RESUMO
Experiments using an on-chip sensor in silicon technology for dielectric measurements at 120 GHz are presented. The passive sensor element, a coplanar strip line (CPS) bandpass filter, consists of a combination of short-ended T-stubs placed inside a CPS, yielding a resonant transmission behavior of the sensor. The high quality factor of this bandpass filter is achieved by both: using edge-coupled lines and removing the substrate beneath the transducer by silicon back-side etching. Measurements showed that the unloaded transducer exhibits a quality factor of 11. The sensor is applied to characterize the cultivation progress of yeast in a glucose medium. Sparameter measurements using RF probes show a recorded S21 center frequency that shifts from 124GHz to 125GHz within 22 hours of cultivation. The typical dynamic behavior and cultivation phases of yeast are confirmed by millimeter-wave monitoring the cell culture. Experiments prove that detection and characterization of dielectric samples in small volumes can be performed without contact to the sample and label-free.