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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