The polarization of an antenna is the polarization of the wave radiated by the antenna. At a given position, the polarization describes the orientation of the electric field.
Suppose an electromagnetic wave, radiated by an antenna, has an electric field E ( a vector) with two components: E We are going to explore the figure traced by the tip of vector E at a given position along the z axis as the time changes.
Let us assume that the components E _{ x} and b is the amplitude of component E_{ }. Phi is the difference of phase between the two components.
## 1 - Linear polarizationUse the scrollbar to set Phi to 0. Set a = 1 and b = 1. (these values might be set already). Press the button "START/STOP animation". The trace of the field vector E should be linear of the hence this is linear polarization. Change a and b and observe the angle of the segment changing.The condition for linear polarization is that Phi should take values such as : Phi = n*Pi, where n is an integer. Use different values for Phi = n*Pi and check that the polarization is linear. ## 2 - Circular polarizationSet a = b = 1 and Phi to 0.5Pi. Press the button "START/STOP animation". The trace is now a circle.The conditions for circular polarization is that Phi should take values such as : Phi = (n+1)Pi/2. Example: Phi = Pi/2 , 3Pi/2, -Pi/2 ... and a = b. Take different values for Phi and a and b according the stated conditions and check that the polarization is circular. ## 3 - Elliptical polarizationSet a = b = 1 and Phi to any value other than 0, Pi, 0.5Pi, say 0.7Pi for example. Press the button "START/STOP animation". The trace is now an ellipse.The conditions for elliptical polarization is that Phi should take values such as : Phi = (n+1)Pi/2. Example: Phi = Pi/2 , 3Pi/2, -Pi/2... Take different values for Phi according the stated conditions and check that the polarization is an ellipse if a is NOT equal to b. More on antennas antennas and parabolic reflectors. |