiator causes the jamming signal to emanate from a position sufficiently behind the aircraft so as to be outside the destructive radius of weapon fire directed at the apparent source of the jamming signal by fire control radar. A ventriloqual-like deception of the radar is thus achieved. A wave launcher couples the jamming signal to the leading end of the transmission line and for this purpose includes an electrically conducted horn-shaped structure, a tunable coaxial feed end at the constricted end of the horn structure, an inner transition conductor connecting the inner conductor of the coaxial feed to a leading end of the single wire transmission line, and a plurality of annular dielectric lenses and dielectric guides cooperatively shaped and fitted to the horn structure in a manner that effectively matches the bounded electromagnetic transmission wave characteristics of the coaxial feed cable with the surface wave transmission characteristics of the single wire transmission line. Coacting with the ventriloqual-like radiation of the jamming signal from the trailing end of the transmission line is an anti-integration network that hides the return radar signal reflected off the target aircraft in a signal energy “hole” created for such purpose in a secondary low level noise signal transmitted directly from the aircraft.

Driving simulator apparatus

Abstract: Apparatus for vehicle driving simulation including a cabin capable of being swivelled and having therewith a screen, control devices and the driver's seat, from where the road picture can be observed and controlled. The cabin is capable of being swivelled around an axis which is parallel to the viewing direction and above the center of gravity of the driver. The cabin is driven by a power drive dependent upon the signal of the centrifugal acceleration via a control amplifier and by use of a measuring device, a tipable back which is driven by a power drive dependent upon the acceleration signal via a control amplifier, elastic buffers which support the driver's seat and a vibrator which is intermittingly switched on dependent upon the rotation signal via a frequency divider and a control amplifier.

Acousto-optic signal processing: Convolution and correlation

Abstract: The use of acousto-optic devices in real-time signal convolution and correlation has increased dramatically during the past decade because of improvements in device characteristics and implementation techniques. Depending on the application, processing can be implemented via spatial or temporal integration. Two-dimensional signal processing (including image processing) is possile, in spite of the inherent one-dimensional nature of the acousto-optic device as a spatial light modulator.

Dual band communication receiver

Abstract: Diclosed is a dual band communication receiver for use in a burst communication sytem. The receiver is capable of esentially simultaneous reception at a first carrier frequency (L), such as L-band and a higher carrier frequency (H), such as S-band, using distinct codes and replying in the frequency band received. A typical system is composed of a transponder and an interrogator. The incoming coded signal is down converted to an i.f. frequency compatible with surface acoustic wave (SAW) convolvers. The i.f. signal is then divided between two SAW convolvers, each having a convolution interval of two times the message symbol length (2T). Reference signals A and B are composite signals comprised of alternate L-band and H-band signals, each having a time period equal to T and each L- or H-band signal operating at a 50% duty cycle. Reference signals A and B are time reversed to the input signals applied to the convolver and are orthogonal to one another. Each of the convolver outputs are processed through log video detection circuits to reduce the dynamic range followed by peak detecting and stretching to reduce the pulse bandwidth. The outputs from each peak detection and stretching circuitry are coupled to a smaple-and-hold circuit which are in turn divided such that one path is to synchronization and interrogation sidelobe suppression (also referred to as sidelobe inhibit, ISLI or control signal) matched filters designed to look for the particular symbol sequences between the two convolver channels characteristic of the preamble and ISLI signals. The synchronization signal and the sidelobe suppression signal are used in order to determine if a valid preamble has been detected by the receiver and if the receiver is in a desired portion of the interrogator radiation pattern; if so, then a timing or address signal and the remaining portion of the message which contains the data is clocked into a memory.

Remote lighting-control apparatus

Abstract: A main control device comprises a plurality of lighting-control signal generators for generating lighting-control signals whose contents can be analogously varied, and a keyboard for specifying the contents of mode signals corresponding to those of the lighting-control signals. The lighting-control signals are supplied to the terminal control devices through a signal line. Mode signals and address signals are supplied to the terminal control devices through the signal lines. A terminal control device selected by the address signal selects a lighting-control signal corresponding to a mode signal. The selected lighting-control signal controls the lighting of a lighting load by phase control.

