IONOSPHERIC DEPOLARIZATION

The layer above the Earth‟s surface carrying charged particles is called ionosphere.This layer is charged because of solar radiation.

Free electrons that are freely (non-uniformly) distributed in this layer form electron clouds. And cause travelling ionospheric disturbances. Signals passing through these clouds face fluctuations and Faraday‟s rotation. 

The motion of these free electrons is within the magnetic field of the Earth. But as soon as the travelling wave passes through them, their direction of motion no longer remains parallel to the electric field of the wave and these electrons react back on these waves. 

This leads to a shift in the polarization. This angular shift in polarization is also dependent on the length of the path in the ionosphere and the electron density of the region of interest. Faraday‟s rotation is inversely proportional to the frequency shared and is not considered as a problem for frequency above 10 GHz. 

Let linear polarization wave have electric fields E at the receiver antenna with no Faraday rotation. 

Thus received power is E2 Faraday rotation of θF degrees results into co-polar component of the received signal being reduced to:

                                                       Eco = E cos θF 

Thus the receiving power in this case is Eco 2 Thus polarization loss (PL) in decibels is: 

PL = 20 log Eco / E 

Thus,

 PL = 20 log (cos θF) Similarly, cross-polar component is: 

XPD = 20 log Eco / Ex

 Thus, XPD = 20 log (cos θF)