ABSTRACT
A novel real-time capacitance estimation methodology for inductive coupling–based wireless sensor systems has been developed by adopting a frequency domain transfer function approach. This chapter presents a novel real-time method called "cascaded filtering" that enables wireless estimation of high-frequency changes in capacitance by algebraically manipulating two measurements. It describes the traditional inductive coupling–based technique requires a sweep of excitation frequencies in order to determine the resonant frequency, and hence this technique is mostly useful for "static" measurements. The chapter contains a novel method to read a passive capacitive sensor in telemetry by using inductive coupling is proposed. A schematic of a basic microfabricated capacitive pressure sensor and its equivalent simplified electrical model. An inductive coupling–based sensor system consists of a transceiver circuit and a sensor circuit, which can be modeled as the primary and the secondary sides of a loosely coupled, air-cored transformer, respectively.
