Explain antenna polarization and its importance.

Polarization describes the orientation of the electric field vector of an electromagnetic wave. Types: Linear polarization has the E-field in one plane (horizontal or vertical). Circular polarization has the E-field rotating as the wave propagates (RHCP or LHCP). Elliptical polarization is general case with unequal axes. Cross-polarization discrimination measures isolation between polarizations. Polarization mismatch between Tx and Rx antennas causes loss (up to 3 dB for 45° mismatch, total loss for orthogonal). Circular polarization is used in satellite communications because it's immune to Faraday rotation and orientation changes. Mobile systems often use dual-polarized antennas (+45° and -45°) for diversity.