https://doi.org/10.1351/goldbook.08224
Technical term for changing the shape of a mathematical function, electrical signal, or optical transmission to remove or smooth a discontinuity at the edges, literally meaning 'removing the foot'.
Notes:
- Originally, 'apodization' described the procedure by which Fourier-transform infrared spectra are corrected for the side lobes that appear in the wings of spectral bands when the interferogram is not zero at its limits, by multiplying the interferogram prior to Fourier transformation by a weighting function that is zero at its limits (see Fourier-transform spectroscopy). Its use has broadened in recent years to include weighting functions that are not zero at their limits.
- Apodization is also used for manipulating FIDs (free induction decay) to enhance specific components of the signal, for example to improve signal-to-noise or resolution, and is achieved by application of specific shapes to the FID, e.g., in nuclear magnetic resonance spectroscopy: exponential, Gaussian or sine-bell; in infrared spectroscopy: Boxcar, Happ-Genzel, Norton-Beer, cosine.