Ultra wideband 3-D tracking of multiple tags for indoor positioning in medical applications requiring millimeter accuracy

Ultra wideband (UWB) wireless positioning systems are robust for use in indoor environments where multipath is a factor. Indoor hospital environments including the operating room provide a challenging medium for wireless propagation. Medical applications for UWB positioning include tracking people and assets as well as computer assisted surgery. Our UWB positioning system can achieve real-time 3-D millimeter accuracy. Simultaneous tracking of multiple tags has been added to our system by designing an integrated tag, incorporating a squaring receiver, and careful real-time digital synchronization of the incoming data. Both static and dynamic experiments have been performed in 3-D. The 3-D dynamic experiment shows that a standalone integrated tag utilizing a high phase noise voltage controlled oscillator can still be tracked within 6.53 mm of 3-D real-time root mean square error. A static reference tag helps in mitigating errors due to receiver clock jitter and drift since these errors are consistent across all tags.