Wireless time reference system and method
First Claim
1. A method of providing normalization of time of local clock circuits of two or more spatially-located receivers of respective monitoring stations, said method comprising:
- transmitting at least two RF pulses to define a time reference interval;
detecting said RF pulses at said receivers;
at respective monitoring associated with said receivers, measuring durations of said time reference interval according to said detecting step;
determining a relationship between durations measured at said monitoring stations; and
providing normalization of time of said local clock circuits at two or more monitoring stations according to said relationship.
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Abstract
Instead of normalizing time reference of independent spatially-located clocks using a reference tag transmission from known location, the present invention uses an interarrival time interval between a pulse pair of UWB pulses as a timing metric. Thus, a method of synchronizing spatially-located clock or normalizing time indications thereof comprises transmitting a UWB pulse pair, determining at first and second monitoring stations a respective count value indicative of a locally measured time interval between received pulse pairs, determining a ratio between clock counts of first and second monitoring stations, and utilizing the ratio to determine clock skew, e.g., a timing correction to be applied to respective local clocks of the monitoring stations. A corresponding system comprises a reference tag transmitter that transmits a pulse pair of UWB pulses to define a time reference interval, a first independent receiver that receives the pulse pair to generate a first count value indicative an interarrival interval between the pulse pair, a second independent receiver that receives the pulse pair to similarly generate a second count value, and a processor hub responsive to the count values to determine a ratio corresponding to the ratio of respective clock frequencies of the first and second receiver clocks. Once the correction is applied, time-of-arrival information from object tag transmissions may be used to determine object location with sub-foot position accuracies.
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Citations
8 Claims
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1. A method of providing normalization of time of local clock circuits of two or more spatially-located receivers of respective monitoring stations, said method comprising:
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transmitting at least two RF pulses to define a time reference interval; detecting said RF pulses at said receivers; at respective monitoring associated with said receivers, measuring durations of said time reference interval according to said detecting step; determining a relationship between durations measured at said monitoring stations; and providing normalization of time of said local clock circuits at two or more monitoring stations according to said relationship. - View Dependent Claims (2, 3, 4, 5)
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6. A method of normalizing independent clocks of respective receivers of remote monitoring stations, said method comprising:
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transmitting an ultra wideband (UWB) pulse pair, determining at first and second monitoring stations a respective clock count indicative of a locally measured time interval between said pulse pair, each said clock count being derived by incremental measurement of time units, determining a ratio between clock counts of said first and second monitoring stations using programmed processor module, and utilizing said ratio as a reference to normalize time of local clocks that generate each said clock count. - View Dependent Claims (7, 8)
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Specification