Non-integer oversampled timing recovery for higher order quadrature modulation communication systems using quadrature and in-phase samples

摘要

Apparatus and method for performing entirely digital timing recovery for high bandwidth radio frequency communications. The received digital data source can be sampled from any (minimum 2×) non-integer oversampled transmitted data. This method re-samples the data through interpolation and phase adjustment. The output phase error adjusts the receiver's Analog-to-digital Convertor sampling clock to improve synchronization with the transmitter's Digital-to-analog Convertor clock phase, thus improving transmitted symbol recovery.

主权项

1. An apparatus for timing recovery in digital communications, comprising:
a timing recovery subsystem into which the in-phase and quadrature components of a digitized communications signal are input and a phase adjustment signal is output; and an interpolation subsystem into which said phase adjustment signal and said in-phase and quadrature components are input and recovered in-phase and quadrature symbols are output; wherein said timing recovery subsystem further comprises:
a buffer into which the in-phase and quadrature components of a digitized communications signal are input;a gain block outputting an update gain signal;timing recovery logic, the output of which is a phase offset signal, and into which is input:
an array of buffered in-phase and quadrature components;said update gain signal; anda feedback sample of said phase offset signal; anda lowpass filter for removing phase variability extremes in said phase offset signal.