Best-In Class RF Integrated Circuits for Multi-Gbps Communication in 22Fdx
Corrado Carta
Technical University Dresden, DE
ABSTRACT
This talk presents an overview of the ongoing circuit design activities in cooperation with GLOBALFOUNDRIES. Several RF integrated circuits for multi-Gbps communication have been demonstrated in 22FDX. Two examples will be presented in details: a Travelling Wave Amplifier (TWA) and a Mach-Zehnder Modulator (MZM) driver.
The gain cell employed for the TWAs is based on a conventional cascode topology and its layout is optimized to avoid performance degradation and instability. The TWA delivers a maximum gain of 10 dB over a 3-dB band of 110 GHz. The measured output power at 1 dB compression of the gain (o1dBcp) is 12.5 dBm at 20 GHz. Compared against the state of the art for TWAs, the presented design achieves the highest frequency of operation, as well as the broadest frequency band, and the highest o1dBcp. This circuit was awarded the best student paper award at the 2017 IEEE Asia Pacific Microwave Conference (APMC).
The high-voltage MZM driver is realized with stacked, low-impedance and low-loss switches which allow a voltage swing significantly larger than the breakdown voltage of individual devices. To enable this topology the signal is transferred to different voltage domains with level shifters, then amplified and conditioned to the rail-to-rail swing which ultimately drives the output power-stage. The bandwidth of the driver is increased with shunt and series inductive peaking. Stacking and coupling inductors result in only 0.018 mm2 of active area, which is the most compact reported for MZM drivers. Measurements show a 3.75 Vpp swing on a 50 O load. Error-free (BER< 10 -12) transmission at 30 Gbit/s is demonstrated. By using a switched output stage, only a small static dc-power is consumed, resulting in the most energy-efficient MZM driver with only 2.2 pJ/bit.
