Patents Assigned to Datum Systems
  • Patent number: 8553805
    Abstract: A method and apparatus at a local terminal are described for demodulating a remote-terminal signal located at a subband offset frequency in a frequency subband of relayed interference from a transponder satellite link. The demodulation of the remote-terminal signal is accomplished by transferring the digital data that produced the local-terminal transmit signal to the local-terminal receiver. The digital data is time-delayed and converted to a narrowband offset-constellation signal that cancels the relayed interference in an adaptive equalizer. Providing cancellation in the subband of the relayed interference produces larger interference cancellation factors than those obtained in conventional broadband cancellation systems. A phase-noise error signal is also generated and used to increase cancellation levels limited by phase noise generated in the satellite link frequency converters.
    Type: Grant
    Filed: May 5, 2011
    Date of Patent: October 8, 2013
    Assignees: Datum Systems, Inc.
    Inventors: Peter Monsen, David Bagby
  • Patent number: 5319679
    Abstract: In a communications system using a synchronous digital data stream employing multiple-amplitude-level symbols, preamble acquisition and d.c. offset correction is achieved simultaneously by receiver averaging of sampled values in amplitude and in time to determine the average d.c. offset and the nominal transition boundaries between symbols. After symbol timing acquisition and d.c. offset acquisition, other circuitry is enabled for symbol tracking, and additional circuitry uses the acquired d.c. offset and symbol timing information to extract the data from the symbol stream. D.c. offset tracking involves subtracting the d.c. offset value from the output of an ADC representing the digitized baseband signal and then adjusting the d.c. offset value by a fraction of the error between the actual value and the expected value relative to the offset corrected signal. Symbol timing tracking is accomplished through examination of the d.c.
    Type: Grant
    Filed: December 9, 1992
    Date of Patent: June 7, 1994
    Assignee: Datum Systems
    Inventor: David Bagby