A Dual-Band Approach for Backscattering Modulation

In typical passive UHF RFID systems, tags rely on backscattering, where they modulate a reflected signal by switching impedance states, powered solely by the reader's RF signal. In contrast, active RFID tags offer enhanced communication capabilities but require an internal power source. This work introduces a novel hybrid approach that combines electromagnetic energy harvesting and backscattering, utilizing two distinct carrier frequencies. A 2.45 GHz transmitter powers a rectenna and encodes a frequency sweep from 20 kHz to 100 kHz using a simple mixer. After energy harvesting, the device modulates its 5.8 GHz backscattering antenna with the down-converted signal. This results in a backscattered 5.8 GHz signal that is easily distinguishable from the transmitter signal owing to the introduced frequency offset. This method enhances the reliability and modulation options of passive RFID tags. Finally, a fully passive, batteryless remote control application is explored to demonstrate the potential of this approach.