Coherent method for signalling and ranging using unsynchronized digital radio transceivers

摘要

A method for determining the range between two points comprising transmitting a downlink radio signal from a base station at a first location to a transponder at a second location, transmitting an uplink radio signal from the transponder to the base station in response to receiving the downlink signal and the base station computing the distance between the two locations by measuring the time delay between the transmission of the downlink signal and the reception of the uplink signal. At least one of the signals comprises Hyperbolic Frequency Modulated (HFM) chirps of a known bandwidth whose phase varies as a logarithmic function of time. The base station and transponder each comprise a single reference oscillator for generating the radio signals and digital clock frequencies. The reference oscillators are not synchronised with each other.