Patents by Inventor Loke Kun Tan
Loke Kun Tan has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Publication number: 20120082277Abstract: Method and apparatuses are disclosed to substantially compensate for various unwanted interferences and/or distortions within a communications receiver. Each of these apparatuses and methods estimate the various unwanted interferences and/or distortions within the communications receiver. Each of these apparatuses and methods remove the estimates of the various unwanted interferences and/or distortions within the communications receiver from one or more communications signals within the communications receiver to substantially compensate for the various unwanted interferences and/or distortions.Type: ApplicationFiled: June 30, 2011Publication date: April 5, 2012Applicant: Broadcom CorporationInventors: Ramon Alejandro Gomez, Bruce J. Currivan, Massimo Brandolini, Young Shin, Francesco Gatta, Hanli Zou, Loke Kun Tan, Lin He, Thomas Joseph Kolze, Leonard Dauphinee, Robindra Joshi, Binning Chen
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Publication number: 20120082276Abstract: Method and apparatuses are disclosed to substantially compensate for various unwanted interferences and/or distortions within a communications receiver. Each of these apparatuses and methods estimate the various unwanted interferences and/or distortions within the communications receiver. Each of these apparatuses and methods remove the estimates of the various unwanted interferences and/or distortions within the communications receiver from one or more communications signals within the communications receiver to substantially compensate for the various unwanted interferences and/or distortions.Type: ApplicationFiled: June 30, 2011Publication date: April 5, 2012Applicant: Broadcom CorporationInventors: Ramon Alejandro Gomez, Bruce J. Currivan, Massimo Brandolini, Young Shin, Francesco Gatta, Hanli Zou, Loke Kun Tan, Lin He, Thomas Joseph Kolze, Leonard Dauphinee, Robindra Joshi, Binning Chen
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Patent number: 8098725Abstract: Improved decision feedback equalizer and decision directed timing recovery systems and methods suitable for use in connection with a dual mode QAM/VSB receiver system are disclosed. A trellis decoder operates in conjunction with a decision feedback equalizer circuit on trellis coded 8-VSB modulated signals. The trellis decoder includes a 4-state traceback memory circuit outputting a maximum likelihood decision as well as a number of intermediate decisions based upon the maximum likelihood sequence path. Any number of decisions, along the sequence, may be provided as an input signal to timing recovery system loops, with the particular decision along the sequence chosen on the basis of its delay through the trellis decoder. Variable delay circuitry is coupled to the other input of the timing recovery system loops in order to ensure that both input signals bear the same timestamp.Type: GrantFiled: December 8, 2008Date of Patent: January 17, 2012Assignee: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe
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Publication number: 20110200091Abstract: An apparatus is disclosed to compensate for non-linear effects resulting from the transmitter, the receiver, and/or the communication channel in a communication system. A receiver of the communication system contains an image cancellation module that compensates for images generated during the modulation and/or demodulation process. The image cancellation module includes a fine carrier correction loop to correct for frequency offsets between the transmitter and receiver. The image cancellation module includes a coarse acquisition mode and a decision directed mode. The decision directed mode allows for a larger signal-to-noise ratio for the receiver when compared against the coarse acquisition mode.Type: ApplicationFiled: February 3, 2011Publication date: August 18, 2011Applicant: Broadcom CorporationInventors: Bruce J. Currivan, Loke Kun Tan, Thomas Joseph Kolze, Hanli Zou, Lin He
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Patent number: 7885323Abstract: An apparatus is disclosed to compensate for non-linear effects resulting from the transmitter, the receiver, and/or the communication channel in a communication system. A receiver of the communication system contains an image cancellation module that compensates for images generated during the modulation and/or demodulation process. The image cancellation module includes a fine carrier correction loop to correct for frequency offsets between the transmitter and receiver. The image cancellation module includes a coarse acquisition mode and a decision directed mode. The decision directed mode allows for a larger signal-to-noise ratio for the receiver when compared against the coarse acquisition mode.Type: GrantFiled: July 23, 2007Date of Patent: February 8, 2011Assignee: Broadcom CorporationInventors: Bruce J. Currivan, Loke Kun Tan, Thomas Joseph Kolze, Hanli Zou, Lin He
