A Method to Extract Dielectric Parameters from Transmission Lines with Conductor Surface Roughness at Microwave Frequencies

This paper details an effective method to extract dielectric parameters including dielectric constant Dk and loss tangent Df from transmission lines containing rough conductor surface. The concept of effective conductivity is firstly introduced to model conductor surface roughness in transmission lines. By using differential extrapolation method, propagation parameters of transmission lines can be extracted by removing the roughness effects. A curve-fitting method based on Genetic Algorithm (GA) is adopted to fit the propagation parameters in the smoothened case and to derive the dielectric parameters. The proposed method is especially accurate for parameter extraction at high frequency and is practical to all types of transmission lines.