Wireless strain sensing microsystem

This paper describes a high-performance wireless strain sensing microsystem. A MEMS capacitive strain sensor converts an input strain to a capacitance change with a sensitivity of 26.5 aF per 0.1 με. Low-noise integrated sensing electronics employing a continuous time synchronous detection architecture convert the capacitive signal to an output voltage for further signal processing. An RF to DC converter based on inductive coupled coils converts a 50 MHz AC signal to a stable DC supply of 2.8 V with a current driving capability of 2 mA, sufficient to power the interface sensing electronics. A two-channel digital phase shift keying (PSK) and amplitude shift keying (LSK) passive telemetry achieve a wireless data transmission rate of 5 Mbps and 250 kbps, respectively, which are adequate for sending the strain data and temperature information for thermal compensation. The prototype microsystem achieves a minimum detectable strain of 0.9 nε/ √Hz with a maximum input strain of 1000 με.