A Multibeam Ambient Electromagnetic Energy Harvester With Full Azimuthal Coverage

Confronting the challenge of replacing or recharging batteries for numerous low-power devices in the Internet of Things, the harvesting of ambient electromagnetic (EM) energy is considered a promising approach. Since EM energy is randomly distributed in the environment, omnidirectional antennas or multibeam antennas are better choices for their large coverages which enable them to collect as much energy as possible. However, omnidirectional antennas usually have low gains resulting in low receiving energy, and most multibeam antennas with high gains require complicated feeding networks. To address these issues, a six-beam antenna without a complex feeding network is proposed in this article. It consists of a triangular patch array layer and a surface waveguide layer. A peak gain of 8.3 dBi, as well as a 3-dB beamwidth of
$62\mathbf {\mathrm {^\circ }}$
in H-plane and
$56\mathbf {\mathrm {^\circ }}$
in E-plane have been achieved, affording full azimuthal coverage within a certain elevation angle range. For demonstration, an EM energy harvester is constructed based on the proposed antenna. It can be observed that the implemented device can harvest almost the same amount of EM energy in different horizontal orientations, and acquire multifold DC power in the case of multiple EM transmitters.