Automatic vehicle identification system capable of vehicle lane discrimination

DETAILED DESCRIPTION A method for identifying an object and determining the location of an object is disclosed.
The method includes the steps of: focusing a first directional antenna on a first area, focusing a second directional antenna on a second area, transmitting a first field strength pulse from the first directional antenna, transmitting a second field strength pulse from the second directional antenna, and comparing in a transponder the first field strength pulse to the second field strength pulse to determine in which of the two areas the transponder is located.
In the preferred embodiment of the present invention the method relates to an Automatic Vehicle Identification (AVI) system capable of vehicle lane discrimination.
In automatic toll booth systems employing RF data links for vehicular identification, it may be necessary to determine in which of two adjacent lanes a vehicle is traveling.
Within the vehicle is a tag or a transponder which receives the interrogation signal from the transmitter of the interrogator or reader and can reply to the interrogation unit by backscatter modulating a continuous wave input.
The receiver of the interrogator then decodes the backscatter modulated signal and may relay the information contained in this signal to a control circuit which, for example, might log the information into a memory.
An analogous principle to the backscatter modulation of a continuous wave signal is that of an LCD wristwatch which sends the wearer data based on reflected light.
The preferred embodiment allows each transponder to determine its lane location by comparing the field strengths of the interrogation signals of each lane.
By comparing the field strengths, an effective discrimination for lane boundary can be provided.
Each transponder can then be polled separately by an interrogator associated with each lane.
Further details of the method for comparing field strengths for the relative interrogation signals will be further described herein.