Patents Examined by T. Ghebretinsae
  • Patent number: 5694417
    Abstract: A direct sequence spread spectrum receiver and method for acquiring radio-frequency signals is provided for acquiring data from signals which have been transmitted in a spread spectrum system. The receiver is capable of receiving short data bursts from transmitters without prior knowledge of the time or location of the transmission and rapidly acquiring the signal before continuing with reliable data demodulation. The system includes one or more antennae for receiving RF signals which may be selectively connected to provide the received signals to the system for processing, a quadrature demodulator for providing I and Q baseband signals to a digital baseband processor which includes A/D converters, dual correlators for despreading the digital I and Q signals, a cartesian to polar converter, a demodulator for demodulating the polar coordinate digital I and Q signals, and a data descrambler for obtaining a serial data stream which may be provided to a serial interface.
    Type: Grant
    Filed: July 31, 1995
    Date of Patent: December 2, 1997
    Assignee: Harris Corporation
    Inventors: Carl Andren, John Fakatselis, Perry W. Frogge, Leonard V. Lucas, Al Petrick, Jim Snell
  • Patent number: 5694426
    Abstract: A new signal quantization scheme is proposed which reduces fluctuation of the output signal by a signal quantizer (10) providing a quantized output signal and multiplying (18) said input signal X by a factor (1-w.sub.1) and finding a difference signal (11) between both the input signal and the previous input signal and multiplying (16) that by a weighting factor w.sub.2 from a control (13). The previous quantizer output signal Q.sub.prev is summed (17) with the weighted difference signal w.sub.2 and the sum is weighted by a weighting factor w.sub.1 at a multiplier (19) to yield w.sub.1 (Q.sub.prev +w.sub.2 This signal is then summed at an adder (21) and applied to the quantizer (10) so that the quantizer is forced to match the fluctuation in the input signal as well as the signal itself.
    Type: Grant
    Filed: June 7, 1995
    Date of Patent: December 2, 1997
    Assignee: Texas Instruments Incorporated
    Inventors: Alan V. McCree, Vishu R. Viswanathan
  • Patent number: 5689529
    Abstract: A method and apparatus for single signal, multiple channel digital information transfer through pulses with time slot allocation. The apparatus consists of one or more transmitting devices and one or more receiving devices. Multiple source signals are each allocated a unique time slot between successive synchronization pulses. Digital signals from each source are converted to analog information pulses synthesized from a combination of a fundamental frequency wave and a finite number of its harmonics. The total signal, which consists of successive synchronization pulses interspersed with information pulses for each signal source, each within its allocated time slot, is transmitted to the receivers. Each receiving device extracts the fundamental frequency and harmonic components through the use of narrow bandpass, high Q filters for each information pulse in its time slot and uses the known algorithm to reproduce the input digital signals.
    Type: Grant
    Filed: April 5, 1996
    Date of Patent: November 18, 1997
    Assignee: International Automated Systems, Inc.
    Inventor: Neldon P. Johnson
  • Patent number: 5673286
    Abstract: A spread-spectrum system and method for providing high capacity communications through multipath compensation. A multipath processor including a first plurality of correlators, a second plurality of correlators, a first adder, a second adder, and a selector device or a combiner device is provided for tracking a spread-spectrum signal arriving in a plurality of groups. The first plurality of correlators despreads a first group of spread-spectrum signals as a first group of despread signals which are added by the first adder to generate a first combined-despread signal. The second plurality of correlators despreads a second group of spread-spectrum signals as a second group of despread signals which are added by the second adder to generate a second combined-despread signal. The selector device selects either the first or the second combined-despread signal and outputs the selected signal.
