Interrogating Passive Wireless SAW Sensors with the USRP

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Typical interrogator design for wireless SAW sensor systems require many discrete components and lengthy build times, making it difficult to rapidly adapt to sensor designs in a research environment. We have employed the USRP B200 as a SAW sensor interrogation system. Interrogation of wideband orthogonal frequency coded (OFC) SAW sensors imposes strict requirements on the timing and synchronization of the transceiver. The USRP FPGA has been modified to operate in a synchronous, pulsed mode of operation, allowing rapid data acquisition and the full 56MHz bandwidth to be utilized. Data from the USRP is passed to a custom matched filter correlator routine to extract sensor parameters. The system is capable of interrogating multiple sensors, simultaneously. Demonstration of the system is accomplished by wirelessly interrogating SAW sensors at 915MHz and extracting temperature.

Application Note Number: AN-5501

Authors: Trip Humphries

Organization: Ettus Research

Last Modified Date: 2016/04/15