Patents Assigned to FreeSystems Pte. Ltd.
  • Patent number: 7555031
    Abstract: A receiver system that receives and recovers digital data on a fixed frequency channel of a radio frequency band in the presence of interference from at least one FHSS interference source. The digital data has a duration of data frames compacted then replicated to form duplicated time compressed data frames. The duplicated time compressed frames of data are transmitted to a communication receiver that has a time diversity data recovery circuit. The time diversity data recovery circuit buffers the received compressed and replicated data frames, evaluates whether each of the duplicated time compressed data frames are received correctly. If any one of the duplicated time compressed data frames is destroyed, the copy of the destroyed duplicated time compressed data frame is used to recover the data frame.
    Type: Grant
    Filed: November 8, 2005
    Date of Patent: June 30, 2009
    Assignee: FreeSystems Pte. Ltd.
    Inventors: Chee Oei Chan, Beng Huat Chua
  • Patent number: 7551681
    Abstract: A transmitter system that transfers digital data on a fixed frequency channel of a radio frequency band in the presence of interference from at least one FHSS interference source includes a time diversity generation circuit. The time diversity circuit compacts a duration of data frames then replicate the time compressed data frames. The duplicated time compressed frames of data are transmitted to a communication receiver that has a time diversity data recovery circuit.
    Type: Grant
    Filed: November 8, 2005
    Date of Patent: June 23, 2009
    Assignee: Freesystems Pte. Ltd.
    Inventors: Chee Oei Chan, Beng Huat Chua
  • Patent number: 7289560
    Abstract: A communication system compensates pulse positioned modulated data signals for channel induced intersymbol interference and extracts pulse positioned encoded data from a received signal corrupted with the channel induced intersymbol interference. The communication system has a transmitter and a receiver. The transmitter includes a modulation apparatus that has a symbol mapping circuit, which receives data symbols to be transmitted and maps the data symbols to a transmission code. The receiver has a demodulation apparatus to recover data symbols in the presence of the channel induced intersymbol interference. The demodulation apparatus has a sampling circuit in communication with a signal receiving circuit within the receiver to sample at a regular period received data symbols acquired by the receiving circuit. The samples of the data samples are retained by a sample retaining circuit in communication with the sampling circuit.
    Type: Grant
    Filed: January 17, 2003
    Date of Patent: October 30, 2007
    Assignee: FreeSystems Pte. Ltd.
    Inventor: Chua Beng Huat
  • Patent number: 6741659
    Abstract: A system for transmitting digitized samples of analog signals while concealing unrecoverable digitized samples of analog signals to maintain a level of fidelity in reproducing the analog signals. The digitized samples of the analog signals are burst transmitted such that the probability of interference with the transmission and thus corruption of the digitized samples of the analog signals is minimized. The digitized samples are received without synchronizing a receiving clock with a transmitting clock to capture the digitized samples of the analog signals. The digitized samples are converted from various sampling rates to digitized samples of the analog signals having a rate. Any large groups of digitized samples that are in error or corrupted in transmission are softly muted to avoid annoying clicks. Any long term difference between a transmit clock and a receive clock is tracked and the digitized samples are interpolated or decimated to eliminate any underrun or overrun of the digitized samples.
    Type: Grant
    Filed: October 25, 1999
    Date of Patent: May 25, 2004
    Assignee: FreeSystems Pte. Ltd.
    Inventors: Chee Oei Chan, Beng Huat Chua, Chee Kong Siew, Kah Yong Lee
  • Patent number: 6510182
    Abstract: A system for transmitting, receiving, recovering, and reproducing digitized samples of analog signals while concealing unrecoverable digitized samples of analog signals to maintain a level of fidelity in reproducing the analog signals. The digitized samples of the analog signals are burst transmitted such that the probability of interference with the transmission and thus corruption of the digitized samples of the analog signals is minimized. The digitized samples are received without synchronizing a receiving clock with a transmitting clock to capture the digitized samples of the analog signals. The digitized samples are converted from various sampling rates to digitized samples of the analog signals having a rate. Any large groups of digitized samples that are in error or corrupted in transmission are softly muted to avoid annoying clicks.
    Type: Grant
    Filed: October 25, 1999
    Date of Patent: January 21, 2003
    Assignee: FreeSystems Pte. Ltd.
    Inventors: Kah Yong Lee, Bena Huat Chua, Chee Oei Chan, Chee Kong Siew