The Multitag Microwave RFID System with Extended Operation Range

The problems of radio frequency identification are discussed. It was shown that the use of passive transponders is preferable, but weak energy of system in this case reduces the operation distance and decreases the noise-immunity of the system. The problems of traditional radio-frequency identification systems are discussed. In this chapter the use of homodyne method of useful signal selecting was proposed. The augmentation signal of transponder was obtained by means of frequency shift with the help of controlled phase shifter. 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 in this case. Additionally the use of one-port transistor amplifier for increasing of operation range was proposed. The energy consumption of such amplifier and its cost are very low, but the gain of amplifier can reach 20 dB and more.