Methods and apparatus are disclosed for measuring position and motion of a "marker" antenna (14), disposed on a subject (12) at a physical location to be tracked. Relative distance of the marker antenna (14) from receiving antennas (18) is measured by phase differences of its microwave signals (40) at...http://www.google.es/patents/US6784826?utm_source=gb-gplus-sharePatente US6784826 - Body motion tracking system
