An Efficient Approach to Find the Truncation Frequency for Transmission Line-Based Dielectric Material Property Extraction

Material properties of dielectric substrates play an important role in high-speed printed circuit board (PCB) design. The Transmission Line-Based material property extraction method is an effective way to obtain substrate properties. However, the method requires transmission line dominated S-parameter data. Even with de-embedding, S-parameters may include non-transmission line effects. Thus, to obtain correct material properties, it is necessary to truncate the S-parameter data at a frequency before non-transmission line effects begin to dominate. In this paper, a novel binary fitting-based method is proposed to find the truncation frequency accurately and efficiently. By using a binary search algorithm and physics-based fitting method, the proposed method is able to find the truncation frequency in only a few iterations. This method has been validated for hundreds of real measurement cases and has shown good adaptability and rationality.