Standalone SAW sensor interrogator using an embedded computer and software defined radio

Modern software defined radio (SDR) technologies have enabled surface acoustic wave (SAW) sensor interrogation systems that are small, inexpensive, and fully integrated. The universal software radio peripheral (USRP) is available as a commercial-off-the-shelf (COTS) SDR that can be programmed to fit a wide variety of applications and needs. Recent work at the University of Central Florida has demonstrated the USRP B200 as a SAW sensor interrogator. This paper expands upon previous efforts by implementing a standalone interrogation platform which utilizes the USRP B200 and embedded microcomputer. Recent advances in embedded processing platforms have enabled full Linux environments to be run, enabling high performance computation in a compact package. One such embedded platform, the MinnowBoard MAX, has been employed to perform the complex matched filter correlator post processing techniques as well as handle programming and communication with the USRP. The unit is self contained and can be operated without a traditional Desktop or Laptop. Performance of the interrogator has also been improved by adding and external RF switch and amplifier. The system is demonstrated by interrogating orthogonal frequency coded (OFC) SAW sensors at 915MHz and extracting the sensor temperature.