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This paper provides an overview and preliminary results of a newly awarded NSF project on civil structure health monitoring under CMS Sensor Program. The goal of this project is to develop the fundamental concepts, theoretical frameworks and implementation techniques for a self-contained active sensor skin in the context of highway bridge structural safety monitoring. The proposed sensor skin will be composed of (1) active sensing patches using piezoelectric materials for damage diagnosis, (2) radio frequency (RF) transceivers for wireless data transmission, and (3) embedded planar spirals for contact-less power delivery. The self-contained sensor skin will be designed such that it does not require any embedded batteries nor have any wire connection for power delivery and data transmission. Once data are retrieved at the inspection platform, an innovative damage detection algorithm will identify structural damage without replying on prior reference data. In this paper, preliminary results are presented on building a practical contact-less power delivery system and an on-chip signal generator for active sensors. A prototype of the contact-less power delivery circuit, which consists of a transformer and a AC-to-DC converter/regulator, is built using discrete circuit components. The transformer is composed of a ferrite core which is wound around by a pair of coils. One of the coils is connected to the high voltage power terminal and the other one is connected to the rectifier terminal. Then an AC-to-DC converter/regulator will provide an appropriate voltage level necessary for the operation of the on-chip signal generator. The on-chip signal generator is designed to realize a targeted inspection signal for activation of Macro Fiber Composite (MFC). The Colpitts LC-tank oscillator topology is chosen for the generation of the carrier frequency, and a low-frequency modulation signal is directly applied to the core circuit of the oscillator to finalize the predetermined inspection signal. In the future, the contact-less power delivery circuits will be integrated with the on-chip signal generator to complete the circuit designs for driving MFC.
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