TRANSPONDER FOR DISCRIMINATING APPARATUS OF MOVING BODY

PURPOSE:To enable miniaturization by a construction wherein an antenna for receiving an interrogation wave and an antenna for transmitting a reflection wave modulated in accordance with discrimination information are made to be used jointly. CONSTITUTION:An antenna B1 for transmission and reception receives an interrogation signal S1 from an interrogator A. Next, a detector F distributes a power of the signal S1 to first and second powers of prescribed amounts by a reflection coefficient of a detecting element. When a determining element G determines that a voltage level of the first power of the prescribed amount distributed by the detector F is a prescribed level or above, it outputs a transmission instruction signal so as to transmit a response signal S1, and when a code generating element D receives this transmission instruction signal as an input, it generates discrimination information stored beforehand. Moreover, a modulator E changes a bias amount of the detecting element in accordance with the discrimination information outputted from the generating element D and changes a reflection coefficient of the detecting element in accordance with the discrimination information. Thereby the discrimination information is modulated to a reflection wave of the signal S1 having the second power of the prescribed amount and sent as a signal S2 in response from the antenna B1.