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.
Repressive coping before and after diagnosis of breast cancer
Objective: The aim was to investigate to which extent emotional repression is a premorbid coping tendency of cancer patients and/or a coping response to the threat posed by a cancer diagnosis. The results of one previous study of breast cancer patients suggest the latter possibility, and our aim was to replicate and extend these findings.