Aligning carrier phase in data transmission - using nonlinear limiting member in digital filter loop

摘要

Information for regulating the carrier phase is derived from the comparison between postulated and measured phase deviations. When the reception is mixed with background noise the regulator circuit is affected and may produce far too large a carrier phase correction. The digital loop filter contains an integrating branch consisting of a delay member and an accumulator. Multipliers permit each element to be weighted for optimal results. The proportionality branch comprises a limiter element by which large deviations due to background noise from a postulated value are no longer processed. This limiter does not diminish the regulator sensitivity to genuine carrier phase deviations.