Communication Method for Noncontact RF ID System, Noncontact RF ID System, and Transmitter and Receiver

Abstract

A communication method for a noncontact RF ID system that uses a first waveform, a second waveform, and a third waveform, wherein the first waveform and the second waveform are formed by a basic waveform having one of a rising or falling state transition at the approximate center of the waveform, the third waveform is formed by a plurality of basic waveforms that have one state transition at the approximate center part of the waveform, and the third waveform generates one state transition only at the approximate center of the plurality of basic waveforms. In addition, communication is carried out by using the third waveform in place of the first waveform and the second waveform in the case in which communication is carried out using a first waveform and a second waveform and one state transition is generated outside the approximate center part of the basic waveform.

1 - 9 . (canceled) 
   
   
       10 . A noncontact RF ID system comprising:
 a reader for transmitting data information that include data and a clock; and   a transponder which receives the data information from the reader comprising an antenna for receiving the signal from a reader, a DC power detecting circuit; a signal detecting circuit, an input amplifier, a clock generating circuit, a demodulator, a control logic circuit, and a memory, wherein   the DC power detecting circuit comprising a power accumulating capacitor that activates the transponder when a signal is received;   the clock generating circuit that generates an internal clock such that the state transition of the internal clock is generated in synchronism with the timing of the rise of the modulating signal and generates a data sequence having a first waveform which corresponds to one of codes “0” or “1” and which has a length of time T, 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, and a second waveform which corresponds to one of codes “0” or “1” opposite to the first waveform and which has a length of time T, 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,   the clock generating circuit further operates to replace consecutive instances of the second waveform in the data sequence with a third waveform when the second waveform occurs consecutively in the data sequence, the third waveform 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 which has a length of time mT and 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   the control logic circuit that operates in synchronism with the state transition of the clock generated by the clock generating circuit.   
   
   
       11 . A transmitter in a noncontact RF ID system comprising:
 a clock generating circuit that generates an internal clock such that the state transition of the internal clock is generated in synchronism with the timing of the rise of a modulating signal and generates a data sequence having a first waveform which corresponds to one of codes “0” or “1” and which has a length of time T, 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, and a second waveform which corresponds to one of codes “0” or “1” opposite to the first waveform and which has a length of time T, 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,   the clock generating circuit further operates to replace consecutive instances of the second waveform in the data sequence with a third waveform when the second waveform occurs consecutively in the data sequence, the third waveform 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 which has a length of time mT and 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   a control logic circuit that operates in synchronism with the state transition of the clock generated by the clock generating circuit.   
   
   
       12 . A receiver in a noncontact RF ID system comprising:
 a clock generating circuit that generates an internal clock such that the state transition of the internal clock is generated in synchronism with the timing of the rise of a modulating signal and generates a data sequence having a first waveform which corresponds to one of codes “0” or “1” and which has a length of time T, 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, a second waveform which corresponds to one of codes “0” or “1” opposite to the first waveform and which has a length of time T, 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 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 which has a length of time mT and 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);   the clock generating circuit further operates to detect the third waveform in the data sequence and replace the third waveform with consecutive instances of the second waveform in the data sequence; and   a control logic circuit that operates in synchronism with the state transition of the clock generated by the clock generating circuit.   
   
   
       13 . A noncontact RF ID system comprising:
 a reader for transmitting data information that include data and a clock; and   a transponder which receives the data information from the reader comprising an antenna for receiving the signal from a reader, a DC power detecting circuit; a signal detecting circuit, an input amplifier, a clock generating circuit, a demodulator, a control logic circuit, and a memory, wherein   the DC power detecting circuit comprising a power accumulating capacitor that activates the transponder when a signal is received;   the clock generating circuit that generates an internal clock such that the state transition of the internal clock is generated in synchronism with the timing of the fall of the modulating signal and generates a data sequence having a first waveform which corresponds to one of codes “0” or “1” and which has a length of time T, the first 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 falls only at a position of T/2, and a second waveform which corresponds to one of codes “0” or “1” opposite to the first waveform and which has a length of time T, the second 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 falls only at a position of T/2,   the clock generating circuit further operates to replace consecutive instances of the second waveform in the data sequence with a third waveform when the second waveform occurs consecutively in the data sequence, the third waveform 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 which has a length of time mT and 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 falls only at a total of m positions of T/2+nT (n=0, . . . , m−1); and   the control logic circuit that operates in synchronism with the state transition of the clock generated by the clock generating circuit.   
   
   
       14 . A transmitter in a noncontact RF ID system comprising:
 a clock generating circuit that generates an internal clock such that the state transition of the internal clock is generated in synchronism with the timing of the fall of a modulating signal and generates a data sequence having a first waveform which corresponds to one of codes “0” or “1” and which has a length of time T, the first 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 falls only at a position of T/2, and a second waveform which corresponds to one of codes “0” or “1” opposite to the first waveform and which has a length of time T, the second 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 falls only at a position of T/2,   the clock generating circuit further operates to replace consecutive instances of the second waveform in the data sequence with a third waveform when the second waveform occurs consecutively in the data sequence, the third waveform 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 which has a length of time mT and 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 falls only at a total of m positions of T/2+nT (n=0, . . . , m−1); and   a control logic circuit that operates in synchronism with the state transition of the clock generated by the clock generating circuit.   
   
   
       15 . A receiver in a noncontact RF ID system comprising:
 a clock generating circuit that generates an internal clock such that the state transition of the internal clock is generated in synchronism with the timing of the fall of a modulating signal and generates a data sequence having a first waveform which corresponds to one of codes “0” or “1” and which has a length of time T, the first 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 falls only at a position of T/2, a second waveform which corresponds to one of codes “0” or “1” opposite to the first waveform and which has a length of time T, the second 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 falls only at a position of T/2, and 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 which has a length of time mT and 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 falls only at a total of m positions of T/2+nT (n=0, . . . , m−1);   the clock generating circuit further operates to detect the third waveform in the data sequence and replace the third waveform with consecutive instances of the second waveform in the data sequence; and   a control logic circuit that operates in synchronism with the state transition of the clock generated by the clock generating circuit.