Adaptive Cross Polarization Interference Cancellation for Satellite Downlinks: Architecture Trades and Performance Analysis

Dual Polarization Frequency Reuse (DPFR) effectively doubles the available frequency spectrum by simultaneously transmitting two independent signals over the same frequency band by using orthogonal polarizations. The result is a communication link whose capacity is essentially doubled. Such system gain does not come without its potential impairments. At higher frequencies, depolarization can occur due to several factors such as rain or poor antenna axial ratio thereby inducing interference and reducing link availability. For satellite-to-ground links, Adaptive Cross-Polarization Interference Cancellation (AXPIC) can be employed to mitigate the effects of depolarization and maximize link availability. Using the framework of a modem to be employed in a satellite downlink, AXPIC design trades and their system impacts are discussed. Laboratory tests producing cross-polarization channels are described along with performance test results for a minimum mean-square error (MMSE) AXPIC. As a benchmark with respect to un-restricted system complexity, modulation constrained information rate analysis for DPFR with cross-polarization interference is derived. Information theoretic analysis for a MMSE AXPIC is also presented with laboratory test results showing performance gains consistent with analysis.