Timing acquisition in voiceband data sets
Digital data receiver including timing adjustment circuit Patent #: 4577334
ApplicationNo. 07/163357 filed on 03/02/1988
US Classes:375/222, Modems (data sets)375/231, Training period or initial set up375/232, Adaptive375/377MISCELLANEOUS
ExaminersPrimary: Griffin, Robert L.
Assistant: Huseman, Marianne
Attorney, Agent or Firm
International ClassH04L 25/03 (20060101)
Foreign Application Priority Data1987-11-16 GB
AbstractA multipoint data modem communication system includes a control modem (12) and a plurality of tributary modems (14, 16, 18). During an initial training mode, receiver parameters and equalizer coefficients are determined and stored in a storage device (156) in the control modem receiver at addresses associated with the tributary modems. During subsequent relatively short training signals, the stored parameters are accessed. The remote modems transmit identification address tones in parallel with the subsequent training signals, at frequencies separated by 200 Hz intervals from the training signal spectrum frequencies. A plurality of Discrete Fourier Transform (DFT) filter circuits (190) are utilized to determine the transmitted addresses by measuring the correlation of the received signal with locally-generated frequencies.