  When interference affecting various communication and sensor systems contains
clearly identifiable outliers (e.g. an impulsive component), it can be
efficiently mitigated in real time by intermittently nonlinear filters
developed in our earlier work, achieving improvements in the signal quality
otherwise unattainable. However, apparent amplitude outliers in the
interference can disappear and reappear due to various filtering effects,
including fading and multipass, as the signal propagates through media and/or
the signal processing chain. In addition, the outlier structure of the
interference can be obscured by strong non-outlier interfering signals, such as
thermal noise and/or adjacent channel interference, or by the signal of
interest itself. In this paper, we first outline the overall approach to using
intermittently nonlinear filters for in-band, real-time mitigation of such
interference with hidden outlier components in practical complex interference
scenarios. We then introduce Complementary Intermittently Nonlinear Filters
(CINFs) and focus on the particular task of mitigating the outlier noise
obscured by the signal of interest itself. We describe practical
implementations of such nonlinear filtering arrangements for mitigation of
hidden outlier interference, in the process of analog-to-digital conversion,
for wide ranges of interference powers and the rates of outlier generating
events. To emphasize the effectiveness and versatility of this approach, in our
examples we use particularly challenging waveforms that severely obscure
low-amplitude outlier noise, such as broadband chirp signals (e.g. used in
radar, sonar, and spread-spectrum communications) and ``bursty," high crest
factor signals (e.g. OFDM).
