Equalizers Patents (Class 333/28R)
  • Patent number: 6167082
    Abstract: Adaptive equalization methods and adaptive equalizers used with precoded systems dominated by intersymbol interference (ISI) monitor the output of a DFE and compare it to a reference for updating a precoder in response to the comparison.
    Type: Grant
    Filed: March 3, 1998
    Date of Patent: December 26, 2000
    Assignee: Level One Communications, Inc.
    Inventors: Stanley K. Ling, Ping An, Hiroshi Takatori
  • Patent number: 6114922
    Abstract: A network line equalizer is provided in combination with a compensation circuit. The network line equalizer includes first and second nodes, first and second current sources respectively connected to the first and second nodes, first and second transistors respectively connected also to the first and second nodes with a gate of the first transistor receiving a first signal of a differential pair of transmitted signals and a gate of the second transistor receiving a second signal of the differential pair of transmitted signals, a third transistor connected between the first and second nodes, and a control line connected to a gate of the third transistor.
    Type: Grant
    Filed: February 11, 1999
    Date of Patent: September 5, 2000
    Assignee: Advanced Micro Devices, Inc.
    Inventor: Vadim Tsinker
  • Patent number: 6111755
    Abstract: A computer system having an enclosure, a motherboard in the enclosure, one or more disk drive bays in the enclosure each defining a bay opening in the front, a plurality of daughter card slots each having a slot opening in the back, a sound card mounted in one of the daughter card slots, and a graphic audio equalizer having an equalizer enclosure including an equalizer front panel sized and configured for mounting in one of the drive bays with the front panel in the bay opening. The equalizer further having manually operable controls, a first and second visual indicator means, a master volume control, a bracket mounted in another one of the card slots, a plurality of equalizer connectors including equalizer inputs and equalizer outputs on the bracket, and a cable operatively interconnecting the equalizer connectors to the audio equalizer.
    Type: Grant
    Filed: March 10, 1998
    Date of Patent: August 29, 2000
    Inventor: Jae-Sung Park
  • Patent number: 6107896
    Abstract: A linear attenuation equalizer and a method for designing such an equalizer using the cable attenuation curve to determine the D.C. attenuation and the lower or first corner frequency. The D.C. attenuation and the lower corner frequency are used to fix the design. A curve fit technique is used to determine the cable attenuation parameter which fixes the D.C. attenuation of the equalizer. The lower corner frequency is set at between about 10% and less than about 50% of the data rate, and preferably at approximately 20% of the data rate.
    Type: Grant
    Filed: May 1, 1998
    Date of Patent: August 22, 2000
    Assignee: Berg Technology, Inc.
    Inventors: Richard A. Elco, Frederick J. Young
  • Patent number: 6104750
    Abstract: A method and apparatus for equalizing the frequency response of a transmission line is provided. The method includes the steps of modelling the frequency response of the transmission media for a predetermined frequency range to a predetermined accuracy; determining a desired equalizer response by taking an inverse of the modelled frequency response of the first step; implementing an equalizer that exhibits the desired response; and utilizing the equalizer to equalize the frequency response of the transmission line. The apparatus includes an adaptive equalizer circuit which includes a plurality of signal processor circuits which each take an input signal from the transmission line and process it to mimic a term in a transfer function which represents an inverse of the transfer function of the transmission line. The signals from these processors are then summed and multiplied by a programmable gain term. Then the input is added to the output of the multiplier to form an output equalizer signal.
    Type: Grant
    Filed: July 31, 1998
    Date of Patent: August 15, 2000
    Assignee: LSI Logic Corporation
    Inventor: Lee-Chung Yiu
  • Patent number: 6044110
    Abstract: A method and apparatus for equalizing the frequency response of a transmission line is provided. The method includes the steps of modelling the frequency response of the transmission media for a predetermined frequency range to a predetermined accuracy; determining a desired equalizer response by taking an inverse of the modelled frequency response of the first step; implementing an equalizer that exhibits the desired response; and utilizing the equalizer to equalize the frequency response of the transmission line. The apparatus includes an adaptive equalizer circuit which includes a plurality of signal processor circuits which each take an input signal from the transmission line and process it to mimic a term in a transfer function which represents an inverse of the transfer function of the transmission line. The signals from these processors are then summed and multiplied by a programmable gain term. Then the input is added to the output of the multiplier to form an output equalizer signal.
    Type: Grant
    Filed: August 15, 1996
    Date of Patent: March 28, 2000
    Assignee: LSI Logic Corporation
    Inventor: Lee-Chung Yiu
  • Patent number: 6031432
    Abstract: This invention discloses a balancing circuit for providing a substantially fixed level of attenuation within a given return path frequency passband, while preventing noise related harmonics from distorting signal transmissions within the return path frequency passband. The balancing circuit includes coupling capacitors which are connected in series between input and output end nodes. A series connected inductor and capacitor pair is connected between each of the input and output end nodes and ground to form end sections. Another inductor is connected between the coupling capacitors and ground. A resistor is connected in parallel with the respective capacitor of each end section. The balancing circuit is placed in series at each subscriber port, and may be mounted on a printed circuit board and enclosed within a tubular housing with mating male and female "F" connections.
