Restoring the Orthogonality of Two Polarizations in Radio Communication Systems, II

A method of recovering the orthogonality of two polarizations in a radio communication system was presented recently. 1 Two arbitrary polarization ellipses are first transformed simultaneously into two nonorthogonal linear polarizations by a differential phase shifter, and then the nonorthogonality is removed by a differential attenuator. It is of interest to ask whether that transformation is optimum for system applications. Before proceeding further, we will define the optimum transformation. Clearly, it is desirable to minimize the differential attenuation that we must introduce to correct for nonorthogonality. However, in order to achieve maximum bandwidth, we also should minimize the differential phase shift even if we assume, as we do here, that the polarization characteristics of components in the system are not very frequency sensitive over the operating bandwidth. This assumption is, for example, expected to be valid for any depolarization in the main 319 320 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1 9 7 3