| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a VPM (Variable Phase Modulation) modulation system in an RFID communication, which is capable of performing stabilization of a load modulation operation and extension of a communication distance. <P>SOLUTION: In the RFID communication for performing data transmission between an interrogator and a transponder in a non-contact IC card or a radio ID tag system, as a load modulation system for performing data transmission to the transponder side by short-circuiting an antenna circuit of the interrogator side, load modulation is performed by a VPM coding system in which a negative logical pulse signal is outputted for a Tg time as a pulse gap signal for the head of each data indicative of "1" and "0", an H level signal is outputted for a T1 time after the pulse gap signal in the case of "1" data, and the H level signal is outputted for a T0 time after the pulse gap signal in the case of "0" data. In this case, the Tg time is very short compared to the T1 time and T0 time, the T1 time is longer than the T0 time, and Tg, T1 and T0 times can be arbitrarily set. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
