Special Events - High Speed Digital Symposium

Dr. Eric Bogatin, Editor of Signal Integrity Journal and Dean of the Teledyne LeCroy Signal Integrity Academy, will chair the symposium. This special event is sponsored by Signal Integrity Journal and requires a conference pass.

Session chair Eric Bogatin is editor at Signal Integrity Journal and the Dean of the Teledyne LeCroy Signal Integrity Academy. Additionally, he is an Adjunct Professor at the University of Colorado - Boulder in the ECEE Dept.

Planned presentations include:

Insitu Glass Fabric Characterization
Brandon Gore and Scott McMorrow, SAMTEC Inc.

A PCB-based glass fabric characterization vehicle will be presented that yields statistically worst-case glass skew for single-ended transmission lines. It also demonstrates the behavior of best/worst case differential trace pitch design. We characterize three mechanically spread glass fabrics and two common PCB dielectric materials. Repetitive traces with a period of 0.001 inch and several positions relative to the fabric grain direction produce maximum realizable skew and repetitive discontinuity resonances. These are used to identify glass style and positioning to aide in PCB characterization.

Extraction of Frequency-Dependent Dielectric Constant: Loss and conductor effects of high-speed digital laminate materials for high-speed channel simulation
Chris Caisse, Allen F. Horn, and Patricia LaFrance, Rogers Corporation.

Over many years of measurements of the propagation and attenuation characteristics of high-frequency copper clad laminate materials, we have noted a number of discrepancies of measured results with generally accepted models, particularly with thin (<0.5 mm) dielectric layers and higher profile copper foils. In order to provide high-speed and high-frequency circuit designers with properties that result in good agreement with measured performance, we measure the complete differential S-parameters of 50 ohm microstrip transmission lines made with the specific grade of copper foil of interest. We generally cover the frequency range of 50 MHz to 50 GHz with laminates of 0.05 to 1.5 mm thickness and up to 110 GHz on materials of 0.2 mm or less.

Test Vehicle Development for Systematic Development and Verification of Materials Models to 50 GHz
Alfred P. Neves, Founder and Chief Technologist at Wild River.

The lack of systematic methodology to extract material models that are verified and are EDA friendly continues to be a sticky signal integrity problem for greater than 10 Gbpsec digital designs. There is a need for uniting the EDA methodology of extracting wide-band loss models with simple robust optimization methods. In this presentation, we show the design of a well-characterized test vehicle and how precision and quality tested measurements are taken using VNA instruments up to 50 GHz. After de-embedding, these measurements are used to compare with predictions from an electromagnetic simulator. We show the very close measurement-simulation correlation possible when measurement artifacts are not present and when accurate design information and materials models are used in the simulator.

A Case Study of Effective Surface Roughness Acquisition
Jason Ellison, The Siemon Company.

Today, engineers quantify surface roughness by cutting a PCB and viewing the copper profile along the edge of the cross-section. This method destroys the sample and finds the surface roughness at one point in the transmission line. A better solution is finding the surface roughness without destroying the sample, and extracting the surface roughness behavior over the entire sample. This presentation shows a method of extracting the "effective surface roughness" of a sample without a cross section. Effective surface roughness is a proposed parameter that quantifies the behavior of the surface roughness of a sample instead of a single point. It is found by measuring the S-parameters of two stripline traces that differ slightly in length. This method also isolates the rough copper attenuation from the dielectric attenuation. Thus, accurate, broadband permittivity of the PCB laminate can be calculated using the same two measurements.

Practical Modeling of High-Speed Channels Based on Data Sheet Input
Bert Simonovich, Lamsim Enterprises Inc.

When designing high-speed serial links beyond 10 GB/s, everything matters. In order to ensure first time success at these speeds, accurate channel modeling is a prerequisite. This is especially true for long backplane channels. Although many EDA tools include the latest models for conductor surface roughness and wideband dielectric properties, obtaining the right parameters to feed the models is always a challenge. So how do we get these parameters? Often the only sources are from data sheets. In most cases, the numbers do not translate directly into parameters needed for the EDA tools. By using copper foil roughness and dielectric material properties, obtained solely from manufacturers’ data sheets, a practical method of modeling high-speed channels is presented.