    Type: Grant
    Filed: February 27, 1998
    Date of Patent: February 29, 2000
    Inventor: Ronald C. Schreuders
  • Patent number: 5999568
    Abstract: A method and apparatus for equalizing the frequency response of a transmission line is provided. The method includes the steps of modelling the frequency response of the transmission media for a predetermined frequency range to a predetermined accuracy; determining a desired equalizer response by taking an inverse of the modelled frequency response of the first step; implementing an equalizer that exhibits the desired response; and utilizing the equalizer to equalize the frequency response of the transmission line. The apparatus includes an adaptive equalizer circuit which includes a plurality of signal processor circuits which each take an input signal from the transmission line and process it to mimic a term in a transfer function which represents an inverse of the transfer function of the transmission line. The signals from these processors are then summed and multiplied by a programmable gain term. Then the input is added to the output of the multiplier to form an output equalizer signal.
    Type: Grant
    Filed: July 31, 1998
    Date of Patent: December 7, 1999
    Assignee: LSI Logic Corporation
    Inventor: Lee-Chung Yiu
  • Patent number: 5995544
    Abstract: In a receiver for signals in a multilevel partial response class-IV communication system, the coefficients of a digital adaptive equalizer need to be updated to minimize the error due to noise and signal distortion. After initial convergence of the equalizer coefficients to near-optimum settings, an estimate of the mean-square error gradient for coefficient updating can be obtained in decision-directed mode from an estimate of the error signal. In the absence of a reference signal, initial convergence must be achieved in self-training mode. The decision-directed error signal is then replaced by a pseudo-error signal for the computation of an approximation of the mean-square error gradient. The invention provides a particular self-training procedure which outperforms known methods in terms of speed of convergence and achieved mean-square error values, and does not require timing recovery prior to equalizer convergence.
    Type: Grant
    Filed: May 8, 1997
    Date of Patent: November 30, 1999
    Assignee: International Business Machines Corporation
    Inventors: Giovanni Cherubini, Sedat Oel.cedilla.er, Gottfried Ungerbock
  • Patent number: 5987065
    Abstract: An equalizer comprising a pair of high pass filters for receiving an input signal, each filter having gain, a first of the filters having gain which is substantially flat within its passband, a second of the filters having gain over a range of its passband which is controlled by an error signal, a differential amplifier for generating the error signal, having an output applied to a control input of the second filter, a pair of broadband amplitude peak detectors each for receiving an output signal of a respective one of the filters, apparatus for applying loop signals derived from outputs of the filters and passing though the peak detectors to corresponding inputs of the differential amplifier, apparatus for providing an offset to a loop signal derived from the output of the first filter, and apparatus for providing an output signal from the output of the second filter.
    Type: Grant
    Filed: June 25, 1997
    Date of Patent: November 16, 1999
    Assignee: PMC-Sierra Ltd.
    Inventor: Anthony B. Candage
  • Patent number: 5978417
    Abstract: An adaptive cable equalizer is provided with a simple architecture, wherein a single control structure: controls the adaptation of the filter for compensating for cable length while simultaneously compensating for process and temperature variations; optimizes the SNR at any cable length by controlling biasing current sources; and uses a two-stage architecture which eliminates start-up problems and optimizes output levels to obtain optimal dc restoration while simultaneously allowing for independent optimization of the output levels of the recovered data in accordance with other requirements as desired. An analog adaptive equalizing filter is used for accurately synthesizing the inverse transfer function of cables of variable lengths. Data rates up to and beyond 400 Mbps are supported and the adaptive behavior automatically compensates for different cable lengths as well as process variations (with respect to the process(es) used for fabricating the equalizer in a monolithic form) and temperature variations.
    Type: Grant
    Filed: September 13, 1996
    Date of Patent: November 2, 1999
    Assignee: National Semiconductor Corporation
    Inventors: Alan J. Baker, Marc H. Ryat
  • Patent number: 5970094
    Abstract: An equalizer for filtering a received signal to generate a filtered signal.
    Type: Grant
    Filed: November 5, 1997
    Date of Patent: October 19, 1999
    Assignee: Hyundai Electronics Industries Co., Ltd.
    Inventor: Duck Myung Lee
  • Patent number: 5963593
    Abstract: A method of controlling a line equalizer such as a modem includes an extracting step of extracting plural tone signals each superimposed on a transmission signal and having a specific frequency component; a judging step of judging levels of the extracted tone signals; and a controlling step of controlling characteristic of a line equalizer which equalizes a receive signal, based on the levels of the judged tone signals. A line equalizer is controlled without performing an exchange of a training signal prior to starting a data transmission and without increasing the amount of hardware of a modem or the like.
