Single antenna position and direction detection system

摘要

The present invention analyzes a backscattered modulated RF signal received from a remote transponder to determine whether the transponder is stationary or moving towards or away from the reader and, if so, the speed at which the transponder exits and enters Circuit. The circuit of the present invention can be associated with a reader of the type disclosed in U.S. Patent No. 4,739,328 and requires only a single antenna. In response to a signal received from the transponder. The circuit of the present invention generates three signals each having a different phase. By analyzing the pattern and frequency of signal state changes in these three signals, the present invention can measure the speed and direction of movement of the transponder.