Patents Examined by M. Huseman
  • Patent number: 4654863
    Abstract: Superior performance, better tracking, and stability of an adaptive predictor are realized by employing a so-called high order (eighth) prediction filter and by updating the filter coefficients in accordance with an algorithm based on the sign of a reconstructed signal sample (s.sub.q (k)) multiplied by a quantized version (e.sub.q (k)) of a differential error signal normalized by an expected magnitude of the reconstructed signal sample.
    Type: Grant
    Filed: May 23, 1985
    Date of Patent: March 31, 1987
    Assignee: AT&T Bell Laboratories
    Inventors: William R. Belfield, Raymond S. Medaugh
  • Patent number: 4653044
    Abstract: A communicating method for a data communications apparatus capable of transmitting data in a full-duplex mode over a two-wire circuit. Prior to the transmission of data, a transmit and a receive terminals exchange training signals to test circuit conditions in order to see if full-duplex communication therebetween is allowable. Depending upon the result of the test, either a full-duplex mode or a semiduplex mode is set up for data communication.
    Type: Grant
    Filed: April 26, 1985
    Date of Patent: March 24, 1987
    Assignee: Ricoh Company, Ltd.
    Inventor: Shozo Kudo
  • Patent number: 4653075
    Abstract: A bit synchronizer for a BPSK input signal having a sinusoidal carrier frequency f that is much greater than the modulating signal bit rate. The synchronizer comprises means (29, 31) for repetitively sampling the amplitude of the input signal over a preselected sampling interval portion of each modulating signal bit period (T). For each sampling interval, three numbers are recorded: N1, the total number of samples; N2, the number of samples that do not change sign with respect to a reference sample; and N3, the number of samples that do change sign with respect to the reference sample. When the number of samples not changing sign exceeds a preselected threshold value, which takes into account noise corruption of the input signal, bit synchronization is declared, a synchronized output clock (39) is generated, and digital data having a 180.degree. ambiguity is sent to subsequent ambiguity resolution means.
    Type: Grant
    Filed: March 29, 1985
    Date of Patent: March 24, 1987
    Assignee: Ford Aerospace & Communications Corp.
    Inventor: Jacob H. Wisniewski
  • Patent number: 4653114
    Abstract: The output signal level of a data node connected with a headend for use in a two-way cable communication network is monitored and adjusted at the node so that the signals received at the headend from all of the nodes in the network are substantially at the same level. The node terminal signal, which includes information identifying the address of the node, is initially transmitted from the node at a minimum level and is thereafter incrementally increased until a correct return signal is detected at the node, thereby indicating that the signal transmitted from that node is at a sufficient level to achieve the desired signal level equalization at the headend.
    Type: Grant
    Filed: June 21, 1984
    Date of Patent: March 24, 1987
    Assignee: General Instrument Corporation
    Inventor: Michael J. Berman
  • Patent number: 4653076
    Abstract: A direct sequence spread spectrum transmitter and receiver can be synchronized when the timing reference frequency is less than or equal to the data sampling rate and the ratio of the data sampling rate to the timing reference is an integer by combining two, four or eight consecutive data samples to yield one data sample point. By combining these data samples, an optimum data sample point may be determined while receiving an alternating sign preamble by comparing the magnitudes of all possible summations and selecting the sample which gives a maximum output. If each sample is assigned to its own synchronization point, then synchronization may be accomplished by locking to the time that gives the maximum output.
    Type: Grant
    Filed: March 23, 1984
    Date of Patent: March 24, 1987
    Assignee: Sangamo Weston, Inc.
    Inventors: John W. Jerrim, Lawrence B. Horwitz
  • Patent number: 4651330
    Abstract: The node of a point to multipoint data telecommunications system needs a receive clock to regenerate the data. The conventional method of regenerating the clock from received signals is difficult because there are gaps when no outstation is active. The invention reduces these problems by synchronizing the receive clock with the master send clock when there is no reception.
