System and method for communication with radio frequency identification tags using tow message DFM protocol
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United States of America Patent
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Sep 17, 2002
Grant Date -
N/A
app pub date -
Sep 24, 1999
filing date -
Sep 24, 1999
priority date (Note) -
Expired
status (Latency Note)
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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.
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