Submarine UHF SATCOM (25 kHz CPM) Narrowband Interference and Multipath Mitigation with Nonlinear Adaptive Filtering

Xenotran proposes to design an adaptive filtering system capable of mitigating the effects of narrowband interference and multi-path distortion on a Multi-h Continuous Phase Modulation (CPM) modulated channel. The adaptive filtering system will be based on the Least-Mean-Square (LMS) algorithm and will exploit the non-linear behavior of LMS to improve system performance. This system will also capitalize on turbo equalization techniques, iterating between equalizer and soft-input soft-output (SISO) demodulation of the quaternary, Multi-h CPM trellis to further improve system performance. Such an iterative adaptive filtering system is directly applicable to UHF SATCOM receivers, specifically receivers complying with the MIL-STD-188-181B/C standards, where narrowband interference and multi-path distortion are of concern. This system is particularly useful in littoral environments, where reflections from the sea surface create multi-path distortion and where ducting conditions can cause an increase in received interference.