Application of Kalman Filtering in Computer Relaying

Abstract: During the first cycle following a power system fault, a high speed computer relay has to make a decision usually based on the 60 Hz information, which is badly corrupted by noise The noise in this case is the nonfundamental frequency components in the transient current or voltage, as the case may be For research and development purposes of computer relaying techniques, the precise nature of the noise signal is required The autocorrelation function and variance of the noise signal was obtained based on the frequency of occurrence of the different types of faults, and the probability distribution of fault location A new technique for modelling the signal and the measurements is developed based on Kalman Filtering theory for the optimal estimation of the 60 Hz information The results indicate that the technique converges to the true 60 Hz quanitities faster than other algorithms that have been used The new technique also has the lowest computer burden among recently published algorithms and appears to be within the state of the art of current microcomputer technology

Amplitude modulation using digitally selected carrier amplifiers

Abstract: An amplitude modulator (10) is disclosed which generates an amplitude modulated carrier signal by selectively combining varying numbers of other carrier signals. A circuit (20) is included which provides plural carrier signals of like frequency and phase where the number of carrier signals being provided is dependent upon the level of an input signal. A combiner circuit (22) combines the plural carrier signals to thereby provide a combined signal which is the desired amplitude modulated carrier signal. In one embodiment (FIG. 3) the carrier signals which are combined are all equal in amplitude. In another embodiment (FIG. 4) the amplitudes of some of the carrier signals are weighted in a binary progression. In yet another embodiment (FIG. 9) the carrier signals are all frequency modulated whereby the output signal has both a varying frequency and amplitude.

Ripple detector for automotive alternator battery charging systems

Abstract: Detector (28) monitoring the voltage ripple in the rectified electrical output signal of an alternator (22) in a multiphase alternator battery charging system. A circuit monitors the undulating alternator output signal and produces a signal level in response. To correct the detector operation for various magnetic phenomena present in the alternator, a first circuit measures the rotational speed of the rotor and produces a proportional signal. A second circuit determines the excitation current supplied to the field coil. The measurement and determination are separately weighted and combined to form a corrected comparison threshold value. A variable threshold circuit combines the signal proportional to the rotational speed of the rotor and the determined field coil excitation current to produce a combined signal level. Comparison means compare the signal level from the monitored alternator output signal with the combined signal level and produce an output signal level indicative of the detection of a voltage ripple in excess of the combined signal level. The output signal is corrected for the effects of significant alternator performance characteristics.

Data record with pre-recorded transducer positioning signals, and system for utilizing same

Abstract: A recording member for digital data, particularly a recording tape, has a plurality of generally parallel, closely-spaced recording tracks which each contain pre-recorded track-identifying and transducer-positioning servo information, as well as defined data-recording areas. The pre-recorded track-identifying information preferably comprises a digitally-encoded individual track address, and the servo information comprises separate bursts used in centering the transducer upon a particular track. Preferably, each such track has a dedicated area at its beginning, end, or both, which contain continuous repetitions of such positioning information, there being no data areas in such dedicated portions. Digital encoding of track addresses utilizes binary-type code format, accomplished by defining a binary "zero" as a recorded burst present at a first number of sampling points, and defining a binary "one" as a burst present at a second number of sampling points of a second duration. The pre-recorded positioning information includes certain non-recorded "gaps" which serve as initializing signals, and the preferred system for utilizing the pre-recorded, servo-controlled record member utilizes peak-detection and minimum-threshold techniques to accurately distinguish unrecorded gaps from noise, or the like, on the one hand, and to distinguish coded signal bursts from other possible recorded signals, or noise, on the other hand. The preferred system is entirely self-clocking, i.e., the record member does not carry a recorded clock track, and thus does not require the additional transducer required where recorded clock tracks are used; at the same time, the area on the record member otherwise occupied by the clock track is available for data-recording usage.

