Body motion tracking system

Abstract

Methods and apparatus are disclosed for measuring position and motion of a “marker” antenna ( ), disposed on a subject ( ) at a physical location to be tracked. Relative distance of the marker antenna ( ) from receiving antennas ( ) is measured by phase differences of its microwave signals ( ) at the receiving antennas ( ) for at least two successive marker positions. Alternatively, actual distances ( ) are calculated by choosing a source position ( ) and iterating the distances ( ) until the calculated phase differences match those measured. Four to six receiving antennas ( ) are positioned at edges of a volume ( ) where activity is conducted. Each received signal ( ) is amplified and down-converted in a mixer ( ). A single reference oscillator ( ) feeds all the mixers ( ) to preserve phase relationships of the received signals. Received signals ( ) are digitized and presented to a multi-channel digital tuner ( ). Phase relationships are preserved because all of the signal processing up to this step is “coherent”. The digital data is fed ( ) to a main computer and processed by algorithm to estimate the marker antenna's position relative to each receiving antenna ( ). The apparatus is especially applicable to clinical gait analysis, sports medicine, industrial, military and entertainment uses.