Design of Flyover QSFP (FQSFP) for 56+ Gbps applications

We introduce Flyover QSFP (FQSFP) approach for 56+ Gbps applications to overcome the limitations from a large loss on typical QSFP ports with surface mount to PCB traces. By replacing the PCB traces to the twinax cables, we have achieved 7 dB lower insertion loss at 40 GHz for the 12-inch path from the switch IC to connector than that of PCB trace with a low loss substrate. To investigate EMI aspect of FQSFP approach, we developed a simulation model of FQSFP. The model showed a good correlation with measured TDR at FQSFP port and TRP (total radiated power) from FQSFP in a test vehicle. TRP from FQSFP without a shielding cage is -8 dBW, -12 dBW at 15 GHz from 1 W input power for common-mode and differential-mode, respectively.