Circularly polarized 4-element array fed by aperture coupling for rectennas application

The circularly polarized antennas fed by aperture coupling, which are applied in rectennas, have been researched. The double-layer structures, which put the feed networks and the radiating patches in the different sides, provide several good performances. First, it minimizes the influence of feedlines on the patches. Then, the gain and bandwidth can be improved in some degrees and it is easy to be integrated with other passive or active devices to construct rectennas of the RF front-ends. It also reduces the bulk of the rectennas. The influences of the array distance d on the XPD, return loss, gain and axial ratio have been analyzed in detail. A 4-element array has been designed with measured 800 MHz bandwidth of S/sub 11/ less than -15 dB and optimized 450 MHz bandwidth of AR less than 3 dB being obtained.