A Radio Assay for the Study of Radio Frequency Tag Antenna Performance
Griffin, Joshua David
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In recent years, passive radio frequency (RF) tags that communicate using modulated backscatter radiation have shown great potential for use in inventory management, parcel and postal tracking, for use as remote sensors, and in a host of other Radio Frequency Identification (RFID) applications. However, for the widespread use of these tags to become reality, much basic research is needed to reduce the cost, increase the range, and increase the reliability of the RF tag. This research seeks to enhance the performance of passive RF tags by developing a series of tests, or radio assay, to measure the following: the performance of RF tag antennas as a function of antenna material and manufacturing technique and the antenna performance when attached to various materials. The radio assay experiments are designed for RF tag antennas that operate in the far field of the tag reader and communicate using modulated backscatter radiation at 915 MHz. Three flexible, folded dipoles, printed on plastic substrates, were measured in the radio assay experiments. The results of the experiments include the following: the antenna gain penalty (relative to a baseline antenna) for each antenna material and manufacturing technique, the antenna gain penalty (relative to the free space antenna gain) due to material losses when the tag antenna is attached to an object, and the benefits (in terms of antenna gain) of tuning each tag antenna to the material to which it is attached. The results are presented in a form to aid RF engineers in the design of RF tag system link budgets.