Liquid jet recording device

Abstract: PURPOSE:To swiftly and easily render printing conditions most suitable by providing a discharge control means which furnishes a recording unit control means with an electric signal that can form a flying droplet and has energy larger than the one used for recording, and causes a liquid jet recording unit to preliminarily discharge a flying droplet. CONSTITUTION:The title device is provided with the following components: (a) a liquid jet recording unit 100 which has a discharge energy generating means 102 which, corresponding to an electric signal supplied, can produce a flying droplet through application of energy to liquid, and discharges the flying droplet produced to perform recording on a material P to be recorded; (b) a recording unit control means 110 which can set an electric signal, and corresponding to the input of a recording signal SA, furnishes the discharge energy generating means 102 with an electric signal to form a flying droplet; (c) a discharge control means 150 which has a setting means 152 which sets an electric signal for the recording unit control means 110, and furnishes the recording unit control means 110 with an electric signal which can form a flying droplet and has energy larger than the signal used for recording, and causes the liquid jet recording unit 100 to preliminarily discharge a flying droplet.

Collision avoiding system and protocol for a two path multiple access digital communications system

Abstract: With the advent of digital communications, it is common to transfer packets of information among a plurality of stations, e.g., digital computers. In order to control the transfer of the packets, various protocols have been introduced. However, the efficiency related to known multiples access digital communications system protocols tends to decrease as the digital signal rate increases. To overcome such problems, the instant communications system and protocol contemplate a communications loop having first and second oppositely directed signal paths. At least two stations are coupled to both the first and the second signal paths. A station includes an arrangement for writing a first signal on the first path and an arrangement for reading a second signal from the second path. In addition, the station includes an arrangement for reading a third signal from the first path. The third signal is coupled from the first path to the station by an arrangement which electrically precedes the arrangement for writing the first signal on the first path. If the station has a packet to transmit, it can overwrite a busy control field of the third signal packet on the first path. Having read the third signal on the first path, a logical interpretation may be made within the station as to whether the first path is busy or not busy. If the first path is not busy, the packet may be written on the first path by overwriting the third signal thereon. If the first path is busy, the station may overwrite a request control field of the third signal for indicating that the station was unable to transmit the packet. The packets flow around the loop and are monitored on the second path. Eventually all packets will be transmitted and the request control field may be detected at the receive side of a head station for indicating the event that all packets have been transmitted, in which event a new cycle may be started by initializing each station on the loop and by permitting each station to transmit.

Large-signal circuit model for simulation of injection-laser modulation dynamics

Abstract: A new large-signal circuit model of a heterojunction injection laser is presented. The model includes the current/voltage characteristics of the semiconductor heterojunction and the electro-optical dynamics of the active layer. It enables the laser and its electrical drive circuit to be analysed in a unified manner. The model can be easily implemented on general-purpose nonlinear circuit analysis programs, and does not require specialised laser analysis software. The model is illustrated with a number of simulated laser response characteristics.

Door operation control apparatus

Abstract: A motor for operating the door is controlled for forward and reverse rotations and stoppage by a control circuit responsive to an operation command signal, an upper-lower limit signal, an obstruction detection signal and a maximum drive time over signal, thus controlling the door stepwise for opening, stoppage, closing, stoppage and opening in that order. Upon generation of an obstruction detection signal or a maximum drive time over signal during the closing operation, the control circuit controls the motor in a manner to open the door for a certain period of time, and subsequently upon application of an operation command signal, the control circuit is set in a manner to open the door again.

Control system for reading device

Abstract: A plurality of image sensors cover overlapping regions and provide output signals which are selected during nonoverlapping times and combined into a synthetic video signal. The timing of all sensor selections except the first are keyed to the first so that adjustment of the first starting time can move the entire scanning interval.

Range finding device

Abstract: This invention presents a range finding device when 1st and 2nd detection images of an object are scanned by signal storing type image sensing means to obtain image scan signals, which are quantized by quantization means to produce quantized image data for said 1st and 2nd detection images. On the basis of the thus obtained quantized image data, the location within the 2nd detection images of one set of M successive elements of the 2nd detection image which is most similar to M successive elements of the 1st detection image is detected, and with the aid of the data of this location, the distance between the device and the object is determined. According to this improved device, sequence control means, which controls a series of operations for range finding, will firstly cancel the signals stored in said image sensing means as unnecessary signals, when said series of operations is initiated, and then enables proper storing of image signals in the image sensing means so as to properly control the device.