IMPROVEMENTS IN OR RELATING TO TIME-OF-FLIGHT RANGING SYSTEMS

A time-of-flight ranging system, such as a keyless access Control system, comprises a first part and a second part, e.g., a portable device such as a key fob. Both parts have a transceiver for effecting communication with each other. At least the first part includes a device, e.g., a processor, for...

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Bibliographische Detailangaben
1. Verfasser:	LEITCH ADAM S
Format:	Patent
Sprache:	eng
Schlagworte:	ACCESSORIES THEREFOR ANALOGOUS ARRANGEMENTS USING OTHER WAVES ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDEDFOR ELSEWHERE CHECKING-DEVICES DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES FIXED CONSTRUCTIONS GENERATING RANDOM NUMBERS HANDCUFFS KEYS LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION ORRERADIATION OF RADIO WAVES LOCKS MEASURING PERFORMING OPERATIONS PHYSICS RADIO DIRECTION-FINDING RADIO NAVIGATION REGISTERING OR INDICATING THE WORKING OF MACHINES SAFES TESTING TIME OR ATTENDANCE REGISTERS TRANSPORTING VEHICLES IN GENERAL VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISEPROVIDED FOR VOTING OR LOTTERY APPARATUS WINDOW OR DOOR FITTINGS
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Beschreibung
Zusammenfassung:	A time-of-flight ranging system, such as a keyless access Control system, comprises a first part and a second part, e.g., a portable device such as a key fob. Both parts have a transceiver for effecting communication with each other. At least the first part includes a device, e.g., a processor, for determining the distance between the two parts based on time-off-light. To save power, when the two parts are a relatively great distance apart, a time-of-flight measuring device computes the time based on a relatively coarse algorithm, and when the parts are relatively close, the computation is carried-out using a more precise algorithm. The clock frequency may be reduced when the two parts are a relatively great distance apart, and increased when they are closer. Further the transmitter power may be reduced when the two parts are relatively close together and increased when they are a relatively great distance apart.