Patent ID: 7542303

Claim:
A printed circuit board (PCB) comprising: first and second signal layers sandwiching a dielectric layer therebetween; and a differential pair having a positive differential trace and a negative differential trace, the positive differential trace disposed within the first signal layer and the negative differential traced disposed within the second signal layers, wherein two ground parts are disposed in the first signal layer on opposite sides of the positive differential trace in the first signal layer, and two ground parts are disposed in the second signal layer on opposite sides of the negative differential trace in the second signal layer; wherein a single-ended impedance of a differential trace of the differential pair is calculated with this formula: Z 0 ≈ 87 ɛ r + 1.41 ⁢ ln ⁢ 5.98 ⁢ S 0.8 ⁢ W + T wherein, Z 0 is the single-ended impedance of the differential trace, ε r is the dielectric constant, W is the width of the differential trace, T is the thickness of the differential trace, S is the distance between the differential trace and the adjacent coplanar ground part, and wherein the widths of the positive and negative differential traces are both approximately 4 mils, the distance between the positive and negative differential traces is approximately 8 mils, the thicknesses of the positive and negative differential traces are both approximately 2.1 mils, the distances between each of the positive and negative differential traces and the corresponding adjacent coplanar ground part are both approximately 4.8 mils.