A novel polarization smart antenna

The wave propagating through the mobile channel becomes partially depolarised by polarization-dependent scattering. Measurements of the amount of depolarization (XPD-cross polarization discrimination) for linear polarizations reveal an energy transfer of -8 to -15 dB to the orthogonal polarization in outdoor propagation, indicating that the wave is essentially polarized. The independent fading of the wave components are commonly interpreted as being randomly polarized but the histogram of the incident wave appears to be bounded by an eccentric ellipse-like shape with an axial-ratio equal to the value of XPD. Moreover, the measured projection of the averaged-in-time polarization of the incident wave is found to be highly correlated over a wide frequency bandwidth. This observation serves as the foundation for a new polarization-matching algorithm, whereby the time-average polarization of the incident wave serves to adjust the polarization of the transmission back to each individual mobile station (MS). This process recovers a substantial portion of the polarization-induced transmission losses that may exceed 10 dB, and serves to reduce the forward power control variations, and the average transmit power of the base-transceiver-station (BTS), as well as the induced interference. The paper presents the proof-of-concept polarization matching trial, and the analysis of the results. A novel polarization-matching smart-antenna system architecture is described.