Transfer functions for the reference clock jitter in a serial link: theory and applications

Transfer functions for the reference clock jitter in a serial link such as the PCI express 100 MHz reference clock are established for various clock and data recovery circuits (CDRCs). In addition, mathematical interrelationships between phase, period, and cycle-to-cycle jitter are established and phase jitter is used with the jitter transfer function. Numerical simulations are carried out for these transfer functions. Relevant eye-closure/total jitter at a certain bit error rate (BER) level for the receiver is estimated by applying these jitter transfer functions to the measured phase jitter of the reference clock over a range of transfer function parameters. Implications of this new development to serial link reference clock testing and specification formulation are discussed.