Definition

Symmetric stripline (also called centered stripline) positions the signal trace exactly at the geometric center between two parallel reference planes, embedded in homogeneous dielectric. The equal spacing to both planes produces the most predictable impedance and best signal integrity. However, achieving true symmetry is difficult in practice since materials above (typically prepreg) and below (typically core) often have slightly different dielectric properties. Symmetric stripline supports true TEM mode propagation and provides excellent EMI shielding.