EBG-Based Common-Mode Stripline Filters: Experimental Investigation on Interlayer Crosstalk

This paper deals with the filters based on EBG cavities employed for reducing common-mode currents along differential stripline traces. The crosstalk among differential interconnects routed in close proximity to EBG-based filters, and next to filtered pairs, is accurately quantified. The comparison between the experimental and simulation frequency-domain results validate the proposed filter´s effectiveness and make the simulation model reliable for investigating the complex multichannel crosstalk problem. This paper focuses on the stripline environment, where crosstalk occurs among traces routed on adjacent layers, with the EBG cavity acting as a coupling path. Multichannel time-domain simulations complete the characterization of the filter, showing the limited effects of the filter on the intentional differential signal, and the beneficial impact on reducing the potentially radiating common-mode harmonics. The quantification of the common-mode spectrum shows that the filtered harmonics are reduced by 10-15 dB; thus, minimizing the corresponding electromagnetic interference. Design guidelines are defined for the filter layout according to the relative position of unfiltered differential traces, when constraints force them to be placed in close proximity to EBG cavities and filtered pairs. In particular, the best layout for unfiltered traces on adjacent layers is orthogonal with respect to the filtered pair, whereas the parallel routing should be carefully used taking into account the signal bandwidth on the victim pairs.