LIGHT RECEIVER FOR HIGH-SPEED DATA TRANSMISSION

摘要

PURPOSE: To make data transmission between a beacon and a vehicle in a traffic guide system immune to the effect by its surrounding to the utmost by using a sampling threshold value adjusted depending on a surrounding luminous intensity. CONSTITUTION: The receiver is provided with a photo diode FD and with a variable resistor RS through which a current of the photo diode FD based on an infrared ray IR and the sun light SL flows. A threshold voltage US set by voltage division resistors R2, R3 through a resistor RU is increased depending on the 'sun current' and a signal current SI is fed to an amplifier stage VER via a coupling capacitor CK. An output signal AS of the stage VER is given to a 1st input of a comparator stage KOMP and the sampling threshold voltage US is fed to a 2nd input of the stage KOMP. A resistance of the resistor RS depends on the 'sun ray' and the resistor RS is made up of resistors R21-23 and Zener diodes Z1, Z2 and an ideal threshold voltage USid is approximated by the three resistors.