Investigation of Differential Twisted-Pairs Implemented on Silicon IPD and High Performance Multilayer Organic Platforms

In this paper, results of twisted pairs implemented in silicon IPD and low loss MLO up to 20 GHz is reported. First, origin of differential lines is explained, followed by explanation of differential twisted pairs' natural ability to suppress noise. Issues related to differential twisted pairs (DTPs) are also discussed. In this paper, differential lines with and without (i.e., the coupled lines) twists were focused. Their transmission properties, including Common Mode Rejection Ratio (CMRR), were obtained. An aggressor line (single-ended transmission line terminated with Zc by a probe head, or a 50 W resistor) and victim differential lines were created on silicon IPD and Rogers MLO. The victim differential lines include coupled and twisted pairs, and they were terminated at open, short, and matched load. In analyzing cross-talk noise (Near and Far ends -- NEXT and FEXT), S-parameter measurements for the aggressor-victim configurations were conducted, and they agreed well with HFSS simulated results. Moreover, Hx and Hy fields were obtained using EMI/EMC Near field measurement tool EM-ISight-4 (10 kHz - 6 GHz) by APREL. The near field results can be used to obtain the current distributions on the victim differential twisted pairs. The current distributions are in good agreement with HFSS simulated results.