  Most radio signals can be described as a form of sinusoidal carrier
modulation. These signals have the property that when observed over a
sufficiently short period of time, the waveform is approximately sinusoidal,
exhibiting constant magnitude, frequency, and phase. When coherently digitized
with sufficiently high sample rate, it is possible to discern this sinusoid.
The associated signal can be represented as a sinusoid with time-varying
frequency, magnitude, and phase. These parameters can subsequently be used for
detection and characterization, including identification. The parameters can
also be used to synthesize a noise-free estimate of the signal. The synthesized
signal can be coherently subtracted from the original data in order to cancel
the signal, nominally without distortion of the associated noise or nearby
signals. In this report, the conditions required for the short-time sinusoidal
approximation are described. Performance of the canceling technique is examined
in the case of a VHF-band narrowband FM-modulated signal.
