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

We propose to further develop and implement innovative nonlinear adaptive filtering techniques to simultaneously mitigate the effects of narrowband interference and multipath distortion for the 25 kHz Continuous Phase Modulation (CPM) MIL-STD-188-181B waveform for submarine communications and other DoD applications. Our approach is based on an extension of nonlinear adaptive filtering techniques that we developed and successfully applied to the 5kHz Shaped Offset Quadrature Phase Shift Keyed (SOQPSK) MIL-STD-188-181B waveform in previous work. These algorithms will be redesigned to provide effective performance with the 25 kHz CPM waveform in the presence of both CW interference and multipath distortion. In Phase II, we will produce an FPGA/DSP prototype implementing a complete software/hardware capable of signal acquisition and subsequent tracking of frequency, phase, timing, and the Reed-Solomon coding and Viterbi detection functions specified in MIL-STD-188-181B. The signal processing approach based filtering we develop will be robust to high levels of narrowband interference, as frequently encountered in tactical networks, and will solve the tactical requirement of interference mitigation with minimal signal distortion by the development of a multi-stage nonlinear adaptive filtering approach that is able to recognize the start of the preamble and acquire and track the 25 kHz coded CPM waveform in the presence of severe CW narrowband interference.