Importance

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Abstract

A vehicle borne transmitter transmits a spread spectrum transmit signal which is pseudo (PN) encoded. The transmitted signal is reflected off of a reflector on known position which may be a highway guardrail, tunnel wall, or the like. The reflected signal is detected by a receiver in the vehicle and a pseudo noise code (PN code) is synchronized to the reflected signal to accomplish maximum correlation. The phase delay between the transmitted PN code and received PN code is thereby utilized to determine the distance between the vehicle and reflector to maintain the vehicle in the center of a roadway lane. Roadway transponders may be periodically located adjacent the roadway and will be responsive to the vehicle borne interrogation signal. The periodically located transducers produce a reply signal including a PN code and imbedded data which data may represent transponder ID and position, roadway or map data, or other data which is desirable to transmit between the transducer and the vehicle travelling the highway.

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First Claim