ON-VEHICLE COMMUNICATION EQUIPMENT

PROBLEM TO BE SOLVED: To provide passive on-vehicle communication equipment that can be configured small while keeping the communication performance satisfactory. SOLUTION: In this on-vehicle communication equipment 1, a modulator circuit 30 consists of a Schottky diode 32, a capacitor 34 and an impedance change setting circuit 36. In the on-vehicle communication equipment 1, a control circuit 72 inputs voltage for a reverse bias as a modulation signal to the Schottky diode 32 and power consumption needed when a down signal 114 is modulated is reduced. One terminal is shared by an input terminal for the down signal 114 and an output terminal for an up signal 116 in the modulation circuit 30, and one antenna 10 is shared by an antenna for receiving the down signal 114 and an antenna for transmitting the up signal 116.