Monitoring of movement with radio frequency transducers

Two approaches to the problem of monitoring human movement using radio frequency transducers are described. A simple two dimensional solution can monitor movement restricted to one plane, whilst a three dimensional transducer (linked to a computer), can follow movement in any plane. In both cases, by measuring the magnetic field produced by a set of small coils powered with high frequency current it is possible to calculate their relative displacement. If the coils are attached to the surface of the human body they can thus be used as a monitor of human movement.