    Type: Grant
    Filed: April 17, 1995
    Date of Patent: September 30, 1997
    Assignee: InterDigital Technology Corporation
    Inventor: Gary R. Lomp
  • Patent number: 5671252
    Abstract: A data receiving and processing channel including analog signal processing circuitry operable for receiving data in the form of an input analog signal, and modifying the input signal in accordance with selected parameters so as to generate a modified analog input signal. According to one embodiment, there is provided a charge domain signal equalizer which initially transforms the modified analog input signal into a corresponding analog charge domain signal, the equalizer performing waveform shaping of the analog charge domain signal in accordance with a predetermined signal response template; a charge domain analog-to-digital converter operable for converting the analog charge domain signal into a corresponding digital signal; and a digital signal processor operable for recovering a digital bit stream from the digital signal which is indicative of the original data.
    Type: Grant
    Filed: September 21, 1994
    Date of Patent: September 23, 1997
    Assignee: Analog Devices, Inc.
    Inventors: Janos Kovacs, Scott C. Munroe
  • Patent number: 5666380
    Abstract: A digital communication system and method, in which a convolutional coding of input data sequence Bm (m=1, 2, 3, . . . ) is carried out, and first coded data X1 of first coded data sequence Xm are deleted to output second coded data sequence Xn onto a transmission line. First receive data X1' are uniquely determined on the basis of receive data sequence Xn' transmitted via the transmission line, corresponding to the second coded data sequence Xn, and the last decoded data B0' of a data sequence which is previously received and decoded, to produce data sequence Xm' which are decoded by a maximum likelihood coding to obtain a decoded data sequence. Hence, a fixed amount of information of the data can be always compressed to transmit the compressed data even in a low line quality environment.
    Type: Grant
    Filed: June 29, 1994
    Date of Patent: September 9, 1997
    Assignee: NEC Corporation
    Inventor: Noriyoshi Sonetaka
  • Patent number: 5663989
    Abstract: In a frequency modulated digital radio transmission system, frequency differences between transmitter and receiver which give rise to DC offsets at the output of the demodulator are countered for any one data transmission by establishing a frequency controlling or DC level controlling signal during a preamble sequence having a known constant DC component, such as the sequence 10101 - - - used for clock or data synchronization, and retaining that controlling signal substantially unaltered for use during the remainder of that data transmission.
    Type: Grant
    Filed: October 18, 1994
    Date of Patent: September 2, 1997
    Assignee: Plessey Semiconductors Limited
    Inventor: Ian Godfrey Fobbester
  • Patent number: 5661373
    Abstract: In a binary digital signal transmission system, a transmitter generates a binary digital signal including at least a rise portion where a level of the binary digital signal steeply rises in accordance with inputted binary digital data of a first value, and at least a fall portion where the level of the binary digital signal steeply falls in accordance with the inputted binary digital data of a second value, and then transmits the binary digital signal via a cable to a receiver. On the other hand, the receiver receives the transmitted binary digital signal, and first and second resonance circuits respectively have two resonance frequencies which are even multiples of each other, and extract first and second resonance signals respectively having resonance frequency components of the two resonance frequencies, from the received binary digital signal.
    Type: Grant
    Filed: March 13, 1995
    Date of Patent: August 26, 1997
    Inventor: Atsushi Nishizawa
  • Patent number: 5657348
    Abstract: A method in connection with digital mobile radio communication systems for forming, in a receiver, a quality measure SQ of the signal vector received in a signal burst comprises forming a first estimate E.sub.s of the energy of the useful signal of the signal vector, forming a second estimate E.sub.n of the energy of the remaining signal components of the signal vector, and forming the quality measure SQ of the signal vector in accordance with the formula SQ=K.sub.1 E.sub.s /(K.sub.2 +E.sub.n), where K.sub.1 and K.sub.2 are predetermined constants.
    Type: Grant
    Filed: January 2, 1996
    Date of Patent: August 12, 1997
    Assignee: Telefonaktiebolaget LM Ericsson
    Inventors: Leif Linus Ericsson, Andras Antal Toth, Johan Skold
  • Patent number: 5654987
    Abstract: A clock recovery circuit has at least two comparators that detect timings at which a digitally modulated signal crosses different levels, and generate level crossing signals at these timings. A classifying circuit classifies sequences of these level crossing signals and issues corresponding classification signals. A timing control circuit generates timing pulses from certain combinations of the level crossing signals and classification signals. A digital phase-locked loop outputs a clock signal synchronized to these timing pulses.
