  Tiny batteryless sensors are desirable since they create negligible impacts
on the operation of the system being monitored or the surrounding environment.
Wireless energy transfer for batteryless sensors is challenging since they
cannot cooperate with the charger due to the lack of energy. In this paper, a
Magnetic Blind Beamforming (MagBB) algorithm is developed for wireless energy
transfer for batteryless sensors in inhomogeneous media. Batteryless sensors
with randomly orientated coils may experience significant orientation losses
and they may not receive any energy from the charger. MagBB uses a set of
optimized current vectors to generate rotating magnetic fields which can ensure
that coils on batteryless sensors with arbitrary orientations can receive
sufficient voltages for charging. It does not require any information regarding
the batteryless sensor's coil orientation or location. The efficiency of MagBB
is proven by extensive numerical simulations.