    Type: Grant
    Filed: September 5, 1984
    Date of Patent: March 17, 1987
    Assignee: British Telecommunications public limited company
    Inventor: John W. Ballance
  • Patent number: 4648101
    Abstract: The decoding circuit of the invention comprises essentially a digital filter 16, a pulse-width recognition circuit 17 a pulse peak amplitude selection circuit 23 and a circuit for decoding MLS boosted scanning pulse pairs 32 to 38. This decoding circuit makes it possible to eliminate parasite pulses from a clutter source whose width is incorrect when compared to the width of useful pulses and also to eliminate pulse pairs that have the right width but do not have the right interval.
    Type: Grant
    Filed: March 11, 1985
    Date of Patent: March 3, 1987
    Assignee: LMT Radio Professionnelle
    Inventors: Salim Hamzaoui, Michel Schilliger
  • Patent number: 4648100
    Abstract: A carrier recovery circuit which phase aligns receiver-generated, quadrature-related carrier signals to incoming modulated, quadrature-related carrier signals is disclosed. The amplitudes of these modulated carriers determine data points in a signal-space diagram. In the carrier recovery circuit, the amplitude of each of said modulated carrier signals is sensed relative to thresholds which pass through the outermost data points in the signal-space diagram. These outermost data points form a periphery when interconnected by straight lines which encompass all of the data points. A phase error signal is generated which maintains phase alignment of the receiver-generated carriers to the incoming carriers when the sensed amplitudes fall in selected regions of the signal-space diagram lying outside of the aforementioned periphery.
    Type: Grant
    Filed: March 28, 1985
    Date of Patent: March 3, 1987
    Assignee: AT&T Bell Laboratories
    Inventor: John Mardirosian
  • Patent number: 4646329
    Abstract: A frame alignment word has N predetermined bits distributed in the frame of a digital transmission signal. Each frame is divided into a number of sectors. Each sector has a heading made up of a bit or a bit group from the alignment word such that when placed end to end the headings in the frame form the alignment word. According to a frame alignment recovery method, bit groups are successively taken from the digital signal received at the sector frequency, each taken group having a maximum bit number equal to the bit number in each heading. The taken bit groups are compared with the heading bits corresponding in the frame alignment word and N-1 circular permutations thereof. The comparison are halted before reaching the full alignment word once the comparison of bits between the heading bits and taken successive groups reveals some disagreement.
    Type: Grant
    Filed: April 22, 1985
    Date of Patent: February 24, 1987
    Inventor: Alain Bojarski
  • Patent number: 4644523
    Abstract: A plurality of transmitters synchronized to a common clock each transmit a data signal spread by a common bipolar pseudo-random code having a different assigned code sequence shift. A receiver, synchronized to the clock, discriminates the signal transmitted by a predetermined transmitter from signals transmitted by the others by generating a first pseudo-random code that is a replica of the common bipolar pseudo-random code and has a code sequence shift corresponding to that of the predetermined transmitter, and a second bipolar pseudo-random code that is a replica of the common bipolar pseudo-random code and has an unassigned code sequence shift. The difference between the first and second bipolar pseudo-random code sequences, which is a trinary code sequence, is cross-correlated with the incoming signal. The cross-correlation despreads only the signal having the predetermined code sequence shift.
    Type: Grant
    Filed: March 23, 1984
    Date of Patent: February 17, 1987
    Assignee: Sangamo Weston, Inc.
    Inventor: Lawrence B. Horwitz
  • Patent number: 4644526
    Abstract: A full duplex frequency division multiplex communication system which comprises a number of transceivers constituting user stations which communicate with one another over a common channel, such as a wireless link or a two-direction coaxial cable, with each transceiver operating on a single fixed intermediate frequency for transmission and reception. The system includes a network frequency converter for shifting the transmission frequency band used by the transceivers into a different receiving frequency band which does not overlap the transmission frequency band. Single sideband modulation of the intermediate frequency carrier is used, and full duplex communication is achieved by using one of the sidebands of the intermediate frequency carrier for transmission, and the other sideband for reception. Each transceiver includes a programmable frequency synthesizer for channel selection, and upper and lower sideband filters, with one of the filters being used for transmission and the other for reception.
