Scientists from the IHP-Leibniz Institute for Innovative Microelectronics and the German aerospace research center DLR have developed a compact, cost-effective sensor system for gas spectroscopy in the frequency range of 245GHz. A world's first, the transmitter of the system as well as the receiver use silicon germanium (SiGe) ICs.
Laboratory setup of 245GHz gas spectroscopy system with the transmitter and receiver module and gas absorption cell.
The institute claims it devised a cost-effective way to manufacture the SiGe semiconductors -- a transmitter and a receiver with integrated antenna, working in the frequency range from 238GHz to 252GHz. Since these devices are manufactured in standard silicon technology, the process is basically compatible with the ones established across the semiconductor industry. This translates into low production cost for eventual series production and establishes a technology basis for a gas sensor at a price level hitherto impossible.
The application potential is huge, the institute says in a release. In safety applications it can be used to detect toxic gases. Other application fields are chemical process control -- for instance for plasma etching in the semiconductor industry. Such sensors could also be used in the healthcare segment: Analyzing the respiratory gas of a patient could help to early detect lung diseases.
Millimeter absorption spectroscopy is an established laboratory technique, used in the molecular spectroscopy as well as in radio astronomy to exactly determine the concentration of molecules. The RF sources traditionally used in this field -- Schottky diodes with downstream frequency multipliers -- however are very expensive and clumsy. Since a couple of years commercial sources are available based on multiplying the frequency of millimeter waves. These systems are more compact but their price remains relatively high.
Recently a U.S. research team introduced a gas spectroscopy system for the frequency range from 210 to 270GHz that has been built with commercially available millimeter wave components. The costs for such a system are currently determined by the high manufacturing costs for the millimeter wave components. The challenge therefore was to develop a sensor system based on integrated circuits and an established chip technology such as SiGe or CMOS -- which would contribute to reducing the manufacturing costs significantly.