Roadside beacon system
First Claim
1. A roadside beacon system in which a roadside antenna installed at a predetermined position in a road traffic network transmits data to a vehicle and receives data from a vehicle, comprising;
- means for transmitting from said roadside antenna a first signal of constant amplitude, said first signal being modulated according to transmission data, and a second signal amplitude-modulated with a predetermined frequency, andnavigator means located on said vehicle for receiving signals transmitted from said roadside antenna, said navigator means including means for detecting said second signal to perform position detection and to output a position decision signal, and means for calibrating at least position data stored in said navigator means in response to said position decision signal and in accordance with data received via said first signal.
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Accused Products
Abstract
A roadside antenna system permitting the transmission of data to a vehicular navigation system and providing for the recalibration of positional data carried by the navigation system includes an antenna structure and transmitter system which permits the data transmission signal to be broadcast in a wide pattern. Meanwhile, the signal that provides for positional recalibration is broadcast in a high directivity signal or split beam. The positional accuracy of the navigator system is improved by performing the positional calibration only when intercepting the narrow beam pattern. Data transmission and reception can be carried out within a larger effective reception area without affecting the positional accuracy.
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Citations
18 Claims
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1. A roadside beacon system in which a roadside antenna installed at a predetermined position in a road traffic network transmits data to a vehicle and receives data from a vehicle, comprising;
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means for transmitting from said roadside antenna a first signal of constant amplitude, said first signal being modulated according to transmission data, and a second signal amplitude-modulated with a predetermined frequency, and navigator means located on said vehicle for receiving signals transmitted from said roadside antenna, said navigator means including means for detecting said second signal to perform position detection and to output a position decision signal, and means for calibrating at least position data stored in said navigator means in response to said position decision signal and in accordance with data received via said first signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A roadside beacon system in which a roadside antenna installed at a predetermined position in a road traffic network transmits data to a vehicle comprising;
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a plurality of antenna units arranged laterally; means for generating a first signal modulated with a constant amplitude according to transmission data, and means for supplying said first signal to said antenna units so that the directivity of said roadside antenna exhibits electric field strengths higher than a predetermined value over a predetermined range; means for generating a second signal amplitude-modulated with a predetermined frequency, and means for supplying said second signal to said antenna units so that the directivity of said roadside antenna exhibits a sharp lobe pattern, and navigation means on said vehicle for receiving signals from said roadside antenna, comprising; position decision means for detecting said second signal and for generating a position decision signal; and calibrating means for calibrating at least said position data in response to said position decision signal and in accordance with said transmission data. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification