Re: polarization
Co and Cross polarizations exist only in the case of linearly polarized antennas.
Power received by an antenna is proportional to Cos(θ), where θ is the angle between the E-vectors of the received wave and that would induce in the Rxr antenna (depends on its geometry and orientation of feed ).Rxr antenna will receive maximum power only when θ=180• , which is co-polarization.When θ=90• minimum power is received, which is cross-polarization.
For a circularly polarized antenna, the same power is received irrespective of θ