NONAP stands for Nonlinear Adaptive Processor.
NONAP suppresses interference in direct-sequence spread-spectrum communications receive systems. It accomplishes this by optimizing the detection process dynamically against the current received interference.
The characteristics of interference are estimated statistically and then, using this information, are used to derive a nonlinear transform
to apply to the combination of signal and noise. As the statistical characteristics of the interference change, the resulting transformations change to match. Large improvements (tens of dB) can be achieved for a wide range of interference modulations.
For more information see J. H. Higbie’s paper, ADAPTIVE NONLINEAR SUPPRESSION OF INTERFERENCE, presented at MILCOM 88.