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  2. Fourier inversion theorem - Wikipedia

    en.wikipedia.org/wiki/Fourier_inversion_theorem

    Some problems, such as certain differential equations, become easier to solve when the Fourier transform is applied. In that case the solution to the original problem is recovered using the inverse Fourier transform. In applications of the Fourier transform the Fourier inversion theorem often plays a critical role. In many situations the basic ...

  3. Sine and cosine transforms - Wikipedia

    en.wikipedia.org/wiki/Sine_and_cosine_transforms

    By applying Euler's formula (= ⁡ + ⁡), it can be shown (for real-valued functions) that the Fourier transform's real component is the cosine transform (representing the even component of the original function) and the Fourier transform's imaginary component is the negative of the sine transform (representing the odd component of the ...

  4. Discrete Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Discrete_Fourier_transform

    Left: A continuous function (top) and its Fourier transform (bottom). Center-left: Periodic summation of the original function (top). Fourier transform (bottom) is zero except at discrete points. The inverse transform is a sum of sinusoids called Fourier series. Center-right: Original function is discretized (multiplied by a Dirac comb) (top).

  5. Fast Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Fast_Fourier_transform

    A fast Fourier transform (FFT) is an algorithm that computes the Discrete Fourier Transform (DFT) of a sequence, or its inverse (IDFT). A Fourier transform converts a signal from its original domain (often time or space) to a representation in the frequency domain and vice versa.

  6. Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Fourier_transform

    While the Fourier transform can simply be interpreted as switching the time domain and the frequency domain, with the inverse Fourier transform switching them back, more geometrically it can be interpreted as a rotation by 90° in the time–frequency domain (considering time as the x-axis and frequency as the y-axis), and the Fourier transform ...

  7. Indirect Fourier transformation - Wikipedia

    en.wikipedia.org/wiki/Indirect_Fourier...

    This is an brief outline of the method introduced by Otto Glatter. [2] For simplicity, we use = in the following.. In indirect Fourier transformation, a guess on the largest distance in the particle is given, and an initial distance distribution function () is expressed as a sum of cubic spline functions evenly distributed on the interval (0, ()):

  8. DFT matrix - Wikipedia

    en.wikipedia.org/wiki/DFT_matrix

    In this case, if we make a very large matrix with complex exponentials in the rows (i.e., cosine real parts and sine imaginary parts), and increase the resolution without bound, we approach the kernel of the Fredholm integral equation of the 2nd kind, namely the Fourier operator that defines the continuous Fourier transform. A rectangular ...

  9. Multidimensional transform - Wikipedia

    en.wikipedia.org/wiki/Multidimensional_transform

    The 2D Z-transform, similar to the Z-transform, is used in multidimensional signal processing to relate a two-dimensional discrete-time signal to the complex frequency domain in which the 2D surface in 4D space that the Fourier transform lies on is known as the unit surface or unit bicircle.