The multitag microwave RFID system

The problems of RF identification are discussed. It is shown that the use of passive transponders is preferable, but weak energy of the system in this case reduces the operation distance and decreases the noise immunity of the system. In this paper, it is proposed to use the homodyne method of selecting the useful signal. This solution allows to increase the energy and the noise immunity of the system (the operation distance is increased). Furthermore, the interrogator can treat several transponders simultaneously. Index Terms--Homodyne detection, microwave phase shifter, modulator, transponder.