    Type: Grant
    Filed: November 13, 1984
    Date of Patent: February 17, 1987
    Inventor: Chialin Wu
  • Patent number: 4644568
    Abstract: An arrangement for selectively connecting a first or a second frequency synchronous timing signal to an outgoing conductor is disclosed. When a transition from the first to the second timing signal occurs, the first timing signal is inhibited from being transmitting on the outgoing conductor and the logical AND of the second timing signal and a delayed version of the second timing signal is transmitted on the outgoing conductor for approximately one period of the timing signals. Thereafter, the second clock signal is transmitted on the outgoing conductor. Arrangements are also disclosed for switching from the second timing signal to the first timing signal.
    Type: Grant
    Filed: March 28, 1985
    Date of Patent: February 17, 1987
    Assignee: AT&T Bell Laboratories
    Inventors: Ronald J. Canniff, Mike A. Derrenberger
  • Patent number: 4644524
    Abstract: A communication system for simultaneous exchange of signals between first and second stations in which a timing signal of low frequency alternately switches a first station between receive and transmit with equal time periods and simultaneously switches a second station between transmit and receive with the same time periods. During a receive period, signals for transmission are delayed until the next transmit period. During the transmit period, the delay signal is combined with the signal occupying the transmit period. The combined signal along with the timing signal is transmitted by the first station to the second station, after which the first radio station switches to receive under control of the timing signal. The second station under the control of the same timing signal now transmits a similar combined signal which is received by the first station for processing.
    Type: Grant
    Filed: January 22, 1985
    Date of Patent: February 17, 1987
    Inventor: David L. Emery
  • Patent number: 4641327
    Abstract: Frame synchronization is accomplished in a trellis-coded communication system by causing the sequence of signal points that results when the receiver incorrectly determines the start of each frame to be an impermissible sequence, and detecting the existence of the impermissible sequence by monitoring the rate of occurrence of non-zero difference between the minimum branch metric and the minimum path metric of a maximum likelihood decoding algorithm, such as the Viterbi decoding algorithm. In another aspect, an interleaver and a deinterleaver are used to assure that impermissible sequences result when frame synchronization is lost.
    Type: Grant
    Filed: July 9, 1985
    Date of Patent: February 3, 1987
    Assignee: Codex Corporation
    Inventor: Lee-Fang Wei
  • Patent number: 4641325
    Abstract: Method and apparatus are disclosed for providing a local oscillator signal which is in phase and frequency synchronism with a carrier signal wherein the frequency of the carrier is a constant multiple of the frequency of a reference waveform. A phase detector detects the phase of the local oscillator relative to the carrier and provides a signal to a microprocessor indicative of this phase. The microprocessor provides the local oscillator and responds to a reference waveform threshold detector to determine the number of local oscillator pulses provided during one cycle of the reference and to maintain this number to equal the constant multiple. The microprocessor further responds to the phase detector to adjust the phase of the local oscillator and thereby maintain phase synchronism with the carrier.
    Type: Grant
    Filed: February 4, 1985
    Date of Patent: February 3, 1987
    Assignee: General Electric Company
    Inventor: William C. Hughes
  • Patent number: 4641324
    Abstract: A closed loop circuit corrects digital data baseline shift resulting from perturbing interferences. Samples of the signal amplitude are stored at each clock time; and a correction signal is derived from the stored information. The correction signal is subtracted from the data signal to produce a resultant signal that is devoid of baseline shift, such resultant signal being also used to control clock regeneration in a phase locked loop.
