A simple depolarization compensator for very wideband communications links an experimental evaluation

A simple cancellation-type compensator was built and subjected to limited testing in a terrestrial link using dual polarization frequency reuse (DPFR) with 3.2 Gb/s in each polarization. A wideband complex (four quadrant) weighting circuit was developed which was capable of about 20 dB of cancellation at midband in a 3.4 GHz band. Control of the weighting circuit was effected by use of two pilot tones near the band edges, from which magnitude and phase of cross-polarization interference (XPI) were estimated. Integration of the compensator, which operated at RF, had negligible impact on clear weather performance of the link, and impacted receiver noise figure by 0.2-0.3 dB. In rain, cancellation of the order of 5-10 dB was observed at values of cross-polarization discrimination (XPD) as low as 10 dB. Post-experiment analysis of the data suggested that there had been errors in the estimation of the phase of the XPI. In spite of this, useful improvement in link performance was demonstrated.<
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