This question appears in Mumbai University > Satellite Communication and Network subject

Marks: 5 M

Year: May 2015

Orthogonal Polarization & the Importance of this in Satellite Communication

The propagation path between a satellite and earth station passes through the ionosphere, and possibly through layers of ice crystals in the upper atmosphere and rain, all of which are capable of altering the polarization of the wave being transmitted. An orthogonal component may be generated from the transmitted polarization, an effect referred to as depolarization. This can cause interference, and this is when orthogonal polarization is used to provide isolation between signals.

Orthogonal polarization is the polarization of an elliptically polarized wave for which the electric field strength vector at a given point in space rotates in the same plane and in an opposite sense to that of a reference elliptically polarized wave of the same direction of propagation, the axial ratios of both polarization ellipses being the same and their major axes at right angles. In other words, it is a state of two electromagnetic waves which show mutually orthogonal polarizations at a given point in space.

It is primarily used to avoid interference from celestial disturbances. it compensates for various types of natural polarization that occur like rain depolarization. However, both the sending and receiving ends have to be so adjusted to receive these polarized signals efficiently.