Fundamental component enhancement via adaptive nonlinear activation functions

In many real world oscillatory signals, the fundamental component of a signal f(t) might be weak or does not exist. This makes it difficult to estimate instantaneous frequency signal. A traditional approach is apply rectification trick, working with |f(t)| ReLu(f(t)) instead, enhance component. raises an interesting question: what type nonlinear function g:R?R has property that g(f(t)) more pronounced frequency? g(t)=|t| and g(t)=ReLu(t) seem work well in practice; we propose variant g(t)=1/(1?|t|) provide theoretical guarantee. Several simulated signals are analyzed demonstrate performance proposed solution.