General

General

Mode Conversion Path Vias in Differential Via Pairs in ANSYS HFSS

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      This signal integrity video explores unwanted mode conversion, from differential signal to common signal, due to unbalanced ground return current via paths in a multilayer differential pair simulated in HFSS 3D Layout. Starting at 1:35, the video shows how to move a differential pair, including the port, from one lower layer up to another layer in one operation. At 2:46 the video describes the engineering relation between asymmetry and mode conversion in terms of mixed mode S-parameters. The HFSS 3D Layout unbalanced (asymmetric) design, with a ground return path via missing, is created after 4:58. The change to an HFSS fully arbitrary 3D (FA3D) design starts at 7:19, with the symmetrical S-parameters shown at 8:34. The asymmetrical (unbalanced) FA3D design consideration starts at 9:14