The use of DFT windows in signal-to-noise ratio and harmonic distortion computations

The author presents a method for estimating the root-mean-square (RMS) value of a sine wave from the magnitude of its discrete Fourier transform (DFT), with special attention to the selection of the DFT window. The set of DFT frequencies that constitute a harmonic depends on the DFT window, the length of the DFT, and the number of bits of the digitizer. Criteria are developed for choosing the DFT frequencies that correspond to a sine wave. These criteria lead to better choices of DFT windows for SNR and harmonic distortion calculations.<<ETX>>