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We describe a spectrometer consisting of a vector network analyzer, a gas absorption cell, and a quasi-optical bench that acquires terahertz spectra of gaseous substances and mixtures. We tested volatile organic compounds that are medical biomarkers or chemicals which can be found on the US Environment Protection Agency list of harmful substances. Absorption spectra at gas pressures between 10 Pa and 5000 Pa were recorded. A subsequent multivariate data analysis demonstrated excellent qualitative and quantitative identification of pure substances and complex mixtures. The applied multivariate algorithms are principal components analysis, partial least square regression and soft independent modelling of class analogy.

A 245 GHz transmitter (TX) with an integrated antenna for sensing applications has been realized, which consists of a push-push VCO with a 1/64 frequency divider, a transformer-coupled one-stage power amplifier, a frequency doubler, and an on-chip antenna with localized backside etching. The frequency of the TX is tunable by an external PLL in the range from 239.5 GHz to 250.8 GHz. The TX is fabricated in 0.13 µm SiGe:C BiCMOS technology with f T /f max of 300GHz/500GHz. The output power of the TX is 1 dBm at 245 GHz. The TX including the frequency divider dissipates 0.38 W. The EIRP of the transmitter with antenna was measured using an external receive horn antenna. The EIRP reaches about 7 dBm at 245 GHz. This value represents the highest EIRP reported for a 245 GHz transmitter with integrated single antenna so far. Index Terms -SiGe, mm-wave, 245 GHz, VCO, power amplifier, frequency doubler, transmitter, integrated antenna.