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The simplest example is provided by () = which is equivalent to considering the Schrödinger equation for the quantum harmonic oscillator. [24] The corresponding solutions provide an important choice of an orthonormal basis for L 2 ( R ) and are given by the "physicist's" Hermite functions .
Time/frequency distribution. The main application of the Gabor transform is used in time–frequency analysis.Take the following function as an example. The input signal has 1 Hz frequency component when t ≤ 0 and has 2 Hz frequency component when t > 0
Gaussian functions are widely used in statistics to describe the normal distributions, in signal processing to define Gaussian filters, in image processing where two-dimensional Gaussians are used for Gaussian blurs, and in mathematics to solve heat equations and diffusion equations and to define the Weierstrass transform.
While the ordinary DFT corresponds to a periodic signal in both time and frequency domains, = / produces a signal that is anti-periodic in frequency domain (+ =) and vice versa for = /. Thus, the specific case of a = b = 1 / 2 {\displaystyle a=b=1/2} is known as an odd-time odd-frequency discrete Fourier transform (or O 2 DFT).
As an example of propagation without dispersion, consider wave solutions to the following wave equation from classical physics =, where c is the speed of the wave's propagation in a given medium. Using the physics time convention, e − iωt , the wave equation has plane-wave solutions u ( x , t ) = e i ( k ⋅ x − ω ( k ) t ...
The response value of the Gaussian filter at this cut-off frequency equals exp(−0.5) ≈ 0.607. However, it is more common to define the cut-off frequency as the half power point: where the filter response is reduced to 0.5 (−3 dB) in the power spectrum, or 1/ √ 2 ≈ 0.707 in the amplitude spectrum (see e.g. Butterworth filter).
If the considered function is the density of a normal distribution of the form = [()] where σ is the standard deviation and x 0 is the expected value, then the relationship between FWHM and the standard deviation is [1] = .
I.e., for each frequency in a desired set of frequencies, sine and cosine functions are evaluated at the times corresponding to the data samples, and dot products of the data vector with the sinusoid vectors are taken and appropriately normalized; following the method known as Lomb/Scargle periodogram, a time shift is calculated for each ...