Method and Apparatus for Reducing Jitter in Multi-Gigahertz Systems

[0028]One experimental embodiment and supporting theory is now disclosed. Because testing at multi-gigahertz frequencies is so dependent on high-accuracy timing signals, it may be necessary to utilize more automated test equipment (“ATE”) resources for the most critical signals (such as clocks and timing references). In one experimental embodiment, multiplexing and demultiplexing modules were added to loadboards to synthesize multi-gigahertz test patterns using multiple 1 Gbps ATE channels.

[0029]Several “Driver” and “Receiver” modules were used to provide over 80 multi-Gbps differential channels in a combination of HyperTransport (1.6 Gbps per channel) and PCI-express (at 2.5 Gbps per channel). The ATE jitter level was typically in the range of 4 ps-8 ps, which is not sufficiently low for our testing needs in the 3 to 10 Gbps range. Therefore, a low-jitter (˜1.4 ps) RF clock source was used to provide a programmable timing reference to each of the modules. This level of jitter is a fac