245-GHz Transmitter Array in SiGe BiCMOS for Gas Spectroscopy

A 245-GHz transmitter (TX) array with an integrated antenna-array for a gas spectroscopy system has been realized. It consists of a push-push VCO with a 1/64 frequency divider, power amplifiers, frequency doublers, and on-chip antennas with localized backside etching. The TX-frequency is tunable in the range from 238 to 252 GHz. The TX-array has been fabricated in a 0.13- μm SiGe:C BiCMOS technology with f T /f max of 300 GHz/500 GHz. Its output power is approximately 7 dBm at 245 GHz, and the effective isotropically radiated power (EIRP) reaches 18 dBm at 245 GHz. The main components of the gas spectroscopy system are a TX and a receiver (RX) in SiGe BiCMOS as well as a gas absorption cell. The sensitivity of this spectroscopy system is demonstrated by measuring the high-resolution absorption spectrum of gaseous methanol ( CH3OH). Due to the increased power provided by the TX-array, the sensitivity of the spectrometer can be increased significantly.