    Type: Grant
    Filed: June 1, 1995
    Date of Patent: August 5, 1997
    Assignee: Oki Electric Industry Co., Ltd.
    Inventor: Seizo Nakamura
  • Patent number: 5654982
    Abstract: An apparatus and method for a data communications device such as a modem (100, 101) to determine carrier frequency offset and timing frequency offset, from a received probe signal. The various embodiments utilizing a processor (108) or digital signal processor (106) receive first and second sets of a transmitted probe signal having known characteristics, and determine a set of phase differences for the tones comprising the probe signal (702, 703, 704, 705). The various method and apparatus embodiments then form a linear approximation from the set of phase differences to determine the carrier frequency offset and the timing frequency offset (706). In the preferred embodiments, the linear approximation is formed from a minimization of a least square error estimate proportionally weighted by either signal to noise ratios or normalized, average amplitudes of the set of tones of the received probe signal.
    Type: Grant
    Filed: June 29, 1995
    Date of Patent: August 5, 1997
    Assignee: Motorola, Inc.
    Inventors: Richard L. Goodson, Mickey C. Rushing, Gary D. Hunt, Lee T. Gusler
  • Patent number: 5652764
    Abstract: Transmission data is spread by spreaders through two orthogonal codes generated by orthogonal code generators, the spread signals are subjected to binary phase modulation with a given carrier wave by BPSK modulators, and are then transmitted from separate antennas positioned in differing spatial locations. Thus, it is possible to provide a radio communication system capable of realizing transmission diversity even in the case of initial transmission where there is yet no information regarding the location, direction, etc., of a partner station, or where a base station is to transmit data directed to all of a plurality of mobile stations, such as in mobile communication systems.
    Type: Grant
    Filed: January 17, 1996
    Date of Patent: July 29, 1997
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Kiyoko Kanzaki, Hidehiro Takahashi
  • Patent number: 5652766
    Abstract: A two-way transmitting apparatus which transmits display data and audio signal from an audio reproducing device to a remote controller and headphones with display by wireless transmitting, and transmits control signals to the audio reproducing apparatus according to one of the operation of a plurality of operation unit established on the remote controller and the headphones. The control data is divided into a predetermined number of blocks, the discrimination code "d" is inserted between respective blocks to generate the data sequence, and the data length per unit block is set to most approximate to the value of square root of the control data length.
    Type: Grant
    Filed: July 28, 1994
    Date of Patent: July 29, 1997
    Assignee: Sony Corporation
    Inventors: Noboru Matsumura, Kazuaki Okuyama, Mitsuru Kashimura
  • Patent number: 5646956
    Abstract: A system and method for estimating top contributing stations of a local area network. A traffic analyzer of the present invention determines the top N stations producing and receiving traffic on a local area network. The traffic analyzer performs this technique with limited storage space. To determine the top contributors the present invention utilizes a method of matching, sorting, creating, and purging records in storage in relation to captured frames received from stations on the LAN.
    Type: Grant
    Filed: February 9, 1996
    Date of Patent: July 8, 1997
    Assignee: Hewlett-Packard Company
    Inventor: Robert W. Pinna
  • Patent number: 5646962
    Abstract: Apparatus for reducing electromagnetic radiation from a differentially driven transmission line for high data rate communication in a computerized tomography system is provided. The apparatus includes a carrier generator to generate carrier signals having an adjustable phase shift angle between one another. The phase angle differential is selected to avoid formation of leakage signals due to misalignment occurring between the coupler and the transmission line during relative movement therebetween, thereby reducing electromagnetic radiation from the transmission line and the coupler.
    Type: Grant
    Filed: December 5, 1994
    Date of Patent: July 8, 1997
    Assignee: General Electric Company
    Inventor: Daniel David Harrison
  • Patent number: 5644593
    Abstract: A parallel interface is provided between a standard parallel port of a computer system and a modem so as to increase the data transfer rate between the two systems without modifying the hardware of the computer system and independently of the application program running on the computer system.
