| 摘要 |
PROBLEM TO BE SOLVED: To attain efficient demodulation by using phase change by providing a phase shifter between a carrier wave oscillator and a multiplier, and changing the phase of the carrier wave for operating multiplication. SOLUTION: A phase shifter 6 is inserted between a carrier wave oscillator 5 and a multiplier 7 of a reader/writer unit(RWU) of a non-contact IC card system. In a load switch system for changing a capacitor to be inserted in parallel into the coil antenna of the non-contact IC card, when the capacity of the capacitor is changed, parallel oscillation frequency with the coil antenna is deviated from the frequency of a carrier wave received for a power, and the amplitude and phase of a carrier wave transmitted from a coil antenna 1 of the RWU is changed. In this case, the amplitude difference is changed by changing the phase shift amounts of the phase shifter 6. That is, the phase shift amounts for obtaining the maximum amplitude difference value is set by the phase shifter 6 so that an efficient data demodulator can be obtained. |
