An Enhanced Broadband Continuous Extraction Approach for Complex Propagation Constants of Differential Transmission Lines

This article proposes an automatic and robust extraction method for broadband complex propagation constants of differential transmission lines, which demonstrates a reliable performance in on-wafer measurements, for the first time, up to 110 GHz. The proposed method is also suitable for asymmetric measurement fixtures when the mode conversion between differential and common modes cannot be ignored. The method first determines the order of each propagation mode at the first frequency and then applies a mode-tracking method to solve the propagation constants at the remaining frequencies. In addition, a multiline differentiation method is adopted to numerically eliminate the resonance-related glitches and noise of the attenuation constant curve by measuring several transmission lines with different lengths. Compared to the conventional approaches, the proposed method exhibits higher reliability and robustness in extracting broadband complex propagation constants, which is validated by a full-wave simulation between 0.01 and 130 GHz and an on-wafer measurement between 0.01 and 110 GHz.