    Type: Grant
    Filed: September 2, 1994
    Date of Patent: July 1, 1997
    Assignee: Microcom Systems, Inc.
    Inventors: Jay Patrick Bailey, Brian J. Copley, Mark J. Freitas
  • Patent number: 5642378
    Abstract: A dual mode cellular telephone contains modulator and demodulator circuitry that use the same I and Q signals for processing both analog and digital voice data, A power amplifier (PA) bias voltage is varied in coordination with the phone operating mode and geographical location to increase energy efficiency. The power supply for the PA is controlled in combination with a controlled ramp up and ramp down of the modulated I and Q signals to eliminate "spectral splatter" of the transmission band into adjacent frequencies. A variable gain amplifier is coupled to the front end of the phone receiver circuitry to increase the overall dynamic range for the gain of the demodulated I and Q signals. A switching power supply is used in the dual mode phone to increase energy efficiency and reduce the required size of the battery pack.
    Type: Grant
    Filed: November 17, 1994
    Date of Patent: June 24, 1997
    Inventors: Brian John Denheyer, John David Terry
  • Patent number: 5640419
    Abstract: A covert communication system utilizes a series of low level duty cycle coded pulse train transmissions which at the necessary end have signal to noise ratios much smaller than unity. Such transmissions are buried in noise and hence are undetectable by ordinary means. The coded pulse trains do not carry data and their sole purpose is only to be compressed by a code matched correlator into a single large pulse per pulse train. Data are encoded in the timing between adjacent compressed pulses of adjacent pulse trains. The low duty cycle of the pulse trains is used to force an unfriendly receiver, which does not know the code of the pulse train transmissions, to integrate its own receiver noise into its detection circuits, thus making the transmissions even less detectable.
    Type: Grant
    Filed: July 19, 1994
    Date of Patent: June 17, 1997
    Assignee: Grumman Aerospace Corporation
    Inventor: Saulius Janusas
  • Patent number: 5640424
    Abstract: A digital downconverter circuit for a digital data transmission system is provided, comprising (i) a bandpass filter circuit for filtering a received analog intermediate frequency (IF) carrier signal onto which baseband information has been modulated, and outputting a bandpass analog IF signal; (ii) an analog-to-digital converter for converting the bandpass analog IF signal into a bandpass digital IF signal; (iii) a phase shifter device for outputting a complex pair of phase shifted baseband signals operating at a local baseband frequency; (iv) a mixer device for mixing the bandpass digital IF signal separately with each of the complex pair of phase shifted baseband signals and outputting a complex combined baseband/bandpass signal comprising inphase and quadrature components; (v) filtering circuitry for recovering the baseband information onto the phase shifted baseband signals; and (vi) sampling circuitry for sampling the information-bearing recovered baseband signals and outputting a sampled complex baseba
    Type: Grant
    Filed: May 16, 1995
    Date of Patent: June 17, 1997
    Assignee: Interstate Electronics Corporation
    Inventors: Noi N. Banavong, George Gomez, Long Quoc Nguyen, Dan Q. Tu
  • Patent number: 5640422
    Abstract: A method and apparatus for single signal, multiple channel digital information transfer through waves with time slot allocation. The apparatus consists of one or more transmitting devices and one or more receiving devices. Multiple source signals are each allocated a unique time slot between successive synchronization waves. Digital signals from each source are converted to analog information waves having a positive wave segment and a negative wave segment. The ratio of the amplitude of the positive wave segment to the amplitude of the negative wave segment, the positive-to-negative ratio, for each signal source, is a function of the magnitude of the source digital. The sum of the amplitude of the positive wave segment and the absolute value of the amplitude of the negative wave segment, the positive-to-negative offset, is maintained at a pre-set value at transmission.
    Type: Grant
    Filed: September 26, 1995
    Date of Patent: June 17, 1997
    Assignee: International Automated Systems, Inc.
    Inventor: Neldon P. Johnson