Determining the Permittivity of a PCB Dielectric Using Striplines Considering Copper Roughness

The relative permittivity of printed circuit board laminates is determined from the experimental propagation constant obtained from striplines. For this aim, the phase constant associated with the dielectric media is obtained by applying an equation that removes the delay effect introduced by the interaction between the electromagnetic field and the conductor surface. Unlike previous approaches, no previous knowledge of the characteristic impedance or support from electromagnetic simulations is required. Consistent results are obtained when separately considering single-ended, differential, and common mode propagation data in different arrays of striplines up to 50 GHz. Furthermore, the dielectric loss tangent is inferred from the obtained permittivity by applying a multipole Debye model.