DC to 10-GHz mixer and amplifier GaAs IC's for coherent optical heterodyne receiver

The authors describe a number of design techniques that are effective for enhancing sensitivity and bandwidth. A Gilbert-cell circuit with a single-to-balance conversion input buffer and a peaking circuit are adopted for the mixer. In addition, a wideband amplifier is proposed that adopts a novel multiple-feedback cascode FET amplifier configuration with an LC input matching network. Finally, a novel interconnection technique is proposed that improves impedance matching between ICs and the package over a wide frequency range up to 10 GHz. These ICs were fabricated using a 0.2- mu m gate self-aligned GaAs MESFET process. These techniques could enable a highly sensitive multigigabit-per-second coherent optical heterodyne receiver to be implemented. >