Automatic polarization decoupling network

Abstract

An automatic polarization decoupling circuit for decoupling first and second signals originally transmitted with orthogonal polarizations comprising a rotatable quarter-wave plate and a rotatable half-wave plate for linearizing the first signal and rotating its polarization direction to a reference polarization direction, an Orthomode (trademark) transducer for separating energy in the reference polarization direction from energy with a polarization in quadrature thereto and utilizing this quadrature energy as the decoupled second signal. The system further comprises a second Orthomode transducer for recombining the in-phase and quadrature energy separated by the first Orthomode transducer and applying this recombined energy to a second rotatable quarter-wave plate and a second rotatable half-wave plate for linearizing the second signal and rotating its polarization direction to a direction in quadrature with the reference polarization direction. A third Orthomode transducer is provided to separate the energy in this quadrature reference polarization direction from the energy polarized in the reference direction. The reference direction energy separated by this third Orthomode transducer comprises the first signal in decoupled form.This system further includes a correlator for generating control signals from the two decoupled output signals to thereby control the alignments of the first and second quarter-wave plates and the first and second half-wave plates. In respective embodiments of the invention, the correlator employs a phase comparison process, one using pilot signals, the other without pilot signals.