An Accurate Jitter Estimation Technique for Efficient High Speed I/O Testing

This paper describes a technique for estimating total jitter that, along with a loopback-based margining test, can be applied to test high speed serial interfaces. We first present the limitations of the existing estimation method, which is based on the dual-Dirac model. The accuracy of the existing method is extremely sensitive to the choice of the fitting region and the ratio of deterministic jitter to random jitter. Then, we propose a high-order polynomial fitting technique and demonstrate its value for a more efficient and accurate total jitter estimation at a very low Bit-Error-Rate level. The estimation accuracy is also analyzed with respect to different numbers of measurement points for fitting. This analysis shows that only a very small number (i.e., 4) of measurement points is needed for achieving accurate estimation.