Abstract: Disclosed is a correlation method to adaptively operate in a time varying phase and a correlator thereof. A correlation method according to the present invention includes performing the first correlation according to a certain reference value and a certain reference interval for correlation of a received signal; calculating an average variation of the received signal through the result of performing the first correlation; deciding a new reference value for the second correlation through the average variation; performing the second correlation according to the new reference value and the reference interval; and selecting the maximum value among the result of performing the second correlation. Accordingly, plural references are decided considering variation of a response signal between tags and also separate plural references are decided considering bit variation of a response signal in the same tag, so that a digital signal can be ideally demodulated in the environment where signal phase variation occurs.

Abstract: Disclosed is a correlation method to adaptively operate in a time varying phase and a correlator thereof. A correlation method according to the present invention includes performing the first correlation according to a certain reference value and a certain reference interval for correlation of a received signal; calculating an average variation of the received signal through the result of performing the first correlation; deciding a new reference value for the second correlation through the average variation; performing the second correlation according to the new reference value and the reference interval; and selecting the maximum value among the result of performing the second correlation. Accordingly, plural references are decided considering variation of a response signal between tags and also separate plural references are decided considering bit variation of a response signal in the same tag, so that a digital signal can be ideally demodulated in the environment where signal phase variation occurs.

Abstract: A reader, tags, an RFID system, and a method of simultaneously identifying a plurality of tags having colliding reply signals and reducing the reading time. In the RFID system including a reader and plural tags assigned unique IDs, the reader stores a comparison code which identifies ID codes generated based on the unique IDs of the tags, and issues a query signal to the tags to inquire into the presence of the tags. In response to the received query signal, the tags generate the ID) codes based on their unique IDs and sends the ID codes to the reader. The reader stores the received ID codes and identifies the responding tags by comparing the stored comparison code with the ID codes. When the ID codes are orthogonal, colliding reply signals can be resolved through a correlation technique.