Printed circuit board having differential line pairs with a percentage of their lengths disposed as an outer signal layer

摘要

A printed circuit board includes an outer signal layer, a first ground layer, a first ground layer located below the outer signal layer, an inner signal layer located below the first ground layer, an second ground layer located below the inner signal layer, and a first differential signal transmission pair and a second differential signal transmission pair laid on the outer signal layer and the inner signal layer. A value h is equal to a distance between the inner signal layer and its closest ground layer. A distance between the first pair and the second pair is not more than h×3.

主权项

1. A printed circuit board, comprising:
an outer signal layer; a first ground layer located below the outer signal layer; an inner signal layer located below the first ground layer; an second ground layer located below the inner signal layer; a first differential signal transmission line pair and a second differential signal transmission line pair routed on each one of the outer signal layer and the inner signal layer, the first differential signal transmission line pair are parallel to the second differential signal transmission line pair that are routed on the outer signal layer; a value h is equal to a distance between the inner signal layer and the closest one of first and second ground layers, and a distance between the first differential signal transmission line pair and the second differential signal transmission line pair routed on the outer signal layer or the inner signal layer is not more than h×3; wherein part of the first differential signal transmission line pair which are placed on the outer signal layer is a first microstrip line pair, and a length of the first microstrip line pair is not more than 10% of a length of the first differential signal transmission line pair; part of the second differential signal transmission line pair which is placed on the outer signal layer is a second microstrip line pair, and a length of the second microstrip line pair is not more than 10% of a length of the second differential signal transmission line pair.