Mitigating differential skew by rotating meshed ground for high-density layout in flexible printed circuits

Abstract

Asymmetry of differential transmission lines over a meshed ground plane causes differential skew, which leads to signal integrity issues. We measured to evaluate how the angle between the differential transmission lines and meshed ground (the rotation angle) affected differential skew. We also investigated the effect of the lines' position on characteristic impedance and the feasibility of high-density layout of the differential transmission lines, including the bend structure. We found that the differential skew and characteristic impedance are not significantly affected by the position of the differential transmission lines and meshed ground when the rotation angle is set to 30 • , a relatively small value. Measurements showed that our design is effective.

A low loss microstrip line on thin flexible substrate film by defected ground structure

“…But A CPW could hardly be arranged multiple line in narrowed substrate because the ground plane sets along the line at same planar layer. An MSL fabricated on a mesh-type ground has been proposed to reduce insertion loss [5]. However, it is difficult to match the characteristic impedance of the line on the mesh-type ground.…”

Improving Signal Integrity by Reducing Mode Conversion in Differential Pairs on a Meshed Ground in Flexible Printed Circuit Boards

“…However, the guard traces take up space that is already lacking. Wang et al [15] proposed rotating a meshed ground by 30° rather than the conventional 45° relative to differential traces. While the impedance variation was reduced, the mode conversion did not significantly improve.…”