This paper describes a convenient method of polarization analysis for a circular multimode aperture antenna by decomposing the field distribution into two components calledA,B-polar. The new idea in this technique is the separation of theA,B-polar for field expression into a rotationally symmetric magnitude function and an orientation function independent of the antenna off-axis. This leads to easily sketched figures of the multimode polarization patterns which give a clear physical picture on their effects and applications. Several examples are done in the context of the frequency reuse capabilities of earth-station antennas.

This paper presents fundamental concepts, operational principles, and typical experimental results of a differential technique for detections of circularly polarized satellite signal parameters at low axial ratios. The approach is to equip a rotating π-polarizer with an orthomode transducer in the antenna front end. A two-channel phase-locked receiver is used to detect the differential phase (DP) and the differential level (DL) between the two output channels. The required parameters are then readily available from the displays of the DP and DL values on a strip chart recorder.

The use of orthogonal polarizations sharing the same frequency is attractive in satellite communications due to its efficiency in utilizing the spectrum. The main problem remaining to be solved is that of the various cross polarization effects which cause interference between the orthogonal channels. The technique using cascaded heterodyne phase-locked loops (PLL's) to accurately detect the phase as well as amplitude of both copolarized and cross-polarized satellite beacon carriers under poor carrier-to-noise ratio conditions is developed and presented in this paper. Such a technique is very useful not only in satellite beacon measurements and cross polarization experiments, but also in the implementation of cross polarization restoration networks currently developed for satellite communication systems.