Temperature-compensated wideband VCO integrated in dielectric spectroscopy

Abstract

Dielectric constant refers to the ability to store electron energy in the E-field. The dielectric constant has a unique value for each material, and it can be distinguished by the characteristic that the dielectric constant relaxation section varies depending on the frequency. This research is mainly focus on the analysis and design process of a silicon-based dielectric spectroscopy integrated with a temperature-compensated wideband VCO (Voltage-Controlled Oscillator) that is easy to realize miniaturization and low cost. In order for the dielectric spectroscopy to accurately measure various materials, VCO with wideband characteristics and a small frequency error according to the measurement environment is required. In this research, VCO with wideband characteristics is designed using a switched coupled inductor and verified through measurement. It oscillates in the 4.74-8.77 GHz, ensuring an additional 21% frequency tuning range compared to the conventional structure. In this case, the root mean square (RMS) frequency error of the measurement and simulation result is 0.29 GHz. In order to compensate for the change in the oscillation frequency according to the temperature of the designed VCO, a phase shifter is integrated to reduce the frequency change from ± 6300ppm to ± 52ppm when the temperature is from -40 to 100 ℃. The proposed temperature compensation wideband VCO is integrated into the dielectric constant sensing circuit to produce a silicon-based dielectric spectroscopy that measures materials in various temperature environments.