    Type: Grant
    Filed: March 27, 1997
    Date of Patent: October 5, 1999
    Assignee: Fujitsu Limited
    Inventors: Takashi Kaku, Noboru Kawada, Hideo Miyazawa, Yuri Nigaki
  • Patent number: 5963110
    Abstract: An equalizing filter with an optimized frequency response and improved reliability and quality, for equalizing a reception signal so as to regain its original waveform. The equalizing filter comprises a low-pass filter and a high-frequency booster circuit. With its limited passband, the low-pass filter rejects the noise components contained in the signal being processed. The high-frequency booster circuit has such a frequency response that exhibits a stepwise gain increase at high frequencies. Those two elements, composed of reliable passive components, are coupled in series to provide a combined frequency response that is optimized for the design of highly sensitive optical receivers. As integral part of the high-frequency booster circuit, the equalizing filter employs an inductor made of a bonding wire.
    Type: Grant
    Filed: March 3, 1998
    Date of Patent: October 5, 1999
    Assignee: Fujitsu Limited
    Inventors: Takeshi Ihara, Hiroshi Hamano
  • Patent number: 5953373
    Abstract: An equalizing circuit and method for data communication terminal equipment includes: a level detecting unit for detecting respective levels of a high frequency signal and a low frequency signal which are frequency shift keying signals inputted through a telephone line during a handshake and for outputting the detected respective levels; a control unit for comparing the levels of the high and low frequency signals detected by the level detecting unit and for generating a frequency compensation amplification control signal according to a level difference between the high and low frequency signals; and an equalizing unit for inputting a level detection signal outputted from the level detecting unit and for compensating any attenuation and distortion of received signals in response to the frequency compensation amplification control signal of the control unit, so as to effect equalization.
    Type: Grant
    Filed: July 12, 1996
    Date of Patent: September 14, 1999
    Assignee: SamSung Electronics Co., Ltd.
    Inventor: Joo-Seung Park
  • Patent number: 5940441
    Abstract: A method and apparatus for equalizing a communications signal transmitted through a transmission medium includes an integrated continuous-time filter and circuitry for developing a feedback signal to compensate for distortion in the signal caused by the transmission medium. The control signal adjusts the transfer characteristics of the integrated continuous-time filter thereby compensating for loss and distortion of the signal caused by the transmission medium and further tunes the integrated continuous-time filter thereby compensating for semiconductor process variations in the integrated continuous-time filter.
    Type: Grant
    Filed: October 29, 1996
    Date of Patent: August 17, 1999
    Assignee: International Business Machines Corporation
    Inventors: Hayden Clay Cranford, Jr., Scott David Huss
  • Patent number: 5901174
    Abstract: An equalizer-combiner for a diversity receiver using at least two receive channels computes equalization coefficients for each channel allowing for a first channel error signal representative of a comparison between the demodulated signal and a channel estimate of the transmitted source signal delivered by a channel estimator fed with the demodulated signal in the channel during an acquisition phase and a second channel error signal representative of a comparison between the demodulated signal and the global estimate of the transmitted source signal during a normal operation phase.
    Type: Grant
    Filed: June 19, 1997
    Date of Patent: May 4, 1999
    Assignee: Alcatel Telspace
    Inventor: Joel Richard
  • Patent number: 5898731
    Abstract: An auto-coefficient renewal digital channel equalizer is disclosed, including an auto-coefficient renewing device for automatically renewing a coefficient using received data and an error signal, an error detecting device for detecting an error signal from a signal of the auto-coefficient renewing device, a device for determining convergence or divergence of the error signal detected in the error detecting device to produce a convergence or divergence signal according to a result of the determination, and an error processing device for shifting down the error signal detected in the error detecting device a certain number of bits in response to a convergence signal to produce a signal smaller than the received error signal to the auto-coefficient renewing device, thereby processing the coefficient renewal at the same rate with the data for all of the taps of an equalizer. The equalizer converges at an increased rate, and operation of the equalizer is made more stable even in diversion of a reception channel.
    Type: Grant
    Filed: February 3, 1997
    Date of Patent: April 27, 1999
    Assignee: LG Electronics Inc.
    Inventor: Heung Sik Kwak
  • Patent number: 5892412
    Abstract: A passive positive-gain equalizer comprises a ferrite (100, 300) electromagnetically coupled to a single conductor (111, 311) of a digital signal defined in the frequency domain by a plurality of frequencies. Although it has no external power source other than the digital signal, the equalizer amplifies some of the signal's frequencies. In one embodiment, the equalizer (100) comprises a "C"-shaped body portion (101) whose legs (103, 104) extend through holes in a PC board (110) to be spanned by an "I"-shaped body portion (102). A tunnel (106) formed thereby surrounds a stripline (111) and the PC board portion (112) which carries the stripline. In another embodiment, the equalizer (300) comprises an "E"-shaped body portion (301) whose legs (303-305) extend through holes in a PC board (310) to be spanned by an "I"-shaped body portion (302). A pair of tunnels (306, 307) is formed thereby, and the stripline (311, 511) loops through each of the tunnels one or more times.
    Type: Grant
    Filed: February 20, 1997
    Date of Patent: April 6, 1999
    Assignee: Lucent Technologies Inc.
