Thomas Alberty

A new pattern jitter free frequency error detector

One method to enable fast acquisition of a phase-locked loop (PLL) in spite of large frequency offsets and small PLL bandwidths is to use an additional AFC (automatic frequency control) loop. A suitable frequency error detector (FED) for large frequency offsets is the well-known balanced quadricorrelator. This FED is shown to produce great pattern jitter if it is to work with digital modulated MQAM and MPSK signals (M>2) and random data. The authors describe how this pattern jitter for MQAM and MPSK signals can be overcome completely. Another understanding of the balance quadricorrelator is also given. >

Frequency domain interpretation of the Cramer-Rao bound for carrier and clock synchronization

The Cramer-Rao bound is a fundamental lower bound on the variance of unbiased estimates. Applied to carrier phase and clock phase synchronization for digital communications, it is shown that the corresponding bounds can be derived from the power density spectrum of the transmitted signal-irrespective of the particular modulation scheme. This allows the localization of the available information about the parameters in the frequency domain. If the incoming signal is only partly exploited, the resulting performance loss is now easily attainable. >