A Self-Sustained CMOS Microwave Chemical Sensor Using a Frequency Synthesizer

Abstract

In this paper, a CMOS on-chip sensor is p resented to detect dielectric constant of or ganic chemicals. The dielectric constant of these chemicals is measured using the oscillation fre- quency shift of an LC voltage-controlled oscillator (VCO) upon the change of the tank capacitance when exposed to the liquid. To make the system self-sustained, the VCO is embedded inside a fre- quency synthesizer to convert the freq uency shift into voltage that can be digitized using an on-chip analog-to-digita