    Inventors: David A. Norte, Woong K. Yoon
  • Patent number: 5887030
    Abstract: A reproducing apparatus includes an equalizer for equalizing reproduced data, a clock generating circuit for generating a clock synchronized with the reproduced data, and a phase difference detector for detecting a phase difference between the reproduced data equalized by the equalizer and the clock. The clock generating circuit receives an output from the phase difference detector as a control signal, and generates a clock of frequency according to the output from the phase difference detector. The equalization characteristic of the equalizer is controlled by the control signal of the clock generating circuit. With this arrangement, it is possible to generate a clock which follows a variation in the frequency of the reproduced data, and it is also possible to realize an optimum equalization characteristic according to the variation in the frequency of the reproduced data.
    Type: Grant
    Filed: December 18, 1995
    Date of Patent: March 23, 1999
    Assignee: Canon Kabushiki Kaisha
    Inventors: Yoshiyuki Sasaki, deceased, Hana Sasaki, legal representative, Shinichi Yamashita
  • Patent number: 5880645
    Abstract: The analog adaptive equalizer provides convergence of an error signal by decoupling the error canceller, the automatic gain control and the filter to provide truly adaptive error minimization. The invention includes an automatic gain control (AGC) circuit for providing broadband amplification of an input signal to generate an AGC output signal, a filter for receiving the AGC output signal and providing high frequency signal conditioning to generate a filter output signal, an error detection circuit for generating an error signal representing the difference between the filter output signal and an expected output signal and a calculator for receiving the error signal and providing a gain correction signal to the automatic gain circuit to adjust the gain of the automatic gain circuit and a filter control signal to adjust the filter range of the filter, the gain correction signal and the filter control signal being used to cancel the error signal.
    Type: Grant
    Filed: July 3, 1997
    Date of Patent: March 9, 1999
    Assignee: Level One Communications, Inc.
    Inventors: James W. Everitt, Paul J. Hurst, Daniel L. Ray
  • Patent number: 5848167
    Abstract: A distributed pre-emphasis equalizer comprises a partial pre-emphasizer and a (50) microsecond pre-emphasizer. The partial pre-emphasizer receives an input signal and produces a partially pre-emphasized output signal. The (50) microsecond pre-emphasizer receives the partially pre-emphasized output signal from the partial pre-emphasizer and adds a (50) microsecond equalization to produce a pre-emphasized output signal equal to a standard (75) microsecond pre-emphasis curve. The distributed pre-emphasis equalizer allows an FM audio processor to produce only the "dulling" effect of a (50) microsecond pre-emphasis even when generating a (75) microsecond pre-emphasis curve. The distributed pre-emphasis equalizer also creates a pre-emphasizing method which is inherently compatible with both the (75) microsecond and (50) microsecond standards. Furthermore, the distributed pre-emphasis equalizer creates a pre-emphasizing method which is easily switchable between the (75) and (50) microsecond standards.
    Type: Grant
    Filed: March 17, 1997
    Date of Patent: December 8, 1998
    Assignee: Aphex Systems, Ltd.
    Inventor: Donn R. Werrbach
  • Patent number: 5828699
    Abstract: A circuit and method for automatically reducing an electrical path length difference between two electromagnetic signal paths. A counter converts the electrical path length difference to a multi-bit digital signal, and each bit in the signal operates a different one of plural switches which selectively inserts a time delay into one of the two electromagnetic signal paths to reduce the electrical path length difference. A comparator determines whether the electrical path length difference exceeds a threshold. The rectified AC component of a phase detector output is fed to the comparator which activates the counter when the threshold is exceeded. The counter drives the switched time delays in a sweeping fashion until the detected error falls below the threshold, whereupon the sweeping action is terminated.
    Type: Grant
    Filed: January 30, 1997
    Date of Patent: October 27, 1998
    Assignee: Harris Corporation
    Inventor: James J. Heinemann
  • Patent number: 5828700
    Abstract: An adaptive equalizer is configured to reconstruct electronic signals which are transmitted over signal cables, such as twisted pair cables. The equalizer satisfactorily reconstructs the signals over a broad range of cable lengths. The degradation characteristics of a signal cable varies with cable length. Using the degradation characteristics for a cable over a desired range of lengths, the adaptive equalizer includes multiple parallel paths each of which are configured to reconstruct the input voltage signal optimized for a particular cable length. The degraded input signal is split according to a predetermined relationship into multiple partial signals, each signal for transmission through one each of the paths. Though each path is optimized to reconstruct the signal for a particular length of cable, the adaptive control adds a function of the actual cable length for more accurately reconstructing the signal. Each path forms a partial reconstructed signal.
    Type: Grant
    Filed: August 5, 1993
    Date of Patent: October 27, 1998
    Assignee: Micro Linear Corporation
    Inventor: Thomas H. Korn
  • Patent number: 5805031
    Abstract: A CMOS transmission line equalizer is provided for receiving distorted signals transmitted through a transmission line and for compensating for the signal distortion. The equalizer has a transfer function characteristic with a single pole and a single zero. The transfer function includes a mirroring ratio circuit (CMR) for controlling the ratio between the single pole and the single zero. The mirroring ratio circuit is controlled by transistor size ratio. The single zero serves to cancel the dominant pole in the transfer function of the transmission line so as to compensate for the signal distortion caused by the transmission line.
    Type: Grant
    Filed: September 3, 1996
    Date of Patent: September 8, 1998
    Assignee: Advanced Micro Devices, Inc.
