Mode-selective periodic transmission line filters to reduce radiated common-mode emissions

摘要

Numerous techniques have been devised to counter unintended common-mode signals on differential structures. These signals, if unfiltered, can lead to radiated emissions from cables and connectors. A periodic transmission line structure is described in this paper that selectively filters common-mode signals while passing differential signals. The structure does not rely on any modifications to the reference structure. Additionally, the wiring density can be maintained without incurring excessive crosstalk on the same PCB layer or adjacent layers. The design of the structure is described, and a test PCB is designed, measured, and compared with modeling.