  RF Wireless Power Transfer (WPT) emerges as a technology for charging
autonomous devices, enabling simultaneous power and information transfer.
However, with increasing distance, single-input, single-channel rectenna
systems are not able to meet the power requirements of large scale IoT
applications. In this paper, we tackle this problem on two levels. First, we
minimize the energy consumption at the energy-constrained device on three
levels. Second, we evolve to a dual-band solution increasing RF WPT. One
frequency band is used to provide a base charge to many nodes in a shared
transmission. Beam steering, on the other hand, allows for more power hungry
operations while introducing as minimal interference as possible. We showcase
this method for a hybrid RF-acoustic positioning system. Practical measurements
conducted in a multi-antenna indoor testbed (Techtile) show the additional
power gain and positioning rate.
