A variety of industrial, public service, and government occupations would benefit from a personnel tracking system capable of precisely tracking personnel working mixed indoor / outdoor worksites. Such a system would increase the safety and efficiency of personnel working these sites, especially in the case of critical operations such as public service. No currently available systems fit the needs of this application. A field deployable system is defined herein that specifically addresses the needs of tracking personnel working small area indoor / outdoor environments.
The Theseus tracking system is a two part system composed of a ground station deployed at a work site and one or more Radio-Frequency Identification (RFID) beacons deployed with personnel assigned to the work site. The ground station emits a Frequency-Modulated Continuous-Wave (FMCW) pulse that the beacons echo and return to the ground station. The ground station uses tracking / radar algorithms to discern the distance and direction to the RFID beacon. For a finalized system, elevation tracking would be included as well.
Particular focus is given to the RFID beacon as the researcher’s efforts were directed predominately at this device. The RFID beacon is a bent-pipe transceiver, meaning that any signal received is re-transmitted at a slightly different frequency. The RFID beacon has evolved several times during the duration of this project due to system level changes, and in its current form it transmits and receives within a narrow band between 420 and 450 MHz that the Federal Communications Commission (FCC) has allocated to tracking systems. The narrow gap between transmit and receive frequencies has placed taxing requirements on the filtering used in the RFID beacon. A Surface-Skimming Bulk Wave (SSBW) filter was specified to meet the tight requirements of the RFID beacon, but was not procurable for the proof of concept. In the place of these filters, the proof of concept incorporates an Intermediate-Frequency (IF) filtering scheme as well as accommodations to add manually tuned coaxial cable filtering. Potential antennas, enclosures, and power sources are also discussed.
Remaining efforts to validate the system have been identified. Future work that could make this system cheaper as well as more robust and reliable has been identified. These efforts range from simplifying the RFID beacon and trimming its production costs to expanding the functionality of the RFID beacon and potentially integrating the beacon with existing communication equipment using intelligent Software Defined Radio (SDR) systems. The current Theseus system provides a solution to tracking personnel working small area indoor / outdoor work sites not currently rivalled by existing products. Additional research should be considered that may produce more robust solutions.