49-Gb/s, 7-tap transversal filter in 0.18 μm SiGe BiCMOS for backplane equalization

This paper describes the first integrated transversal filter for feed-forward equalizers (FFE) operating above 40 Gb/s. Equalization of a 2³¹-1 PRBS over a 9-ft and 6.5-ft cable with SMA connectors is demonstrated on-wafer at 40 Gb/s and 49 Gb/s respectively. The circuit is implemented in a commercial 0.18 μm SiGe BiCMOS process and is based on a differential distributed 7-tap fractionally spaced transversal filter topology. Microstrip transmission lines are employed as delay elements. With input and output return loss better than -10 dB up to 55 GHz, and a 1 × 2 mm² die area, the circuit draws 150 mA from a single 5-V supply.