Novel architecture and algorithm for remote interrogation of battery-free sensors

This paper presents an inductive telemetry platform system for the continuous, real-time and simultaneous remote measurement in harsh environment. First, a SOL (self-oscillating loop) topology for the remote interrogation of wireless battery-less passive sensors is described. This system uses a capacitive sensor configured as an LC-tank whose resonant frequency shifts with the physical measurement. Such a system is generally based on an impedance analyzer in order to measure this frequency shift. In fact, if you increase the distance between the sensor and the reader, the sensibility is not sufficient to use the SOL technique. To overcome this issue, an anti-resonance cancellation, realized with a simple RC cell, is implemented. However, this architecture is dedicated only for a single capacitive sensor. Second, based on an efficient algorithm used for system identification purpose, a readout unit for multiple sensors is proposed. The overall performances of these architectures are analyzed with respect to coupling factor and sensor parameters. Using these two approaches, tests show promising results at mutual coil distances up to 5 cm.