초록 ▼

An asset management radio location system uses time-of-arrival differentiation for random and repetitive spread spectrum, short duration transmissions from object-attached tags, to geolocate objects within a monitored environment. An object location processor is coupled to distributed tag transmissi

An asset management radio location system uses time-of-arrival differentiation for random and repetitive spread spectrum, short duration transmissions from object-attached tags, to geolocate objects within a monitored environment. An object location processor is coupled to distributed tag transmission readers over signal transport paths having different transport delays, and carries out time-of-arrival differentiation of first-to-arrive transmissions from a tag to determine where its object is located. Geolocation errors associated with variations in parameters of the signal transport paths are effectively removed by installing one or more `reference' tags, whose geolocations are precisely known. Using a background calibration routine that is exercised at a relatively low cycle rate, emissions from the reference tags are processed and coupled to the geolocation processor. The calculated geolocations of the reference tags are compared with their actual locations. Any offset between the two geolocation values is used to adjust time delay offsets associated with signal transport paths between the readers and the geolocation processor.

대표청구항 ▼

1. A method of controlling the operation of a system for geolocating objects within a monitored environment, wherein transmissions from tags associated with said objects are detected at a plurality of spaced apart monitoring locations containing tag transmission readers, each respective monitoring l

1. A method of controlling the operation of a system for geolocating objects within a monitored environment, wherein transmissions from tags associated with said objects are detected at a plurality of spaced apart monitoring locations containing tag transmission readers, each respective monitoring location containing a plurality of transmission readers respectively employing mutually diverse antennas to minimize multipath interference at said antennas simultaneously, and outputs of said tag transmission readers are coupled over signal transport paths, having associated signal transport delays, to an object location processor which processes said outputs of said tag transmissions to geolocate said tags and thereby their associated objects within said monitored environment, said method comprising the steps of:(a) providing within said monitored environment at least one `reference' tag whose geolocation is known, and which is operative to transmit a reference tag signal encoded with information representative of the identification of said reference tag; (b) receiving said reference tag signal at said transmission readers, and coupling outputs thereof over said signal transport paths to said object location processor for processing thereby to determine the geolocation of said reference tag; (c) comparing the geolocation of said reference tag as determined in step (b) with the known geolocation of said reference tag; and (d) controllably adjusting the processing operation carried out by said object location processor to compensate for errors, such as those associated with delays through said signal transport paths, in accordance with a difference between the geolocation of said reference tag as determined in step (b) and the known geolocation of said reference tag.