Broadband dielectric spectroscopy for liquid permittivity measurement

Abstract

The dielectric spectroscopy for information of biomaterials and chemical has a great potential in a variety application. The trend towards dielectric sensor for biomedical application requires small area, low price. The receiver-based sensor in CMOS reduces cost, area, power and has a wideband frequency range. This research is mainly focused on the analysis and realization of the broadband dielectric spectroscopy architecture. In the design of the sensing capacitor to detect the dielectric characteristics, on-chip interdigitated capacitor is adopted achieving low cost, small area. The on-chip capacitor is realized with a top metal in a CMOS process, which has a small size of 150 x 195 $μm^{2}$. Also, a permittivity sensing method of liquid is proposed to demonstrate that the designed capacitor detects permittivity of material under test (MUT). It shows less than 6.4% rms error of ε′for propanol ($C_{3}H_{8}0$) at 100 MHz-5 GHz. A current-mode dielectric spectroscopy in 28-nm CMOS is presented for permittivity detection of liquids at microwave frequency range. The proposed architecture can achieve high linearity for sensor sensitivity. Also, decoupling the noise and bandwidth trade-off is possible by increasing output impedance of the first stage. Through proposed sensor, we measured permittivity of propanol and ethanol, similar to the theoretical value, and rms permittivity error is less than 0.9 at 0.03-10 GHz.