Active UHF antennas for demanding RFID applications

The UHF RFID systems are used, on an everyday basis, for identification of millions of different items of goods. Yet there are identification tasks, where a correct and reliable identification is difficult to be accomplished. One of these applications concerns identification of goods equipped with TAGs, densely and randomly accommodated in a larger space. This refers e.g. to the identification of many TAGs fixed on clothes in large cartoon boxes. The TAGs can be located very close to each other, mutually coupled, screened, randomly oriented and placed in an environment with a wide range of wave propagation parameters. The identification of such a set of TAGs represents a difficult problem, because standard configurations are rather prone to fail. The presented paper describes one of the possible solutions. The identification system is equipped with active reader antennas that enable the illumination and the read-out of the TAGs from many different locations as well as angles, and with a wide range of illuminating power. The whole process can be accomplished very fast. In fact, many different scanning procedures can be performed. According to preliminary measurements, such conditions conduce to 100% correct and reliable identification even in case that the tested scenarios include several hundreds of TAGs. The designed RFID system is very likely to be able to work well even in more demanding identification tasks.