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  2. Fourier series - Wikipedia

    en.wikipedia.org/wiki/Fourier_series

    A Fourier series (/ ˈ f ʊr i eɪ,-i ər / [1]) is an expansion of a periodic function into a sum of trigonometric functions. The Fourier series is an example of a trigonometric series. [2] By expressing a function as a sum of sines and cosines, many problems involving the function become easier to analyze because trigonometric functions are ...

  3. Fourier analysis - Wikipedia

    en.wikipedia.org/wiki/Fourier_analysis

    The inverse transform, known as Fourier series, is a representation of () in terms of a summation of a potentially infinite number of harmonically related sinusoids or complex exponential functions, each with an amplitude and phase specified by one of the coefficients:

  4. Spectral density - Wikipedia

    en.wikipedia.org/wiki/Spectral_density

    Electronic instruments called spectrum analyzers are used to observe and measure the power spectra of signals. The spectrum analyzer measures the magnitude of the short-time Fourier transform (STFT) of an input signal. If the signal being analyzed can be considered a stationary process, the STFT is a good smoothed estimate of its power spectral ...

  5. Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Fourier_transform

    An example application of the Fourier transform is determining the constituent pitches in a musical waveform.This image is the result of applying a constant-Q transform (a Fourier-related transform) to the waveform of a C major piano chord.

  6. Square wave - Wikipedia

    en.wikipedia.org/wiki/Square_wave

    (Odd) harmonics of a 1000 Hz square wave Graph showing the first 3 terms of the Fourier series of a square wave. Using Fourier expansion with cycle frequency f over time t, an ideal square wave with an amplitude of 1 can be represented as an infinite sum of sinusoidal waves: = = ⁡ (()) = (⁡ + ⁡ + ⁡ + …

  7. List of Fourier analysis topics - Wikipedia

    en.wikipedia.org/wiki/List_of_Fourier_analysis...

    List of Fourier-related transforms; Fourier transform on finite groups; Fractional Fourier transform; Continuous Fourier transform; Fourier operator; Fourier inversion theorem; Sine and cosine transforms; Parseval's theorem; Paley–Wiener theorem; Projection-slice theorem; Frequency spectrum

  8. SigSpec - Wikipedia

    en.wikipedia.org/wiki/SigSpec

    SigSpec (acronym of SIGnificance SPECtrum) is a statistical technique to provide the reliability of periodicities in a measured (noisy and not necessarily equidistant) time series. [1] It relies on the amplitude spectrum obtained by the Discrete Fourier transform (DFT) and assigns a quantity called the spectral significance (frequently ...

  9. Periodogram - Wikipedia

    en.wikipedia.org/wiki/Periodogram

    It is the most common tool for examining the amplitude vs frequency characteristics of FIR filters and window functions. FFT spectrum analyzers are also implemented as a time-sequence of periodograms.