The instrumentation of rotating machinery with sensors typically requires wires and sliprings
for electrical connection to measurement equipment. These wired connections are
subject to noise and have a high failure rate. Conventional wireless sensors are bulky,
require delicate electronics, and their batteries need to be replaced periodically. Passive
wireless sensors based on surface acoustic wave (SAW) devices, which are miniature,
rugged, and require no electronics have been developed.
These sensors have been shown to measure strain wirelessly in a multipath, time-variant
environment. Sensors were fabricated on langasite using electron beam lithography.
Detailed characterization of these SAW sensors is preformed. An RF interrogation
system has been developed to record the strain measurements and convert the data into
usable information. Measurements from SAW sensors have been correlated with
conventional strain measurements at high frequencies. A rugged package has been
designed to encapsulate the delicate sensor and protect it from harsh environments. A
miniature patch antenna was integrated into this package. Finally, conclusions and future
work are discussed.