    Inventor: Yi Cheng
  • Patent number: 5805637
    Abstract: An automatic equalizer having a high convergence performance and broad pull and lock ranges. In converting playback signals into multi-level signals, a transversal filter output is processed with maximum likelihood decoding using a maximum likelihood decoder for calculating transmission errors and the coefficients of the transversal filter are again set based on the calculated errors.
    Type: Grant
    Filed: September 25, 1996
    Date of Patent: September 8, 1998
    Assignee: Sony Corporation
    Inventors: Hisato Hirosaka, Akio Tanaka
  • Patent number: 5796778
    Abstract: Circuitry, and an associated method, for a receiver which receives data signals transmitted upon a non-ideal transmission channel. The circuitry includes an equalizer circuit and a variable gain amplifier circuit together operable to counteract the effects of the signal degradation. Characteristics of the equalizer circuit and of the amplifier circuit are together selected responsive to detection of the signal envelope of the data signal.
    Type: Grant
    Filed: September 26, 1995
    Date of Patent: August 18, 1998
    Assignee: Symbios, Inc.
    Inventor: Christopher M. Kurker
  • Patent number: 5793264
    Abstract: An equaliser circuit arrangement for compensating for the frequency-dependent characteristics of a transmission line such as an untwisted pair, for lines of lengths up to, say, 125 meters and at data rates up to, say, 155MBits/sec., in which signals from the transmission line are applied by way of a unity gain path and a frequency-selective path including a first wide-band amplifier of variable gain to a summing node. The signals at the summing node may be further amplified by a second wide-band variable gain amplifier using gain control signals derived for the first amplifier.
    Type: Grant
    Filed: October 2, 1996
    Date of Patent: August 11, 1998
    Assignee: Plessey Semiconductor Limited
    Inventors: Craig M. Taylor, Nicholas Mihailovits
  • Patent number: 5789993
    Abstract: A device (1) for correcting the amplitude/frequency characteristic of an input signal (FI), particularly from transmission cables (40), having a minimal frequency f1, a center frequency f0 and a maximal frequency f2, the input signal (FI) having an attenuation as a function of frequency characteristic that increases between f1 and f2, the correction device (1) supplying a corrected output signal (). The correction device includes two cascaded filters (41, 42), the first of the filters receiving the input signal (FI) and supplying a filtered signal (SFI) to the second of the filters, the second of the filters supplying the corrected output signal (). One of the filters is a band-stop filter (41) having a center frequency f3 less than or equal to f1, the other of the filters being a band-pass filter (42) having a center frequency f4 greater than or equal to f2. The center frequencies f3 and f4 satisfy the equation:f3.times.f4=f0.sup.
    Type: Grant
    Filed: February 11, 1997
    Date of Patent: August 4, 1998
    Assignee: Alcatel N.V.
    Inventors: Michel Comte, Nathalie Roche
  • Patent number: 5754943
    Abstract: In a wireless communication apparatus arranged by an indoor unit, an outdoor unit, and a cable used to connect the indoor unit with the outdoor unit, a gain of an amplifier is automatically set. This amplifier amplifies a lowered level of a signal caused by a cable loss. To perform such an automatic gain setting operation, a cable loss equalization system is used in this wireless communication apparatus. The cable loss equalization system compensates for a reduction in a level of a main signal caused by the cable.
    Type: Grant
    Filed: June 21, 1996
    Date of Patent: May 19, 1998
    Assignee: NEC Corporation
    Inventors: Masami Arai, Hiroki Iwasaki
  • Patent number: 5724390
    Abstract: There is an equalizer or a receiver including an equalizer which has means to factor detected symbols transmitted over a transmission channel into a magnitude portion and a repetitive phase portion. The receiver further has means to generate modified tap weights by multiplying the repetitive phase portion by tap weights representative of the channel. Modified tap weights are generated by multiplying the repetitive phase portion by tap weights representative of the channel. The modified tap weights are convolved with bits of possible states to generate possible transmitted symbols. A maximum likelihood sequence estimation is performed on the possible transmitted symbols comparing each possible transmitted symbol to a received symbol to generate an MLSE detected symbol. The detected symbol is multiplied by a rotating vector to generate a decoded symbol.
    Type: Grant
    Filed: March 2, 1994
    Date of Patent: March 3, 1998
    Assignee: Lucent Technologies Inc.
    Inventors: David Mark Blaker, Marc Stephen Diamondstein, Gregory Stephen Ellard, Mohammad Shafiul Mobin
  • Patent number: 5714918
    Abstract: In an equalizer with n number of frequency ranges for digitized signals in which by means of n-1 cascaded filter circuits containing parallel connected digital low-pass filters and digital high pass filters whose respective frequency responses are linked by complementary transfer functions. A desired amplitude response is implemented via an increase or decrease in the amplitudes of adjacent frequency ranges in the associated filter circuit by weighting the outputs of the digital high-pass and low-pass filters, and a control unit forms the respective weighting factor from an equalizer control signal which contains the desired amplitude response as information.
