DesignCon 2022 Schedule Builder

The glass-weave periodic loading and periodic layout usually cause additional trace losses. These losses occur when the integer multiples of the half wavelength of the propagating signal equal the period length, usually manifesting as resonances in the insertion and return loss. A printed circuit board (PCB), whose operating frequency encounters this kind of resonance, will face signal integrity issues. In actual PCB designs, to avoid the skew influence of glass-weave effect, designers will rotate the high-speed signal traces. For saving the layout space, some periodic layout methods are employed. Both methods will introduce resonances. To solve this problem, a lot of work on predicting resonance frequency and intensity has been carried out. The mechanism of this resonance has been well studied by using basic transmission line theory. Three-dimensional full-wave simulation also proves that simple numerical calculations can accurately predict the resonance frequency due to the periodic structure. However, most of early studies are based on single layer PCB models, instead of high-speed products composed of multilayer PCBs. Due to the complexity of the real laminates, the uncertainty of the processing technology will also affect the resonance. For the complicated actual situation, new experiments and simulation studies are necessary.

Takeaway

1, Review the mechanism of the resonances in PCBs.
2, The influences of designs, material characteristics and processes on the resonances are discussed.
3, A simulation method is proposed and verified with measure data.
4, The effect of resonance on the actual product is confirmed by active simulations.

Intended Audience

1, Familiar with signal integrity knowledge, such as basic transmission line theory and S parameter.
2, Know about PCB materials and processes.