Multiple antenna rectifiers for radio frequency energy scavenging in wireless sensors

Wireless sensors with radio frequency (RF) energy scavenging capabilities can operate batteryless and thus are promising for a wide range of applications. For sensor nodes with a single antenna, radiation from certain incoming directions cannot be received due to zeros in the antenna radiation pattern. This can result in sensor nodes that will not power up and thus are not functional. To overcome these spatial zeros and to improve the RF-DC rectification efficiency, multi-antenna rectification schemes are considered. Multi-antenna schemes known from communications, e.g. beam steering architectures, are not suitable for ultra-low power sensor nodes, as they require an on-chip power supply as well as a large area. With these practical constraints on power and area, we address an alternative approach to multi-antenna rectification schemes dedicated to RF energy scavenging. Using circuit simulations, we show that the proposed scheme achieves a good balance between directional uniformity and RF-DC rectification efficiency.