A Novel Front-End Circuit for the Digital Conversion of QCM-D Responses for FPGA-Based Frequency Measurements.

This work presents a front-end circuit aimed at enhancing the performance of counter-based digital frequency meters for Quartz Crystal Microbalances with Dissipation Monitoring (QCM-D) applications. The proposed electronics converts the QCM-D vanishing sinusoidal transient response into a square wave signal with voltage levels compliant with standard digital I/O ports. The front-end electronics is designed to preserve the QCM-D response oscillation frequency during the analog-to-digital conversion by means of an Automatic Gain Control (AGC) amplifying stage.