Channel shortening for enhancing passive UHF RFID performance

This paper proposes using a channel shortening equalizer (CSE) to improve the performance of passive ultrahigh frequency radio frequency identification (UHF RFID) systems. In UHF RFID systems, the reader interrogates RF tags by transmitting continuous wave (CW) signals that power up the internal integrated circuitry of the tags that in turn, backscatter these signals to the reader after embedding their unique information. The overall performance of passive UHF RFID systems depends heavily on the power level of the signal impinged on the tag which is a function of the multipath channel environment in which the reader and the tags are deployed. In this paper, a channel shortening equalizer with a new constraint that exploits the knowledge of the propagation channel and the nature of the CW signal is proposed to boost the power of the impinged signal on the tag. The results show that using the proposed equalizer enhances the power level significantly which results in better performance.