Transport delay and jitter measurements based on cross correlation on real-time oscilloscopes

摘要

In clock driven high speed digital systems, the reference clock propagates through different paths. The layout of the paths introduces delay on the clock signals. Certain blocks along the path such as clock data recovery (CDR) units also introduce delays. This paper describes a method to measure the transport delays and jitters effectively using real-time oscilloscope based on cross correlation. The method provides accurate measurements in least mean squared (LMS) sense. The transport delay effects on jitter measurement are analyzed in frequency domain. This method is compared to other means for measuring transport delay based on instruments such as VNA, TDR/TDT and spectrum analyzers. Measuring transport delay using transfer function is compared with using cross-correlation function.