A signal processing module with a timing comparator such as a time to digital converter is provided. The timing comparator comprises an error cancellation stage to remove a predicted effect of the imparted jitter from the timing comparator output signal. A jitter detector is used to detect the jitter from the comparator output signal, preferably residual jitter after the predicted effect of the jitter has been removed. Synchronous detection, such as correlation with the predicted jitter may be used to detect the jitter. The jitter detector adjusts a calibration factor of the timing comparator dependent on the detected jitter.