| 摘要 |
PROBLEM TO BE SOLVED: To read/write data outputting an optimal modulated wave signal to each of IC cards, which can be accessed with respectively different amplitude transit modulated signals. SOLUTION: A modulation circuit 12 for a card reader/writer is provided with a modulation part 41 for outputting a first signal of the same phase as a clock CLK or second signal delayed by 90 deg., a circuit EXOR, a control means 12B composed of gates NAND1-NAND6 or the like and switches SW1 and SW2 and the control means inputs the first signal. When a transmitting code (a) is H, the respective switches are alternately opened/closed for each 1/2 cycle of the clock. When the transmitting code is L, the respective switches are opened and the modulated wave signal of modulation factor 100% is outputted. When the second signal is inputted and the transmitting code is H, on the other hand, the respective switches are opened for 1/4 cycle while being deviated for 1/2 cycle of the clock. When the transmitting code is L, the respective switches are closed for 1/4 cycle being deviated 1/2 cycle of the clock and the modulated wave signal of modulation factor 100% is outputted. |
