Roadside beacon system
First Claim
1. In a roadside beacon system in which various data are transmitted between roadside antennas installed along roads at predetermined positions and vehicles, and each of said roadside antennas is a split beam antenna having a directivity such that an electric field strength of the signal radiated therefrom abruptly decreases in front of said antenna, a navigational device carried on a vehicle receiving a signal from said roadside antenna to calibrate and display vehicle position data, said navigational device comprising:
- signal dividing means for dividing a signal received from said antenna into two division signals;
smoothing means for eliminating instantaneous level variations in a first of said division signals to provide a smoothed signal;
position detection region determining means for outputting, when a level of said smoothed signal provided by said smoothing means exceeds a first predetermined reference level, a position detection region determination signal indicating that said vehicle is existing near said roadside antenna;
position determining means for detecting when an electric field strength level of said received signal decreases abruptly to fall below a second predetermined reference level;
position determining gate means for receiving said position detection region determination signal as a control input signal, and for supplying the second division signal directly to said position determining means in response to said control input signal; and
calibrating means for calibration said navigational device according to a position determination signal outputted by said position determining means and received data.
1 Assignment
0 Petitions
Accused Products
Abstract
A roadside beacon system having improved reliability in the face of multi-path fading and the presence of large vehicles or the like which shield or scatter the received signal. The roadside antenna is of the split beam type. In the navigation system on the vehicle, the received signal is divided into two parts. The first part is smoothed and its level detected to determine when the vehicle is approaching an antenna. The remaining signal is then employed directly to detect the null in the transmitted beam when the vehicle passes directly in front of the antenna.
21 Citations
12 Claims
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1. In a roadside beacon system in which various data are transmitted between roadside antennas installed along roads at predetermined positions and vehicles, and each of said roadside antennas is a split beam antenna having a directivity such that an electric field strength of the signal radiated therefrom abruptly decreases in front of said antenna, a navigational device carried on a vehicle receiving a signal from said roadside antenna to calibrate and display vehicle position data, said navigational device comprising:
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signal dividing means for dividing a signal received from said antenna into two division signals; smoothing means for eliminating instantaneous level variations in a first of said division signals to provide a smoothed signal; position detection region determining means for outputting, when a level of said smoothed signal provided by said smoothing means exceeds a first predetermined reference level, a position detection region determination signal indicating that said vehicle is existing near said roadside antenna; position determining means for detecting when an electric field strength level of said received signal decreases abruptly to fall below a second predetermined reference level; position determining gate means for receiving said position detection region determination signal as a control input signal, and for supplying the second division signal directly to said position determining means in response to said control input signal; and calibrating means for calibration said navigational device according to a position determination signal outputted by said position determining means and received data. - View Dependent Claims (2, 3, 4, 9, 10)
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5. In a roadside beacon system in which various data are transmitted between vehicles and roadside antennas installed along roads at predetermined positions, and each of said roadside antennas is a split beam antenna having a directivity such that an electric field strength abruptly deceases in front of said antenna, a navigational device carried on a vehicle receiving a signal from said roadside antenna to calibrate and display vehicle position data, said navigational device comprising:
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signal division means for dividing a signal received from said antenna into two division signals; position detection region determining means for outputting, when a level of a first of said two division signals exceeds a first predetermined reference level, a position detection region determination signal indicating that said vehicle is located near said roadside antenna; position determining means for detecting when an electric field strength level of said received signal decreases abruptly to fall below a second predetermined reference level; position determining gate means for receiving said position detection region determination signal as a control input signal, and for supplying the second of said two division signals directly to said position determining means in response to said control input signal; reference signal forming means for detecting a peak value of said received signal, and for supplying a signal proportional to said peak value thus detected as a second predetermined reference signal to said position determining means; and calibrating means for calibrating said navigator device according to a position determination signal outputted by said position determining means and received data. - View Dependent Claims (6, 7, 8, 11, 12)
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Specification