The basic working mode of radio frequency identification system is divided into full duplex (Full Duplex) and half duplex (Half Duplex) system and sequence (SEQ) system. Full duplex means that the radio frequency tag and the reader can transmit information to each other at the same time. Half-duplex means that the radio frequency tag and the reader can transmit information in both directions, but can only transmit information in one direction at the same time.
In full-duplex and half-duplex systems, the response of the radio frequency tag is sent out under the electromagnetic field or electromagnetic wave emitted by the reader. Because compared with the signal of the reader itself, the signal of the radio frequency tag is very weak on the receiving antenna, so a suitable transmission method must be used to distinguish the signal of the radio frequency tag from the signal of the reader.