Influence of a measurement time window on the FFT frequency spectrum

The rectangular measurement window effects loss of resolution and accuracy of investigated spectrum. In digital signal processing (in particular by FFT method) the problem is not simple and required detailed analysis. In this case the signal and obtained spectrum are given as numerical series of values. It is possible to prove that the discrete form of spectrum accomplishes function of filtr eliminating disturbed informations and distortions don't appear in the spectrum.