Convert UHF RFID Tag From Passive To Semi-passive Tag Using External Power Sources

Abstract

In this thesis, I present novel circuit designs that convert a passive radio frequency identification (RFID) tag into a semi-passive RFID tag. Passive RFID tags are relatively inexpensive to purchase and to integrate into objects and devices. However, in some environments and on some objects the performance of the pure passive tags is not sufficient for the intended applications. A semi-passive tag, in comparison to a pure passive tag, has significantly greater communication range since the semi-passive tag derives its operational power from an on-tag power source instead of just from an interrogator's communication signal. As a result, semi-passive tags have greater usability in a broad range of applications. My novel circuit designs act as an additional on-tag power source and are intended to be low-cost additions to an existing passive tag operating in the UHF (Ultra-High Frequency) frequency range. Thus, currently deployed tags may be retrofitted in the field as their intended applications change and demand greater communication range. Prototype implementations of my designs were able to increase the read range of a passive UHF RFID tag by up to 39%.