Dirac comb

In mathematics, a Dirac comb (also known as an impulse train in electrical engineering) is a periodic Schwartz distribution constructed from Dirac delta functions for some given period T. Some authors, notably Bracewell as well as some textbooks authors in electrical engineering and circuit theory, refer to it as the Shah function (probably because its graph resembles the shape of the Cyrillic letter sha Ш). Because the Dirac comb function is periodic, it can be represented as a Fourier series:
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