Patent ID: 7738838

Claim:
A communication method for a noncontact RF ID system comprising: communicating a data sequence having a first waveform which corresponds to one of codes “0” or “1” and which has a length of time T; communicating a data sequence having a second waveform which corresponds to the other of said codes “0” or “1” and which has a length of time T; communicating a data sequence having a third waveform which corresponds to m (m is a natural number equal to or greater than 2) codes that are the same as the codes of the second waveform and where the third waveform has a length of time mT, wherein the first waveform with 50% duty ratio is in a low level state at a starting point, is in a high level state at an end point and rises only at a position of T/2, the second waveform with 50% duty ratio is in a high level state at a starting point, is in a low level state at an end point and rises only at a position of T/2, and the third waveform with 50% duty ratio is in a high level state at a starting point, is in a low level state at an end point and rises only at a total of m positions of T/2+nT (n=0 . . . , m−1); and replacing consecutive instances of the second waveform in the data sequence with the third waveform when the second waveform occurs consecutively in the data sequence, where the data sequence is communicated from a transmitting device to a receiving device.