An Automatic Control System for Compensating Cross-Polarization Coupling in Frequency-Reuse Communication Systems

In frequency-reuse communication systems using orthogonally polarized waves, depolarization due mainly to rain and Faraday rotation (in satellite systems) reduces channel isolation. The control system described, incorporating a network suggested by T. S. Chu, automatically compensates for cross-polarization coupling without using iterative methods or computations. Control voltages are generated on the receive side by phase-sensitive demodulation of beacons contained in the communication channels. Slightly modified conventional tracking receivers may be used for the demodulation. The system can be used for the reception of dual linear or dual circular polarizations without modification. An analysis of the control system behavior is given and a method for automatic initial balancing of the systemindependent of its initial state-is proposed.