Improvement of null zone avoidance capability for HF-band RFID using diversity combining of loop antennas

摘要

A method to avoid null zone for HF-band RFID without expanding antenna size is proposed. A loop antenna is split into four parts, which work as a planar array antenna. Combining circuit for loop antennas consists of three phase inverters. Phase inverters are controlled to obtain maximum power to drive RFID chip. We have validated by FDTD simulation that the proposed scheme enlarges worst received power by 6.6 dB.