Comparison of time-domaim and frequency-domain characterization procedures for printed circuit board interconnects

Time-domain and frequency-domain procedures that measure electrical responses of two PCB interconnects or transmission lines with unequal lengths to extract characteristic impedance Zo and propagation constant γ=α+jβ are evaluated. Experimental results indicate that there exist some minor discrepancies between these two procedures. Based on them, the extraction of characteristic impedance Zo and phase constant β are more immune to discontinuity defects of test samples and well-behaved dispersive data can be obtained. However transition discontinuities deteriorate the extracted attenuation constant α when the frequency-domain procedure is used.