Circularly and Linearly Polarized Electromagnetic Waves

Linear polarization (LP) has been the traditional transmission strategy employed in current mobile wireless communication systems. Recently, circular polarization (CP) has regained much interest as CP proves to be a potential candidate to maximize the polarization efficiency component of the link budget. In this paper, the essential concepts of CP are first reinforced by a tutorial description in terms of mathematical insight, propagation characteristics, as well as related applications. Most reported works on CP chiefly focus on the theoretical description of its propagation benefits, such as significant amplitude fade and delay spread (DS) reduction, without simultaneously providing convincing proofs. In other words, CP propagation has not been investigated in sufficient depth. Therefore, we then propose a method for synthesizing CP that is implementation friendly to practical antennas.

The engineering validity is subsequently verified by a series of chamber measurements. Intuitively, the polarization trajectory of a synthetical circularly polarized electromagnetic wave is illustrated to further prove the point. Finally, by conducting channel measurement campaigns in a typical urban macrocell scenario, radio propagation characteristics with a dipole as the receive apparatus are analytically extracted for both LP and CP. To facilitate fair competition, the radiation field patterns of two relevant transmitting antennas are intentionally designed to be identical. Numerical results quantitatively demonstrate that, compared with LP, CP can significantly alleviate branch power imbalance between vertical and horizontal polarizations and decrease DS. These advantages are in line with theoretical anticipation and can be fully exploited to upgrade the performance limits of current mobile wireless communication systems.