Decoupled dual-dipole rectennas on a conducting surface at 2.4 GHz for wireless battery charging

A linearly polarised decoupled dual-dipole rectenna (DDDR) with a novel microstrip-decoupling structure is presented for wireless battery charging applications at the 2.4-GHz industrial, scientific and medical (ISM) band. It consists of decoupled dual dipole (DDD) antenna and a Villard´s voltage doubler (VVD) rectifier, and is able to operate close to a conducting surface. The DDD provides 5.6% bandwidth centralised at ~2.42 GHz and about 4 dBi gain from each element. The half power beam width (HPBW) of this design in the XZ-plane is about 120° from each antenna. High isolation is achieved with only 3-mm edge-to-edge separation. The DDD is 37° smaller than two standard patch antennas located on the same substrate without a decoupling structure. The DDDR is able to fully charge a standard 4.8-V NiMH battery to 5.1°V in 5°h over a distance of 23°cm.