System and method for communication with radio frequency identification tags using tow message DFM protocol
US6452504B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Sep 24, 1999 |
| Grant date | Sep 17, 2002 |
| Priority date | — |
| Expiry date | Sep 24, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S5/10
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The system comprises a plurality of stationary sensors located in an array within certain physical areas. Each sensor comprises a plurality of antenna coils arranged in unique physical orientations and capable of transmitting radio frequency signals of differing phase. The RFID transponder includes an antenna which receives the signals generated by the antenna coils, and compares the phase of at least two of the signals to determined the relative position of the transponder. The antenna coils may emit two direction finding mode (DFM) signals in succession; the first signal with all antenna coils turned on, the second with a subset of the coils turned off. The spatial relationship of the transponder antenna and individual antenna coils precludes all of the signals in each sensor from being rejected by the transponder during emission of both the first and second DFM signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.