Timing recovery for synchronous binary data transmission

This paper analyzes different methods of adjusting the sampling time for detecting synchronous binary data, based on properties of the random data signal itself. The static error and the variance of the jitter of the resultant sampling instant are calculated where the effects of frequency offset, additive noise, signal overlap, and jitter of the reference source are included. The threshold crossing timing recovery system adjusts the sampling time in response to the times at which the data signal crosses the amplitude threshold. The sampled-derivative system uses the time derivative of the signal at the sampling time to adjust sampling phase. It is shown that both systems lead to approximately the same amount of jitter in the presence of noise and signal overlap for a given bandwidth of the control loop. An improved timing recovery system is presented which is constructed by adding correction signals to the sampled-derivative system. This system accounts for intersymbol interference in a manner that tends to set the sampling time at the point of maximum eye opening, where the error probability is minimum for the most adverse message sequence.