Design and Implementation of a Long-Range RFID Reader for Passive Transponders

This paper presents a long-range RF identification (RFID) reader that has proven to work at up to 5 m with 2-W effective radiated power transmit power at 868 MHz. For the validation, a phase-shift keying backscatter modulator has been implemented, thus complementing the reader to form a complete passive RFID system focused on backscattering communication. The system has been first analyzed by means of a simulation tool, and as a result, reader design considerations are derived. Guidelines for the design of the backscatter modulator are also put forward. The reader and modulator have been fabricated and two measurement setups have been built to validate the reader performance. First, the system has been tested without antennas; -61.6-dBm reader sensitivity with only 11^deg phase difference has been measured. Finally, both the reader and modulator have been complemented with their respective antennas and the system has been evaluated in a real scenario. Reflections and interferences are demonstrated to degrade reader performance; nevertheless read ranges up to 8.1 m have been measured.