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Publication number: 20090086808Abstract: Improved decision feedback equalizer and decision directed timing recovery systems and methods suitable for use in connection with a dual mode QAM/VSB receiver system are disclosed. A trellis decoder operates in conjunction with a decision feedback equalizer circuit on trellis coded 8-VSB modulated signals. The trellis decoder includes a 4-state traceback memory circuit outputting a maximum likelihood decision as well as a number of intermediate decisions based upon the maximum likelihood sequence path. Any number of decisions, along the sequence, may be provided as an input signal to timing recovery system loops, with the particular decision along the sequence chosen on the basis of its delay through the trellis decoder. Variable delay circuitry is coupled to the other input of the timing recovery system loops in order to ensure that both input signals bear the same timestamp.Type: ApplicationFiled: December 8, 2008Publication date: April 2, 2009Applicant: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe
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Patent number: 7474695Abstract: Improved decision feedback equalizer and decision directed timing recovery systems and methods suitable for use in connection with a dual mode QAM/VSB receiver system are disclosed. A trellis decoder operates in conjunction with a decision feedback equalizer circuit on trellis coded 8-VSB modulated signals. The trellis decoder includes a 4-state traceback memory circuit outputting a maximum likelihood decision as well as a number of intermediate decisions based upon the maximum likelihood sequence path. Any number of decisions, along the sequence, may be provided as an input signal to timing recovery system loops, with the particular decision along the sequence chosen on the basis of its delay through the trellis decoder. Variable delay circuitry is coupled to the other input of the timing recovery system loops in order to ensure that both input signals bear the same timestamp.Type: GrantFiled: July 21, 2004Date of Patent: January 6, 2009Assignee: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe
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Publication number: 20080187038Abstract: An apparatus is disclosed to compensate for non-linear effects resulting from the transmitter, the receiver, and/or the communication channel in a communication system. A receiver of the communication system contains an image cancellation module that compensates for images generated during the modulation and/or demodulation process. The image cancellation module includes a fine carrier correction loop to correct for frequency offsets between the transmitter and receiver. The image cancellation module includes a coarse acquisition mode and a decision directed mode. The decision directed mode allows for a larger signal-to-noise ratio for the receiver when compared against the coarse acquisition mode.Type: ApplicationFiled: July 23, 2007Publication date: August 7, 2008Applicant: Broadcom CorporationInventors: Bruce J. Currivan, Loke Kun Tan, Thomas Joseph Kolze, Hanli Zou, Lin He
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Patent number: 7403579Abstract: A television receiver system capable of receiving and demodulating television signal information content that has been modulated and transmitted in accordance with a variety of modulation formats is disclosed. In particular, the system is able to accommodate receipt and demodulation of at least 8 and 16-VSB modulated signals in order to support US HDTV applications, as well as 64 and 256-QAM modulated signals, for European and potential US CATV implementations. The system includes carrier and timing recovery loops adapted to operate on an enhanced pilot signal as well as decision directed carrier phase recovery loops. Phase detectors operate on I and Q rail signals, or generate a Q rail from a Hilbert transform of the I rail. Decision directed loops incorporate a trellis decoder in order to operate on sequence estimated decisions for improved reliability in poor SNR environments.Type: GrantFiled: January 7, 2005Date of Patent: July 22, 2008Assignee: Broadcom CorporationInventors: Steven T. Jaffe, Tian-Min Liu, Loke Kun Tan
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Patent number: 7277481Abstract: A system for reducing the complexity of an adaptive decision feedback equalizer, for use in connection with a dual-mode QAM/VSB receiver system is disclosed. QAM and VSB symbols, which are expressed in two's compliment notation, include an extra bit required to compensate for a fixed offset term introduced by the two's compliment numbering system. A decision feedback equalizer includes a decision feedback filter section which operates on symbolic decisions represented by a wordlength which excludes the added bit representing the offset. The vestigal word is convolved with the decision feedback filter's coefficients, while a DC component, corresponding to the excluded bit, is convolved with the same coefficient values in a correction filter. The two values are summed to provide an ISI compensation signal at the input of a decision device such as a slicer. A DC component representing a pilot tone in VSB transmission systems also introduces a DC component, and additional bits, to a VSB wordlength.Type: GrantFiled: April 23, 2004Date of Patent: October 2, 2007Assignee: Broadcom CorporationInventors: Loke Kun Tan, Tian-Min Liu, Hing “Ada” T. Hung
