Abstract
This paper will discuss a SAW passive, wireless multi-sensor system under development by our group for the past several years. The device focus is on orthogonal frequency coded (OFC) SAW sensors, which use both frequency diversity and pulse position reflectors to encode the device ID and will be briefly contrasted to other embodiments. A synchronous correlator transceiver is used for the hardware and post processing and correlation techniques of the received signal to extract the sensor information will be presented. Critical device and system parameters addressed include encoding, operational range, SAW device parameters, post-processing, and antenna-SAW device integration. A fully developed 915 MHz OFC SAW multi-sensor system is used to show experimental results. The system is based on a software radio approach that provides great flexibility for future enhancements and diverse sensor applications. Several different sensor types using the OFC SAW platform are shown.
Highlights
Surface acoustic wave (SAW) technology is beginning to attract serious interest for a broad range of sensor applications, especially in aerospace and health monitoring applications [1,2]
The SAW sensors all fabricated on YZ LiNbO3 using well know fabrication techniques
This paper provides the latest results of a successfully operating orthogonal frequency coded (OFC) SAW sensor system at 915 MHz and various sensors have been simultaneously interrogated and data extracted
Summary
Surface acoustic wave (SAW) technology is beginning to attract serious interest for a broad range of sensor applications, especially in aerospace and health monitoring applications [1,2]. A short list of system specifications may include simultaneous multi-sensor interrogation and reception, wireless, passive, radiation hard, and range of several centimeters to 100s of meters. The sensors should be small, rugged, provide radio frequency identification (RFID) on chip, operate under conditions ranging from cryogenic to high temperature, and differing embodiments should provide temperature, gas pressure, strain, chemo- or bio- detection and others. The implementation of OFC in a SAW structure provides the greatest flexibility in time, frequency and code diversity. This adaptability has advantages in a multi-sensor system for identification and sensor accuracy, which will be discussed. The five chip OFC reflectors are used for encoding each device on YZ LiNbO3 and the devices are connected to a folded dipole antenna for reception and re-transmission of the interrogation signal
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