Figure 1From: On the performance of MIMO RFID backscattering channelsTo read a passive RF tag, the RF reader transmitter broadcasts an unmodulated carrier signal, and then the RF tag conveys its information (e.g., the ID of the tag) to the reader by reflecting the unmodulated carrier signal back to the reader receiver using load modulation. The reflection coefficient Δ(t) of the tag antenna load, which actually represents the tag information, can be changed by switching the RF tag antenna load between different states[9].Back to article page