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Patent number: 7203227Abstract: All digital reference frequency locking. An all digital approach is provided for operation within one or more CMs within a cable modem communication system to lock the upstream of the one or more CMs to the downstream symbol clock provided from a CMTS. The locking of the CM's upstream may be performed using one of at least three different functions: (1) Locking the upstream symbol clock phase to the downstream symbol clock phase, (2) Locking the downstream symbol clock phase to the headend reference clock phase (typically 10.24 MHz or integer multiple thereof), and (3) Locking the upstream carrier frequency to the downstream symbol clock frequency. The all-digital techniques for supporting all digital reference frequency locking functionality provide high performance to support S-CDMA and other synchronous modulation techniques.Type: GrantFiled: November 14, 2002Date of Patent: April 10, 2007Assignee: Broadcom CorporationInventors: Bruce J. Currivan, Ravi Bhaskaran, Thomas J. Kolze, Kevin Lee Miller, Jeffrey S. Putnam, Fang Lu, Tak K. Lee, Thuji S. Lin, Loke Kun Tan, Gopal Triplicane Venkatesan, Hsin-An Liu, Jonathan S. Min, James P. Cavallo
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Patent number: 7161613Abstract: An electronic, programmable filter is disclosed which selectively removes interference, noise or distortion components from a frequency band without perturbing any of the other signals of the band. An input frequency band such as a television channel spectrum is initially demodulated to baseband and applied to the input of the filter. The baseband spectrum is combined in a complex mixer with a synthesized frequency signal that shifts the spectrum a characteristic amount, in the frequency domain, so as to position an interference component in the region about DC. Once shifted, the frequency components about DC are removed by DC canceler circuit and the resulting spectrum is mixed with a subsequent synthesized frequency signal which shifts the spectrum back to its original representation and baseband. The frequency signals are developed by a programmable frequency synthesizer which a user may program with an intelligence signal that defines the frequency location of an interference signal within the spectrum.Type: GrantFiled: April 16, 2004Date of Patent: January 9, 2007Assignee: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe, Robert A. Hawley
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Patent number: 7027528Abstract: Improved carrier recovery and symbol timing systems and methods suitable for use in connection with a dual-mode QAM/VSB receiver system is disclosed. Carrier and symbol timing acquisition and tracking loops are phase/frequency locked to an inserted pilot signal provided in an input VSB spectrum at a given frequency. An input spectrum is centered about baseband and the pilot is extracted by an equivalent filter which functions as a bandpass filter having pass bands centered about the pilot frequency. Since the pilot signal's frequency is given, its position in the frequency domain for any sampling frequency, is deterministic. The receiver's sampling frequency is provided such that the relationship is expressed as fc=fS/4. When tracked by a phase-lock loop, the pilot signal will appear at the correct location in the spectrum if the sampling frequency fS is correct, and will be shifted in one direction or the other if the sampling frequency fS is too high or too low.Type: GrantFiled: July 21, 2004Date of Patent: April 11, 2006Assignee: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe
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Patent number: 6842495Abstract: A television receiver system capable of receiving and demodulating television signal information content that has been modulated and transmitted in accordance with a variety of modulation formats is disclosed. In particular, the system is able to accommodate receipt and demodulation of at least 8 and 16-VSB modulated signals in order to support US HDTV applications, as well as 64 and 256-QAM modulated signals, for European and potential US CATV implementations. The system includes carrier and timing recovery loops adapted to operate on an enhanced pilot signal as well as decision directed carrier phase recovery loops. Phase detectors operate on I and Q rail signals, or generate a Q rail from a Hilbert transform of the I rail. Decision directed loops incorporate a trellis decoder in order to operate on sequence estimated decisions for improved reliability in poor SNR environments.Type: GrantFiled: November 3, 1999Date of Patent: January 11, 2005Assignee: Broadcom CorporationInventors: Steven T. Jaffe, Tian-Min Liu, Loke Kun Tan
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Publication number: 20040258184Abstract: Improved decision feedback equalizer and decision directed timing recovery systems and methods suitable for use in connection with a dual mode QAM/VSB receiver system are disclosed. A trellis decoder operates in conjunction with a decision feedback equalizer circuit on trellis coded 8-VSB modulated signals. The trellis decoder includes a 4-state traceback memory circuit outputting a maximum likelihood decision as well as a number of intermediate decisions based upon the maximum likelihood sequence path. Any number of decisions, along the sequence, may be provided as an input signal to timing recovery system loops, with the particular decision along the sequence chosen on the basis of its delay through the trellis decoder. Variable delay circuitry is coupled to the other input of the timing recovery system loops in order to ensure that both input signals bear the same timestamp.Type: ApplicationFiled: July 21, 2004Publication date: December 23, 2004Applicant: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe
