Passive Radio Frequency Identification Tag with Frequency Doubler and Energy Harvesting

Abstract

The paper presents the simulation and experimental results obtained for a passive RFID tag based on the integration of microstrip patch antennas and a frequency doubler circuit on the same low-cost FR-4 substrate. The fundamental frequency used for the interrogation signal is f0=2.5 GHz, with the second order harmonic 2f0=5 GHz generated by the doubler used to send back the information from the tag. Nonlinear simulations based on the NSR201MXT5G diode parameters showed that an input power of only 400 mW at 2.5 GHz is enough to generate a DC current of 2.3 mA and a DC voltage of 4.6 V across a 2kOhm load resistance, and provide an output power of 7.8 mW at 5 GHz. Measurement results demonstrating the energy harvesting feature of the RFID tag show a detected DC current of 0.226 mA at 2.6 GHz for a 300 mm distance between reader and tag antennas for a power of ~30 mW (15 dBm) at the reader antenna input. The results show an increase of the readout distance compared to previous work, with a demonstrated RFID link at 100 cm showing a clear rectangular demodulated signal.