Fundamental Limitations on Reading Range of Passive IC-Based RFID and SAW-Based RFID

For the first time, fundamental read-range limitations are calculated for two major types of "passive" (i.e. battery-less) RFID systems. Many applications require large read range. But, in shorter range applications excess read range provides read-path signal margin which enhances reading reliability, signal penetration, and/or flexibility in RFID system design, layout, and installation. Analysis was restricted to passive technologies because passive tags are required for the majority of future RFID applications. The analysis shows 2.44 GHz surface acoustic wave (SAW) based RFID potentially has a 30X read range superiority compared to passive semiconductor IC-based RFID operating near 900 MHz.