Date Added: Jul 2010
Passive RFID tags are traditionally assumed to be downlink limited since typical tag sensitivity is considerably poorer than reader sensitivity, due to stringent power limitations. On the other hand, semi-passive tags are generally uplink limited since tag and reader sensitivity are comparable. In this paper, it is demonstrated that judicious choice and use of IC impedance for backscatter modulation will be needed to simultaneously maximize tag read and write ranges as passive tag designs improve. Optimal backscatter modulation indices for amplitude-shift-keying are derived for range maximization of next generation low-power RFID tags.