Agricultural and Environmental Applications of RFID Technology

2. Rfid Principle

RFID technology hangs on the idea of assigning a unique number to each individual item (object, animal, human being). To setup an RFID system, three main components are required as shown in the Figure 1:

Figure 1.

RFID architecture

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  The tag: also called transponder, is an integrated circuit, commonly referred to as microchip, attached to a minuscule (metallic) antenna. Every tag has its own identifier code that will be used to uniquely identify the item associated to it.

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  The reader: is used to create an interrogation zone in which the RFID tag will be read. It collects information from the tags, filter them and transfer them to the processing unit. In the case of a passive tag, the reader also serves to power the tag up. Moreover, the reader manages the different antennas it is connected to in order to achieve a maximum read rate.

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  The server / host: is the processing part of the RFID system. The host is a computer that runs, in addition to the enterprise application, an application called middleware that is an interface between the reader and the application layer. The middleware, the brain behind the smart system, manages the different readers and instructs each one on how to interact with the RFID transponders. It is also the component that is responsible for communicating filtered events back to the application. The host may be one processing unit or an entire enterprise system composed of servers (web, databases...). The host may be one processing unit or an entire enterprise system composed of servers (web, databases...)

The operating principle of an RFID system is the following. The reader starts a communication process by emitting electromagnetic wave. This wave will be intercepted by the antenna of the RFID tag, generally a passive tag. An induced current will activate the integrated circuit, enabling it to communicate. To transmit data stored in its memory (chip), the tag modulates the digital signal using phase or amplitude modulation on a predefined frequency carrier. The reader receives information and redirects it to the host where it will be processed. Figure 1 explains the principle.

Table 1 outlines a comparison between the LF, HF and UHF.