Patent ID: 7944356
Filing Date: 2011-05-17
Classification: G01S

Abstract:
1. A method implemented in a radio frequency identification (RFID) system, the method comprising: an RFID reader generating an antenna feed signal and transmitting a first electromagnetic wave to an RFID tag according to the antenna feed signal; the RFID reader receiving a backscattered electromagnetic wave from the RFID tag to create a received signal; generating a combined signal based on the antenna feed signal and the received signal, wherein the combined signal includes a plurality of inflection points, each inflection point corresponding to a different position of the RFID tag relative to the RFID reader, wherein the plurality of inflection points comprises a first inflection point, a last inflection point, and at least one intermediate inflection point between the first inflection point and the last inflection point; and determining a relative velocity between the RFID tag and the RFID reader by detecting the inflection points of the combined signal over a predetermined time period, wherein the predetermined time period begins at a time associated with the first inflection point and ends at a time associated with the last inflection point.