Crosstalk mitigation techniques in high-speed serial links

One of the primary challenges in high-speed chip-to-chip serial link design is maintaining signal integrity in the presence of inter-symbol interference and crosstalk. Far-end crosstalk (FEXT), the interference from an adjacent aggressor line, has become a major noise source as data rates continue to increase. In addition to reducing the effective signal-to-noise and interference ratio (SNIR), FEXT introduces deterministic crosstalk-induced jitter (CIJ) in the received signal, thereby degrading the receiver's bit error rate (BER). By mitigating FEXT, inter-chip I/Os can have higher aggregate data throughput and interconnects can be placed closer together, which reduces the board area needed and the cost associated with it. In this thesis, two different techniques have been proposed to mitigate the effect of FEXT. The first technique employs FIR filters to implement FEXT cancellation (XTC) at the transmit end, which removes FEXT on each channel to further improve the SNIR of the received data and reduce the CIJ. The second technique staggers the multilane I/Os by adding a variable delay to every other channel at the transmit end, thus shifting the coupled FEXT away from the zero-crossing points of the victim channel. Although I/O staggering can lower CIJ and increase timing margin with relatively little added power, it comes at a cost of decreasing the existing voltage margin. The proposed techniques provide the required groundwork for developing MIMO communication methods that will effectively extricate additional information from FEXT to further reduce the BER during data detection. New I/O transceiver designs with the two techniques have been implemented and fabricated in CMOS processes. In addition, a novel multilane PRBS generator has been designed to test the fabricated multilane transceivers. As data rates approach higher speeds and FEXT becomes a dominant noise source, the research presented has shown that FEXT mitigation is critical to enhance jitter performance and improve eye openings in high-speed serial links.