Cross Polarization Interference Reduction Techniques.

摘要

The objective of this program was to design, fabricate and test the optimum algorithm developed on the previous contract (Contract F30602-76-C-0041) to improve the performance of cross-polarization on line-of-sight (LOS) digital microwave channels. Specifically, an adaptive equalizer which would function with cross-polarization discrimination ratios from 5 dB to 40 dB and provide up to 20 nanoseconds of linear and parabolic group delay compensation was desired. An experimental equalizer was constructed and successfully tested both in the laboratory and at RADC. All primary design objectives were met with the exception of automatic operation in the copolar mode. Theoretical limitations of the performance measurement techniques used in the equalizer restrict copolar operation to a manual mode. In the automatic cross-polar mode, the equalizer can reduce an input cross-polarization discrimination ratio (CPDR) of 5 dB to a CPDR near 25 dB with the modem signal meeting FCC 19311 requirements over an LC8D radio. Non-dispersive cross-pole interference can be reduced by 25 dB. In back-to-back modem tests, the equalizer's residual interference level is near the design objective of -40 dB.