X-Nico

9 unusual facts about Fourier transform


Box spline

Fourier transform of the box spline, in d dimensions, is given by

Brain connectivity estimators

The above measures provide information on the directionality of interactions in terms of delay (correlation) or coherence (phase), however the information does not imply causal interaction.

Cylindrical harmonics

It can be seen that the Z(k,z) functions are the kernels of the Fourier transform or Laplace transform of the Z(z) function and so k may be a discrete variable for periodic boundary conditions, or it may be a continuous variable for non-periodic boundary conditions.

Finite Fourier transform

Equivalently, it is the Fourier transform of a function x(t) multiplied by a rectangular window function.

Jan Mikusiński

His operational calculus is based upon an algebra of the convolution of functions with respect to the Fourier transform.

Network synthesis filters

The driving point impedance is a mathematical representation of the input impedance of a filter in the frequency domain using one of a number of notations such as Laplace transform (s-domain) or Fourier transform (jω-domain).

Point spread function

It can be shown (see Fourier optics, Huygens-Fresnel principle, Fraunhofer diffraction) that the field radiated by a planar object (or, by reciprocity, the field converging onto a planar image) is related to its corresponding source (or image) plane distribution via a Fourier transform (FT) relation.

Weather derivative

The daily temperature (or rain, snow, wind, etc.) model can be built using common statistical time series models (i.e. ARMA or Fourier transform in the frequency domain) purely based only on the features displayed in the historical time series of the index.

Zebbler

During this tour, he used custom Fourier analysis of EOTO's live sounds to trigger pre-made visual events.


Aliasing

Sinusoids are an important type of periodic function, because realistic signals are often modeled as the summation of many sinusoids of different frequencies and different amplitudes (with a Fourier series or transform).

Fedor Nazarov

In 1999 Nazarov was awarded the Salem Prize "for his work in harmonic analysis, in particular, the uncertainty principle, and his contribution to the development of Bellman function methods".

Gabor filter

Because of the multiplication-convolution property (Convolution theorem), the Fourier transform of a Gabor filter's impulse response is the convolution of the Fourier transform of the harmonic function and the Fourier transform of the Gaussian function.

Hartley transform

It was proposed as an alternative to the Fourier transform by R. V. L. Hartley in 1942, and is one of many known Fourier-related transforms.

Remote sensing

Several research groups in Silicon Valley including NASA Ames Research Center, GTE and ESL Inc. developed Fourier transform techniques leading to the first notable enhancement of imagery data.

Side lobe

Because an antenna's far field radiation pattern is a Fourier Transform of its aperture distribution, most antennas will generally have sidelobes, unless the aperture distribution is a Gaussian, or if the antenna is so small, as to have no sidelobes in the visible space.

Yu-Chi Ho

Before Kalman, time series analysis and classical control theory studied the frequency domain, using harmonic analysis, especially Laplace and Fourier transforms.


see also

Chemical laser

Part I of this was a companion paper that dealt with Hermite-Gaussian Expansion and has received little use compared with the Fourier Transform method which has now become a standard tool at United Technologies Corporation (SOQ), Lockheed Martin (LMWOC), SAIC (ACS), Boeing (OSSIM), tOSC, MZA (Wave Train), and OPCI.

DHT

Discrete Hartley transform, a Fourier-related transform of discrete, periodic data similar to the discrete Fourier transform

Focus recovery based on the linear canonical transform

M. Haldun Ozaktas, Zeev Zalevsky and M. Alper Kutay, “The fractional Fourier transform with applications in optics and signal processing,” JOHN WILEY & SONS, LTD, New York, 2001.

Fractional Fourier transform

The discrete fractional Fourier transform is defined by Zeev Zalevsky in

Hexagonal sampling

Russell M. Mersereau developed hexagonal discrete Fourier transform (DFT) and hexagonal finite extent impulse response filters.

Lindsey–Fox algorithm

The Lindsey–Fox algorithm uses the FFT (fast Fourier transform) to very efficiently conduct a grid search in the complex plane to find accurate approximations to the N roots (zeros) of an Nth-degree polynomial.

Parseval's theorem

More generally, given an abelian topological group G with Pontryagin dual G^, Parseval's theorem says the Pontryagin–Fourier transform is a unitary operator between Hilbert spaces L2(G) and L2(G^) (with integration being against the appropriately scaled Haar measures on the two groups.) When G is the unit circle T, G^ is the integers and this is the case discussed above.