Retrodirective rectenna arrays for passive SHF-RFID transponders

In this work we combine the retrodirectivity of Van Atta arrays with the direction-independent power reception capability of rectenna arrays to compensate for the high free-space path loss in the super high frequency (SHF) band. Currently the range of SHF systems using modulated backscattering at passive transponders is limited by this effect. To overcome this problem we propose a new array structure connecting multiple antennas and rectifiers through a passive network. By using the proposed approach on an N×N array, energy and backscatter range can both be increased by a factor of N. This enables radio frequency identification (RFID) systems in the SHF band to achieve similar coverage as ultra high frequency (UHF)-RFID systems, while gaining the advantage of higher available bandwidth. Influences from the direct environment of the transponders can be compensated for and the possibility of high accuracy transponder localization arises.