| 摘要 |
PURPOSE:To demodulate a digital data from an information signal without using a filter or a frequency/voltage converter while avoiding any influence caused by noise by transmitting the digital data as the information signal which frequency is converted. CONSTITUTION:When a non-contact IC card 2 is loaded to a reader/writer 1, a transmission line is formed by magnetically coupling a coil 4 of the non- contact IC card 2 and a coil 3 of the reader/writer 1. When transmitting the digital data from the reader/writer 1 to the non-contact IC card 2, the frequency of a carrier for power supply is converted by the digital data. Then, the information signal, which frequency is converted by the digital data, is received and a part having a level higher than a previously set threshold value in the information signal is detected. Then, by comparing the time width with the reference time of each part, a signal is generated so as to get the low level in the part having the time width longer than the reference time and to get the high level in the part having the time width shorter than the reference time. Thus, the digital data in the information signal is obtained. |
