Vladimir Dmitriev-Zdorov

In this detailed study of jitter, Vladimir Dmitriev-Zdorov considers its conversion into vertical noise and the propagation of this noise in a channel. It applies to many, if not all, linear systems. Read on to see his analysis as illustrated in both the frequency and time domains for small and large magnitude jitter.

The first available roughness models, such as Hammerstad, Hemispherical, Huray aimed to predict loss increase due to metal roughness. However, there was a problem. Read on to find out more.

In the GB/s regime, accurate modeling of insertion loss and phase delay is a precursor to successful high-speed serial link designs. We propose a causal (physically meaningful) form of the Hammerstad and Cannonball-Huray metal roughness frequency dependent complex correction factor. Compared to the widely used, non-causal form, it considerably increases the inductive component of internal metal impedance. Transmission lines simulated with a causal version demonstrate increased phase delay and characteristic impedance. By obtaining the dielectric and roughness parameters solely from manufacturers' data sheets, we validate the model through a detailed case study to test its accuracy.

We analyze the computational procedure specified for Channel Operation Margin (COM) and compare it to traditional statistical eye/BER analysis. There are a number of differences between the two approaches, ranging from how they perform channel characterization, to how they consider Tx and Rx noise and apply termination, to the differences between numerical procedures employed to convert given jitter and crosstalk responses into the vertical distribution characterizing eye diagrams and BER. We show that depending on the channel COM may potentially overestimate the effect of crosstalk and, depending on a number of factors, over- or underestimate the effect of transmit jitter, especially when the channel operates at the rate limits. We propose a modification to the COM procedure that eliminates these problems without considerable work increase.