Circular cross-polarization measurements on earth-space paths at 11.7 GHz

Measurements of the cross-polarization of circularly polarized 11.7 MHz transmissions from the CTS satellite to four locations across Canada are presented which were undertaken as part of a design study for dual-polarization frequency reuse satellite systems. A dual-linearly polarized 1.85-m antenna was used at St. John's, Halifax, Toronto and Vancouver to receive the linear horizontal and vertical components of the circularly polarized satellite beacon, and a special purpose single-channel phase-lock receiver was used to measure the vertically polarized signal level and the hydrometeor-induced differential attenuation and phase shift, allowing the circular cross-polarization discrimination and co-polar attenuation to be calculated. Periods of reduced cross-polarization discrimination are observed which are attributed to ice-crystal depolarization but which have only a marginal effect on cross-polarization discrimination statistics at small percentages of time in the cumulative distributions. A relationship between the cross-polarization discrimination and the co-polar attenuation is derived for cases when rain is the dominant depolarization mechanism, and shown to be in agreement with previous semi-empirically derived prediction equations.