    Type: Grant
    Filed: August 9, 1996
    Date of Patent: February 3, 1998
    Assignee: Deutsche ITT Industries, GmbH
    Inventor: Andreas Menkhoff
  • Patent number: 5694422
    Abstract: A fixed equalizer and a fixed equalization method compensates for amplitude distortion, delay distortion, etc., of a signal transmitted over a transmission line. A processor unit carries out filtering process, such as amplitude equalization, delay equalization, line equalization, etc., in accordance with parameters read from a memory. In view of the fact that amplitude equalization process can be achieved by a combination of a highpass filter and a lowpass filter and line equalization process can be achieved by a filter having an attenuating characteristic which is negative at low frequencies and positive at high frequencies, the present invention stores parameters providing a characteristic corresponding to the synthesis of the characteristics of such filters in the memory and performs filtering computation on the basis of the parameters.
    Type: Grant
    Filed: July 29, 1996
    Date of Patent: December 2, 1997
    Assignee: Fujitsu Limited
    Inventors: Takashi Kaku, Hideo Miyazawa
  • Patent number: 5684827
    Abstract: An adaptive equalizer decision circuit for a digital television signal, including a field synchronizing signal, consisting of multilevel symbols and a DC offset representing a pilot. The variation of the DC level of the received signal during the field sync with respect to a predetermined threshold is derived for placing the equalizer in a training signal or data directed operating mode. Another approach determines the difference between a current value of the field sync and each of a plurality of values of the field sync in previous fields and determining therefrom whether the equalizer should be in its data directed mode of operation or in its training signal mode of operation. A modification consists in controlling the step size of the equalizer based upon either the DC level variation or the field sync differences of the received signal. The modification may be used alone or in combination with the equalizer operating mode control.
    Type: Grant
    Filed: October 4, 1995
    Date of Patent: November 4, 1997
    Assignee: Zenith Electronics Corporation
    Inventor: Larry E. Nielsen
  • Patent number: 5682406
    Abstract: A method and apparatus for setting the parameters of an equalizer. Equalizers are used for equalizing distorted signals. However, optimum equalization is only achieved when the parameters of the equalizer are optimally set. To set the parameters of an equalizer optimally, the output signal of the equalizer is rectified in a full-wave rectifier. The output signal of the latter is integrated in an integrator. The parameters of the equalizer are set by a microprocessor according to an algorithm. In one embodiment, when the integration time is predetermined, the parameters of the equalizer is changed until the level of the integrated signal becomes a maximum. In another embodiment, when the maximum level of the integrated signal is predetermined, the parameters of the equalizer are changed until the integration time becomes a minimum.
    Type: Grant
    Filed: April 18, 1995
    Date of Patent: October 28, 1997
    Assignee: Deutsche Thomson-Brandt GmbH
    Inventors: Klaus Mager, Edgar Wursthorn
  • Patent number: 5682125
    Abstract: An analog, adaptive generalized transversal equalizer for use in the filtering system of a disc drive PRML read channel, the transversal equalizer employing the use of non-ideal delay elements. The filtering system comprises the equalizer connected in series with an adaptive, analog prefilter. The prefilter is comprised of a plurality of serially connected, adaptive, analog filter stages having variable transfer functions determined by adaptive parameter signals received by the filter stages. The generalized transversal equalizer comprises a plurality of serially connected, adaptive, analog low pass filters, having taps on either side of each low pass filter, a plurality of multipliers that receive signals at the tap locations of the delay circuit, and a summing circuit that receives the outputs of the multipliers.
    Type: Grant
    Filed: September 29, 1995
    Date of Patent: October 28, 1997
    Assignee: Seagate Technology, Inc.
    Inventors: Vadim B. Minuhin, Vladimir Kovner, Srinivasan Surendran
  • Patent number: 5670916
    Abstract: An equalizer circuit for equalizing waveform distortion of a signal that propagates through a lossy transmission cable connected between a receiver and a transmitter, the equalizer circuit including a plurality of equalizer units which are connected in series with one another and a plurality of taps, each tap providing a different equalized representation of a signal being transmitted through the transmission cable to which the equalizer circuit is connected, and a control circuit for determining the tap at which appears an equalized signal that exhibits minimum error relative to the transmitted signal, the determination being made by applying an envelope detector to each tap for obtaining low frequency envelope signals for the signal appearing at each tap and for comparing the low frequency envelope signals thus obtained with a common DC reference signal that is related to the ideal transmitted signal amplitude.
    Type: Grant
    Filed: October 27, 1995
    Date of Patent: September 23, 1997
    Assignee: Cypress Semiconductor Corp.
