An UHF RFID tag emulator for precise emulation of the physical layer

In this paper the implementation of a configurable hardware for an UHF RF identification (RFID) tag emulator at 868 MHz is demonstrated. The tag emulator is used for reader performance verification under worst case conditions. The characteristics of a tag can precisely be emulated: reflection coefficient dependent on received signal strength, variation of the frequency, and timing jitter of the backscattered signal. The implemented tag emulator is segmented into an RF transceiver board and a baseband processing board with a powerful field programmable gate array (FPGA). Both boards are connected by optical links to not influence the electromagnetic field. The compact low power RF transceiver board is placed in the reader's electromagnetic field and is optically powered. The baseband processing board handles the signal processing for the implemented backscatter modulator and evaluates and monitors the signal strength and signal characteristics received by the reader. For being prepared to upcoming standards, an I/Q backscatter modulator with a variable modulation index is implemented. The higher protocol layers are processed by a microcomputer for rapid prototyping. In this paper the underlaying hardware, the synchronization algorithm for the optical links, and the modulator properties of the UHF RFID tag emulator are discussed.