In the context of signal processing, and in particular time–frequency analysis, uncertainty principles are referred to as the Gabor limit, after Dennis Gabor, or sometimes the Heisenberg–Gabor limit. The basic result, which follows from "Benedicks's theorem", below, is that a function cannot be both time limited and band limited (a function and its Fourier transform cannot both have bounded domain)—see bandlimited versus timelimited. More accurately, the time-bandwidth or duration-bandwidth product satisfies σ σ energy , t ⋅ ⋅ σ σ energy , f ≥ ≥ 1 4 π π ≈ ≈ 0.08 cycles , where σ σ energy , t and σ σ energy , f are the standard deviations of the time and frequency energy or power (i.e. squared) representations respectively. The minimum is attained for a Gaussian -shaped pulse (Gabor wavelet) [For the un-squared Gaussian (i.e. signal amplitude) and its un-squared Fourier transform magnitude σ σ t σ σ f = 1 / 2 π π ; squaring reduces each σ σ by a factor 2 .] Another common measure is the product of the time and frequency full width at half maximum (of the power/energy), which for the Gaussian equals 2 ln ⁡ ⁡ 2 / π π ≈ ≈ 0.44 (see bandwidth-limited pulse).