Importance

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Abstract

A time code receiver 18 is used to provide a rough estimate of an elapsed time, which is then enhanced by additional circuitry 53. The time code receiver 18 uses a square wave reference oscillator to produce a digital time value 56. This reference oscillator is also fed into a phase detection circuit 34 along with an output 30 from a second oscillator circuit which is triggered upon detection of the occurrence of the event 24. The measured phase difference of the time code receiver reference oscillator 20 and the second oscillator signal 30 is used to produce digital values 38 and 40 that represent a fraction of the clock cycle. This fractional clock cycle or 'fine time' value is added to digital time value 56 from the time code receiver 18 to increase the resolution of time measurement. This method of measuring times of events can be used to measure events such as the arrival of radio frequency signals at remotely based receivers in order to determine the distance of the transmitter from the receivers.

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First Claim