Read range enhancement by harmonic energy in passive UHF RFID

A new approach of integrating the passive UHF Radio Frequency Identification (RFID) technology with electromagnetic energy harvesting function is presented in this letter. The approach is based on using a passive RFID tag operating at 868 MHz for communication purposes whereas a rectifying circuit is designed to harvest its third harmonic i.e., 2.604 GHz generated by the non-linear behavior of the RFID chip. An innovative concept to re-inject the energy harvested into the RFID chip is proposed. Experimental results on the energy feedback operation has shown an RF-to-direct current (dc) conversion efficiency of 33% at -16 dBm input power for the harvesting function and a read range improvement of 2.5 m for the communication function.