Patent ID: 8026848
Filing Date: 2011-09-27
Classification: G01S,H01Q

Abstract:
1. A radio-based position location system for determining a relative position of a first object with respect to a second object, comprising: a first radio operatively associated with the first object, said first radio including a first radio antenna; a first directional antenna mounted to the second object, the first directional antenna having a radiation pattern that comprises a high gain region, the first directional antenna being oriented so that the high gain region is directed generally outwardly from the second object and defines a first detection zone; a second directional antenna mounted to the second object, the second directional antenna having a radiation pattern that comprises a high gain region, the second directional antenna being oriented so that the high gain region is directed generally outwardly from the second object and defines a second detection zone, wherein the high gain region of said first directional antenna is flanked on either side by a low gain region and wherein the high gain region of said second directional antenna is flanked on either side by a low gain region, the first and second directional antennas being oriented with respect to one another so that a flanking low gain region of said first directional antenna is located adjacent a flanking low gain region of said second directional antenna, the adjacent flanking low gain regions of said first and second directional antennas defining a zone of diminished sensitivity between the first and second detection zones; and a second radio connected the first and second directional antennas, said first and second radios exchanging radio signals to determine the relative position of the first object with respect to the second object at least in part by determining a time-of-flight of a radio signal, the radio signals being exchanged via said first directional antenna and the first radio antenna when said first object is in the first detection zone, the radio signals being exchanged via said second directional antenna and the first radio antenna when said first object is in the second detection zone.