Extraction of Frequency-Dependent Characteristic Impedance and Complex Permittivity in Single-Ended and Edge-Coupled Transmission Lines Using the Calculated Series Parasitic Effects

This paper presents a method to obtain the characteristic impedance (Z(C)) and the complex permittivity ((epsilon) over cap) of single-ended and edge-coupled interconnects on printed circuit board (PCB) technology. For this purpose, experimentally determined propagation constant (gamma) data are used in combination with the frequency-dependent resistance (R) and inductance (L). Due to the difficulty of directly obtaining R and L from measurements, closed-form equations are used to perform the corresponding calculation. In this regard, the current distribution effects are considered within the cross section of the signal traces and the ground plane. The proposal was validated for both, single-ended and edge-coupled PCB interconnects considering three cases: standard, medium-loss, and in low-loss materials. The results show that the extracted data are in agreement with values reported in material datasheets at 4 GHz. In this regard, the method is a good alternative to characterize planar transmission lines on PCB technology within the whole frequency range where the S-parameter measurements are performed.