Lossless network and method for orthogonalizing dual polarized transmission systems

摘要

A technique is disclosed for restoring the orthogonality of dual polarized signals in frequency reuse communications systems. The technique may be characterized as polarization coding at the transmitter and polarization decoding at the receiver. Coding and decoding is accomplished solely by means of phase shifters and sum and difference networks which are lossless in the dissipative sense. The required phase shifts are determined by defining the transmission media in terms of a transmission matrix. All depolarization effects including those attributable to antennas, feeds and media are lumped into this matrix. The transmission matrix may be determined empirically, and the phase shifts fixed for a given transmission media. Where the characteristics of the transmission media vary with time due to atmospheric and other effects as is the usual case, an automatic, closed loop orthogonalization network is employed wherein a pilot signal is generated at one or both ends of the communications system and used to derive error signals for phase shifter control. The technique disclosed is applicable to systems using either linearly or circularly polarized waves.