    Type: Grant
    Filed: September 14, 1984
    Date of Patent: February 3, 1987
    Assignee: Eastman Kodak Company
    Inventors: Herbert Karsh, Ward M. Calaway
  • Patent number: 4638473
    Abstract: A two-wire bidirectional transmission system for transmitting electrical signals simultaneously in opposite directions between terminals over a pair of wires wherein the transmitter at one terminal transmits a voltage signal over one of said wires while the transmitter at the second terminal generates a voltage signal over the same wire, the second wire being grounded at each end. Impedance matching resistors, that is resistors matched to the impedance of the two wires, are coupled between each of the transmitters and the wire upon which the voltage signal is generated. A subtractor circuit is provided at each of the terminals for linearly subtracting a signal proportional to one-half of the voltage transmitted and thereby receiving at each terminal a voltage signal equal to one-half of the voltage transmitted by the opposite terminal.
    Type: Grant
    Filed: December 28, 1984
    Date of Patent: January 20, 1987
    Assignee: GTE Laboratories Incorporated
    Inventors: Michael Cooperman, Richard W. Sieber
  • Patent number: 4637037
    Abstract: The illustrated receiver 6, in flip-flops 16A-D, stores four sequential samples of a biphase-L signal A1 and shifts the samples into four shift registers 24A-D. The sampled signals are clocked through their respective shift registers 24A-D by selected phases of multiphase clock .phi..sub.1, .phi..sub.2, .phi..sub.3, .phi..sub.4. Thus, each set of four samples is stationary at some location in their respective shift registers for the same clock cycle. A decoder section 10 responds to a transition between adjacent signal levels at the output of the shift registers 24A-D and to a previously sampled signal level A44. The decoder section 10 generates a control signal A32-D32 indicating the detection of a mid-bit biphase-L signal transition. A second storage means responds to the control signal A32-D32 and stores a shift register 24A-D signal level A19, B20-D20 which occurred subsequent to the detected mid-cell transition.
    Type: Grant
    Filed: August 29, 1984
    Date of Patent: January 13, 1987
    Assignee: AT&T Teletype Corporation
    Inventor: Philip Chao
  • Patent number: 4637064
    Abstract: A global network equalization system for equalizing all modem receivers and modem transmitters connected to a local area network. A calibration signal is injected over the local area network from a reference or common point and received by each of the receivers. A parameter of the received signal (e.g. amplitude, power, or spectral density) is compared to a reference value and the gain of the receiver is adjusted in response thereto. When each of the receivers has been equalized, each transmitter and the associated receiver is tuned to a common vacant frequency. The transmitter transmits a signal that is then received by the associated receiver via the reference point. The received signal is compared to another reference value and the transmitter gain is adjusted in response thereto. In this way each transmitter and each receiver is equalized to the reference point of the local area network, and completely equalized communications can occur between any transmitter and receiver connected thereto.
    Type: Grant
    Filed: April 10, 1985
    Date of Patent: January 13, 1987
    Assignee: Harris Corporation
    Inventors: Richard D. Roberts, William D. Walker
  • Patent number: 4635278
    Abstract: In a digital communications system, one of two tones is selected for each bit, a first tone for a "0" and a second tone for a "1"; the tones are unique for each bit. The tones for all of the bits of a byte are sent simultaneously, in a burst or pulse. At the receiver, a parametric model-based spectrum analysis is performed to find the constituent frequencies which produced the composite spectrum. This spectrum analysis uses autoregressive parameter estimation techniques to determine the most likely combination of frequency components which would have generated the composite spectrum. The combination of frequency components so found is then decoded to yield the corresponding bit values represented by those frequencies. The use of autoregressive spectral analysis techniques to recover the frequency components in the composite signal provides both bandwidth compression (by virtue of increased resolution) and faster signalling rates in transmitting just such signals.
    Type: Grant
    Filed: September 12, 1983
    Date of Patent: January 6, 1987
    Assignee: Sanders Associates, Inc.
    Inventors: Richard A. Maloon, Harvey C. Woodsum