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Radio Frequency Identification System

Radio Frequency Identification System

The project was designed as a representation of the library application of a complete RFID system. The requirements were that four unique tags be detected within a distance of .5 m or more from the transmitter/receiver, with the programming set to identify each tag, and list information about each object tagged.
This paper presents a novel, complete RFID system consisting of the following elements:

�� A transmitter, operating with a 915 MHz RF signal
�� Four tags, consisting of a small circuit passively reflecting a modulated identifying signal to the receiver; to provide a power supply for the timer and BJTs of the tag, the tag is energized by the RF electromagnetic field of the transmitter; the tag then sends back a modulated signal to the receiver by means of an oscillator connected to the base of a BJT, with the tag antenna connected across the collector and emitter
�� A receiver, which amplifies and filters the incoming signal by means of operational amplifiers and band-pass filters set at the resonant frequency of each tag
�� A microcontroller, which inputs the modulated, filtered signal, and outputs a digital signal into the computer
�� Software, which reads the digital signal and then processes the information to determine which tags are within the detection range (approximately 50 cm), and then displays the tag information on a computer display.


The project was successful in that a complete, fully functional RFID system was demonstrated, with a reader that sent out a 915 MHz signal, and was able to not only wirelessly detect and distinguish between four unique objects, but also display data regarding each object onto a computer display.

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