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Publication number: 20040258180Abstract: Improved carrier recovery and symbol timing systems and methods suitable for use in connection with a dual-mode QAM/VSB receiver system is disclosed. Carrier and symbol timing acquisition and tracking loops are phase/frequency locked to an inserted pilot signal provided in an input VSB spectrum at a given frequency. An input spectrum is centered about baseband and the pilot is extracted by an equivalent filter which functions as a bandpass filter having pass bands centered about the pilot frequency. Since the pilot signal's frequency is given, its position in the frequency domain for any sampling frequency, is deterministic. The receiver's sampling frequency is provided such that the relationship is expressed as fc=fS/4. When tracked by a phase-lock loop, the pilot signal will appear at the correct location in the spectrum if the sampling frequency fS is correct, and will be shifted in one direction or the other if the sampling frequency fS is too high or too low.Type: ApplicationFiled: July 21, 2004Publication date: December 23, 2004Applicant: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe
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Publication number: 20040232951Abstract: A detector circuit for determining whether synchronization lock has been optimally achieved in feedback-type control systems. The detector circuit evaluates an error signal developed by a phase/frequency detector and compares the absolute magnitude of the error signal to a first threshold signal corresponding to a magnitude metric. When the value of the error signal is less than the magnitude threshold value, an event signal initiates a time interval counter which continues counting so long as the error signal remains below the magnitude threshold value. The time interval counter continues until it counts to a second threshold value corresponding to a timing metric. At this point, synchronization lock is declared.Type: ApplicationFiled: June 30, 2004Publication date: November 25, 2004Applicant: Broadcom CorporationInventors: Loke Kun Tan, Farzad Etemadi, Denny Yuen, Shauhyurn (Sean) Tsai
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Patent number: 6803828Abstract: A detector circuit for determining whether synchronization lock has been optimally achieved in feedback-type control systems. The detector circuit evaluates an error signal developed by a phase/frequency detector and compares the absolute magnitude of the error signal to a first threshold signal corresponding to a magnitude metric. When the value of the error signal is less than the magnitude threshold value, an event signal initiates a time interval counter which continues counting so long as the error signal remains below the magnitude threshold value. The time interval counter continues until it counts to a second threshold value corresponding to a timing metric. At this point, synchronization lock is declared.Type: GrantFiled: May 9, 2003Date of Patent: October 12, 2004Assignee: Broadcom CorporationInventors: Loke Kun Tan, Farzad Etemadi, Denny Yuen, Shauhyurn Tsai
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Publication number: 20040196361Abstract: An electronic, programmable filter is disclosed which selectively removes interference, noise or distortion components from a frequency band without perturbing any of the other signals of the band. An input frequency band such as a television channel spectrum is initially demodulated to baseband and applied to the input of the filter. The baseband spectrum is combined in a complex mixer with a synthesized frequency signal that shifts the spectrum a characteristic amount, in the frequency domain, so as to position an interference component in the region about DC. Once shifted, the frequency components about DC are removed by DC canceler circuit and the resulting spectrum is mixed with a subsequent synthesized frequency signal which shifts the spectrum back to its original representation and baseband. The frequency signals are developed by a programmable frequency synthesizer which a user may program with an intelligence signal that defines the frequency location of an interference signal within the spectrum.Type: ApplicationFiled: April 16, 2004Publication date: October 7, 2004Applicant: Broadcom CorporationInventors: Tian-Min Liu, Loke Kun Tan, Steven T. Jaffe, Robert A. Hawley
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Publication number: 20040196897Abstract: A system for reducing the complexity of an adaptive decision feedback equalizer, for use in connection with a dual-mode QAM/VSB receiver system is disclosed. QAM and VSB symbols, which are expressed in two's compliment notation, include an extra bit required to compensate for a fixed offset term introduced by the two's compliment numbering system. A decision feedback equalizer includes a decision feedback filter section which operates on symbolic decisions represented by a wordlength which excludes the added bit representing the offset. The vestigal word is convolved with the decision feedback filter's coefficients, while a DC component, corresponding to the excluded bit, is convolved with the same coefficient values in a correction filter. The two values are summed to provide an ISI compensation signal at the input of a decision device such as a slicer. A DC component representing a pilot tone in VSB transmission systems also introduces a DC component, and additional bits, to a VSB wordlength.Type: ApplicationFiled: April 23, 2004Publication date: October 7, 2004Applicant: Broadcom CorporationInventors: Loke Kun Tan, Tian-Min Liu, Hing "Ada" T. Hung