sineaaltosignaalia

Sineaaltosignaalia is a term used in theoretical discussions of signal processing to denote a family of non-stationary signals that alternate between two sine-wave components over successive time intervals. The concept is primarily discussed in academic contexts and is not tied to a single standard definition.

A typical mathematical form is s(t) = (-1)^k [A1 sin(2π f1 t) + A2 sin(2π f2 t)], for t in [kT, (k+1)T), where k is an integer, T is the block duration, and A1, A2, f1, f2 are fixed parameters. Variants may include phase shifts or amplitude envelopes within each interval.

The alternating sign across blocks produces a non-stationary spectrum with time-varying energy around the frequencies f1 and f2, and it can generate spectral sidebands. The signal is used in theoretical studies of demodulation, envelope detection, and pattern recognition, and it can serve as a test case for algorithms handling non-stationary signals.

Origins and usage: The term appears to be a neologism formed from elements of sine, alto, and signaali, with a Finnish-tinged morphology. It is not widely standardized and appears in a limited set of papers or educational materials exploring alternating-sum signals. Related concepts include non-stationary signals, modulation, and signal-switching phenomena.