Layer misregistration in PCB and its effects on signal propagation
Layer misregistration is one of the common issues in PCB manufacturing processes. In addition to physical limitations of manufacturability (large via pad/anti-pad), it may also have impact on the electrical performance of signal lines running through via fields with anti-pad openings. In order to quantify its effects on signal propagation, comprehensive test vehicles were designed, measured, and analyzed. Significant increases in layer-to-layer crosstalk and common-to-differential mode conversion were observed, when corresponding layers were misaligned. The results helped understand the mechanisms, validate modeling methodology, and define design rules.
Techniques for de-embedding a high port count connector to PCB via interposer
In this paper, we propose, design, fabricate and test an interposer that provides a convenient and stable connection between a via-array-type device under test (DUT) and coaxial interface measurement instruments in a frequency band up to 20GHz. A 3D EM model based de-embedding technique is adopted to remove the influence of the interposer from measurements. The validity and repeatability of the apparatus and de-embedding technique are verified by comparing to microwave probe measurements on individual channels. The impact of misregistration arising from PCB fabrication is analyzed based on the measurements of up to three differential pairs in adjacent layers using a 12 port configuration.
Chapter 1 – Nanotechnology: A Toolkit for Cell Behavior
Tissue engineering seeks to effectively manipulate cellular populations to improve the function of damaged or diseased tissues and organs. Many techniques can affect cell behavior; however, in order to maintain desirable function, scientists and engineers design solutions that are as biomimetic as possible. True biomimeticity is very challenging without the incorporation of nanotechnology. Since cells in human tissues are surrounded by a 3D hierarchical tissue extracellular matrix containing numerous nano components, a revolutionary change in tissue engineering is to explore biomimetic nanobiomaterials and advanced 3D nano/microfabrication techniques for creating novel tissue constructs and regulating cell behavior. This chapter will provide an overview of recent nanotechnology in tissue engineering applications. We will put special emphasis on integrating cutting-edge 3D nano/microfabrication techniques with nanobiomaterials for complex tissue and organ regeneration.