A 300-GHz Transmitter Front End With −4.1-dBm Peak Output Power for Sub-THz Communication Using 130-nm SiGe BiCMOS Technology

This article presents a compact 300-GHz transmitter front end manufactured in a 130-nm SiGe BiCMOS process. The transmitter consists of a 240-GHz amplifier multiplier chain (AMC) and a modified 300-GHz Gilbert mixer. Limited by the space between top two thick metal layers of the SiGe process, the coupling coefficient between the coils, which form a transformer-based balun, is usually small at subterahertz (THz). Therefore, the vertical or horizontal coupling single-turn transformer-based balun will exhibit large insertion loss at around 300 GHz. In this work, a self-shielded Marchand balun (SSMB) with an enhancement to the coupling coefficient is proposed, which is realized by a novel multilayer metal topology with self-shielded coupling (SSC). The AMC is composed of a 120-GHz frequency doubler, a 120-GHz two-stage power amplifier (PA), and a two-way power synthesis balanced frequency doubler. This AMC exhibits a measured peak output power of 5.5 dBm at 252 GHz, with 48-GHz 3-dB bandwidth from 212 to 260 GHz. The transmitter chip achieves a maximum output power of −4.1 dBm at 300 GHz and delivers an output power better than −10 dBm from 270 to 315 GHz. Over the 30-GHz 3-dB bandwidth from 280 to 310 GHz, the transmitter shows a maximum OP_1dB of −6.5 dBm at 296 GHz, a peak conversion gain of −11.2 dB at 298 GHz, and a local oscillator (LO)-to-RF leakage rejection better than 40 dB, with only 300-mW dc power consumption. Compared with other state of the arts, the transmitter exhibits a comparable output power among silicon-based transmitters near 300 GHz.