Heterodyne Spectroscopy with a 225 – 255 GHz SiGe BiCMOS Receiver for Space Applications

Molecular spectroscopy of gases is an important method for various applications on Earth and in space. In the millimeter-wave / terahertz range, many molecules have rotational transitions and are distinguishable by their spectral fingerprint. We analyze the performance of a heterodyne receiver fabricated in SiGe BiCMOS technology, which operates at room temperature and is tunable from 225 GHz to 255 GHz. At 241 GHz, the double sideband noise temperature of the receiver is approximately 20,000 K at 1.5 GHz intermediate frequency and the Allan time is 1 s. First heterodyne measurements of methanol emission lines were successfully performed in laboratory experiments.