Content area
Full Text
Introduction
Due to the low cost of barcodes, automation identification (auto-ID) systems have been applied to various aspects of daily life. In solving the problem of insufficient storage in barcodes, one of the better solutions is the IC chip, such as a memory card or a smart card, to store and identify information. These kinds of IC cards must utilize a contact to a power supply and must transmit data by way of a reader. Drawbacks include more operational time and wear at the point of contact. The contactless IC card technique transmits data between card and reader through radio waves. The power also can be converted from a radio wave or built-in batteries in cards. Because of the transport of power and information through radio waves, contactless auto-IDs are called radio frequency identification (RFID) systems.
RFID is not a new technique. In 1948, Harry Stockman published a paper entitled "Communication by means of reflected power" that discussed the theory and implementation of RFID ([17] Stockman, 1948). Vernon and Harris published papers entitled "Application of the microwave homodyne" and "Radio transmission systems with modulatable passive responder", respectively ([18] Vernon, 1952; [7] Harris, 1960). After that, the development of RFID continued. From 1980 to 1990, RFID systems gradually matured, including use by, for example, the Association of American Railroads and the Container Handling Cooperative Program. RFID initiatives simplified the identification and tracing procedures in the process of merchandise delivery. As a result the application of RFID soared ([14] Landt, 2001).
Structure and principle
As Figure 1 [Figure omitted. See Article Image.] shows, the principles of an RFID system can be divided into three components:
the RFID tag (or transponder);
the RFID reader (or interrogator); and
the application system which is used for the reader to transmit or receive data from a tag ([12] Kern, 2004).
In general, a tag consists of one coupling element (providing the function of antenna) and one electronic chip. A reader consists of one RF module (providing the signal process of transmitting or receiving), one control module, and one coupling element, through an input/output interface such as the RS232 or RS285, to connect with applications. Another very important feature is the power supply. Passive tags do not contain power and all...