    Inventor: Thomas Korn
  • Patent number: 5668833
    Abstract: A decision-feedback type equalizer comprising a forward equalizer for receiving digital pre-equalization signals and error signals as input signals, for reducing intersymbol interference caused by the lead echo of the pre-equalization signals, and for outputting forward equalization signals; a backward equalizer for reducing intersymbol interference caused by the delay echo of input signals, and for producing output in the form of backward equalization signals; an adder for adding forward equalization signals and backward equalization signals, and for outputting equalization signals; a decision device for comparing the equalization signals with reference values, and for outputting decision signals; a subtracter for subtracting the equalization signals and decision signals, and for producing and outputting error signals which are differences; an alarm emitter for detecting, from the signal states of the error signals, whether an abnormal state exists, and for emitting an alarm when an abnormal state is detecte
    Type: Grant
    Filed: March 15, 1996
    Date of Patent: September 16, 1997
    Assignee: NEC Corporation
    Inventors: Yuzo Kurokami, Hideki Matsuura
  • Patent number: 5608757
    Abstract: A high speed signal transport system (10) provides data transmission across a balanced channel (14). The balanced channel (14) carries differential signals from the output of a differential transmitter (12). An equalizer (18) compensates for distortion in the balanced channel in order to reduce timing jitter of the signal. The signal is applied to the input of a differential receiver (20) which exploits the precise quantization threshold inherent in differential data to accurately convert the signal to digital data. The differential receiver (20) also employs a known frequency reference along with digital transition detection to rephase the digital data to the local clock. No duty-cycle limitation is placed on the signal carried by the balanced channel (14) and therefore the differential transmitter (12) and differential receiver (20) are not required to encode the signal.
    Type: Grant
    Filed: June 3, 1994
    Date of Patent: March 4, 1997
    Assignee: DSC Communications Corporation
    Inventors: David M. Smith, Oscar A. Tovar
  • Patent number: 5590154
    Abstract: An equalizer circuit (11) and a method for adjusting tap weights in the equalizer circuit (11) to provide an equalized signal. The equalizer circuit (11) includes an adaptation circuit (16) coupled to an FIR filter (17) and to an error sign generating circuit (18). The FIR filter (17) provides the signs of a plurality of delay signals to the tap weight adaptation circuit (16). Likewise, the error sign generating circuit (18) provides a sign of the error of an output signal of the FIR filter (17) to the tap weight adaptation circuit (16). The tap weight adaptation circuit (16) uses the signs of the delay signals and the sign of the error signal to generate the tap weights which are passed to the FIR filter (17) for adjusting the tap weights of the FIR filter (17).
    Type: Grant
    Filed: June 26, 1995
    Date of Patent: December 31, 1996
    Assignee: Motorola, Inc.
    Inventors: William R. Forni, Scott A. Kaylor
  • Patent number: 5586144
    Abstract: An arrangement for producing a digital signal from an input (e.g., analog) signal obtained from a transmission medium. The arrangement includes a variable equalizer for equalizing the input signal as regards magnitude and phase as a function of frequency to produce an equalized signal, an equalizer control signal generator for generating first and second control signals for controlling the variable equalizer and a detector for producing the digital signal from the equalized signal. The arrangement further includes a bit array selector (i.e., a bit sequence detector) for generating one or two selection signals upon detection of one or more specific bit arrays (i.e., bit sequences) in the digital signal, and a sample-and-hold unit which samples one or more portions of the equalized signal under the influence of the one or two selection signals so as to produce at least one first sample value and at least one second sample value.
    Type: Grant
    Filed: May 1, 1995
    Date of Patent: December 17, 1996
    Assignee: U.S. Philips Corporation
    Inventors: Josephus A. H. M. Kahlman, Albert M. A. Rijckaert
  • Patent number: 5586143
    Abstract: An apparatus and method as shown in for processing digital signals in a communications system including a non-equaliser detector and a equaliser each for receiving an input signal and outputting a quality estimate and bit decision, respectively, so that the quality estimates are compared and a bit decision is made based on the comparison. The apparatus and method further include retraining the equaliser based on the comparison of the quality estimates of the detector and equaliser.
    Type: Grant
    Filed: July 10, 1995
    Date of Patent: December 17, 1996
    Assignee: Motorola, Inc.
    Inventor: Nicholas W. Whinnett
  • Patent number: 5579336
    Abstract: A transceiver circuit for use in a high speed data transmission network is disclosed that provides for simultaneous bidirectional transmission of data over coaxial or twisted pair media for replacing fiber optic cables. A transmitter circuit provides and output data signal to a bridge network. The bridge network develops a cancelling signal and a combined signal. A receiver section includes a high speed subtracting circuit that determines the difference between the cancelling signal and the combined signal to effectively cancel data supplied by the transmitter section.
    Type: Grant
    Filed: October 2, 1995
    Date of Patent: November 26, 1996
    Assignee: Digital Equipment Corporation
    Inventors: John J. Fitzgerald, Donald G. Shuda
  • Patent number: 5566237
    Abstract: An audio selection circuit (10) having time selectable equalization, comprising a plurality of inputs (24, 26) for coupling the audio selection circuit to a plurality of audio signal sources, a variable equalization circuit (32) having an equalization input and an equalization output, the variable equalization circuit (32) providing variable attenuation in a plurality of frequency bands to an audio signal coupled to the equalization input, processing means (12) operatively coupled to the plurality of inputs (24, 26) and to the variable equalization circuit (32), memory means (12) operatively coupled to the processing means (12) and timebase means (14) operatively coupled to the processing means (12), the timebase means (14) enabling the processing means (12) to determine a time of day, wherein the processing means (12) is operative to couple one of the plurality of inputs (24, 26) to the equalization input and to vary the attenuation of the variable equalization circuit (32) when the time of day is equal to o
    Type: Grant
    Filed: February 3, 1994
    Date of Patent: October 15, 1996
    Assignee: Dobbs-Stanford Corporation
    Inventors: James F. Dobbs, Kevin S. Christian
  • Patent number: 5561404
    Abstract: A wide-band high-frequency analog amplifier is provided in the signal path between an input cable connector and an integrated-circuit based cable equalizer. The amplifier is preferably a common base transistor amplifier. The amplifier serves multiple purposes, including providing additional gain to compensate for losses incurred in the equalizer, increasing return loss on the input line, and allowing different gain levels in the input stage and operating stages of the equalizer.
