Patent ID: 7932814
Filing Date: 2011-04-26
Classification: G01S

Abstract:
1. A method comprising: generating an antenna feed signal; transmitting a first electromagnetic wave to a radio frequency device by coupling the antenna feed signal to a reading antenna; receiving a backscattered electromagnetic wave from the radio frequency device to create a received signal; calculating a combined signal based on the antenna feed signal and received signal, wherein the combined signal includes a plurality of inflection points, each inflection point corresponding to a different position of the radio frequency device relative to the reading antenna, 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 radio frequency device and the reading antenna 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.