amplitudeshift

Amplitudeshift is a term used in signal processing to describe a change in the instantaneous amplitude of a waveform. It refers to alterations in the envelope of a signal while its frequency content and phase trajectory remain constant or change independently. The concept is closely related to amplitude modulation and dynamic range control but is sometimes used to describe nonmodulatory amplitude changes caused by gain adjustments, distortion, or environmental factors.

Mathematically, for a carrier signal x(t) = A(t) cos(ω0 t + φ(t)), an amplitudeshift by ΔA results in x'(t) = (A(t) + ΔA) cos(ω0 t + φ(t)). When ΔA is constant over time, it is a static amplitude shift; if ΔA varies with time, the shift is time-varying and constitutes amplitude modulation of a particular envelope. In practice, amplitudeshift is often analyzed by extracting the envelope of the signal, for example via the analytic signal formed with the Hilbert transform or by full-wave rectification followed by low-pass filtering.

Amplitudeshift has implications for signal quality and processing. In audio, unintended amplitude shifts produce clipping, compression artifacts, or noise floor changes. In communications, intentional shifts are used in modulation schemes that alter envelope amplitude. In measurement systems, amplitude shifts may indicate gain drift or sensor saturation and are corrected through calibration or normalization.

Related concepts include amplitude modulation, envelope, envelope detector, dynamic range, and amplitude distortion. The term amplitudeshift is not standard in formal textbooks but appears in some practitioner literature and software documentation as a concise label for amplitude changes applied to a signal.