pseudofrequencies

Pseudofrequencies are a term used in signal processing and related fields to describe frequency-like quantities that arise from analysis or modeling rather than representing true, intrinsic oscillations of a system. They often reflect artifacts of measurement, discretization, windowing, or model simplifications, or they may serve as convenient proxies for changing spectral content in nonstationary signals.

In practice, pseudofrequencies commonly appear when data are sampled or processed in a way that couples time and frequency. For example, discretization and aliasing can cause components outside the Nyquist range to masquerade as apparent frequencies within the observed spectrum. In time–frequency analysis, instantaneous or local frequencies derived from analytic signals or reassigned spectrograms are sometimes called pseudofrequencies because they depend on the chosen analysis method and window, and may not correspond to a single, fixed physical frequency.

In modeling and estimation, pseu-dofrequencies are used as a finite or tunable set of basis frequencies to approximate a signal with evolving spectral content. Sparse representations, parametric models, or grid-based searches may yield estimated frequencies that are best viewed as pseudo-frequencies—parameters that describe the data within a chosen framework rather than exact physical constants.

Interpretation of pseudofrequencies requires caution. Analysts should consider sampling rate, windowing effects, noise, and model assumptions, and corroborate findings with time-domain behavior or alternative analyses. See also: aliasing, instantaneous frequency, spectral estimation, time–frequency analysis.