Improved method for characterizing transmission lines using frequency-domain measurements

This work presents an improved and accurate methodology for extracting lossy frequency-dependent transmission parameters from S-parameter measurements. The presented technique first uses the multiline method to accurately determine the propagation constant. Then, it proposes a new approach to compute the characteristic impedance by determining the admittance first, based on the fact that the admittance can be modeled as a linear function of frequency. This process ensures both frequency dependent conductor and dielectric losses are accurately determined. It is demonstrated, through several practical examples, that the resulting transmission line parameter is free of common modeling errors at resonant frequencies.