Patent ID: 6493653
Filing Date: 2002-12-10
Classification: G01R

Abstract:
A clockless method of measuring time of flight in a system that outputs an energy pulse correlatable with a START pulse, and that detects a DATA signal reflected from a target, the method comprising the following steps:(a) providing a tapped delay line comprising a series-coupled chain of N substantially identical delay elements, denoted D(x) where 0&lE;x&lE;Nâˆ’1; (b) coupling said START pulse as input to a latch circuit; (c) coupling an output from said latch circuit to an input of said tapped digital delay line such that the latched START pulse propagates through said N delay elements; (d) providing a channel register comprising N series-coupled storage elements, denoted FF(x) where 0&lE;&lE;Nâˆ’1; (e) coupling said DATA signal to a comparator block; (f) coupling an output of said comparator block to an input of said channel register; and (g) synchronously clocking storage element FF(x) with a delayed version of said latched START pulse from delay element D(x) to sample said output of said comparator block; and (h) digitally processing signal information available from step (f) to determine at least one of (i) first time over threshold of said DATA signal, and (ii) total time over threshold of said DATA signal.