Propagation theory in adaptive cancellation of cross-polarization

The application of propagation theory to the structure and control of adaptive networks designed to cancel hydrometeor-induced cross-polarization in microwave communication links is summarized. When adaptive cross-coupling networks are realized at radio frequency as variable waveguide polarizers, desirable simplifications are to make them lossless devices with at most two free parameters. Performance calculations for such simplified forms are fully reviewed. Several new approaches to the design of controllers for the cancelling networks are also made possible. New results are presented on the performance of systems which use only one pilot tone, or even dispense with cross-polar measurement completely. It is also shown that the reciprocity of the hydrometeor medium, an apparently safe assumption, makes possible an extract precorrection of a transmitted polarization if control is based on a beacon signal of the orthogonal polarization sent back from the receiving point.