Periodic jitter (PJ) measurement methodology

#The present subject matter relates to the characterization and measurement of jitter as related to various communications signals. More particularly, the present subject matter relates to methodologies for measuring periodic jitter using time interval analysis methodologies.

#Jitter is defined as deviations of signal edges from their ideal positions in time. Jitter characterization is an integral part of performance qualification for a wide variety of application, such as wideband serial communication (SONET, SDH), high-speed serial input/output (IO) devices (HyperTransport, PCI-Express, Infiniband, RapidIO), and timing circuits including clock generators, and data recovery units. In serial communication applications, jitter affects the link bit-error-rate (BER), which is a key performance parameter.

#To qualify this impact, it is necessary to decompose jitter to its various components, because each jitter type has a different effect on BER. Different types of jitter include, Random jitter (RJ), Data-dependent jitter (DDJ), Duty-cycle distortion (DCD), Periodic jitter (PJ), and Bounded uncorrelated jitter (BUJ)

#A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

#FIGS. 1a and 1b illustrate the autocorrelation function obtained from the direct and N-variance methods;

#FIGS. 2a-2c show how differing levels of interpolation affect the noise floor in PSD for a 2 Gbps signal and arbitrary pattern selection to adjust the number of interpolated point;

#Repeat use of reference characters throughout the present specification and appended drawings is intended to represent same or analogous features or elements of the invention.

#As discussed in the Summary of the Invention section, the present subject matter is particularly concerned with methodologies involving the use of a continuous time interval analyzer (CTIA) to provide effective periodic jitter (PJ) measurement.

#Selected combinations of aspects of the disclosed technology correspond to a plurality of different embodiments of the present invention. It should be noted that each of the exemplary embodiments presented and discussed herein should not insinuate limitations of the present subject matter. Features or steps illustrated or described as part of one embodiment may be used in combination with aspects of another embodiment to yield yet further embodiments. Additionally, certain features may be interchanged with similar devices or features not expressly mentioned which perform the same or similar function.