Extending the Interrogation Range of a Passive UHF RFID System With an External Continuous Wave Transmitter

This paper introduces an interrogation enhancer (IE) as an external system that boosts a reader continuous wave (CW) with its auxiliary CW. The boosted reader CW powers the backscatters from a passive ultrahigh frequency radio frequency identification (UHF RFID) tag to reach the reader in extended range. The system performance is verified according to the measured ranges in practical tests. The IE permits the reader to successfully interrogate the tag in tripled or doubled range (e.g., 80-290 and 182-370 cm). The measurement results imply that the IE can be used for readers that may not transmit enough CW due to the local regulation or its limited battery capacity.