Antenna device and tire pressure monitoring system including same

摘要

An antenna device is composed of a plurality of units of a same structure connected in series. Each of these units includes a single antenna, a level signal generating part for generating a level signal indicative of the intensity of a received signal, or that of its carrier wave, from the antenna, a demodulated signal generating part for generating a demodulated signal by demodulating a received signal from the antenna, a level signal input terminal for receiving an inputted level signal from outside, a demodulated signal input terminal for receiving an inputted demodulated signal from outside, and a selector which serves to compare the level signal generated by the level signal generating part and the inputted level signal received through the level signal input terminal, to select the level signal generated by the level signal generating part and the demodulated signal generated by the demodulated signal generating part if the level signal generated by the level signal generating part is greater than the inputted level signal, to select the inputted level signal and the inputted demodulated signal if the inputted level signal is greater than the level signal generated by the level signal generating part, and to output the selected level signal and the selected demodulated signal through a level signal output terminal and a demodulated signal output terminal, respectively.