Software Defined Radio Based Backscatter RFID Reader for Tag Tracking and Sensing

In this talk, we present a software defined radio (SDR) based backscatter Radio Frequency IDentification (RFID) reader capable to rapidly prototype and explore advanced RFID signal processing techniques to perform tracking and sensing of batteryless – or rather passive – sensor transponders (tags). First, we present the RFID reader setup. The core of the reader is a flexible SDR by National Instruments controlled by a laptop computer. The reader exploits two transmitting antennas and two receiving antennas for the communication with the passive tags. At the transmitter side, two power amplifiers ensure a sufficient power transfer towards the tags. At the receiver side, a switch matrix is integrated into the reader setup for system calibration. After presenting the prototyping platform, we demonstrate the feasibility of the SDR based reader to rapidly prototype and explore advanced RFID signal processing techniques. With respect to tag tracking, we present a novel and fast two-dimensional tracking algorithm to track tag movements. Initial verification measurements of the tracking system in a realistic application environment show mean absolute errors of 8.4cm and 1.3cm for the x-coordinate and the y-coordinate, respectively. With respect to tag sensing, we present the implementation of a novel sensing approach based on tag signal pattern detection at the reader receiver. Again, initial verification measurements show that similar signal patterns can be detected for different tag positions, especially in harsh multipath environments.