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Design007-Nov2018

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86 DESIGN007 MAGAZINE I NOVEMBER 2018 while the trace of the inverting signal could cross many resin regions. As a result, due to the consistent change in propagation delay experi- enced by the inverting signal, the phase differ- ence between non-inverting and inverting sig- nals in common mode could be much less than 180°C at the receiving end. The large extent of skew or misalignment between the rising and falling edges leads to the reduction of width and height of the eye diagram. Ultimately, a high bit error is experienced by the receiver. Two case studies are performed to investi- gate the effect of fiber weave on high-speed signal integrity. In the first case study, the effect of various non-homogeneous substrates (i.e., when the substrate segment of the non- inverting signal does not have the same dielec- tric properties as the inverting signal) and segment length experienced by the signal are studied. The entire transmission channel is fixed at 5 inches in length. The non-homoge- neous substrate segment increases from 10% to 50% of the total channel length. This case study is performed for channel models on PCB microstrip and stripline. All of the simulation models for Case Study 1 are listed in Table 1, where NE-glass fiber is applied. In the second case study, the effect of differ- ent fiberglass materials on the signal transmis- sion is investigated. The entire transmission channel length is set at 5 inches, while the non-homogeneous substrate segment length is set as 0.5 inches or 10% of the total channel length. This case study is performed for chan- nel models on PCB microstrip and stripline respectively. All of the simulation models for Case Study 2 are listed in Table 2, where NE- glass and E-glass fiber are chosen as materi- Table 1: Simulation models for Case Study 1. Table 2: Simulation models for Case Study 2.

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