Short-range precision navigation and tracking system

A precision ranging system, utilizing a phase-locked loop (PLL), has been developed for use in high-accuracy short-range navigation and tracking. Initial studies and laboratory experimentation indicate that an accuracy of 0.1 m is within feasibility limits. The system utilizes a PLL to maintain a constant phase relationship between the modulation of the carrier frequency of a master station and the return signal from a fixed position repeater station. The fixed phase relation implies that as range varies, the modulation frequency varies inversely. Range measurement is determined by means of frequency measurement.