    Type: Grant
    Filed: March 28, 1995
    Date of Patent: October 1, 1996
    Assignee: Ross Video Limited
    Inventor: John D. Ross
  • Patent number: 5526378
    Abstract: A blind multipath equalizer for a digital communication channel is disclosed. The equalizer includes a sparse digital filter, responsive to a source of a received signal including a digital data signal, and including a plurality of taps, each responsive to a tap coefficient and time displacement, which produces a multipath corrected digital output signal. A filter controller is responsive to the received signal for detecting a multipath signal by calculating the autocorrelation of the received signal, detecting a multipath signal based on the autocorrelation and supplying a tap coefficient and time displacement to one of the plurality of taps to cancel the detected multipath signal.
    Type: Grant
    Filed: December 14, 1994
    Date of Patent: June 11, 1996
    Assignee: Thomson Consumer Electronics, Inc.
    Inventors: Paul G. Knutson, Dong-Chang Shiue
  • Patent number: 5517523
    Abstract: An equalizer (100) is suitable for removing the delay distortion from a switched digital signal received from a telephone channel, where the delay distortion is caused by a bridge-tap connected to the telephone channel. The equalizer includes a feedback delay circuit (200) which is arranged to delay the output signal (150) by an amount of time based on the square of the predominant frequency of the output signal. The resulting delayed feedback signal (130) is then combined with the input signal, thereby compensating for the delay distortion. The equalizer also includes an amplifier (103) which may be adjusted to compensate for the attenuation distortion caused by the bridge-tap.
    Type: Grant
    Filed: June 16, 1993
    Date of Patent: May 14, 1996
    Assignee: Motorola, Inc.
    Inventors: David H. Nabors, David P. Nelson
  • Patent number: 5506549
    Abstract: A cable equalizer (10) receives signals transmitted over a coaxial cable (12) at a multi-path simulator (14). The multi-path simulator (14) includes a splitter (16) that places the signal along a first path (26) and a second path (28), wherein the signal on the first path (26) is 180.degree. out of phase with the signal along the second path (28). The signal along the first path (26) propagates to a combiner circuit (18). The signal along the second path (28) propagates through a delay circuit (20) having a delay value of .tau. that determines the notch spacing of the equalized signal. The signal along second path 28 propagates from delay circuit 20 to a variable attenuator circuit (22) that determines the notch depth for the equalized signal. The combiner (18) receives the signal along the first path (26) and the second path (28) and generates an equalized signal at the output of the multi-path simulator (14).
    Type: Grant
    Filed: November 14, 1994
    Date of Patent: April 9, 1996
    Assignee: DSC Communications Corporation
    Inventor: William L. Crutcher
  • Patent number: 5481564
    Abstract: A digital adaptive equalizer equalizes received signals through digital filtering operations by changing filtering coefficients. It comprises a coefficient calculating unit for calculating the filtering coefficients by using one kind of parameters, such as distance, as an input to a function corresponding to the filtering coefficients and a filtering operation executing unit for executing digital filtering operations based on the filtering coefficients. A variable lag filter for adjusting the phase delay of received received signals is provided. A coefficient converting unit calculates a part or all of tap coefficients of the filter using at least one piece of timing control information.
    Type: Grant
    Filed: July 22, 1991
    Date of Patent: January 2, 1996
    Assignee: Fujitsu Limited
    Inventors: Mitsuo Kakuishi, Yutaka Awata, Norio Ueno, Seiji Miyoshi, Norio Murakami, Atsushi Manabe
  • Patent number: 5455843
    Abstract: Adaptive analog equalizer permitting 16 Mbit/s token ring (TR) transmission over unshielded twisted-pair (UTP) cables. The equalizer (29) is located at the wiring concentrator (25), and consists of a variable and a fixed filter section. The existing TR receiver (49) and transmitter (53) remain unchanged. To compensate for distortion introduced by the cable section (19b) preceding the equalizer, the level of the signal (B) at the equalizer output (35) is used as a control criterion. The additional distortion contributed by the cable section (21a) following the equalizer is accounted for by measuring the level of the signal (D) received from the transmitter (53) of the next TR station. By these two measurements, the equalizer is adjusted such that the cable-length dependent distortion is eliminated at the next receiver (49).
    Type: Grant
    Filed: September 15, 1993
    Date of Patent: October 3, 1995
    Assignee: International Business Machines Corporation
    Inventors: Giovanni Cherubini, Sedat Oelcer, Gottfried Ungerboeck