Patent ID: 7683825

Claim:
A method of measuring distance between a target and a receiver in a ranging system, the method comprising: transmitting a first pulse at a first time determined by a sampling clock in the receiver; receiving the first pulse; sampling the received first pulse at a predetermined amplitude threshold using the sampling clock; determining a time of arrival of the received first pulse in terms of a number of periods of the sampling clock after the first pulse was transmitted; transmitting a second pulse at a second time determined by the sampling clock; receiving the second pulse; sampling the received second pulse at a predetermined amplitude threshold using the sampling clock; determining a time of arrival of the received second pulse in terms of a number of periods of the sampling clock after the second pulse was transmitted; controlling a jitter of the sampling clock such that the jitter is distributed over a predetermined interval and such that the jitter has a predetermined amount of variation within the predetermined interval in short periods of time so as to vary the time of arrival of one or more pulses as measured by the sampling clock; determining an average time of arrival of the first and second pulses to obtain an averaged estimated time of arrival; and determining the distance between the target and the receiver by multiplying the averaged estimated time of arrival by a speed of propagation of the transmitted pulses.