  Wireless communication using fully passive metal reflectors is a promising
technique for coverage expansion, signal enhancement, rank improvement and
blind-zone compensation, thanks to its appealing features including zero energy
consumption, ultra low cost, signaling- and maintenance-free, easy deployment
and full compatibility with existing and future wireless systems. However, a
prevalent understanding for reflection by metal plates is based on Snell's Law,
i.e., signal can only be received when the observation angle equals to the
incident angle, which is valid only when the electrical dimension of the metal
plate is extremely large. In this paper, we rigorously derive a general
reflection model that is applicable to metal reflectors of any size, any
orientation, and any linear polarization. The derived model is given compactly
in terms of the radar cross section (RCS) of the metal plate, as a function of
its physical dimensions and orientation vectors, as well as the wave
polarization and the wave deflection vector, i.e., the change of direction from
the incident wave direction to the observation direction. Furthermore,
experimental results based on actual field measurements are provided to
validate the accuracy of our developed model and demonstrate the great
potential of communications using metal reflectors.
