| 摘要 |
PROBLEM TO BE SOLVED: To improve the safety of data at the time of radio transmission in a non-contact identification system. SOLUTION: A reader/writer 10A outputs an ASK modulation signal with a first modulation degree to the side of a data carrier 11A. The data carrier 11A detects the signal of the first modulation degree, provides reception data and inputs them to a communication logic circuit 24. A transmission signal from the data carrier is sent out by changing the load of a resonance circuit 20 with a second modulation degree shallower than this. By subtracting an ASK modulation output from a signal provided at a coil L1, the reader/writer 10A extracts a load fluctuation component on the side of the data carrier, detects that component and defines it as a reception signal. Thus, fully duplex communication is enabled and data contents are hardly detected by the third person. |
